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Resource-consumption systems can be defined by a resource inlet, a control volume where the resource is used, and a waste outlet. Specific to water, many existing conservation strategies focus on reducing the in-flow of water into a control volume. Instead, this work explores reducing waste out-flow, which causes accumulation in the control volume. This strategy aims to motivate users to reduce resource in-flow in response to accumulation in the control volume, and thus modify behavior. To test this strategy, Amazon Mechanical Turk workers completed three randomly ordered handwashing simulations with different sink-outflow rates online. Study participants (N = 74) significantly reduced consumption of water when it accumulated quickly in the sink (p < 0.0001). Participants reduced water consumption, on average by 14% at lower outflow rates, as they decreased inflow rates to prevent sink overflow. Many pro-environmental behavior interventions are limited in their reliance on user motivation and intention to reduce resource consumption. In contrast, the reduced-outflow intervention significantly reduced water usage (p < 0.001) of individuals, regardless of self-reported daily pro-environmental behavior. This result suggests that the developed intervention relies less on user intention. Overall results support that reducing outflow can increase sustainable user behavior when properly executed. In-person testing is discussed as future work.

Exhaust gas of an automotive fuel cell is enriched with water vapour and has a pressure potential which can be utilized by a turbine. The gas expansion in the turbine leads to droplet nucleation and condensation. This results in a release of latent heat and a decrease of the gaseous mass flow which has a considerable influence on the turbine performance. This study aims to numerically investigate the influence of these phenomena on the performance map of the radial turbine of an automotive fuel cell turbocharger. For this purpose, the classical nucleation theory and Young’s droplet growth law are integrated into an Euler-Lagrange approach. The results show an almost linear relation between the pressure ratio and the condensation while the specific aerodynamics of an operating point has only a minor influence. At 80 % relative humidity of the inflow, the investigated turbine showed condensation above a total-to-static pressure ratio of 1.8. Condensation leads to thermal throttling of the turbine and to a temperature increase of the rotor outflow of up to 50 K. Increasing humidity of the inflow increases the power output, but condensation losses reduce the efficiency.

The pipeline industry is increasingly utilizing reliability methods as a basis for decision-making when managing the integrity of pipeline systems. In this paper we present a methodology for developing reliability benchmarks for onshore low vapour pressure (LVP) liquids transmission pipelines to enable an operator to evaluate the performance of their pipelines relative to their industry peers. The goals of this methodology are to use an approach that is calibrated to historical performance, that remains interpretable, that can readily be adjusted over time, and that reflects the increased sensitivity of High Consequence Areas (HCAs). On this basis, the Top Quartile (Q1) and Average historical environmental performance of the top 20 largest liquid pipelines operators were identified as two primary benchmarks of interest. Top Quartile (Q1) environmental performance represents an industry leading benchmark performance while the Average historical environmental performance is representative of typical pipelines. This group of operators was selected on the basis that these major companies operate pipeline networks with comparable complexity, similar integrity challenges and a diverse range of operating environments (urban, rural, etc.). In addition, the length of their respective systems decreases the impact of small sample size issues. The dataset used for calculating the historical environmental performance of these operators was the 2010–2018 PHMSA Hazardous Liquids Incidents and Annual Mileage datasets. The framework presented in this paper, allows specific reliability benchmarks to be calculated for a given pipeline dependent on the environmental consequences associated with failure of the line. Consequences are considered in order to be risk-consistent between pipelines with different outflow potentials and different land use surroundings (HCA vs. Non-HCA). The heightened sensitivity of HCA areas is considered by including an impact ratio in calculating the reliability benchmarks. These benchmarks can be used to identify pipelines for additional scrutiny when the expected environmental performance does not meet benchmark levels and to flag areas for further evaluation. Quantifying the failure potential of pipeline segments gives operators insights into which maintenance actions will make the most effective use of the available resources to improve reliability. These benchmarks are calculated directly from historical data using a simple methodology and are easily recalibrated in the future as the performance of the pipeline industry continuously improves to meet increasing societal expectations.

Radial outflow turbines are an alternative for axial turbines for example in heat recovery applications. They are, however, also often characterized by ultra-low aspect ratios. In these designs, the secondary losses dominate the overall loss share, and under a certain aspect ratio, the secondary structures from the hub and shroud begin to interact. This interaction causes a decrease in aerodynamic performance. Previous studies have suggested that the general flow phenomena between radial outflow and axial turbines could share several similarities due to observed trends in performance prediction. The blade outlet Mach number is known to affect the spanwise positions of the secondary vortices in axial turbine blading and therefore, its effect is also tested here for an ultra-low aspect ratio radial outflow turbine cascade. In addition, there are currently no cascade level experimental data publicly available, and the suitability of axial turbine loss correlations under these conditions remains an open question. From this background, the current study presents an experimental, numerical, and loss correlation analysis of the effects of an isentropic Mach number in a radial outflow turbine cascade. An experimental campaign is used to validate the numerical model both quantitatively and qualitatively. In addition, the validity of the axial turbine loss correlation is extended to ultra-low aspect ratios by introducing a new variable called penetration length. The main findings are: 1. The flow phenomena do not differ significantly from what has been observed with axial turbines, 2. The effect of penetration length calculation method on the loss breakdown is relatively low, and 3. With ultra-low aspect ratio radial outflow turbines, the loss breakdown is markedly changed when the extended Benner’s approach is employed.

Turbine secondary flow system calculations are usually performed by utilizing the thermal-fluid network approach. The network consists of branches and nodes. Fluid branches usually describe the flow resistance of the correspondent fluid path section, while fluid nodes are used to connect fluid branches between each other. Fluid flow in branches and nodes is described by the set of conservation equations such as mass and momentum equations. For fluid nodes, usually total or static pressure is used as a variable in these equations. However, such an approach may yield a system of equations that cannot be solved (for theoretical cases where zero resistance branches are present) or may produce significant differences in results compared to the more precise CFD solution (for real cases with resistances). This paper provides an approach on how to create a model of a fluid lossless junction in order to solve the mentioned problems. Such a junction enables the connection of any number of inflow and outflow fluid branches without bringing any flow resistance, which allows fluid branches to handle flow resistance influence by themselves. The proposed model is based on the idea, that each node should contain not just one pressure (static or total) as a variable, but two variables — both static and total pressures. Such a node can be used to model junctions of different types with flow mixing, as well as separation and sudden cross-sectional area changes. With this approach it is also possible to model chambers by modifying just one equation. Also, this new method can be applied for both compressible and incompressible calculation types and can handle chocked flows as well.

