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The ability of particles to flow with very low resistance is characteristic of superfluid and superconducting states, leading to their discovery in the past century (1,2). Although measuring the particle [...]

The prediction of macroscopic diffusion coefficients in dry and wet porous media still strongly relies on measurements, and numerous semi-empirical correlations have been proposed over the years to replace burdensome experimentations, but the range of validity of these correlations can be limited and is not even well-defined. Here, we present ab initio numerical calculations of the diffusion coefficient of two classes of porous media, namely consolidated and unconsolidated soils, where the water phase distribution is obtained by a lattice Boltzmann technique incorporating interracial tension and wetting. We show that these reconstructed media can well represent two categories of soils generally encountered, namely undisturbed and repacked soils, whose diffusivities, to first order, exhibit two distinct dependencies on porosity under dry conditions, but a similar dependence on the water saturation level. We provide a theoretical support to the popular Buckingham law for dry undisturbed soils in the 0.2 to 0.45 porosity range investigated here. This semi-empirical correlation also compares well with our results on wet consolidated soils, although the dependence of the diffusion coefficient on the water saturation level does not seem to be a simple power law. These results, supported by available experiments on gases such as oxygen, hydrogen, or carbon dioxide, appear to be representative of large classes of porous media. The data and their correlations relative to radon are discussed. Finally, some discrepancy with experimental data regarding the value of the percolation threshold remains, which should be investigated further in the future. doi: 10.2136/sssa12009.0474

A method has been developed for high-accuracy analysis of forced response levels for mistuned bladed disks vibrating in gas flow. Aerodynamic damping, the interaction of vibrating blades through gas flow, and the effects of structural and aerodynamic mistuning are included in the bladed disk model. The method is applicable to cases of high mechanical coupling of blade vibration through a flexible disk and, possibly shrouds, to cases with stiff disks and low mechanical coupling. The interaction of different families of bladed disk modes is included in the analysis providing the capability of analyzing bladed disks with pronounced frequency veering effects. The method allows the use of industrial-size sector models of bladed disks for analysis of forced response of a mistuned structure. The frequency response function matrix of a structurally mistuned bladed disk is derived with aerodynamic forces included. A new phenomenon of reducing bladed disk forced response by mistuning to levels that are several times lower than those of their tuned counterparts is revealed and explained. [DOI: 10.1115/1.4000117]

An integrated experimental-numerical study of forced response for a mistuned bladed disk has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the computational fluid dynamics code and a code for the prediction of the nonlinear forced response for a bladed disk. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. The numerical modeling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disk without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disk are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels. [DOI: 10.1115/1.3205031]

The evaluation of fission gas release from spherical fuel during irradiation testing is critical to understand expected fuel performance under real reactor conditions. Online measurements of krypton and xenon fission products explain coated particle performance and contributions from graphitic matrix materials used in fuel manufacture and irradiation rig materials. Methods that are being developed to accurately evaluate fission gas release are described here together with examples of evaluations performed on irradiation tests HFR-K5, -K6, and EUlbis. [DOI: 10.1115/1.3097131]

Perforated panels placed upstream of the premixing tube of a turbulent swirled burner are investigated as a passive control solution for combustion instabilities. Perforated panels backed by a cavity are widely used as acoustic liners, mostly in the hot gas region of combustion chambers to reduce pure tone noises. This paper focuses on the use of this technology in the fresh reactants zone to control the inlet acoustic reflection coefficient of the burner and to stabilize the combustion. This method is shown to be particularly efficient because high acoustic fluxes issued from the combustion region are concentrated on a small surface area inside the premixer. Theoretical results are used to design two types of perforated plates featuring similar acoustic damping properties when submitted to low amplitude pressure fluctuations (linear regime). Their behaviors nonetheless largely differ when facing large pressure fluctuation levels (nonlinear regime) typical of those encountered during self-sustained combustion oscillations. Conjectures are given to explain these differences. These two plates are then used to clamp thermoacoustic oscillations. Significant damping is only observed for the plate featuring a robust response to increasing sound levels. While developed on a laboratory scale swirled combustor, this method is more general and may be adapted to more practical configurations. [DOI: 10.1115/1.3078206] Keywords: perforated plate impedance, passive control, flame-acoustic interaction, combustion instabilities, nonlinear acoustics

A method for gas turbine fault identification from gas path data, in situations with a limited number of measurements, is presented. The method consists of a two stage process: (a) localization of the component or group of components with a fault and (b) fault identification by determining the precise location and magnitude of component performance deviations. The paper focuses on methods that allow improved localization of the faulty components. Gas path analysis (GPA) algorithms are applied to diagnostic sets comprising different combinations of engine components. The results are used to derive fault probabilities, which are then fused to derive a conclusion as to the location of a fault. Once the set of possible faulty components is determined, a well defined diagnostic problem is formulated and the faulty parameters are determined by means of a suitable algorithm. It is demonstrated that the method has an improved effectiveness when compared with previous GPA based methods. [DOI: 10.1115/1.3078793]

