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To optimize the design parameters of rectangular primary settling tanks, we used two-dimensional laser Doppler velocimetry (2D LDV) to conduct flow field measurements in five cases and used a previous model to simulate the flow field. The relative baffle submergence height and the ratio of tank length to height were optimized in a low suspended solid (LSS) concentration (LSS < 150-200 mg/L). The experimental and simulation results show that a large recirculation zone exists behind the reaction baffle and the flow magnitude is small in the recirculation region; the length of recirculation increases with an increasing flow rate; the length of recirculation increases as the depth of the submerged reaction baffle increases; and the variation of the reaction baffle height can affect the flow field more significantly than does the variation of the flow rate. We also determined that to reach a higher removal rate and to optimize the area dimensions of a sedimentation tank, a length-to-height design ratio between 8 and 12 is optimal. DOI: 10.1061/(ASCE)EE.1943-7870.0000186 CE Database subject headings: Sedimentation tanks; Optimization; Design; Numerical models; Doppler systems; Measurement. Author keywords: Sedimentation tanks; Optimization; Design; Numerical models; Doppler systems; Flow field.

Abstract: Laser Doppler velocimeter (LDV) measurements were carried out to study the effect of depth on the flow over a train of fixed two-dimensional dunes. Conventionally averaged velocity and turbulence [...]

An experimental and numerical analysis of the intake system of a production high performance four-stroke motorcycle engine was carried out. The aim of the work was to characterize the fluid dynamic behavior of the engine during the intake phase and to evaluate the capability of the most commonly used two-equation turbulence models to reproduce the in-cylinder flow field for a very complex engine head. Pressure and mass flow rates were measured on a steady-flow rig. Furthermore, velocity measurements were obtained within the combustion chamber using laser Doppler anemometry (LDA). The experimental data were compared to the numerical results using four two-equation turbulence models (standard k-[epsilon], realizable k-[epsilon], Wilcox k-[omega], and SST k-[omega] models). All the investigated turbulence models well predicted the global performances of the intake system and the mean flow structure inside the cylinder. Some differences between measurements and computations were found close to the cylinder head while an improving agreement was evident moving away from the engine head. Furthermore, the Wilcox k-[omega] model permitted the flow field inside the combustion chamber of the engine to be reproduced and the overall angular momentum of the flux with respect to the cylinder axis to be quantified more properly. [DOI: 10.1115/1.2719265] Keywords: internal combustion engine, laser Doppler anemometry, computational fluid dynamics

In this work, turbulent drag reduction in a pipe is investigated by using laser Doppler velocimetry. The effect of decreasing the friction factor of the flow is obtained by addition of high molecular weight polymers. The mechanism of drag reduction is explained in terms of a stress anisotropy that inhibits the transversal transport of momentum by turbulent fluctuations. Semi-theoretical models based on a nonlinear constitutive equation, which takes into account an extra extensional rate of strain in the flow produced by the local additive orientation, are presented. The semi-theoretical models used to predict the friction factor of the flow in the presence of the polymer have successfully described the experimental measurements. The results have revealed a reduction in the friction factor of 65% for a concentration of 350 ppm in volume of polyacrylamide (PAMA) in an aqueous solution. In addition, the flow statistics, such as the axial and radial velocity fluctuations, the normalized autocorrelation functions as well as the power spectra for both velocity fluctuation components, are examined for the Newtonian flow of pure water and the flow of a 120 ppm solution of PAMA at the same friction velocity. Next, the results are compared in order to characterize the effect of the additive on the turbulent flow. [DOI: 10.1115/1.2436579] Keywords: macromolecules, drag reduction, anisotropy, extensional viscosity, turbulent flow

A method to estimate the radial velocity in swirling flows from experimental values of the axial and tangential velocities is presented. The study is motivated by the experimental difficulties to obtain this component in a draft tube model as evidenced in the Turbine-99 IAHR/ERCOFTAC Workshop. The method uses a two-dimensional nonviscous description of the flow. Such a flow is described by the Squire-Long equation for the stream function, which depends on the boundary conditions. Experimental values of the axial velocities at the inlet and outlet of the domain are used to obtain the boundary conditions on the bounded domain. The method consists of obtaining the equation related to the domain with an iterative process. The radial velocity profile is then obtained. The method may be applied to flows with a swirl number up to about Sw=0.25. The critical value of the swirl number depends on the velocity profiles and the geometry of the domain. The applicability of the methodology is first performed on a swirling flow in a diffuser with a half angle of 3 deg at various swirl numbers, where three-dimensional (3D) laser Doppler velocimeter (LDV) velocity measurements are available. The method is then applied to the Turbine-99 test case, which consists in a model draft tube flow where the radial inlet velocity was undetermined. The swirl number is equal to Sw=0.21. The stability and the convergence of the approach is investigated in this case. The results of the pressure recovery are then compared to the experiments for validation. [DOI: 10.1115/1.2409331]