When cylindrical tanks installed in the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the liquid surface inside the tank called sloshing may occur. If large-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage of the tank roof or outflow of internal liquid of the tank. Also, there is a possibility that the internal components in the tank may be damaged due to the fluid force generated by the flow of the sloshing. In order to evaluate the load acting on the tank roof, it is considered that the liquid surface shape and the liquid surface velocity are required as input parameters. In order to evaluate the load acting on the internal component in the tank, the flow velocity generated by sloshing is required as an input parameter. If the sloshing wave height is small, these values can be calculated based on the linear potential theory. However, when the sloshing wave height increases, the sloshing becomes nonlinear, and the difference between the nonlinear sloshing behavior and the linear sloshing behavior. Therefore, the method of evaluating nonlinear sloshing behavior is necessary to evaluate the design load of tank under the large sloshing wave height condition. In this paper, new methods of evaluating nonlinear sloshing behavior are proposed for the first-order sloshing mode of a cylindrical tank, which can evaluate the maximum nonlinear sloshing wave height, the nonlinear liquid surface shape, the liquid surface velocity, and the flow velocity. Proposed methods, which consist of simplified equations, are expected to be applied to a new sloshing load evaluation method in primary design.1

This paper introduces a new quasi-steady in-ground effect model for rotorcraft unmanned aerial vehicles to predict the aerodynamic behavior when the vehicle’s rotors approach ground plane. The model assumes that the compression of the outflow due to the presence of ground plane induces a change in the induced velocity that can drastically affect the thrust and power output. The new empirical model describes the change in thrust as a function of the distance to an obstacle for a rotor in hover condition. Using blade element theory and the method of image, the model parameters are described in terms of the rotor pitch angle and solidity. Experiments with off-the-shelf, fixed-pitch propellers and 3D-printed variable pitch propellers are carried out to validate the model. Experimental results suggest good agreement with 9.5% root-mean-square error (RMSE) and 97% p-value of statistic significance.

Pulse-synchronous tinnitus (PST) has been linked to multiple anatomical variants of the venous outflow tract, including transverse sinus (TS) stenosis and sigmoid sinus (SS) dehiscence. It is unknown if the size of diameter in the TS part at the symptomatic side will result in PST. In this study, a combined experimental and computational approach is adopted to study the blood flow during PST. A parametric study is performed on the diameter size of one PST patient at the symptomatic side. A Reynold-averaged-Navier-Stokes (RANS) flow solver is employed in ANSYS Fluent to simulate the symptomatic side at different TS diameter sizes. Results have shown distinct differences in the flow characteristics (including pressure, turbulent kinetic energy (TKE), velocity and shear stress) between the symptomatic side at different TS diameter sizes. The result provides evidence to the hypothesis that anatomic differences can be an important element in affecting blood flow in the venous outflow tract. Resulted findings reveal the strong connection between the flow characteristics of a dehiscent SS and resultant PST. The findings help to understand the flow physics of PST and provide insightful guidance for surgical interventions.

As a result of the superior leakage efficiency of brush seals compared to conventional labyrinth seals, compliant contacting filament seals are used to increase the efficiency of jet engines as well as stationary gas and steam turbines. The widespread application of brush seals at different and varying pressure differences combined with variable contacting velocities at the rotor surface requires a profound understanding of the influences of different design parameters on the operational leakage performance. In order to systematically investigate the impact of different design parameters on sealing performance, a new cold air test rig was developed. The new test rig with rotating shaft enables hot-wire anemometry measurements downstream of the seals. These measurements provide insight into the locally resolved flow structure in addition to the integral leakage measurements. For the investigations, one welded and five different clamped brush seals at rotational speeds up to 3000rpm and pressure differences across the seals up to 500kPa are considered. Therefore, the influence of two different designs on the flow through the bristles is presented. For the clamped brush seals, variations of the front and backing plate are investigated. Additionally, the effects of bristle diameter and three different axial inclinations of the bristle pack on the sealing efficiency are shown. Furthermore, initial wear development during the first 30 to 60 hours of brush seal operation at varying experimental conditions is presented and linked to the design parameters. Consequently, the effects of major design aspects on the operational performance of brush seals are examined and presented.

When cylindrical tanks installed on the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the free liquid surface inside the tank called sloshing may occur. If high-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage of the tank roof or outflow of internal liquid of the tank. Therefore, it is important to predict the wave height of sloshing generated by earthquake motion. Sloshing is a type of vibration of free liquid surface, and if the sloshing wave height is small, it can be approximated with a linear vibration model. In this case, the velocity-response-spectrum method using velocity potential can estimate the sloshing wave height under earthquake motion. However, if the sloshing wave height increases, the sloshing becomes nonlinear, and necessary to evaluate the wave height using other methods such as numerical analysis. Design earthquake magnitude levels in Japan tend to increase in recent years, long-period components of earthquake wave which act on the sloshing wave height also increase instead of introducing seismic isolation mechanisms. To evaluate sloshing wave crest impact load acting on the roof of a tank, there are few applications which quantitatively evaluated the crest impact load of nonlinear sloshing. To construct a simple technique to evaluate the sloshing impact load considering the nonlinear sloshing wave height which acts on a flat roof of cylindrical tanks, it is proposed that flow diagram of evaluating the sloshing impact load which newly took into consideration the nonlinearity of sloshing and the dynamic amplification factor. The applicability of the technique was verified with the shaking table tests results for cylindrical tank and flow-analysis results.

Radial inflow turbines offer larger efficiency performance for small power applications due to its geometric configuration in which flow varies its radial position along the flow path. The geometry configuration of radial-inflow turbines demands a careful and adequate design of the flow path, since a 90° change of direction occurs from the radial inflow to the axial outflow. The blade camberline also requires attention since it defines the tangential flow direction along the meridional coordinate and any variation in its geometry affects the turbine performance. In this paper, a method for meridional profile and camberline geometry generation is proposed and tested through CFD. The method consists in using fourth order Bezier curves for defining the hub, shroud and mid-height blade meridional profile and third order Bezier curves for defining the relative flow velocity angle along the meridional coordinate, which leads to the camberline angular position in the rotor considering radial fibered blades. The blade thickness is set to vary linearly along the meridional coordinate and along the blade height. Different configurations of blade geometry are proposed and analyzed. These configurations are fixed to satisfy the design parameters. The code is programed in Python and adjusts the geometry data in files that are readable by meshing software. Thereby numerical calculations are performed to verify which configuration of camberline results in better performance. The calculations are done in models with the same boundary conditions and geometric data except for the variation of relative flow velocity angle along the meridional coordinate but setting the inlet and outlet angle to a fixed value. This way, the most suitable camberline geometry can be selected. The CDF model used for this analysis was validated with the experimental results reported by Kang et al. [1]

Hydrodynamic thrust bearings are vital components of rotating machinery and often undergo high axial loads and temperatures. High loads and the consequent shear heating result in high temperature development and viscosity drop of the lubricant. This phenomenon is captured in the solution of a three dimensional energy equation problem. The inlet flow temperature via a groove mixing model and its interaction with outflow from the previous pad is also included in the analysis. Traditionally, capturing the heat conduction at the lubricant solid interfaces in the energy solution for the fixed pad, lubricant, and rotating disk (runner) have faced significant convergence problems. In this study, an integrated method is proposed to remedy this issue. The effects of various model features on the computed results are investigated.