A wire-rod type electrohydrodynamic (EHD) gas pump was driven by a negative applied voltage with pipes of different inner diameters. An EHD gas flow was generated from a wire electrode to a rod electrode under a negative corona discharge. The flow velocity was proportional to the applied voltage and the square root of the discharge current. Before spark onset, the maximum volumetric flow rate of 43 L/min was achieved with a pipe having an inner diameter 20 mm, and the pump efficiency was higher than that of a conventional dc motor fan. In a narrow channel, the corona discharge became unstable. In addition, the EHD gas flow velocity was smaller because a pressure loss due to the rod electrode became significant, resulting in a lower electromechanical efficiency. Index Terms--Atmospheric pressure plasma, corona discharge, corona wind, electrohydrodynamics (EHD), gas pump.

A surface barrier discharge generated between an exposed and a buried electrode induces a unidirectional gas flow, known as an electrohydrodynamic (EHD) gas flow. The discharge behavior and flow characteristics have been investigated. When the exposed electrode is an anode, several streamers propagate above the buried electrode, whereas when the exposed electrode is a cathode, weak light emission is uniformly observed above the buried electrode. The maximum discharge length increases as both the length of the buried electrode and the amplitude of the applied voltage increase. Independent of the buried electrode length, the velocity of the EHD flow increases monotonically as the discharge extends farther, and is uniquely determined by the maximum discharge length. Index Terms--Electrodynamics, surface discharges, gas flow.

An electrohydrodynamic (EHD) gas pump, utilizing a ring/needle electrode, has been proposed and the effect of the ring electrode to the flow velocity and yield of flow generation of the EHD gas pump was investigated. The needle/ring is used as a corona discharge electrode and the mesh is used as the ion collecting electrode. It was observed that the proposed type of EHD gas pump can generate a higher flow velocity and yield of flow generation as compared with that from the same EHD gas pump without the ring electrode. As a result, a maximum flow velocity of [V.sub.W] = 4.54 m/s from the proposed EHD gas pump can be obtained at V=15.0 kV, which is 1.2 times higher than that of [V.sub.W] =3.82 m/s of the same needle-to-mesh type EHD gas pump without the ring electrode. With the ring electrode, the yield of flow generation of [Y.sub.W]=46.15 m/Ws can be obtained at V=11kV, which is 2.5 times higher than that of the design without the ring electrode of [Y.sub.W]=18.41 m/Ws. These enhancements, however, may be due to the effect of the ring electrode installed near the needle electrode. Index Terms--EHD gas pump, ring/needle electrode, corona discharge, ionic wind, gas flow velocity.

A molecular Rayleigh scattering technique is developed to measure gas velocity, temperature, and density in unseeded gas flows at sampling rates up to 32 kHz. A high-power continuous-wave laser beam is focused at a point in an air flowfield, and Rayleigh scattered light is collected and fiber-optically transmitted to a Fabry-Perot interferometer for spectral analysis. Photomultiplier tubes operated in the photon-counting mode allow high-frequency sampling of the total signal level and the circular interference pattern to provide density, temperature, and velocity measurements. Mean and root-mean-square fluctuation measurements in both an electrically heated jet facility with a 10-mm-diam nozzle and in a hydrogen-combustor-heated-jet facility with a 50.8-mm-diam nozzle at NASA John H. Glenn Research Center at Lewis Field are presented. Measurements are compared with hot-wire anemometry, cold-wire thermometry, and temporally resolved particle image velocimetry to validate the Rayleigh technique.

In the present work, the annular static gaskets are considered as porous media and Darcy's law is written for a steady radial flow of a compressible gas with a first order slip boundary conditions. From this, a simple equation is obtained that includes Klinkenberg's intrinsic permeability factor [k.sub.v] of the gasket and the Knudsen number [Kn'.sub.o] defined with a characteristic length l. The parameters [k.sub.v] and e of the porous gasket are calculated from experimental results obtained with a reference gas at several gasket stress levels. Then, with [k.sub.v] and l, the inverse procedure is performed to predict the leakage rate for three different gases. It is shown that the porous media model predicts leak rates with the same accuracy as the laminar-molecular flow (LMF) model of Marchand et al. However, the new model has the advantage of furnishing phenomenological information on the evolution of the intrinsic permeability and the gas flow regimes with the gasket compressive stress. It also enables quick identification of the part of leakage that occurs at the flange-gasket interface at low gasket stresses. At low gas pressure, the behavior of the apparent permeability diverges from that of Klinkenberg's, indicating that the rarefaction effect becomes preponderant on the leak. [DOI: 10.1115/1.3008031]