The present study investigates turbulent boundary layer separation control by means of streamwise vortices with focus on the instantaneous vortex behavior. A turbulent boundary layer is exposed to a pressure gradient that generates a separation bubble with substantial backflow. The separation bubble is controlled by conventional passive vortex generators creating pairs of counterrotating vortices. Quantitative information is achieved by applying Particle Image Velocimetry (PIV) to the cross-stream plane of the vortices. The characteristics of a pair of counter-rotating vortices shed from a vortex generator is investigated in the near-field downstream of the vortex generator. The vortices were found to grow with the boundary layer in the downstream direction, and the maximum vorticity decreases as the circulation is conserved. The vortices are nonstationary, and the movements in the spanwise direction are larger than those in the wallnormal direction, due to the presence of the wall. The vortices fluctuate substantially and move over a spanwise distance, which is approximately equal to their size. The most probable instantaneous separation between the two vortices shed from one vortex generator equals the difference between their mean positions. The unsteadiness of the vortices contributes to the observed maxima in the Reynolds stresses around the mean vortex centers. The instantaneous vortex size and the instantaneous maximum vorticity are also fluctuating properties, and the instantaneous vortex is generally smaller and stronger than the mean vortex. A correlation was found between a large instantaneous vortex size and a low instantaneous maximum vorticity (and vice versa), suggesting that the vortices are subjected to vortex stretching. [DOI: 10.1115/1.2409327]

The mean velocity, Reynolds stress, and mean vorticity regions of a separated shear layer over a surface mounted block are investigated by 2D Digital Particle Image Velocimetry (DPIV) for three Reynolds numbers ([Re.sub.a] = 500, 1000, and 2500) and two channel-to-block height ratios (H/a = 1.825 and 4.6). The recirculation region's height and length are determined for the separated shear layer by means of [bar.U] = 0 contours. It is observed that the high Reynolds stress regions lay just outside of the [bar.U]=0 contours. The flow visualization and DPIV measurement of vorticity indicate that the differing normalized Reynolds stresses between [Re.sub.a] = 500 and 1000 are most probably due to the initiation of the vortex shedding between these two Reynolds numbers while, differences are minimal between [Re.sub.a] = 1000 and 2500. A sign change in the Reynolds shear stress distribution of the separated shear layer near the leading edge of the block was recognized for every Reynolds number and channel width. [DOI: 10.1115/1.2409359]

The dynamics of the rotating vortex taking place in the discharge ring of a Francis turbine for partial flow rate operating conditions and cavitation free conditions is studied by carrying out both experimental flow survey and numerical simulations. 2D laser Doppler velocimetry, 3D particle image velocimetry, and unsteady wall pressure measurements are performs to investigate thoroughly the velocity and pressure fields in the discharge ring and to give access to the vortex dynamics. Unsteady RANS simulation are performed and compared to the experimental results. The computing flow domain includes the rotating runner and the elbow draft tube. The mesh size of 500,O00 nodes for the 17 flow passages of the runner and 420,000 nodes for the draft tube is optimized to achieve reasonable CPU time for a good representation of the studied phenomena. The comparisons between the detailed experimental flow field and the CFD solution yield to a very good validation of the modeling of the draft tube rotating vortex and, then, validate the presented approach for industrial purpose applications. [DOI: 10.1115/1.2409332]

This study characterizes the axial velocity and axial turbulence intensity patterns noted in the tracheal portion of a cadaver-based throat model at two different steady flow rates (18.1 and 41.1 LPM.) This characterization was performed using Phase Doppler Interferometry (Laser Doppler Velocimetry). Deposition, as assessed qualitatively using fluorescent dye, is related to the position of the laryngeal jet within the trachea. The position of the jet is dependent on the downstream conditions of the model. It is proposed therefore that lung/airway conditions may have important effects on aerosol deposition within the throat. There is no correspondence noted between regions of high axial turbulence intensity and deposition. [DOI: 10.1115/1.1516572]

A new method for detecting spikes in acoustic Doppler velocimeter data sequences is suggested. The method combines three concepts: (1) that differentiation enhances the high frequency portion of a signal, (2) that the expected maximum of a random series is given by the Universal threshold, and (3) that good data cluster in a dense cloud in phase space or Poincare maps. These concepts are used to construct an ellipsoid in three-dimensional phase space, then points lying outside the ellipsoid are designated as spikes. The new method is shown to have superior performance to various other methods and it has the added advantage that it requires no parameters. Several methods for replacing sequences of spurious data are presented. A polynomial fitted to good data on either side of the spike event, then interpolated across the event, is preferred by the authors. DOI: 10.1061/(ASCE)0733-9429(2002)128:1(117) CE Database keywords: Turbulence; Velocity; Measuring instruments; Data processing.