Smaller combustion chambers, as well as pressure gain combustion processes, are desired in terms of reducing the space, weight, lowering engine manufacturing costs, and increasing the efficiency and specific power of gas turbine engines. In this paper, a compact single rotor disk pressure gain combustor engine is introduced with interesting merits compared with existing turbine engine designs. The engine introduced as the Radial Wave Engine (RWE) features purely radial-flow resulting in a compact and light weight design with only two moving parts. The core of the engine is a spinning radial combustor in which constant volume combustion occurs using stationary inlet and exit end walls resembling a valved-combustor. Power output is generated via a radial-outflow turbine forming a purely disk-shape engine. The proposed engine is a hybrid engine concept, midways between piston and turbine engines with improvements to other counterpart designs. This paper discusses the engine background, operating principles, instrumentation, high-speed video recording, and initial testing of a prototype proof-of-concept demonstrator. This study is the first step towards a new pressure gain combustion configuration which has not designed or tested before.

Radial-outflow turbo-expanders have emerged in the recent years to suit some special applications where complex multi-phase and multi-component flows (like liquid-rich gases and solid particle-laden gases) need to be expanded. This paper presents a systematic study on the design and flow behavior of a single stage radial-outflow turbo-expander, which is to be used in organic Rankine power system to covert the low-temperature heat into shaft power. A mean-line code coupled with the optimization algorithm is developed and used to carry out the one-dimensional preliminary design, where 7 non-dimensional parameters are used as design variables (nozzle velocity coefficient, rotor velocity coefficient, reaction, rotor inlet and outlet flow angles, velocity ratio, and rotor diameter ratio). In comparison with the original design, significant design performance gains are achieved with the matched combination of design parameters. Geometric shape design is further performed for the expander. In consideration of the flow features in nozzle and rotor blade passages being nearly two-dimensional, blade shape design of both rows is conducted on the basis of the airfoils used for conventional axial flow turbines, where a conformal mapping method is used to convert the axial profile into the polar coordinate frame and it is then represented by 11 parameters of mean cylindrical diameter, radial and tangential chord, leading and trailing edge radius, blade inlet and outlet angles, blade inlet wedge angle, number of blades, unguided turning, and throat size. Flow and overall performance are simulated and predicted for the designed expander, where the output shaft power and overall isentropic efficiency is respectively predicted as 87.86 kW and 81.60% at design condition.

This article investigates the generation of rotor-alone tones and their contribution to the outflow noise of a transonic centrifugal compressor stage with vaneless diffuser and volute by means of unsteady full-annulus computational fluid dynamics (CFD) simulations. The aerodynamic field and the generation and propagation of sound were simulated simultaneously using the unsteady Reynolds-averaged Navier–Stokes (URANS) approach of the solver trace and a numerical grid consisting of 170 M cells. To assess the accuracy of the predicted fluctuations, the investigation compares the simulated diffuser flow field to measured flow angles and pressure fluctuations obtained from experiments conducted on a large-scale test rig. The analysis explains the different sound generation mechanisms responsible for tonal components in the acoustic spectrum at the compressor outlet based on the Fourier decomposition of the pressure fluctuations in diffuser and volute. Furthermore, this article analyzes the modal structure of the simulated sound field at the volute outlet by means of a radial mode analysis and discusses the influence of changing operating conditions on the sound power emitted. The analyses reveal that supersonic flow phenomena occurring at choked operating conditions cause a significant increase in noise emissions. Furthermore, the investigation shows that the sound field at the volute outlet is dominated by few low-order modes, a fact that justifies the analysis using methods based on the compressed sensing in future experimental investigations.

When a tsunami attacks in harbors, a vessel moored at a wharf is occurred a serious damage. The first wave of the tsunami has two forms and those are called the leading wave and the backwash. And, it is difficult to predict the form of the first wave of tsunamis. Authors have been studying about damage protection measures against the leading wave of vessels moored at wharves. However, it is also necessary that a damage protection measure against the backwash of vessels moored at wharves is considered. In this study, it is examined the damage status of a vessel at a wharf due to the backwash. Then, it is examined the influence of the backwash to the author’s proposal tsunami protection measures. The three dimensional MPS (Moving Particle Semi-implicit) method is used. The Backwash is simulated as the dam break phenomenon. Outflow angles, flow velocities, mooring conditions and with and without of tsunami protection measures are considered.

Wave forces can form a serious threat to offshore platforms and ships. The damage produced by these forces of nature jeopardizes their operability as well as the well-being of their crews. Similar remarks apply to coastal defense systems. To develop the knowledge needed to safely design these constructions, in close cooperation with MARIN and the offshore industry the numerical simulation method ComFLOW is being developed. So far, its development was focussed on predicting wave loads (green water, slamming) on fixed structures, and for those applications the method is already being used successfully by the offshore industry. Often, the investigated object (ship, floating platform) is dynamically moving under the influence of these wave forces, and its hydrodynamic loading depends upon the position of the object with respect to the oncoming waves. Predicting the position (and deformation) of the body is an integral part of the (scientific and engineering) problem. The paper will give an overview of the algorithmic developments necessary to describe the above-mentioned physical phenomena. In particular attention will be paid to fluid-solid body and fluid-structure interaction and non-reflecting outflow boundary conditions. Several illustrations including validation, will demonstrate the prediction capabilities of the simulation method.

As one of the hot topics in ship structures, hull structural fatigue has been widely studied by overseas and domestic scholars in recent years. And fatigue assessment methods can be divided into simplified calculation method and direct calculation method. However most of the calculation methods are based on liner wave load. Some high-speed ships, large external floats and larger ships may have frequent outflows and inflows during the voyage. These ships can be influenced by more serious wave attack. In this situation, the influence of nonlinear slamming load on ship structures cannot be ignored. In this paper, the author selected the deck longitudinal and the bottom longitudinal of the example ship midship section, then calculated the fatigue damage under the action of liner load and total fatigue damage under non-linear slamming load respectively. And the effect of non-linear slamming load on the fatigue life of hull structure can be obtained: it is 49% larger than that without attack fatigue damage in the deck longitudinal, and 35% larger in the bottom longitudinal. Based on the results, the author got the influence coefficient of non-linear slamming load on the fatigue life of the ship. Finally, a nonlinear correction method of fatigue damage is proposed.

A very challenging issue about solar thermal power generation is the use of a high temperature heat transfer fluid (water, oils, or molten salts) for heat transfer and thermal storage material, which may freeze at night or cold weather. When choosing air as the heat transfer fluid, the problem of freezing is eliminated. In order to increase the performance of thermal storage system which uses air as the heat transfer fluid passing through a packed bed (by ceramic spheres of Al2O3), multiple small-diameter tanks are considered to replace a single large-diameter tank with the same packed-bed volume and airflow rate in this paper. Analysis about the thermal storage performance in a short big tank and in cascade thin tanks has been made for comparison. A long passage of airflow and faster flow speed of air in the cascade thin tanks has been found significantly beneficial to thermal storage. Results about the increased thermal storage performance and increased pressure loss will be presented. Longer passage of airflow made it possible to have a longer time of high temperature of outflow air during discharging period. And faster speed of the fluid enhanced the heat transfer between air and thermal storage material. The total effective energy and thermal storage efficiency of cascade thin-tank thermal energy storage (TES) are higher. The thermal storage efficiency in the two types of thermal storage arrangement was compared for optimal design. The obtained results are of great significance to the development of using air as heat transfer fluid and rocks or ceramic spheres as the thermal storage material for thermal storage system in concentrated solar thermal power plants.

