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We present a real-time time-domain Doppler optical coherence tomography (OCT) system based on the zero-crossing method for velocity measurements of fluid flows with attainable velocities up to 10 m/s. In the current implementation, one-dimensional and two-dimensional velocity profiles of fluid flows ranging from 1 cm/s to more than 3 m/s were obtained for both laminar and turbulent flows. The line rate was approximately 500 Hz and the images were treated in real time. This approach has the advantage of providing reliable velocity maps free from phase aliasing or other artifacts common to several OCT systems. The system is particularly well suited for investigating complex velocity profiles, especially in the presence of steep velocity gradients. OCIS codes: 170.4500, 170.3340, 100.2000.

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.

In this paper, three-dimensional turbulent flow field around a complex bridge pier placed on a rough fixed bed is experimentally investigated. The complex pier foundation consists of a column, a pile cap, and a 2 x 4 pile group. All of the elements are exposed to the approaching flow. An acoustic-Doppler velocimeter was used to measure instantaneously the three components of the velocities at different horizontal and vertical planes. Profiles and contours of time-averaged velocity components, turbulent intensity components, turbulent kinetic energy, and Reynolds stresses, as well as velocity vectors are presented and discussed at different vertical and horizontal planes. The approaching boundary layer at the upstream of the pile cap separated in two vertical directions and induced an upward flow toward the column and a contracted downward flow below the pile cap and toward the piles. The contracted upward flow on the pile cap interacts with downflow in the front of the column and deflects toward the side of the pier, which in return produces a strong downflow along the side of the pile cap. The flow at the rear of the pile cap is very complex. The strong downward flow at the downstream and near the top of the pile cap in interaction with the reverse flow behind the column and upward flow near the bed produce two vortices close to the upper and lower comers of the pile cap with opposite direction of rotation. On the other hand, the back-flow from the wake of the pile cap is forced into the top region resulting in a secondary recirculation at the wake of the column. The contracted flow below the pile cap and toward the piles, a strong downflow along the sides of the pile cap at the upstream region, and a vortex flow behind the pile cap and an amplification of turbulence intensity along the sides of the pile cap at the downstream region are the main features of the flow responsible for the entrainment of bed sediments. DOI: 10.1061/(ASCE)EM.1943-7889.0000073 CE Database subject headings: Bridges; Piers; Turbulent flow; Scour; Experimentation; Three-dimensional flow. Author keywords: Bridges; Complex pier; Turbulent flow; Scour.

Laser-Doppler measurements of the mean and turbulent components of the velocity flowfield resulting from the frontal collision of a wall jet with a boundary layer are presented and discussed, together with the visualization of the flow with direct photography and digital film imaging. The experiments were carried out for boundary-layer-to-wall-jet velocity ratios of 0.5 and 0.58. The results revealed the existence of a small counter-rotating recirculating zone located upstream (in the sense of the wall-jet flow) of the separation point, not reported before for this type of flow. This secondary vortex has an oscillating behavior observed in other ground-vortex flows, similar to that which can be observed, namely, through the bimodal histogram of the horizontal velocity (parallel to the wall) measurements, although the power spectra measurements do not exhibit any particular peaks. DOI: 10.2514/1.36619

In this two-part paper, results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry: Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In Part II of the paper, the flow field in the rotor blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor blade tip clearance vortices. Consequently, in the rotor frame of reference, the tip clearance vortices are periodical with the stator blade passing frequency. Due to the wakes, the tip clearance vortices are separated into different segments. Along the mean vortex trajectory, these parts can be characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence, the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time. Keywords: axial compressor, laser Doppler anemometer, periodical unsteady flow field, unsteady profile pressure, rotor-stator-interaction, tip clearance vortex, wake, negative jet effect, wake-tip clearance vortex interaction

In this two-part paper, results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In Part I of the paper, the flow field at midspan of the rotor blade row will be discussed. Different aspects of the blade row interaction process are considered for the design point and an operating point near the stability limit. The periodical unsteady blade-to-blade velocity field is dominated by the incoming stator wakes, while the potential effect of the stator blades is of minor influence. The inherent vortex structures and the negative jet effect, which is coupled to the wake appearance, are clearly resolved. Furthermore the time-resolved profile pressure distribution of the rotor blades is discussed. Although the negative jet effect within the rotor blade passage is very pronounced, the rotor blade pressure distribution is nearly independent of the convectively propagating chopped stator wakes. Keywords: axial compressor, laser Doppler anemometer, periodical unsteady flow field, unsteady profile pressure, rotor-stator interaction, tip clearance vortex, wake, negative jet effect, wake-tip clearance vortex interaction