An analytical--numerical model is developed to calculate the deformation and spreading of axisymmetric and two- dimensional liquid drops in a gas stream for small Ohnesorge numbers and large Reynolds numbers. The model is based on an approximate series solution of the Navier--Stokes equations written for the interior flow of the drop and assuming a quasi-static gas flow. The pressure distribution on the drop surface is provided using a perturbation analysis about a trivial zeroth-order solution. The axisymmetric formulation is used for calculating the deformation of the spherical droplets, and the two-dimensional formulation is used to develop a model for predicting the spreading of the cross section of liquid jets in crossflows. The penetration of the liquid jet in the gas flow is calculated, and the results are compared with experimental and empirical results.

Dust mobilization in a vacuum vessel is one of the key issues endangering the security of the International Thermonuclear Experimental Reactor (ITER) in case of loss of vacuum accidents. The turbulent behavior of particles in turbulent flows has to be modeled for successful numerical simulations about particle mobilization. In this study a Lagrangian approach is adopted to formulate the particle transport especially for dust-dilute flows mostly encountered in the vacuum vessel of ITER. Based on the logic frame of the approach and the used computational fluid dynamics (CFD) computer code in the study, a hybrid turbulent particle dispersion model is proposed. The hybrid model features both a deterministic separated flow model and a stochastic separated flow (SSF) model which are two popular turbulent dispersion models applied in particle simulations, and takes the advantages of the both models. The proposed model is implemented into the particle model of the CFD code successfully and the simulation results are verified against the experimental data. The verifications manifest the validities of the proposed model In this paper general information about the work of dust mobilization is introduced and the particle turbulent dispersion models are reviewed briefly at first. The hybrid model is then proposed based on the SSF model. An experiment about particle dispersions in an advective wind channel flow with decaying turbulence in the streamwise direction is reviewed in the third section. In the following section about model verification, the decaying turbulence parameters in the channel flow are verified against the experimental data as the first step, and the parameters about the particle dispersions in the verified flow field are then verified against the data. The work is concluded finally. [DOI: 10.1115/1.2983142]

Korea Atomic Energy Research Institute is in the process of carrying out a nuclear hydrogen system by considering the indirect cycle gas cooled reactors that produce heat at temperatures in the order of 950[degrees]C. A coaxial double-tube hot gas duct (HGD) is a key component connecting the reactor pressure vessel and the intermediate heat exchanger for the nuclear hydrogen system. Recently; a preliminary, design analysis for the primary and secondary hot gas ducts of the nuclear hydrogen system was carried out. These preliminary design activities include a preliminary decision on the geometric dimensions, a preliminary strength evaluation, and an appropriate material selection. In this study, a preliminary strength evaluation for the HGDs of the nuclear hydrogen system has been undertaken. Preliminary, strength evaluation results for the HGDs showed that the geometric dimensions of the proposed HGDs would be acceptable for the design requirements. [DOI: 10.1115/1.2983141]

A method for 3D mapping of scattering particle concentration in a gaseous medium based on the backscattered light in a single direction has been demonstrated. The technique is originally developed for microscopy but now implemented on larger-scale samples. The technique used is known as structured illumination, where a sinusoidal grid pattern is projected onto the medium, thus marking the in-focus plane. This makes it possible to discriminate against light originating from the out-of-focus parts of the sample, which usually makes it difficult to detect inner structures of the medium. In this study a flow of nitrogen was introduced into a flow of water droplets, with the aim to optically select only the plane where nitrogen was present. The results indicate that the technique could be used to study, e.g., combustion devices with limited optical access. OCIS codes: 110.3010, 280.1350.

The dynamics of gas flow in a hollow core photonic bandgap fiber is studied over four decades of pressure covering free molecular flow as well as hydrodynamic flow. Expressions are derived that allow for determination of the pressure inside the fiber as a function of time and position in the limits of Knudsen number Kn >> 1 and Kn << 1. The expressions, which are validated by using absorption lines of acetylene as probes of the pressure inside the fiber, provide a straightforward way of predicting the temporal response for gas sensors of any fiber geometry. OCIS codes: 060.2280, 060.2370, 060.4005, 060.5295, 280.4788.