Engine turbine blades operate at a high speed of rotation and are subjected to high temperature and pressure prevailing gas from the combustion chamber, making the working condition very harsh. In particular, the leading edge of the blade, which is directly subjected to high-temperature gas impacts, is the hottest part of the turbine. Therefore, it is of great importance to improve the protection of the blade leading edge and enhance the understanding of this part of the flow field and temperature field. This paper will focus on the phenomenon of wake deflection and study the film cooling characteristics of the turbine blade under rotating condition. The characteristics of pressure surface and suction surface of the blade are verified by numerical simulation. The contents cover the influence of the film hole diameter, pitch, blowing ratio, rotation number and the development process, the film cooling efficiency on the outflow of coolant film. The result shows that Coriolis force, centrifugal force and secondary flow induced by rotation will change the mainstream flow along the blade, which will lead to changes of pattern concerning the development of the film on the blade surface. In the process of wake development, deflection occurs in different directions at different positions, and the greater the rotation number is, the more obvious the degree of deflection will be. Studying the model with film holes on the leading edge of the blade, these phenomena can be observed along the downstream on the pressure and suction surfaces. Also, models with film holes independently set on the pressure and suction surfaces can be used as proof of these features. At the same time, this paper studies the flow and heat transfer characteristics of the leading-edge gas film under rotating condition and focuses on the influence of rotation on the outflow and the development processes of the wake. The gas film cooling models in rotating state of different film hole diameters and film hole radial spacing will also be compared to further understand the flow and heat transfer characteristics of film cooling on the leading edge of the blade.

The flow under sluice gates is well known in open channel hydraulics. There are theoretical, semi-empirical and empirical equations to determine the flow rate under a sluice gate Most of these formulas are based on the Bernoulli equation applied at the inflow cross section and in the vena contracta behind the gate. In 2017 Malcherek [1] showed that it is also possible to apply the integral momentum balance to the sluice gate. When assuming hydrostatic pressure distributions in the inflow cross section and on the weir’s plate then the simple formula VA=(3/4) g h0=0.6122 g h0 is obtained, which is in perfect agreement with the classical vena contracta theory for small opening ratios h0/a. In the outflow cross section under the gate the bottom pressure was assumed to be the mean of the hydrostatic bottom pressure before and behind the sluice gate. In this paper Malcherek’s momentum balance theory will be investigated in further detail with numerical CFD RANS computations of the free surface flow below sluice gate. The exact pressure distributions on the bottom as well as on the gate were obtained for different openings ratios and flow conditions at the sluice gate in a systematic parameter study. These pressure distributions have been introduced into the integral momentum equation and the discharge velocity as well as the flow rate at the sluice gate were investigated and compared with the pure numerical results. These results were also compared with the theoretical and empirical approaches of the literature and a detailed analysis is given.

The paper deals with water cut-off walls for offshore waste landfill facilities that are used to prevent leakage of toxic substances to the surrounding water. A new type of a widely used water cut-off wall called Steel Pipe Sheet Piles (SPSP) is investigated with experimental measurements as well as numerical simulations. The main objective is to found out the influence of tidal fluctuations in the sea on the outflow of the contaminant and the results show that the outflow of contaminants is lower when tidal fluctuations are present compared to the case with only a mean water level. The influence of different filler materials on this behavior is also investigated.

To reduce power losses due to oil flows in aeroengine gearboxes, the oil flows should be visualized and measured. In this study, we develop a flow visualization borescope that qualitatively visualizes oil flows along with a two-phase flow probe that quantitatively measures the oil/air ratio and flow velocity. The flow visualization borescope comprises a 16-mm-diameter pipe. Within the pipe, an air purge passage for removing oil mist and a borescope are integrated with an illumination laser and optical lenses, enabling clear, high-speed photography. The two-phase probe consists of a 5-mm-diameter pipe with a 1-mm-diameter measurement hole and an internal pressure adjustment pipe. The borescope and flow probe were demonstrated using a shrouded spur gear with a peripheral speed of 100 m/s and oil supply of 20 l/min. Flow visualization at 30,000 fps revealed that oil outflow from the shroud opening spreads turbulently over the entire width of the opening. Measurements of the oil/air ratio and flow velocity using the two-phase flow probe revealed a thin oil-rich layer on the shroud wall and showed that the flow speed is lower than the gear peripheral speed. The measurement equipment used herein would be easy to install in a gearbox and is therefore expected to be applied in actual aeroengine gearboxes.

To evaluate the application of the impingement cooling in a trapezoidal duct, particularly the influence on internal cooling of the cross flow and swirl flow. Experimental and numerical studies have been performed. The experiment focuses on the heat transfer characteristics in the duct, when the numerical simulation focuses on the flow characteristics. Four Reynolds numbers (10000, 20000, 30000 and 40000), six cross flow mass flow ratios (0, 0.1, 0.2, 0.3, 0.4 and 0.5) and two impingement angle (35° and 45°) are considered in both the experiment and the numerical simulation. The temperature on the target wall and the exit side wall is measured by the thermocouples, when the realizable k-ε turbulence model and enhanced wall treatment are performed using a commercial code Fluent. The results show that only part of the jets contribute in the heat transfer enhancement on the target wall, the other jets improve a large anticlockwise vortex occupied the upper part of the duct and drive strong swirl flow. The heat transfer on the exit side wall is enhanced by the swirl flow. The cross flow is induced in the duct by the outflow of the end exit hole. It deflects the jets and abates the impingement cooling on the target wall in the downstream region but has no evidently effect on the heat transfer on the exit side wall. Higher impingement angle helps to augment the impingement cooling on the target wall and improves the resistance ability of the jets against the effect of the cross flow. The heat transfer enhancement ability on the target wall and exit side wall in the present duct is compared to that of a smooth duct. The Nusselt number of the former is about 3 times higher than that of the latter. It indicates that the impingement and swirl play equally important roles in the heat transfer enhancement in the present duct. Empirical dimensionless correlations based on the present experiment data are presented in the paper.

This paper discusses a method for predicting hot gas migration into turbine disk cavities using two incompressible orifices for ingress and egress flows at the main flow path-to-rim seal interface. The method employs a flow network system that involves axisymmetric disk cavity flow solver elements to model inflows and outflows that exist in a turbine disk cavity subject to a simulated main gas path pressure field. A modified lumped-parameter two-orifice model in which ingress/egress discharge coefficients and the corresponding orifice physical areas are explicitly defined is demonstrated for predicting sealing effectiveness as part of a flow network system. This model has been calibrated against CO2 concentration measurements results previously reported for a 1.5-stage disk cavity research rig at Arizona State University. The boundary pressures for the entire flow network system were defined to be the peak and trough pressures measured. Two fractional variables are introduced in defining the ingress orifice physical area and driving pressure difference between the main gas flow path and the rim cavity. An exponential curve-fit model for the ingress area fraction was developed to compute orifice egress discharge coefficients for a pre-determined ingress discharge coefficient. Excellent agreement with sealing effectiveness data was observed for a radial-gap rim seal geometry for the tested ranges of rotational Reynolds number and non-dimensional purge flow rate. Assumptions employed in developing the model were supported by a 90 degree sector RANS CFD result for the same disk cavity geometry and flow conditions.