The design and analysis of impellers for mixing applications such as stirred tank reactors (STR) have significant application in many engineering processes. In particular, the evaluation of the turbulent flow boundary conditions immediately around a model impeller has been examined using flow visualization, laser Doppler anemometry (LDA) and particle image velocimetry (PIV). Mean and fluctuating velocities are presented for all three velocity components. Good agreement between LDA and PIV measurements was obtained once an optimized PIV arrangement was defined. Turbulence parameters such as kinetic energy, dissipation, and length scales are estimated from the measurements. Several approaches to evaluating dissipation were used. Triggered PIV measurements were used to evaluate the variation in radial and tangential velocities in the entire planes above and below the impeller at constant axial distances. The size and orientation of the vortices shed from the impeller blade tips and the corresponding regions of high kinetic energy and dissipation indicate the importance of these structures in mixing. [DOI: 10.1115/1.1412846]

Three-dimensional structures of the vortical flow field in a propeller fan with a shroud covering only the rear region of its rotor tip have been investigated by experimental analysis using laser Doppler velocimetry (LDV) measurements and by numerical analysis using a large eddy simulation (LES) in Part I of the present study. The propeller fan has a very complicated vortical flow field near the rotor tip compared with axial fan and compressor rotors. It is found that three vortex structures are formed near the rotor tip: the tip vortex, the leading edge separation vortex, and the tip leakage vortex. The tip vortex is so strong that it dominates the flow field near the tip. Its formation starts from the blade tip suction side near the midchord. Even at the design condition the tip vortex convects nearly in the tangential direction, thus impinging on the pressure surface of the adjacent blade. The leading edge separation vortex develops close along the tip suction surface and disappears in the rear region of the rotor passage. The tip leakage vortex is so weak that it does not affect the flow field in the rotor. [DOI: 10.1115/1.1412565]

This paper presents a kinetic theory for modeling the vertical profile of particle concentration in dilute and dense solid-liquid flow conditions. The kinetic theory properly describes the mechanism of suspended sediment transport over a wider range of conditions and gives more detailed microscopic information than previous theories. Experimental data have been measured using laser Doppler anemometry. The results are in agreement with measurements by Wang and Qian in 1989, Michalik in 1973, and Segr6 and Silberberg in 1962. The present work makes a special contribution in predicting the particle concentration distribution in a dense liquid-particle flow with reasonable accuracy.

This paper describes experiments aimed at improving the understanding of vortices that form in water-pump intake bays. Experiments were conducted in a laboratory model of a simple intake bay comprising a vertical intake pipe with a bell mouth in a rectangular channel under conditions for which surface tension and free-surface elevation effects were small. The experiments comprised flow visualization followed by detailed measurements of the velocity field with particle-image velocimetry (PIV) in selected sections across the free-surface and wall-attached (subsurface) vortices. All vortices were found to meander in space. Depending on the submergence of the intake pipe and its position relative to the channel walls, some vortices had well-defined mean positions, while others were intermittent or exhibited bimodal behavior. The subsurface vortex strength depended on the distance between the wall or floor to which the vortex was attached and the intake pipe, with smaller distances promoting stronger vortices. The experiments clearly demonstrate the usefulness of PIV in obtaining the quantitative information that is required about the number, location, size, and strength of the vortices to develop and validate numerical models of pump intake flows.

The flow around two in-line surface-mounted cubes in a thin laminar boundary layer was experimentally investigated as a function of obstacle spacing for a Reynolds number of 22,000 based on approach velocity and cube height. Mean velocity measurements with Laser Doppler Velocimetry and surface flow patterns, obtained with an oil film technique, show that three distinct mean flow field structures exist based on obstacle spacing. Frequency spectra of velocity and surface pressure fluctuations reveal that these structures are related to three regimes of wake flow periodicity. For small spacings, the shear layer separating from the first cube reattaches on the sides of the second obstacle and wake periodicity can only be detected in the wake of the downstream cube. For a critical spacing range, the fluctuations in the gap and wake lock-in. For larger spacings, a second horseshoe vortex appears at the windward base of the second cube. Observations using dye-injection and smoke-wire techniques are consistent with these results.