Measurements were taken of the vortex system and turbulent flow that resulted from the interaction between a stator blade and the approaching endwall boundary layer in a linear cascade of compressor blades. Data were taken at a Reynolds number based on blade chord of 640,000. Five-hole pressure measurements were conducted upstream and downstream of the blade row. The approaching boundary layer was also characterized with the laser-Doppler velocimeter. Downstream three-component laser-Doppler velocimetry surveys were conducted at three streamwise stations to map the location and velocity characteristics of the wake and vortex system. Results clearly showed the extent of the vortex emanating from the separation of the boundary layer on the suction side of the blade. Finally, all components of mean flow velocity and turbulence are documented for the last survey station. These data will form a challenging test case for numerical code validation. [DOI: 10.1115/1.2364883]

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

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, turbulence intensity, etc., were carried out at a very low Reynolds number condition, [Re.sub.out]=3.5 x [10.sup.4]. The data obtained were analyzed from the viewpoints of both an absolute (stationary)frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage. [DOI: 10.1115/1.2464143]

The current paper presents experimental clocking investigations of the flow field in midspan in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine). Laser-Doppler-velocimetry measurements were carried out in order to record rotor phase resolved velocity, flow angle, and turbulence distributions upstream and downstream of the second vane row at several different vane-vane positions. Additionally, a fast-response aerodynamic pressure probe was used to get the total pressure distribution downstream of the second vane row for the same positions. Altogether, the measurements were performed for ten different first vane to second vane positions (clocking positions) for measurements downstream of the second vane row and two different clocking positions for measurements upstream of the second vane row. The paper shows that different clocking positions have a significant influence on the flow field downstream of the second vane row. Furthermore, different measurement lines upstream of the second vane row indicate that clocking has nearly no influence on the flow field close to the rotor exit. [DOI: 10.1115/1.2464144]

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

Abstract: The present study gives details of a methodology for estimating the critical shear stress for erosion of mine tailings and other naturally occurring cohesive sediments. Erosion of a cohesive [...]

A full-field optical method based on the amplitude fluctuation electronic speckle pattern interferometry (AF-ESPI) method with good fringe visibility and noise reduction are used to obtain the resonant frequencies and the corresponding mode shapes of the piezoceramic bimorphs. The results have shown that the particle motions of piezoceramic bimorphs for parallel connection in resonance are three-dimensional, but it is found that only out-of-plane vibration modes can be excited for the specimen in series connection.

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]

Acoustic Doppler velocimeter (ADV) measurements are useful and powerful for measurements of mean and turbulent components of fluids in both hydraulic experimental facilities and fields. However, it is difficult to use the ADV in bubbly flows because air bubbles generate spike noise in the ADV velocity data. This study describes the validity of the ADV measurements in bubbly flows. The true three-dimensional phase space method originally developed by Goring and Nikora in 2002 is significantly useful to eliminate spike noise of ADV recorded data in bubbly flow in comparison with the classical low correlation method. DOI: 10.1061/(ASCE)0733-9399(2007)133:1(122) CE Database subject headings: Two phase flow; Turbulent flow; Bubbles; Experimental data; Noise.

A fundamental study is made of a rotating boundary layer (BL) in the inboard region of a tilt-rotor blade, using an embedded laser Doppler velocimetry probe inside a rotating blade. Velocity measurements have been performed to get insight into the BL behavior around a blade section close to the rotor hub. BL transition and separation phenomena are investigated on the basis of both chordwise and spanwise velocity profiles measured for different collective pitch angles on a two-bladed hovering rotor. The velocity experimental data bank appears to be in good agreement with theoretical velocity profiles in attached flow conditions (laminar, transitional, or turbulent). Moreover, validation of a transitional criterion based on the second thickness of energy [[delta].sub.3] of the BL is extended to the rotational flow configuration. Usually such a configuration classically exhibits a separation of the BL for high collective pitch angles. However, in the particular case of a high twisted tilt-rotor blade operating in hover, centrifugal effects are shown to be responsible for an important delay in the BL separation process.