The surface roughening of fan blade leading-edges on large civil aeroengines, due to Water Droplet Erosion (WDE), can lead to a decrease in engine performance and increase the risk of flutter. To model the impingement of a high-speed water droplet on a surface, researchers have frequently assumed the droplet is (a) perfectly spherical, (b) impinging perpendicularly, on a (c) smooth, flat, homogeneous surface. However, the situation presented by the leading-edge of a fan blade calls into question one of these previously used assumptions. It is reasonable to assume a surface is flat, if in reality it is curved, when the radius of curvature of the surface is significantly larger than the droplet radius. In other contexts where WDE occurs, the typical droplet size has either been sufficiently small (e.g. droplet diameter in steam turbines) or the radius of curvature of the surface sufficiently large (e.g. wind turbine blades) that it has been sensible to assume the surface is flat; this does not appear to be the case for the WDE of fan blades. The equations describing the kinematics of an impinging water droplet on a flat surface were reformulated for a curved surface. These novel equations were used, along with established conditions for the onset of lateral outflow jetting, to model the impingement of a droplet on a curved surface. European Aviation Safety Agency publications provided the input values typical for a large, high-bypass, civil turbofan, operating at 100% rpm. The results suggest the relatively similar radius of curvature of the leading-edge of a fan blade and radius of the impinging water droplet will significantly affect the onset of lateral outflow jetting. Jetting is predicted to commence substantially sooner; with the initial high-pressure stage expected to last less than half the time predicted for a flat surface. This substantially shorter initial stage is likely to have significant implications for the WDE that occurs as a result of multiple droplet impingements. Over the years, various attempts have been made to extend the frequently-used set of assumptions, described at the start of this abstract. However, we can find no studies where the effect of the curvature of the surface has been explored. Thus, currently, there are no appropriate theoretical treatments describing the liquid kinematics of a typical water droplet impingement on the leading-edge of a fan blade; this research seeks to rectify this.

The fluid-dynamic design of a bespoke variable geometry axial inflow turbine, equipped with a diffuser-collector system for turbocharging applications, was numerically investigated with the purpose of replacing the radial flow turbine in a commercial turbocharger. The paper aims to investigate the suitability of axial turbines for turbocharging applications in the automotive field. The turbine outflow is linked to a diffuser-collector system in order to obtain a kinetic energy recovery together with a correct flow direction to the discharge system. Additionally, once completed the turbine design, the operating maps for three different stator positions were numerically obtained. Finally, a turbocharger–engine matching model allowed comparison of the new axial and conventional radial flow turbine in terms of turbine power and efficiency, compressor pressure ratio, engine torque and BSFC.

In this study, blade tip leakages were calculated for a Radial Outflow Turbine (ROT) designed for an Organic Rankine Cycle (ORC) at a 150kW power output. Since the turbine blade sizes are relatively very small for low-capacity systems, the leakages through the blade tip clearances considerably affect the turbine isentropic efficiency. Therefore, labyrinth seals were applied at the blade tips and the ROT’s performance degradation due to blade tip leakages was investigated. In order to determine the preliminary ROT sizes, an in-house developed 1-D code was utilized. The blade profiles were optimized with CFD analyses to reach high power output and isentropic efficiency. The designed ROT has 8 stages. Toluene is used as the cycle fluid at inlet conditions of 24bar of total pressure, 310°C and outlet conditions of 0.25bar of static pressure. These conditions are chosen for exhaust conditions of a common biogas engine. Thus, the ORC is supposed to operate at a heat source temperature of 460°C and a heat sink temperature of 35°C. The turbine speed of 14000 rpm is determined. The CFD model for the entire 3-D turbine geometry is built in the FlowVision software. The real gas equation is employed for the compressible flow. The SST turbulent flow model is employed. The CFD model uses transient state and rotating frame approaches. Four blade tip configurations were analyzed. The CFD results reveal the followings. The turbine isentropic efficiency is calculated to be 87.62% for the unshrouded geometry with no clearance, which is an ideal case. For a manufacturable and manageable blade tip clearance of 0.2 mm, the turbine isentropic efficiency is calculated to be 71.03% for the unshrouded geometry. The shrouded geometry with the same clearance increases the efficiency to 74.03%. When a labyrinth seal is applied to the shrouded geometry, the efficiency reaches to 77.03%. The best practice in terms of turbine power output and efficiency is the shrouded geometry with labyrinth seal applications.

Fatigue life assessment of turbine rotating components is usually performed taking into account the presence of potential defects and their propagation, together with an accurate description of the stress/strain fields acting at components critical regions. In this work, such an approach was applied on a radial outflow turbine: the component investigated in this paper is the tie-rod. An axisymmetric FEM model of the whole turbine was implemented to evaluate the stress field acting at the root of tie-rod thread, the component most critical region. Three different preload procedures were investigated, in order to evaluate the effects of plastic strains on fatigue cycles. It was found that an initial overtightening, performed before machine assembly, induces a larger plastic zone at the root of the thread, which lowers the peak stress and lessens the stress ratio of the fatigue cycle. Stress gradients for the three different preloading conditions were the starting point of a crack propagation model, which calculated crack advancement as a function of service time. The model, which considered crack closure and stress ratio effects, allowed structural integrity assessment and showed that the initial overtightening had also the effect of crack growth rates reduction.

Transcatheter replacement therapies for the atrioventricular (AV) valves are considered as the next frontier for the treatment of valvular regurgitation. The AV valves, tricuspid and mitral, are the regulators of blood flow from the atria into the ventricles. During diastole, blood flows through the open tricuspid and mitral valves to fill the right and left ventricles, respectively. During systole, the ventricles contract, closing the AV valves, and forcing the blood to exit through their respective ventricular outflow tracts (VOTs) to the arterial circulations. Although the current gold standard for the treatment of valvular regurgitation is surgical replacement or repair, the field of transcatheter therapies is rapidly expanding as new treatment options for patients; especially for those individuals considered to be at greater risks for surgical complications. Market released bioprosthetic devices for replacing the aortic and pulmonary valves have shown great promise and success. However, the advancement of similar therapies for either the mitral and tricuspid valves remain in the early stages of development. This slower progress is attributed to the high complexities and variabilities of the AV valves, which present challenges for both device design and post-implantation functions.