Turbulent flowfields resulting from an oblique jet injecting from a rectangular side-inlet duct into a rectangular main duct with an aspect ratio 3.75 without a forced crossflow are presented in terms of laser-Doppler velocimetry measurements. The main focuses are the effects of the side-jet angle ([Theta]) and side-jet flow rate ([Q.sub.s]) on the mass entrainment upstream of side-jet port and the flow field in the rectangular duct. The side-inlet angles investigated were 30, 45, and 60 deg and Reynolds numbers based on the air density, rectangular duct height and bulk mean velocity were in the range of 7.1 X [10.sup.3] to 3.6 x [10.sup.4] corresponding to [Q.sub.s] values of 1 x [10.sup.3] to 5 x [10.sup.3] L/min. The present study suggests the presence of a critical side-injection angle [[Theta].sub.c] (30 [less than or equal to] [[Theta].sub.c] [less than or equal to] 45 deg) above which a recirculation zone appears in the rectangular duct, whereas below which the recirculation zone is absent. For the more tangential angle ([Theta] = 30 deg), almost as much fluid is entrained into the main duct as was injected from the side jet. The mean flow field in the rectangular duct is found to be a weak function of the Reynolds-number for the range of [Q.sub.s] investigated. In addition, a simple linear correlation between the mass entrainment upstream of the side-jet port and side-injection angle is obtained. Complementary flow visualizations and numerical computations with an algebraic Reynolds stress model were also performed. The discrepancies between measured and computed results are documented.

The effects of sediment transport on the fluid velocities and turbulence in oscillatory flow were investigated with the aid of a laser Doppler anemometer (LDA). Measurements were made over flat beds in an oscillatory flow water tunnel with gradually increasing quantities of sediment. The sediment had a specific gravity of 1.137 and a median diameter of 4.0 mm. It was observed that the turbulence intensity at any given height above the initial bed level was less in flows with sediment motion than over a fixed bed provided the bed remained flat. The initial bed level is defined as the mean grain crest level if all sediment settles on the bed. The friction factor and energy dissipation factor at the initial bed level were also reduced by the addition of sediment provided the bed remained flat. On the other hand, the values of friction factor and energy dissipation factor at the bottom of the mobile layer of sediment were greater than the values for a fixed bed.

A number of power spectral density (PSD) estimators were assessed using real laser Doppler anemometer (LDA) data from grid generated turbulence. PSD estimates from the raw data via the slotting technique and direct transform method were compared to those estimated from sample and hold, linear, and Kalman reconstructed velocity time histories. Of the reconstruction schemes, only Kalman reconstruction was shown to significantly reduce the effects of noise on the measurements leading to an additional 2 decades in power of high frequency information.

A simple technique to reduce the Doppler noise influence on measurements of turbulence using the Acoustic Doppler Velocimeter (ADV) is developed, and basic relationships to estimate turbulence characteristics using information about the Doppler noise are derived. The procedure involves, firstly, measurement of instantaneous velocities in the flow under consideration; secondly, measurement of the Doppler noise components in still water taken from the flow investigated (with the same velocity range setting that was used in turbulence measurements); and thirdly, estimation of turbulence characteristics using both sets of measurements and relationships developed in the paper. The technique was tested for three typical environments (water storage basin with silty water, laboratory flume with water containing seeding material of neutrally buoyant hollow glass spheres with a mean size around 8-10 [[micro]meter], and outdoor flume with natural water containing air bubbles and organic particles). It was shown that the Doppler noise can change the measured turbulence characteristics significantly, even for high-level turbulence flows.

This technical note presents the results of an experimental study on the distribution of water in very high velocity water jets in air. Three jets with diameters of 2, 2.5, and 3 mm with velocities in the range of 85-155 m/s were studied. These jets were found to have an inner region that contained most of the water with an outer region in which fine mist was carded by the induced air stream. In between, there was a transition region that might be termed the coarse mist region. In this study, the velocity of the air stream in the central and outer regions was measured with a pitot tube. These measurements were found to merge with the laser Doppler anemometer observations made earlier in the inner and central regions. The water concentration on the axis of the jet decreased rapidly with the axial distance, falling to about 2% at a distance equal to 200d, where d is the jet diameter at the nozzle. As the jet travels away from the nozzle, the relative momentum flux carried by the water phase in the jet continuously decreases and, at an axial distance of 1600d, falls to about 25% of its value at the nozzle.

Using a Laser-Doppler anemometer, mean velocities are measured in developing and fully developed turbulent subcritical smooth open channel flows. Experiments are conducted in a rectangular laboratory channel for 12 different test conditions with Reynolds number ranging from 28,026 to 136,842. From the experiments it is found that the boundary layer along the centerline of the channel develops up to the free surface for a flow aspect ratio b/h [greater than or equal to] 3. Shear velocities are calculated using the measured velocity profiles in the viscous sublayer of the boundary flow. The experiments show that shear velocity varies in an oscillatory manner across the flow section around b/h = 3. In the turbulent inner regions of developing and fully developed boundary flows, the measured velocity profiles agree well with the logarithmic 'law of the wall' distribution when the coefficients in the expression are 2.44 and 5.5, respectively. The 'wake' effect becomes important in the velocity profiles of the fully developed boundary layers. A reasonable agreement between the modified velocity-defect law and the experimental profile in the inner and outer regions is obtained with a profile parameter of 0.1 in the Coles's 'law of the wake.'