Estimation of the local dissociation degree and the local mass-specific enthalpy of a pure oxygen plasma flow determined mainly from laser-induced fluorescence measurements are reported. Measurements have been conducted for several generator parameters in an inductively heated plasma wind tunnel. Additional probe measurements of total pressure together with the deduced translational temperature are used to estimate the local mass-specific enthalpy. For a reference condition, full dissociation has been measured. The measured translational temperature of atomic oxygen for this condition is T = 3500 K. Subsequently, the local mass-specific enthalpy has been derived using these local density and temperature measurements. For the reference condition the estimated value of h = 27 MJ/kg is in good agreement with the probe measurements and results from diode laser absorption spectroscopy. OCIS codes: 300.2530, 120.6200.

Unique physical properties of volcanic ash soils characterize the soil gas transport parameters of gas diffusivity and air permeability. Air permeability controls the density-driven flow that has been recognized as one of the important phenomena for subsurface dense gas. In this study, one-dimensional column experiments were conducted to investigate the effects of the pore structure of a volcanic ash soil on the density-driven flow of a dense gas (isohexane). The results showed that the overall horizontal gas movement in Tachikawa loam (volcanic ash soil) and Toyoura sand (sand) used as reference materials was expressed by Fick's diffusion law. On the other hand, the vertical downward gas movements in Tachikawa loam were considerably enhanced by the occurrence of density-driven flow, especially at high air contents (30-40%). Pore size distribution and pore structure analysis based on the tube model suggest that a greater volume of large pores (>0.01 cm) and a more continuous pore network led to the greater density-driven flow in Tachikawa loam than in Toyoura sand.

A theoretical analysis was carried out to predict the influences of wall inclination angles of large reservoirs on the onset of gas entrainment during single and dual discharges from a stratified two-phase region. The findings reveal that when the wall inclination angle differs from zero, along with low values of Froude number, two distinct flow regimes occur: the gas-entrainment and no gas-entrainment regimes. A new criterion has been developed to predict the critical Froude number at the transition from the gas-entrainment to the no-gas-entrainment regime. The critical Froude number is defined as a function of the wall inclination angle for a single discharge. For dual discharge, the critical Froude number is found to be dependent on the wall inclination angle, the separating distance between the centerlines of the two branches, as well as the Froude number of the second branch. Furthermore, four different flow regions are mapped, representing the flow regime, as well as the two-phase flow for each branch. These maps serve to predict the flow regions, mass flow rates, and quality during single and dual two-phase discharges. For the gas-entrainment regime, the predicted values of the critical height at the onset of gas entrainment are compared with the experimental data reported in literatures. Comparisons showed good concurrence between the measured and predicted results. Furthermore, the influence of the wall inclination angle on the flow regions, the predicted critical height, and the location of the gas entrainment are presented and discussed at different values of independent variables. [DOI: 10.1115/1.2813124] Keywords: gas entrainment, dual discharge, theoretical analysis

Water treatment with ozone has been utilized, but a higher oxidation technology is required to decompose persistent substances such as dioxin. In this paper, water treatment by a direct O radical injection method with dc-driven atmospheric microplasma and fast oxygen gas flow was examined. O radicals and OH radicals are able to realize stronger oxidation processes than those of the ozone method. The effect of water treatment by radical injection was observed by measurement of the acetic-acid (C[H.sub.3]COOH) decomposition. This was examined while varying the discharge current and oxygen gas flow rates. The acetic acid was successfully decomposed by a direct radical flow into the solution; meanwhile, no decomposition was observed with ozone injection. A clear correlation was found between the decomposition rate and the gas-flow velocity estimated by the gas-flow rates. This result indicates that the rapid radical injection is crucial at the gas-liquid interface because a key radical, which is thought to be O, has a very short lifetime in atmospheric oxygen. Index Terms--Advanced oxidation process (AOP), atmospheric plasma, O radical, oxygen gas flow, water treatment.

The boundary-layer feature and the forces on the particle are analyzed in detail, and the motion parameters of the particle in the gas-solid rotary flow are divided into two parts according to the r-z meridian and r-[theta] cross section. The Lagrange method is then applied, the 3-D mathematical model of particle motion in the gas-solid rotary flow is presented, and the Gear integral method is applied to simulate the motion characteristics of the particles. The results show that the centrifugal force and Saffman lift force play important roles in the process of the particle being separated from the gas-solid rotary flow in the rotary boundary layer. The velocity gradient of radial direction is the biggest, and that of tangent direction is the smallest. For a higher density ratio of gas to solid, the deposition performance of the particle depends not only on the inlet flow velocity but also on the range of the particle diameter Reasonable velocity gradient matching of the three directions (r,z,[theta]) in the gas-solid rotary flow is useful to improve the separation efficiency of the rotary separators. [DOI: 10.1115/1.2175166] Keywords: gas-solid rotary flow, particle motion characteristics, boundary layer