Transient fluid velocity and pressure fields in a pressurized water reactor (PWR) steam generator (SG) secondary side during the blowdown period of a feedwater line break (FWLB) accident were numerically simulated employing the saturated liquid flashing model. This model is based on the assumption that compressed water in the SG is saturated at the beginning and decompresses into the two-phase region where saturated vapor forms, creating a mixture of steam bubbles in liquid by bulk boiling. The numerical calculations were performed for two cases where the outflow boundary condition is different from each other; one is specified as the direct blowdown discharge to atmospheric pressure and the other is specified as the blowdown discharge to an extended calculation domain with atmospheric pressure on its boundary. To effectively simulate the saturated water flashing from the SG following the FWLB accident, the physical SG model was simplified as a vertical once-through SG to which a feedwater pipe is attached. However, the physical geometry of the analysis model was modeled as realistically as possible in terms of the SG tube bundle height, the SG inner diameter and porosity, the inner diameter and length of broken feedwater pipe part, etc. It was considered that the SG shell-side and the attached feedwater pipe were initially filled with high pressure saturated water. The pressure in the steam space was 7.5 MPa. For the calculation of the two-phase flow during high pressure saturated water flashing from the SG through the broken feedwater pipe, the inhomogeneous two-fluid model was used. The present simulation results were discussed through a comparison with the predictions using a simple non-flashing model neglecting the effects of phase change. Based on the comparative discussions, the applicability of each of the non-flashing liquid discharge and saturated liquid flashing discharge models to the confirmatory safety evaluations of new SG designs was examined.

Reliability and usability of the analytical results regarding vapor film thickness, vapor velocity, and the mass flow rate of vapor at the plate edge and Nusselt number averaged over the surface are examined to clarify vapor outflow conditions at the plate edge which has not been clarified by conventional experiments. For analysis, we adopt the two-phase boundary layer theory and the integral method which can determine the variation of vapor film thickness in the vapor flow direction to set a velocity profile in a vapor film and a temperature profile in a liquid boundary layer reasonably. In the calculation of the analysis, the inclination angle of the vapor-liquid interface at the plate edge is varied ranging from 0 to 90 degrees. The results of the analysis provide useful guides to future studies in observing the vapor flow conditions in detail and measuring the vapor flow velocity at the plate edge.

The original sump design of Rolls-Royce AE3007 central sump is a tangential sump. An experimental program at Purdue University was conducted to investigate the characteristics of a tangential sump design. The research employed a bespoke experimental rig consisting of modular transparent chamber to allow unprecedented view of the two-phase flow inside the bearing chamber. It was found that a persistent liquid pooling near the drain entrance of a tangential sump obstructs the outflow to the scavenge off-take. While space requirement is minimal, the scavenge performance of a tangential sump is poor. A prototype advanced sump was proposed and built with features to address various issues found in the tangential sump. In this paper, further experimental work on the refinements of the advanced sump is presented. This includes experimental study on the effect of a fence and splitter plate, off-take hole diameter and its location, the effect of gravity by tilting, upstream wall fairing, as well as the depth of the sump itself. The experiments showed that the faired upstream wall modification can reduce residence volume significantly across different operating conditions, indicating improvement in scavenge performance. The other modifications help to reduce residence volume only in certain operating conditions. The results of this study helped towards the birth of an optimized sump design, known as Indy sump. The Indy sump has been accepted as a superior sump design and has been used as a benchmark in many sump design studies.

We present results of experiments on a periodically unsteady compressor stator flow of the type which would be expected in consequence of pulsed combustion. A Reynolds number of Re = 600000 was used for the investigations. The experiments were conducted on the two-dimensional low-speed compressor testing facility in Berlin. A choking device downstream the trailing edges induced a periodic non-steady outflow condition to each stator vane which simulated the impact of a pressure gaining combuster downstream from the last stator. The Strouhal number of the periodic disturbance was Sr = 0.03 w.r.t. the stator chord length. Due to the periodic non-steady outflow condition, the flow-field suffers from periodic flow separation phenomena, which were managed by means of active flow control. In our case, active control of the corner separation was applied using fluidic actuators based on the principle of fluidic amplification. The flow separation on the centre region of the stator blade was suppressed by means of a fluidic blade actuator leading to an overall time-averaged loss reduction of 11.5%, increasing the static pressure recovery by 6.8% while operating in the non-steady regime. Pressure measurements on the stator blade and the wake as well as PIV data proved the beneficial effect of the active flow control application to the flow field and the improvement of the compressor characteristics. The actuation efficiency was evaluated by two figures of merit introduced in this contribution.

In this investigation, CFD calculations are conducted to evaluate the differences between five-hole pressure probe-determined flow quantities and the unaffected flow quantities without the probe’s intrusive influence. The blockage effect of the probe is described and evaluated. Furthermore, the influence of this effect is used to estimate the error when using measured stator outflows as forcing functions for the following rotor blades. To compare the flow field, both with and without the probe’s influence, a five-hole pressure probe is traversed numerically at midspan behind each stator row of a 2.5-stage axial compressor. For reproducing the blockage of the probe accurately, the full annulus of the respective stator row has to be modeled. In order to minimize the calculation time, a study to reduce the number of stator passages was successfully performed. To evaluate the flow quantities using the probe, a calibration polynomial is set up numerically. CFD simulations of the probe geometry within a uniform flow field for each pitch and yaw angle, as well as Mach number combination, are performed for this purpose. Moreover, the pressure probe data for the numerical traverses are corrected to account for velocity gradients in the wake region. The comparison of Mach number, with and without the probe’s influence, shows differences both in the width and the depth of the wake. The results of the Fourier-transformed wake profile for both cases are compared and changes in the first harmonic of Mach number of up to −13% identified. Finally, the first harmonic of the flow quantities is used to perform linearized CFD calculations and to evaluate the influence of disturbed forcing functions on the aerodynamic work of the following rotor blade. The average difference in aerodynamic excitation is about −12% with a maximum deviation of more than −30%. The results presented aim to draw attention to intrusive probe influences and their consequences for validating numerical results against experiments. Special attention is given to the discrepancies of forced response calculations with varying gust boundary conditions.

A study was undertaken to evaluate crack arrestor and mainline block valve (MLBV) spacing distances beyond the limits defined in the 49 CFR Part 192 for Class 1 locations for the design of a 42-inch (1,067-mm) OD arctic pipeline. The study assessed whether an MLBV spacing longer than that required by 49 CFR Part 192 for Class 1 locations can provide a level of safety equivalent to that afforded by the spacing recommended in the code. This was accomplished by comparing the hazards in terms of the volume of natural gas released over time, the potential for damage to surrounding structures, and the life safety risk to personnel and the public. The analysis was performed using the software tool PIPESAFE (version 2.20.0), which was developed for a group of pipeline operators by Advantica Technology (now DNV-GL). A full transient analysis of the flow inside the pipeline and through the rupture opening was carried out with automatic shut-off valve (ASV) closures simulated as boundary condition changes at the locations of the valves triggered by the local transient pressure. Gas outflow rates were fed to a structured flame model that calculates the temperature distribution within the flame and the radiant energy emitted and uses the latter to determine the incident thermal radiation field in the area surrounding the rupture, the associated hazard areas and the accumulated thermal radiation dosage over time. These results were compiled into contour plots of thermal radiation intensity for different times; plots of the total area within specific contours of thermal radiation intensity for different times; and plots of the total area within specific contours of accumulated dosage. The dosage-area curves facilitate a direct comparison of the various MLBV and crack arrestor spacing options considered within this study by providing a simple means to establish if the change in spacing causes a substantial change to the affected areas for dosages up to the limits associated with specific levels of lethality to humans and for piloted ignition of wooden structures. It was found that valve spacing has a strong effect on the time at which closure begins to affect the outflow rate. The decline in flow rate after valve closure had significant influence on the thermal radiation field, but these effects only occurred at a relatively late stage. Increasing fracture length led to considerable changes in the shape of the thermal radiation field, but the total footprint within which casualties might be expected in the event of an ignited rupture release and the severity of injuries within the footprint are unaffected by valve closure under the assumed conditions. Similarly, the damage potential to surrounding buildings was unaffected by valve spacing, indicating that increased valve spacing could be implemented in remote, low population density areas without affecting safety.