To provide experimental data on the hydrodynamic characteristics and features of dynamic positioning (DP) thrusters under variable operating conditions, wake measurements were performed on a DP thruster model using 2D laser Doppler velocimetry (LDV) and stereoscopic particle image velocimetry (SPIV). These tests were performed with and without a nozzle and over a range of advance coefficient values including the bollard pull condition. In this paper, a detailed analysis of the hydrodynamic characteristics of the wake at a plane equal to a distance of 0.5 diameters downstream from the thruster, at advance coefficient values of 0, 0.4, and 0.45 are presented for both the LDV and SPIV measurements showing a comparison between the results of each technique. The effect of the duct and of changes in the advance coefficient values is presented in this paper. [DOI: 10.1115/1.2185680]

The noninvasive optical technique of dynamic light scattering (DLS) is routinely used to characterize dilute and transparent submicrometer particle dispersions in laboratory environments. A variety of industrial and biological applications would, however, greatly benefit from on-line monitoring of dispersions under flowing conditions. We present a model experiment to study flowing dispersions of polystyrene latex particles of varying sizes under varying flow conditions by using a newly developed fiber-optic DLS probe. A modified correlation function proposed in an earlier study is applied to the analysis of extracting the size and velocity of laminar flowing particulate dispersions. The complementary technique of laser Doppler velocimetry is also used to measure the speed of moving particles to confirm the DLS findings. OCIS codes: 290.1350, 290.5850.

This paper presents simultaneous measurements using particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) techniques on the study of a horseshoe vortex system. The horseshoe vortex system is generated near the juncture of a vertical square cylinder and a horizontal base plate. The combination of PIV and LDV not only gives the spatial distribution and time history of velocity near the juncture for spatial and time domain analyses, it also allows phase averaging the PIV velocity data to reduce noise and, in a turbulent flow, result in turbulence statistics. A flow visualization technique displaying particle streaklines has also been used to help the classification of the vortex system and visualize the flow motion and vortex evolution. The classification of the horseshoe vortex was briefly categorized as steady, periodical oscillatory, and turbulence-like chaotic vortex systems through the use of the flow visualization technique and time-domain spectral analysis. Phase-averaged flow characteristics of the periodical oscillatory vortex system with a Reynolds number of 2,250 are presented in detail through the use of PIV and LDV as well as the flow visualization technique. DOI: 10.1061/(ASCE)0733-9399(2003) 129:10(1173) CE Database subject headings: Flow measurement; Vortices; Imaging techniques; Plates; Flow visualization.

We report a method for passive optical directional discrimination in laser-Doppler anemometers. For this purpose frequency-shift elements such as acousto-optic modulators, which are bulky and difficult to align during assembly, have traditionally been employed. We propose to use a quadrature homodyne technique to achieve directional discrimination of the fluid flow without any frequency-shift elements. It is based on the employment of two laser wavelengths, which generate two interference fringe systems with a phase shift of a quarter of the common fringe spacing. Measurement signal pairs with a direction-dependent phase shift of [+ or -] [pi]/2 are generated. As a robust signal-processing technique, the cross-correlation technique is used. The principles of quadrature homodyne laser-Doppler anemometry are investigated. A setup that provides a constant phase shift of [pi]/2 throughout the entire measurement volume was achieved with both single-mode and multimode radiation. The directional discrimination was successfully verified with wind tunnel measurements. The complete passive technique offers the potential of building miniaturized measurement heads that can be integrated, e.g., into wind tunnel models. OCIS codes: 120.7250, 120.3180.

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]

In order to improve peripheral arterial occlusive diseases (PAOD) diagnoses, five de-noising algorithms based on a multiresolution analysis computed with wavelets are applied on reactive hyperemia signals obtained with the laser Doppler flowmetry technique. Results are presented on recordings acquired on patients suffering from PAOD and on healthy subjects. Index Terms--De-noising, laser Doppler flowmetry, peripheral arterial occlusive disease, reactive hyperemia, wavelet.

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.

Research is presented concerning the development of an experimental and computational method of analyzing the airflow around the rotor blades of a hovering helicopter. Laser velocimetry is used to measure the flowfield.

Research illustrates Whittaker method of error analysis for subpixel resolution of correlation peaks to set tolerance limits for optimum image sport sizes. Data demonstrate that by using the tolerances camera alignment manipulations can easily be carried out.

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.

Results show that rotor-generated tip vortices are nonaxisymmetric in structure and no changes are observed in the strength of the vortices through all ages. Data further indicate that there is a logarithmic increase in growth of the viscous core whereas the core swirl velocity decreases logarithmically.