Experiments were performed to measure the mean velocity and turbulence characteristics in open-channel flows with and without suspended sediment (alluvial sand of nearly uniform size). Velocity measurements were obtained by using a newly developed technique, the discriminator laser-doppler velocimeter (DLDV), which can distinguish both liquid and sediment particle velocities. The mean velocity of sediment particles was found to be lower than that of the water. While the velocity fluctuations in the water were not changed with the addition of sediment, those of the sediment were diminished. For the range of concentrations considered, the friction velocity and the free-surface slope increased with sediment concentration unlike other bulk flow parameters, which were practically constant. A uniform method of analysis was developed to facilitate data interpretation and comparison between similar studies.

Turbulence measurements over a smooth wall in unsteady depth-varying open-channel flows were conducted by the simultaneous use of a two-component laser Doppler anemometer (LDA) and a water-wave gauge. In the present study, velocity measurements in the viscous sublayer of highly unsteady flow have been first conducted to evaluate the friction velocity independently of the log-law. The von Karman constant [Kappa] was calculated using this friction velocity. It was proven then that the value of [Kappa] was really a constant of 0.41 even in unsteady open-channel flows. Next, statistical structures of mean velocity and turbulence characteristics were investigated across the whole flow from the near-wall region up to the free surface. In particular, turbulence measurements near the depth-varying water-surface zone of flood flow were conducted successfully for the first time with the LDA; such measurements have been impossible with conventional velocity instruments such as hot-film anemometers. Mean velocity profiles and turbulence characteristics were revealed in both the rising and the falling stages of the flood period.

Investigations of valvular regurgitation attempt to specify flow field characteristics and apply them to the proximal isovelocity surface area (PISA) method for quantifying regurgitant flow. Most investigators assume a hemispherical shape to these equivelocity shells proximal to an axisymmetric (circular) orifice. However, in vivo flow fields are viscous and regurgitant openings vary in shape and size. By using centerline profiles and isovelocity surfaces, this investigation describes the flow field proximal to circular and elliptical orifices. Steady, proximal flow fields are obtained with two- and three-dimensional computational fluid dynamic (CFD) simulations. These simulations are verified by in vitro, laser-Doppler velocimetry (LDV) experiments. The data show that a unique, normalized proximal flow field results for each orifice shape independent of orifice flow or size. The distinct differences in flow field characteristics with orifice shape may provide a mechanism for evaluating orifice characteristics and regurgitant flows. Instead of the hemispherical approximation technique, this study attempts to show the potential to define a universal flow evaluation method based on the details of the flowfield according to orifice shape. Preliminary results indicate that Magnetic Resonance (MR) and Color Doppler (CD) may reproduce these flow details and allow such a procedure in vivo.

In order to clarify the gas transport process in high-frequency oscillation, we measured the axial velocity profile and the axial effective diffusivity in a single asymmetric bifurcating tube, based on the Horsfield airway model, with sinusoidally oscillatory flow. The axial velocity profiles were measured using a laser-Doppler velocimeter, and the effective diffusivities were evaluated using a simple bolus injection method. The axial velocity profile was found to be nonuniform, promoting axial gas dispersion by the spread of the concentration profile and lateral mixing. The geometric asymmetry of the bifurcation was responsible for the difference in gas transport between the main bronchi. The axial gas transport in the left main bronchus was 2.3 times as large as that of the straight tube, whereas the gas transport in the right main bronchus was slightly larger than that of the straight tube. Thus localized variation in gas transport characterized the heterogeneous respiratory function of the lung.

A perspex (plexiglas) tube was locally deformed into an almost bi-lobar interior cross section, representative of the localized throat at the downstream end of a collapsed tube conveying a flow. The axial and transverse (parallel to the long axis of the deformed cross section) components of fluid velocity were measured in a dense rectangular grid of points covering the whole cross section, at 15 axial sites between one diameter upstream of and three diameters downstream of the center of the constriction. The Reynolds number based on undeformed tube diameter and mean velocity was 705. Results are presented both as surfaces showing the variation of each component over the cross section and as velocity vector profiles. The overall changes in velocity in the streamwise direction are presented in terms of the variation of the maximum and minimum of each component with axial position. Flow downstream of the throat consisted of two parallel side-jets with a broad region of reverse flow in between. This pattern persisted until beyond 2.5 diameters downstream, by which point transverse inflow at the top and bottom of the cross section had converted the side jets into a complete annulus of axial velocity surrounding a central deficit. Jet velocities and reverse flow disappeared relatively abruptly before three diameters downstream.

Measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for spatially periodic flows in a duct of width-to-height ratio 2 with a detached solid-rib array. The Reynolds number based on the duct hydraulic diameter and cross-sectional bulk mean velocity ([U.sub.b]), the pitch to rib-height ratio, and the rib-height to duct-height ratio were 2 x [10.sup.4], 10, and 0.133, respectively. The rib-detached-distance to rib-height ratio was varied from 0 to 3.25 (duct axis) to study its effect on wake length and asymmetry, convective velocity and turbulent kinetic energy immediately behind the rib, maximum turbulent shear stress, and turbulence anisotropy. The results showed that the dominant fluid dynamic factors responsible for the reported peak values of local Nusselt number around the detached rib could be identified. Moreover, the turbulence structure parameter distribution and anisotropy were analyzed to examine the basic assumptions embedded in the turbulence models. Furthermore, the secondary-flow mean velocities were found to be one to two order of magnitude smaller than [U.sub.b].

The generalized laws of degradation and spreading of the boundaries of a submerged round jet discharging under oblique and vertical impingements into a channel have been investigated and derived. The laser Doppler anemometry (LDA) technique was adapted for measurement of mean velocities without any interference in the flow, and was utilized for the investigation of the complex three-dimensional circulating flow that was experienced in the channel. In the experiments, the inclination of the jet was varied from 45 [degrees] to 90 [degrees] to the bed of the channel, while differing ratios of channel width and depth to jet diameter were studied for various Froude numbers of the flow. The experimental results have been analyzed and compared with Glauret's theory for a radial wall jet as a first approximation neglecting gravity forces when small compared with turbulent forces. The research provides practical information for determining an efficient form of stilling basin for high velocity discharge from pipe outlets.

Turbulent Taylor-Couette flow in an annulus formed by two concentric cylinders with dead end walls was investigated with Laser Doppler Velocimetry (LDV). The test apparatus was designed to provide refractive index matching between the annulus and a working fluid of aqueous sodium iodide. LDV was used to measure the three components of mean velocity and turbulence intensity, concentrating on end wall effects. The flow Taylor and Reynolds numbers were T = 2.107 x [10.sup.9] and Re = 73,440, respectively. Vector plots of radial-axial component velocities and contour plots of component velocities and turbulence intensities reveal the Taylor vortex flow structure at this high Taylor number.

Latent heat removal is the main heat transfer mechanism under fully developed boiling conditions and the addition of anionic surfactants increases the convection component of the heat flux. A corresponding reduction in the latent heat component of the heat flux is observed. A new photographic/laser-Doppler anemometry method gives the vapor volumetric flow rate, leading to the determination of latent heat. The boiling heat transfer coefficients are measured for an electrically heated platinum wire immersed in saturated water, and in water mixed with surfactants.

Placement of vortex generators directly above the first and fifth ribs in a ribbed duct air flow affects the flow and heat transfer behavior. Flow temperature measurements and laser-Doppler flow measurements at the smallest spacing show that the generator-rib pairs behave as a single unit with an increased effective height. At the larger spacing, the flow expands in the cross-stream direction.

A photographic/laser Doppler anemometry method is used in quantifying vapor volumetric flow rates above a heated wire immersed in a highly wetting dielectric liquid. Several important parameters are considered in the measurements, such as the latent heat and Marangoni flow. Results indicate that the proposed method is capable of estimating vapor volumetric flow rates using only a single video image for each heat flux.

The measurements and theoretical predictions of laminar boundary-layer air flow in natural convection over a vertical backward-facing step show that step height affects the velocity and thermal distribution downstream of the step. Step height also affects the friction and heat transfer coefficients inside the recirculation region. Laser-Doppler velocimeter measures the velocity, cold-wire anemometer measures the temperature distribution, and flow visualization determines the reattachment length. Effect of temperature difference on the heat transfer rate and the friction coefficient are given.

The pulsation in the buoyancy-driven two-directional flow through a horizontal partition's vent due to a brine/water system is created by the interfacial instability of brine and water. The pulsation frequencies and frequency decay are analyzed by laser Doppler velocimetry measurements. Two different decay frequencies in the power spectrum indicate that the flow pulsation is due to more than one flow process.

Laser-Doppler-anemometer measurements of the fluid velocities in combined oscillatory and steady flow over rippled beds are reported. The direction of the steady current was parallel to the ripple crests and at right angles to the oscillatory flow. Measurements with the steady flow alone showed that the velocity distribution was quite well represented by the traditional logarithmic formula if height y were replaced by a transformed coordinate [Eta]. It was not possible to detect a universal velocity distribution based directly on height above the local bed level. On the other hand, the combined flow measurements did not show good agreement with any existing formula in the immediate vicinity of the bed, although there was reasonable agreement with an existing formula further out. This formula also gave quite good prediction of the shear velocity in the combined flow. The importance of large-scale momentum exchanges produced by vortex formation and ejection was demonstrated with reference to the fluctuation in velocity in the steady-current direction.