We have used nuclear magnetic resonance (NMR) to obtain spatially and temporally resolved profiles of gas flow in microfluidic devices. Remote detection of the NMR signal both overcomes the sensitivity limitation of NMR and enables time-of-flight measurement in addition to spatially resolved imaging. Thus, detailed insight is gained into the effects of flow, diffusion, and mixing in specific geometries. The ability for noninvasive measurement of microfluidic flow, without the introduction of foreign tracer particles, is unique to this approach and is important for the design and operation of microfluidic devices. Although here we demonstrate an application to gas flow, extension to liquids, which have higher density, is implicit. hyperpolarization | xenon | magnetic resonance imaging

An adiabatic experiment was conducted to investigate the effect of channel geometry on gas-liquid two-phase flow characteristics in horizontal microchannels. A water-nitrogen gas mixture was pumped through a 96 [micro]m square microchannel and the resulting flow pattern, void fraction and frictional pressure drop data were compared with those previously reported by the authors for a 100 [micro]m circular microchannel. The pressure drop data were best estimated using a separated-flow model and the void fraction increased non-linearly with volumetric quality, regardless of the channel shape. However, the flow maps exhibited transition boundaries that were shifted depending on the channel shape.

For the present study, we developed a three-dimensional numerical method based on the level set method that is applicable to two-phase systems with high-density ratio. The present solver for the Navier-Stokes equations was based on the projection method with a non-staggered grid. We improved the treatment of the convection terms and the interpolation method that was used to obtain the intermediate volume flux defined on the cell faces. We also improved the solver for the pressure Poisson equations and the reinitialization procedure of the level set function. It was shown that the present solver worked very well even for a density ratio of the two fluids of 1:1000. We simulated the coalescence of two rising bubbles under gravity and a gas bubble bursting at a free surface to evaluate mass conservation for the present method. It was also shown that the volume conservation (i.e., mass conservation) of bubbles was very good even after bubble coalescence. [DOI: 10.1115/1.1777232]

We present new experimental results on the interfacial instabilities and breakup of Newtonian liquid drops suddenly exposed to rarefied, high-speed (Mach 3) air flows. The experimental approach allows for the first time detailed observation of interfacial phenomena and mixing throughout the breakup cycle over a wide range of Weber numbers. Key findings are that Rayleigh-Taylor instability alone is the active mechanism for freestream Weber numbers as low as 28 for low viscosity liquids and that stripping rather than piercing is the asymptotic regime as We [right arrow] [infinity]. This and other detailed visual evidence over 26< We

Byline: A. V. Voloshin (1), A. Kh. Gil'mutdinov (1), Yu. A. Zakharov (1), A. A. Sevast'yanov (1) Abstract: Shadow spectral filming is used to study the spatiotemporal dynamics of the formation and dissipation of vapors of potassium sulfate and aluminum and indium nitrates in a transversely heated graphite furnace atomizer. The integrated platform, the Pd--Mg modifier, the internal flow of the sheath gas, the magnetic field of the nonselective background corrector, and the diffusion of oxygen from the ambient air are responsible for specific nonuniformities in the spatial structure of the vapor cloud. The nonuniformities result to a large extent from the transverse nonisothermal conditions of the graphite furnace. The explosive splashes of aluminum vapors interfering with the analysis are generated at the cold side walls of the graphite furnace, where the vapors are condensed in the process, rather than on the particles of the dry residue of the sample. The beating of the magnetic-field induction inside the graphite furnace atomizer caused by the overlapping of the fields of the heating current (50 Hz) and the background corrector (54 Hz) results in low-frequency (4--5 Hz) oscillations of the spatial position of the vapor cloud. The matrix modifier can stimulate these oscillations. Author Affiliation: (1) Physics Faculty, Kazan State University, Kremlevskaya ul. 18, Kazan, 420008, Russia Article History: Registration Date: 06/10/2004

The analysis of flow through a gas chromatography column has traditionally assumed the presence of steady-state conditions. However, when rapid changes in inlet pressure are introduced, a significant transient period is observed, leading to a failure of the steady-state model. Through the introduction of a one-dimensional continuity equation into the basic set of equations, a nonlinear partial differential equation is derived to describe the evolution of pressure profiles in a capillary gas chromatography column. A numerical solution is used to solve the differential equation for the case of a pulse injection under isothermal conditions, and comparisons with experimental holdup and retention times show very good agreement.