Accurate prediction of the gas release rate following a full-bore pipeline rupture is key to risk assessment, safe pipeline routing, effective emergency planning and valve closure strategy. Typical tools adopted by the pipeline industry are developed for a perfect gas and are designed to simulate an isolated line rupture event or for simplistic boundary conditions (e.g. constant inlet pressure or no inflow). In the case of a real-life rupture event, a mainline block valve (MLBV) does not respond instantaneously at the time of rupture. Depending on the operation of the pipeline and the configuration of the network itself, the ruptured section might not be isolated for a period of time. Meanwhile, the inlet boundary condition is driven by the upstream network configuration, valve characteristics and operation protocols. As a result, the amount of mass release can be significantly under-estimated by a predictive tool that does not account for these factors. A program based on the Method of Characteristics was developed, which allows an accurate equation of state and complex boundary conditions that reflect proper upstream conditions and valve closure strategy to be incorporated. An example case demonstrates that a shut-in scenario cannot provide correct out-flow prediction. The resulting outflow amount in a real-life rupture can be a few times higher than a shut-in scenario. This holds important implications in pipeline design, valve closure strategy and risk management.

Centrifugal compressor stages with pipe diffusers are characterized by their high efficiency, especially under high pressure ratio conditions. Although it is believed that pipe diffuser scallop leading edge formed by the intersection of two pipes is a critical point in pipe diffuser design, there is another crucial and influential point, which is how to guide and decelerate the flow from pipe diffuser throat to the inlet of combustor chamber, with minimum loss and maximum outflow uniformity. Fishtail pipe diffuser passage is employed by Pratt&Whitney to connect impeller exit and combustor chamber inlet due to its improved performance characteristics. However, only a few comprehensive results have been published describing the complex flow patterns in the fishtail diffuser. Therefore, in the present work fishtail pipe diffusers with several different geometries were designed for a pressure ratio 8.3 centrifugal compressor stage used on a small turbo engine, aiming at providing detailed understanding of geometric parameter influence on fishtail pipe diffuser performance and flow mechanisms in complex fishtail passages. Cone length, streamwise area distribution and centerline shape are critical parameters of a fishtail pipe diffuser. Hence, parametric studies on fishtail pipe diffuser of this high pressure ratio centrifugal compressor by varying cone length, area distribution and centerline shape of the diffuser passage were performed using a state-of-the-art multi-block flow solver. These three parameters were changed respectively, while keeping other parameters unchanged. Detailed analysis was done to identify the influence on flow field in fishtail diffuser passage when these parameters were changed. It was found that increase of fishtail diffuser cone length could alleviate separation in diffuser passage, thus compressor performance is improved. And linear area distribution along passage centerline could build a more efficient fishtail pipe diffuser. A trumpet-shaped or bell-shaped passage is more likely to make flow separate. The centerline is of vital importance for a fishtail passage and it was built by two lines tangent to an ellipse in this work. It was modified by changing major and minor axes of the ellipse. Stage total pressure ratio and adiabatic efficiency maps for varying fishtail passage centerlines were obtained by numerical method, which indicate that there is an optimum range for both axes to make the fishtail pipe diffuser have a better performance. Through these works, the geometric parameter influence on fishtail diffuser performance was uncovered and physical insight into complex flows in fishtail pipe diffuser passage was obtained to give some guidelines on diffusing system design with fishtail pipe diffuser.

In large modern turbochargers, compressors often constitute the main source of noise, with a frequency spectrum typically dominated by tonal noise at the blade passing frequency (BPF) and its harmonics. In transonic operation, inflow BPF noise is mainly generated by rotor locked shock fronts. These and the resulting acoustic fields can be predicted numerically with reasonable accuracy. Outflow noise, while also dominated by BPF tones, is linked to more complex source mechanisms. Its modal structure and the relationships between sources and modal sound pressure levels (SPL) are less well understood. Perhaps this is linked to the intrinsically non-axisymmetric geometries, which results in the need for full stage simulations if high accuracy is of paramount importance. In order to shed some light on outflow noise generation, a transient simulation of a 360° model of a radial compressor stage, including a vaned diffuser and a volute, was carried out using state-of-the-art CFD. Additionally, experimental data was gathered at a multitude of data points downstream of the volute exit for post processing and modal analysis. The sources and the propagation were calculated directly. Optimized values for tempo-spatial acoustic wave resolution and buffer layer design were chosen, based on extensive studies on simplified models. Two grid refinement levels were used to check grid convergence and time step size independence of the results was ensured. Numerical and experimental data match within 1% for total pressure ratio, volume flow and exit total temperature for the studied operating point. Both show the same modal content at the 1st BPF and indicate the presence of the same single dominating mode. The numerical results underpredict overall sound power levels (PWL) at the 1st BPF by 6.6dB. This difference is expected to decrease with further grid refinement and improved accounting for numerical damping. At the 2nd BPF, the experimental data show a significant broadening of the modal content with homogeneous modal PWL distributions. The multitude of modes leads to the generation of complex interference patterns, which shows that single-point acoustic measurements are often inadequate for component noise qualification and should be substituted by modal techniques. The dominating dipole sound sources are found in narrow areas around the vane leading edges and the rotor blade trailing edges. Because of the non-axisymmetric geometry, vane dipole source strengths become a function of circumferential position. The unsteady shedding of vortices from the vane suction surfaces is identified as a further possible source mechanism. However, the contributions of structural vibrations and mode scattering due to small manufacturing imperfections remain unclear.