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.

Research was conducted to test the hypothesis that the duodenal hyperemic response to acid occurs through activation of capsaicin-sensitive afferent nerves with subsequent release of vasodilatory substances such as calcitonin gene-related peptide and nitric oxide. Findings showed that luminal acid, but not bradykinin, stimulates capsazepine-sensitive receptors on capsaicin-sensitive afferent nerves of rat duodenum.

The increasing popularity of the aerodynamic development of laminar wings for commercial airplanes has stimulated research on a strategy to employ modern experimental and numerical methods to elucidate on the flow velocities around the wings. Laser Doppler anemometry (LDA) was found to be useful in providing local velocity data. However, special LDA systems have to be developed. Studies on LDA systems revealed two optical units suitable for in-flight velocity measurements on airplane wings.

A pressure-based computational fluid dynamics (CFD) code is employed to calculate the flow field and rotordynamic forces in a whirling, grooved liquid annular seal. To validate the capabilities of the CFD code for this class of problems, comparisons of basic fluid dynamic parameters are made to three-dimensional laser Doppler anemometer (LDA) measurements for a spinning, centered grooved seal. Predictions are made using both a standard and low Reynolds number [Kappa]-[Epsilon] turbulence model. Comparisons show good overall agreement of the axial and radial velocities in the through flow jet, shear layer, and recirculation zone. The tangential swirl velocity is slightly under-predicted as the flow passes through the seal. By generating an eccentric three-dimensional, body fitted mesh of the geometry, a quasi-steady solution may be obtained in the whirling reference frame allowing the net reaction force to be calculated for different whirl frequency ratios, yielding the rotordynamic force coefficients. Comparisons are made to the rotordynamic force measurements for a grooved liquid annular seal. The CFD predictions show improved stiffness prediction over traditional multi-control volume, bulk flow methods over a wide range of operating conditions. In cases where the flow conditions at the seal inlet are unknown, a two-dimensional, axisymmetric CFD analysis may be employed to efficiently calculate these boundary conditions by including the upstream region leading to the seal. This approach is also demonstrated in this study.

A study was conducted to examine the influence of spacing ration on the near-wake regions behind porous disks supporting several annular elements. A platinum wire was utilized to carry out the hydrogen bubble method to conduct flow visualization studies while the mean and fluctuating velocity fields were determined using laser Doppler velocimetry. Results indicated that three dimensional large-scale motions for small spacing rations dominated the intermediate wake.

A study was conducted to examine the flow physics of laminar flow control suction surfaces using a three-component laser Doppler velocimetry system. The system supported a 5-W argon-ion laser, a transmitter box and a three-axis traverse mechanism. The Reynolds number of natural transition was determined utilizing a surface-mounted hot-film probe. Results indicated an interaction relationship between crossflow vortices and suction-induced longitudinal vortices.

A laser Doppler velocimeter employing a compact disc pickup for both fringe projection and signal detection is described. The spectrum of the recorded signal gives the information about the speed of the object. The device takes advantage of the Talbot effect to project the grating contained in the pickup onto a moving target, so that no imaging system is required. The peculiar imaging technique allows for the exploitation of several optical configurations and permits the manipulation of the intensity profile of the projected grating. The instrument was used to measure the velocity of dust particles on a solid substrate in the 1-m/s range but could also find an application to the study of liquid flow. of America

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.

An experiment was performed to measure the mean density, turbulence quantities and mean velocities of a supersonic, high-temperature exhaust plume using Rayleigh scattering system and a two-dimensional laser Doppler velocimeter. Results showed that supersonic flow is maintained only up to 15 nozzle diameters while the potential core of the supersonic jet is estimated at 6 nozzle diameters.

The empirical investigation and analysis of the dynamics of helicopter rotor wakes and blade tip vortices have created a variety of challenges for scientists. Some of these dynamics include wake instabilities, vortex/surface interaction, vortex perturbations and blade/vortex interactions. Laser Doppler velocimetry was used in quantitative measurements and flow visualization.

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 study was conducted to provide a comparison between inert and reacting wakes of bluff bodies through velocity measurements. A experimental setup, which facilitates the test numerical predictions, was designed and utilized. The velocity measurements were acquired using a laser Doppler velocimeter. Results showed that the reacting wakes were characterized by the absence of vortex shedding which can be found in inert wakes.