Back-scattering LDV has been used to investigate particulate two-phase flow in a centrifugal slurry pump. The measurements reported here have been made with a dilute suspension of 0.8 mm glass beads at the impeller-casing flow interface. This interface is of practical importance because the corresponding velocity and concentration results can be used to determine the pump head and flowrate. The present study evaluates the connection between the liquid and solids velocity distribution measured around the impeller and the pump performance determined from measurements at the pump inlet and outlet. The analysis of the velocity triangles for both phases shows the effect of the pump flowrate and inlet recirculation on the pump head at the impeller outlet, as well as the effect of particle slip on pump energy efficiency. A separate group of characteristic curves is proposed to represent the periodical fluctuations of the pump flowrate, head, and loss of efficiency due to particle slip, as a function of the impeller position.

A particle tracking velocimetry (PTV) system has been developed to obtain instantaneous two velocity components on several sections in three-dimensional space. The flow visualization is conducted by means of parallel laser-light sheets created by a scanning laser beam and the visualized particle images are taken by a high-speed video system synchronized with the scanning. In order to obtain higher accuracy in velocity measurements than usual PTV, some improvements are made on the analyzing procedures: the extraction of particle images, the determination of their center points, the derivation of velocity components and others. The present PTV was applied to the transient flows in a cylindrical tank with a rotating disk. As a result, two-dimensional transient flow patterns with large scale disturbances are continuously captured in three-dimensional space.

The flow around a half-ellipsoid with axes ratio 12:6:1 mounted on a plane wall at an angle of attack of 25 [degrees] and at a Reynolds number of 47,000 (based on the maximum chord) was studied using a three-dimensional LDV system. In this paper the mean velocity distributions in a volume enclosing the separated region and the near wake are described. The flow is shown to be consistent with the findings of Johnson (1991) based on flow visualization and related topological analysis. The flow on most of the pressure side was attached and laminar, while that on the suction side and in the wake was separated and turbulent. The region of separation had mean negative streamwise velocities as large as 25 percent of the freestream velocity, and the reversed-flow region extended up to one chord length behind the body. The measurements clearly reveal the complex vortex structure that arises from the three-dimensional separation.

Laser Doppler Anemometry measurements of mean (ensemble average) velocities and turbulent (Reynolds) stresses at 140 locations within the left ventricle of the Penn State 70 cc electric artificial heart/ventricular assist device are reported at 8 times during the cardiac cycle. Mean velocity patterns indicate that the surfaces of the blood sac and valve tracts are exposed to significant levels of wall shear stress (good wall washing) during some portion of the flow cycle, and there is no location where the flow is stagnant over the entire flow cycle. This implies that thrombus deposition within the artificial heart should be suppressed. Turbulent stresses in the main pumping chamber and the outflow tracts of the tilting disk valves do not exceed 2000 dynes/cm squared. The highest turbulent stresses (20,000 dynes/cm squared) and smallest turbulent microscales (6 micrometers) are found in the regurgitant jets on the minor orifice side of the aortic valve during diastole and the mitral valve during systole. Taken together, the data suggest that improvements in artificial heart fluid mechanics will come through valve design and pump operating conditions, not pumping chamber design.

Irregular water waves were generated in a flat-bottomed, two-dimensional wave tank with a partially reflecting spending beach. The horizontal and vertical velocity of the fluid particles was measured with a laser Doppler velocimeter at middepth and near bottom in the water column. The results show that a linear theory equation predicts the root-mean-square (rms) water particle velocity to within 10% given the measured incident wave height spectrum, reflection coefficients, and water depth. An extension of the Gaussian probability distribution based on the Gram-Charlier series was applied to the velocity time series. This extended distribution did not fit the measured data better than the ordinary Gaussian distribution. The Beta-Rayleigh probability distribution function was applied to peak velocities. A slight improvement is observed over the ordinary Rayleigh distribution. The parameters of the Beta-Rayleigh distribution are empirically correlated with parameters of the incident wave spectrum.

Laser-Doppler velocimeter measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for periodic fully developed flows in a channel with square rib-disturbed walls on two opposite sides. Quantities such as the vorticity thickness and turbulent kinetic energy are used to characterize the flow. The investigated flow was periodic in space. The Reynolds number based on the channel hydraulic diameter was 3.3 x 10 to the fourth power. The ratios of pitch to rib-height and rib-height to chamber-height were 10 and 0.133, respectively. Regions where maximum and minimum Reynolds stress and turbulent kinetic energy occurred were identified from the results. The growth rate of the shear layers of the present study was compared with that of a backward-facing step. The measured turbulence anisotropy and structure parameter distribution were used to examine the basic assumptions embedded in the k - epsilon and k - epsilon - A models. For a given axial station, the peak axial mean-velocity was found not to occur at the center point. The secondary flow was determined to be Prandtl's secondary flow of the second kind according to the measured streamwise mean vorticity and its production term.