Smoke spread through the elevator shafts of high rise buildings has been numerically investigated using the Fire Dynamics Simulator (FDS), which is a computational fluid dynamics (CFD) program suitable for fire induced heat and mass transfer. A model of a high rise building was developed and a fire was set at the first level. The smoke spread process through the elevator shafts was evaluated. The process can be divided into two phases. In the first phase, the smoke gradually fills the shafts, and the gas temperature and pressure in the shafts are transient. After this phase, the smoke fully fills the shafts, the temperature and pressure in the shaft are almost steady, which suggests that the smoke inflow rate equals the outflow rate. Throughout the process, the spatial distributions of temperature and pressure in the elevator shaft under fire situations were reported. The hot fire product gases entering the shaft causes a stack effect, which transports smoke to the upper levels. A method of partially enclosing the elevator lobbies was also investigated by the CFD simulation. The results were compared with the unenclosed situation, and showed that enclosing lobbies not only increases the time needed for the smoke to fully fill the shafts, but also reduces the temperature and pressure differences in the shafts.Copyright © 2015 by ASME

A series of detailed measurements of various mechanical and hydraulic system states of different excavators was performed. Main purpose of this study was to obtain a reliable information basis for assessing the potentials of hybrid drives, in particular the amount of recoverable energy. Differences concerned the size (tonnage) of the excavators and the hydraulic systems, open center versus load sensing. All machines were tested at the same set of operation scenarios, which are typical for practice, and with different operators. To this end, all test machines have been equipped with pressure, flow rate, temperature, angular and position sensors. These signals (about sixty) and several available from the machines CAN bus were recorded with a standard data acquisition system and electronically stored for later analysis. These raw data were processed to obtain the interesting data, like speeds, power flows, energies. In addition, videos of each test were recorded to facilitate the correct interpretation of the measurements and their correlation with the actual working processes. Power flows from the combustion engine, different pumps, and at each actuator and energetic losses at the different loss sources were plotted for the different operation scenarios. Total efficiencies of the machines for different scenarios and the energy in and outflow at each actuator were computed. From the latter so called relative and absolute recovery degrees for each actuator and for the total machine in the different operation scenarios were derived. The relative recovery degree is the ratio of the total outflow energy (second and fourth quadrant) and the total inflow energy (first and third quadrant). The absolute recovery degree is the ratio of the total outflow energy of an actuator and the total energy delivered by all pumps in an operation scenario. In most operation scenarios the total efficiency of consumed mechanical output energy at the hydraulic actuators relative to delivered hydraulic energy is in the range 15% to 25%. Reasonable recovery potentials do have the swing and the boom drive. For small machines, however, the boom drive dominates.

This investigation assessed detailed characteristics of flow in diverging manifolds, for water and water-oil cases. A 3D Computational Fluid Dynamics (CFD) model of a distributing manifold was carried out. Numerical results showed good agreement with experimental values. Predicted pressure and velocity contours agree with theory, detailed 3D insight on present secondary flows and localized hydraulic losses was obtained, as well as effect on distribution of phases. Moreover, a 3D, multi-phase (oil-water) CFD model of a diverging manifold design, similar to those installed in separation units was conducted. The main pipe had 0.762 m (30 in) in diameter and 24 m in length, with 8 perforated pipes branching out. Branches had 0.305 m (12 in) in diameter and 12 m in length, with 312 holes per branch. Non-uniform outflow distributions were detected, as well as secondary flows. An alternate design was proposed. Numerical results show the new manifold design achieves uniform static pressure distribution across the entire main pipe, reducing secondary flows and hydraulic losses. Outflow distribution is also uniform, thus improving the performance of the separation unit.Copyright © 2014 by ASME

A personal bio-aerosol sampler is a self-contained, operation flexible, high-efficient device for indoor air quality (IAQ) and health risk exposure monitoring and measurement. Bio-aerosols such germ-laden viruses, microbial species, airborne microorganisms and volatile organic compounds (VOC) are sucked into the sampler and are deposited on the inner wall surface based on cyclone principal. The major concern with bio-aerosol samplers is the collection efficiency. In this study, we use computational fluid dynamics (CFD) tools to evaluate key design parameters, specifically the inlet tube angle and collection tube inner wall roughness. 3D incompressible turbulent flow is simulated using commercial software ANSYS FLUENT. Reynolds stress model (RSM) is used to investigate the turbulence effect with the following boundary conditions (velocity-inlet boundary condition at inlet, outflow boundary condition at outlet and no slip at walls). The numerical approach for air-aerosol interaction is based on an Eulerian-Lagrangian fluid dynamics framework, where the particles or droplets trajectories are computed in a Lagrangian method (discrete phase element) and then conjugate these particles to the continuous phase in the Eulerian frame. The variation of inlet angle affects the collection efficiency of the cyclone separator. In addition, the flow characterizations with different velocity fluctuation profiles validate the continuous phase model. The development and evolution of the vortex core region for the axial velocity are obtained and evaluated in the simulation of the cyclonic flow.Copyright © 2014 by ASME

The following paper deals with the development of an optimized fillet and an endwall contour for reducing the total pressure loss and for homogenizing the outflow of a highly loaded cascade with a low aspect ratio. The NACA-65 K48 cascade profile without a fillet and without endwall contouring is used as a basis. Optimizations are performed using the DLR in-house tool AutoOpti and the RANS-solver TRACE. Three operating points at an inflow Mach number of 0.67 with different inflow angles are used to secure a wide operating range of the optimized design. At first only a fillet is optimized. The optimized fillet is small at the leading edge and rather high, wide and thick towards the trailing edge. It reduces the total pressure loss and homogenizes the outflow up to a blade height of 20 %. Following this a combined optimization of the endwall and the fillet is performed. The optimized contour leads to the development of a vortex, which changes the secondary flow in such a way, that the corner separation is reduced, which in turn significantly reduces the total pressure loss up to 16 % in the design operating point. The contour in the outflow region leads to a significant homogenization of the outflow in the near wall region.

Plant transport mechanisms are of interest in developing micropump for engineering devices. We present a two-dimensional phloem loading and transport model incorporating protein level mechanics with cellular level fluid mechanics. Governing Navier-Stokes, continuity, and Nernst-Planck equations are numerically solved to determine fluid flow and sugar transport. Phloem loading mechanics for active loading is incorporated through a six-state proton sucrose pump kinetic model. The influence of binding rates constants, concentrations, and membrane electrical potential differences on resulting sucrose transport is studied. Numerical results show that increasing rates of the sucrose transporter will noticeably increase outflow. Simulation result also show that a lower leaf sieve sucrose concentration improves outflow. In addition, a more negative membrane electrical potential difference will increase outflow. This numerical model offers insight on parameters that may be significant for implementing plant transport mechanisms in microfluidic devices.Copyright © 2013 by ASME

Flow fields in a rectangular S-bend passage were simulated to benchmark the capability of RANS based CFD in modeling such complex flow passages with/without the effects of flow diffusion over a range of Reynolds numbers from 250,000 to 430,000. Numerical results were validated against the experimental data of pressure coefficient, wall static pressure distributions, and outflow velocity contours. Parametric studies were conducted to examine the effects of inlet turbulence properties in conjunction with the use of various turbulence models (k-e, realizable k-e and SST k-ω). Improvements in prediction accuracies using detailed computational domains were also examined including (i) lengthened inlet section to simulate upstream flow development, and (ii) addition of downstream flow domain to better simulate flow diffusion to an ambient outlet. Altering model geometry and inlet boundary conditions along with the use of different turbulence models had minimal improvements in the simulation results. The CFD results demonstrated that the S-bend flow features and the increasing trends of pressure magnitudes with higher Reynolds numbers were reasonably simulated. Limitations in predicting the diffusing flow fields were evident with the over predictions of pressure recovery. The study also showed the better reliabilities of the k-e model for the simulations of S-bend flow fields through the comparisons of outflow velocity profiles.Copyright © 2013 by ASME