A lift force gas flow sensor which uses the force normal to the fluid flow to measure the flow velocity has recently been introduced. Two thin plates mounted at an angle are deflected when they are subjected to fluid flow. For most mechanical flow sensors the flow sensitivity is closely connected to the time response. A weaker structure gives higher flow sensitivity but a lower natural frequency, i.e., a slower response time. The lift force sensor is designed for measurements of respiratory gas flow in ventilators, where, in addition to low flow restriction, both high sensitivity and fast response are required. A new type of suspension has now been realized for the lift force flow sensor. The detection is separated from the suspension of the airfoil plate with the strain gauges placed on separate detector beams. This leads to separate parameters for optimization of the lift force concept with 'independent' control of flow sensitivity and natural frequency. This paper presents an analytical model, simulations and measurements on the new structure. The new edge-detected sensor has been experimentally evaluated for different lengths (100-600 [micro]m), widths (20-100 [micro]m) and thicknesses (8-20 [micro]m) of the detector beams. In accordance with the theory, the measurements show that the new structure has approximately three times the natural frequency of the old, center detected structure and similar or improved flow sensitivity. The evaluation has also resulted in a design scheme for optimal performance. A flow sensitivity of 0.65 [micro]V/V/[(l/min).sup.2] has been obtained for the best edge-detected sensor with a natural frequency of 3.2 kHz. [560]

Gas flows in plasma etching reactors for semiconductor fabrication became a chief consideration in designing second-generation reactors with higher etching rates. An axisymmetrical model based on the direct simulation Monte Carlo method has been developed for analyzing rarefied gas flows in a vacuum chamber with the conditions of downstream pressure and gas flow rate. By using this simulator, rarefied gas flows with radicals and etch-products were calculated for microwave-plasma etching reactors. The results showed that the flow patterns in the plasma chamber strongly depend on the Knudsen number and the gas-supply structure. The ventilation of the etch-products in the plasma chamber was found to be improved both for higher Knudsen numbers and for gas-supply structures of the downward-flow type, as compared with those of the radial-flow or upward-flow types. [DOI: 10.1115/1.1459074]

Numerical prediction of transitional features of turbulent forced-gas flows with strong heating in circular tubes is discussed. A study has been carried out with the object of extending the Abe, Kondoh and Nagano (AKN) model to treat the strongly heated gas flows and of looking at the validity of the extension by comparing to careful measurements for the same situations.

Coupled vapor/liquid flow in miniature passages with micro grooves is discussed. A two-dimensional model was developed to better calculate friction factors. Longitudinal pressure gradients in liquid and vapor flows in a miniature heat pipe were calculated and the capillary limit estimated and compared with existing experimental results showing that coupled liquid-vapor is needed to predict performance characteristics of miniature axially grooved heat pipes. Effect of liquid-vapor frictional interaction on the liquid flow goes down with curvature of the interface. Shear stresses at the interface are significantly nonuniform.

Turbulence-radiation interactions (TRI) are discussed as they relate to nonreactive flow of combustion gases. A numerical study has been carried out. The role of TRI depends to a great degree on how the temperature fluctuations correlate with concentration fluctuations. In most cases of interest in the real world the fluctuations are uncorrelated so there is almost negligible TRI effect on wall heat loads.

A study on the interaction of a gas jet and a liquid bath in industrial systems containing impinging gas jets on a liquid surface was conducted to investigate an air-jet-induced transport in a heated liquid bath. The aim of the study was to obtain a fundamental understanding of the jet impingement flow and heat transfer induced in the heated liquid bath. Experimental methodology, results and conclusions are presented.

A combination of two particular heat transfer models was applied to numerically analyze gas flows and heat transfer in an axially rotating pipe with high heat flux. Among other results, the experiment found that pipe rotation causes a considerable reduction of the local Stanton number in a lower heat flux case where no laminarization occurs in a stationary pipe flow. An increase in tube rotation results in an augmentation in laminarization in a gas flow.

Earlier analytical solutions by White (1980, 1983, 1992, 1993) included Couette effects, transverse diffusion, and mass storage in a model lubrication equation for narrow width wavy surface high bearing number gas films. The model lubrication equation did not include longitudinal diffusion effects due to the high bearing number restriction. Crone et al. (1991), however, reported numerical solutions of the full Reynolds equation for a gimbal mounted slider subject to wavy surface roughness. The first objective of this work is to reconcile the differences observed between the reported results of White and those of Crone et al. for moving and stationary roughness. The second objective is to describe how to best apply what appears to be a universal property of a high bearing number gas film subjected to a rough surface. Each solution of the model lubrication equation by White (1980, 1983, 1992, 1993) produced a product term based on local gas pressure and clearance (Z = Ph) that is independent of roughness details but which is dependent on the statistical properties of the roughness. In the present work, this characteristic is treated as a universal property of all high bearing number rough surface gas films. The product variable Z = Ph is introduced into the generalized full lubrication equation, and the resulting lubrication equation is ensemble averaged before a solution is attempted. This removes the short length and time scale effects due to the surface roughness. Solution of the ensemble averaged equation for Z(x, y, t) then follows by standard analytical or numerical methods. The unaveraged pressure is then given by P(x, y, t) = Z(x, y, t)/h(x, y, t) and the ensemble averaged or mean pressure at a point is computed from [P.sub.m](x, y, t) = Z(x, y, t)E(l/h(x, y, t)), where E(l/h) represents the ensemble average of l/h. Using this technique, numerical solutions of the full generalized lubrication equation based on kinetic theory were obtained for a low flying gimbal mounted slider. Results indicate that the nominal flying height increases and the minimum flying height decreases as surface roughness increases.