Measurements of mean and turbulence characteristics in uniform open-channel flows of constant mean depth over artificial fixed one-dimensional periodic bed features were obtained using two-component laser-Doppler velocimetry. Two types of bed forms, based on triangular elements of the same height (approximately equal to 20% of the flow depth) and wavelength (approximately equal to 12.5 times the height) but of different shape, were studied: (1) 45 degrees triangle ridges separated by a flat region; and (2) triangular elements approximating dunes with a mildly sloping upstream face instead of a flat region. The role of the total shear velocity, based on the mean energy slope and the mean flow depth, as a possible velocity scale is studied. Velocity defect and the Reynolds shear stress profiles were generally well approximated by the flat-bed profiles for regions of flow far from the bed. Sufficiently far from the recirculation and reattachment zones, turbulence characteristics collapsed fairly well when scaled with the total shear velocity over most of the depth, but do not follow the flat-bed behavior in the lower part of the flow. Possible implications of the clear-water measurements for the description of suspended sediment concentration profiles and total suspended load computations are explored.

A two-component LDV system was used to investigate single and two-phase flow in a representative section at the impeller outlet of a centrifugal slurry pump. Measurements were performed at Q(sub n) and 0.5 Q(sub n) with water and dilute slurry flows (C = 0.04 and 0.16 percent by volume). The solids consist of 0.8 mm glass beads. Particle Reynolds number is 65. The point liquid and solid velocities were determined with a Doppler signal amplitude discrimination approach. A rotary shaft encoder was used to represent the velocity as a function of the impeller angular position, and to investigate the effect of a finite number of blades on the flow. The data on liquid and slip velocity distributions show large scale flow structures which dominate the two-phase turbulent flow. Overall, solid particles have a larger radial velocity than the carrier fluid at the impeller outlet, but they lag the fluid in the circumferential direction.

The turbulence characteristics of sediment-laden flows in open channels are investigated using two-component laser-Doppler velocimetry. Suspensions of well-sorted sands with diameters ranging from 0.15 mm to 0.24 mm, flowing over nominally flat beds, both fixed and erodible, are studied in a tiltable, recirculating flume. Various conceptual models that have been proposed to explain the mean-field profiles are examined for consistency with respect to their implications for higher-order characteristics. No evidence is found to support either the traditional model, associated with a decrease in the von Karman constant, or the more recently proposed models based on simple analogies to slightly stably stratified wall-bounded flows. A model based on small-scale fluid-particle interaction is suggested as more promising.

This work presents the results of a study conducted to investigate particle surface interaction characteristics and their effects on the particle dynamics and blade erosion in axial flow gas turbines. The particle restitution velocities measured experimentally using Laser Doppler Velocimetry in a special tunnel are analyzed using statistical methods. The resulting distribution functions of the rebounding particle velocities after surface impacts are introduced in the particle trajectory simulations through the turbine blade passages, using a methodology that combines particle dynamics computations in a probabilistic model. The presented results for the simulated ash particle dynamics demonstrate the effect of the experimentally measured variance in the particle restitution characteristics on the particle surface impacts, and the associated blade erosion in an axial flow turbine., A study is conducted to characterize particle rebound variances after surface interactions and their effects on blade erosion in gas turbines. Theoretical and experimental results were used to determine the probabilistic nature of interactions. A laser doppler velocimetry system was used to measure particle velocities. Particle trajectory simulations were conducted and results show the rotor and stator blade pressure surface erosion are affected by variances in the velocity restitution ratio and directional restitution ratio.

Extreme transient wave kinematics are measured using laser Doppler anemometry. Kinematics are also used to evaluate the effect of wave height and acceleration on fixed offshore structures. Results indicate that transient waves are stronger above the still water level than below and that design wave and random wave approaches tend to underestimate the actual loads of steep extreme waves. The study revealed a need for the development of new predictive techniques for wave kinematics to improve structural designs.

A study is conducted to measure flow structure under an impinging liquid jet striking a flat surface using Laser-Doppler velocimetry. Surface measurements are made on the liquid jet before impingement to determine axial development of jet velocity before impingement and after leaving the nozzle. Results show that free surface velocity profiles of the spreading liquid layer collapsed to a band, if plotted in dimensionless coordinates. The dimensionless coordinates, measured velocity and radial coordinates were normalized by the average jet exit velocity and the nozzle diameter respectively.

An experiment was conducted to study the mixing process downstream of a forced mixer using a two-component laser-Doppler velocimetry system. Results show three regions of vortex development in the mixing region. Secondary motion was first produced by the mixer lobes, then counterrotating vortices around the shear layer region were formed. Finally, the vortices broke down resulting to an increase in turbulent mixing. Turbulent mixing was found to be an essential factor in obtaining a homogenously mixed flow.