The instability of a compressible gas jet injected into a coflowing viscous liquid medium has been studied without considering the effects of gravity. A linear temporal instability analysis is used in monitoring the wave growth rate as a function of wave number. Results show the gas Weber number, Mach number, Ohnsorge number, density ratio and velocity ratio are the parameters that control the growth rates of the instability. There was an increase in unstable wave numbers and in the growth rates of the unstable modes when the Mach number was increased.

Transfer of low-solubility gas between air and flowing water is studied experimentally and through analysis of previous studies. The smallest turbulent motions are seen to have a theoretical advantage in overcoming interfacial resistance, and measurements of oxygen absorption rates are found to agree with small-eddy scaling. Though recent studies have emphasized large motions, this conflict is resolved by a conceptual framework incorporating both scales in terms of the distribution of near-surface turbulent energy dissipation rates. At higher Reynolds numbers, such as in natural streams, transfer rates are expected to be controlled by mean dissipative scales.

Models of dissolved oxygen in streams require accurate estimation of absorption rates of atmospheric oxygen, or 'reaeration rates.' These depend upon gas transfer coefficients, which engineers predict as functions of mean flow depth, velocity, and slope. Though many such equations have been developed, errors remain large, pointing to a need for an additional degree of description. Noting that streams vary widely in hydraulic geometry, a set of laboratory studies finds that reaeration rates are enhanced by 'macroroughness,' large bed variations that produce depth-scale form drag. This enhancement is accurately described by a theory that was successful in smooth-channel flows, upon accounting for increases in near-surface turbulent energy dissipation rates caused by macroroughness. In addition, a set of runs featuring bubble entrainment exhibits very high absorption rates, which are characterized by a Froude number based on macroroughness size.

A study was conducted to analyze the silicon atom densities in silane/oxygen and tetrathoxysilane/oxygen electron cyclotron resonance plasma as functions of microwave power, pressure and gas flow rates. Measurements were carried out using an atomic absorption spectrometer with a silicon hollow-cathode lamp. Experimental results indicated high concentrations of silicon that can support a major portion of the film growth in the silane based chemistry.

Models of dissolved oxygen in streams require accurate estimation of absorption rates of atmospheric oxygen, or 'reaeration rates.' These depend upon gas transfer coefficients, which engineers predict as functions of mean flow depth, velocity, and slope. Though many such equations have been developed, errors remain large, pointing to a need for an additional degree of description. Noting that streams vary widely in hydraulic geometry, a set of laboratory studies finds that reaeration rates are enhanced by 'macroroughness,' large bed variations that produce depth-scale form drag. This enhancement is accurately described by a theory that was successful in smooth-channel flows, upon accounting for increases in near-surface turbulent energy dissipation rates caused by macroroughness. In addition, a set of runs featuring bubble entrainment exhibits very high absorption rates, which are characterized by a Froude number based on macroroughness size.

Transfer of low-solubility gas between air and flowing water is studied experimentally and through analysis of previous studies. The smallest turbulent motions are seen to have a theoretical advantage in overcoming interfacial resistance, and measurements of oxygen absorption rates are found to agree with small-eddy scaling. Though recent studies have emphasized large motions, this conflict is resolved by a conceptual framework incorporating both scales in terms of the distribution of near-surface turbulent energy dissipation rates. At higher Reynolds numbers, such as in natural streams, transfer rates are expected to be controlled by mean dissipative scales.

Reducing emissions is an important issue facing gas turbine manufacturers. Almost all of the previous and current research and development for reducing emissions has focused, however, on flow, heat transfer, and combustion behavior in the combustors or on the uniformity of fuel injection without placing strong emphasis on the flow uniformity entering the combustors. In response to the incomplete understanding of the combustor's inlet air flow field, experiments were conducted in a 48 percent scale, 360 deg model of the diffuser-combustor section of an industrial gas turbine. In addition, the effect of air extraction for cooling or gasification on the flow distributions at the combustors' inlets was also investigated. The following three different air extraction rates were studied: 0 percent (baseline), 5 percent (airfoil cooling), and 20 percent (for coal gasification). The flow uniformity was investigated for the following two aspects: (a) global uniformity, which compared the mass flow rates of combustors at different locations relative to the extraction port, and (b) local uniformity, which examined the circumferential flow distribution into each combustor. The results indicate that even for the baseline case with no air extraction there was an inherent local flow nonuniformity of 10 [similar to] 20 percent at the inlet of each combustor due to the complex flow field in the dump diffuser and the blockage effect of the cross-flame tube. More flow was seen in the portion further away from the gas turbine center axis. The effect of 5 percent air extraction was small. Twenty percent air extraction introduced approximately 35 percent global flow asymmetry diametrically across the dump diffuser. The effect of air extraction on the combustor's local flow uniformity varied with the distances between the extraction port and each individual combustor. Longer top hats were installed with the initial intention of increasing flow mixing prior to entering the combustor. However, the results indicated that longer top hats do not improve the flow uniformity; sometimes, adverse effects can be seen. Although a specific geometry was selected for this study, the results provide sufficient generality to benefit other industrial gas turbines.

The interaction between a normal shock wave and a boundary layer along a wall surface in internal compressible flows causes a very complicated flow. When the shock is strong enough to separate the boundary layer, the shock is bifurcated and one or more shocks appear downstream of the bifurcated shock. A series of shocks thus formed, called 'shock train', is followed by an adverse pressure gradient region, if the duct is long enough. Thus the effect of the interaction extends over a great distance. The flow is decelerated from supersonic to subsonic through the whole interaction region. In this sense, the interaction region including the shock train in it is referred to as 'pseudo-shock' in the present paper, as Crocco called it. The shock train and pseudo-shock strongly affect the performance and efficiency of various flow devices. In the present review some fundamental characteristics of the shock train and pseudo-shock are first described. Some simple predictions are made to simulate these very complicated phenomena. Pseudo-shocks appearing in various flow devices are explained. Control methods of the pseudo-shocks are also described. Finally, the current understanding of self-excited oscillation of pseudo-shock is reviewed.

Some dense gas phenomena that may be observed in nonclassical aero-gas dynamics for simple geometries are investigated by simulation and analyses of selected cases. Shock phenomena over configurations for dilute, perfect gases are compared to two-dimensional shock wave refraction phenomena for dense gases in the high pressure and density area in the thermodynamic critical point. To compute the time-dependent, two-dimensional Euler equations of a van der Waals, a two-step predictor-corrector total variation diminishing scheme is employed. The results are discussed.

The steady and unsteady flow field at the pump and the turbine exit of a 245 mm diameter automotive torque converter was measured by a miniature high-frequency-response five-hole probe and a high-frequency-response total pressure Pitot probe in the stationary reference frame. The data were decomposed into blade periodic, blade aperiodic, and unresolved unsteady components. The periodic flow data shows that the pump exit flow has four major zones; the free-stream flow, the blade wake flow, the core-suction corner separation flow, and the mixing zone. The unsteady flow data shows that the unsteadiness in the free-stream is uniform, and the unsteadiness in the wake mixing flow zone is very high. The turbine exit flow is almost fully developed at the measurement plane, the flow field is uniform in the tangential direction, and only radial gradients in flow properties exist. A region of separated flow with high unsteadiness and high axial component of vorticity was observed at the measurement plane near the core.

One of the source terms of Z-pinch experiments is the gas puff density profile. In order to characterize the gas puff, we have used two interferometrical methods and performed some numerical simulations. The merits of both optical techniques are presented in terms of sensitivity, accuracy, and full time recording. Hence, one technique has been chosen to characterize the gas puff. The computation fluid dynamics (CFD) code (ARES) has been used to simulate the gas flow with the aim of testing its performances. Comparing experimental and numerical data shows off the taking into account of gas viscosity in computations. Given these consistent results, the nozzle geometries can be optimized in order to obtain specific Z-pinch gas puffs and check the computation with the interferometric method. Results obtained with a cylindrical nozzle are presented herein. Index Terms - Boundary layer, hydrodynamic modeling, interferometry, Navier-Stokes computation, nozzle, viscosity.

It is possible to compute highly underexpanded freejets with vibrational relaxation by applying the method of characteristics (MOC) to the simulation of several steady, inviscid, supersonic flowfields. The MOC was implemented numerically to simulate a highly underexpanded freejet flow with vibrational nonequilibrium, and was also applied to freejets of gases with complete vibrational freezing or equilibrium. It was demonstrated that the computational techniques were valid for vibrationally frozen flows and showed the maximum angular spacing of the characteristics launched from the nozzle lip needed to maintain the accuracy of the solution downstream.