Application of a Novel Laser-Doppler Velocimeter for Turbulence: Structural Measurements in Turbulent Boundary Layers

Lowe, K. Todd

doi:10.21236/ada462018

Cited by 16 publications

(23 citation statements)

References 70 publications

(143 reference statements)

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“…The result would produce a particle-image displacement pattern after taking into consideration of image magnification and time delay. The river flow velocity will be obtained using the two cameras in a stereoscopic arrangement allowing a visualization of a full field three-dimensional visualization (Le Coz et al, 2010;Lowe, 2006). By employing the PIV water measuring technique, the surface flow velocity from any water channel can be easily measured.…”

Section: Introductionmentioning

confidence: 99%

Application of Particle Image Velocimetry (PIV) for Measuring Water Velocity in Laboratory Sedimentation Tank

Kuok

Chiu

2017

IRA-JTE

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Section: Introductionmentioning

confidence: 99%

Application of Particle Image Velocimetry (PIV) for Measuring Water Velocity in Laboratory Sedimentation Tank

Kuok

Chiu

2017

IRA-JTE

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“…The CompLDV probe was developed by Lowe [25]. This system was designed to use up to 12 beams to measure velocity fluctuations as well as velocity-acceleration correlations and velocity gradients, however only six beams were used during the present work.…”

Section: Compldv Probementioning

confidence: 99%

“…Signal processing was done electronically using in-house codes developed by Lowe, [25]. The codes included different modules for burst recognition, dual-burst separation and frequency processing, [26].…”

Section: Data Acquisition and Processingmentioning

confidence: 99%

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A Basic Three-Dimensional Turbulent Boundary Layer Experiment to Test Second-Moment Closure Models

Sadek

2010

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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In this work, a three-dimensional turbulent boundary layer experiment was set up with alternating stream-wise and span-wise pressure gradients. The pressure gradients are generated as a result of the test section wavy side wall shape. Each side had six sine waves with a trough to peak magnitude to wavelength ratio of 0.25. Boundary layer control was used so that the flow over the side walls remains attached. The mean flow velocity components, static and total pressures were measured at six plane along the stream-wise direction. The alternating mean span-wise and stream-wise pressure gradients created alternating stream-wise and span-wise vorticity fluxes, respectively, along the test section. As the flow developed downstream the vorticity created at the tunnel floor and ceiling diffused away from the wall.The vorticity components in the stream-wise and span-wise directions are strengthened due to stretching and tilting terms in the vorticity transport equaitons. The positivez half of the test section contains large areas that generate positive vorticity flux in the trough region and smaller areas generating negative vorticity around the wave peak. The opposite is true for the negative-z half of the test-section. This results in a large positive stream-wise vorticity in the positive-z half and negative stream-wise vorticity in the negative-z half of the test-section. The smaller regions of opposite sign vorticity in each half tend to mix the flow such that as they diffuse away from the wall, the turbulent stresses are more uniform.Turbulent fluctuating velocity components were measured using Laser Doppler Velocimetery. Mean velocities as well as Reynolds stresses and triple velocity component correlations were measured at thirty stations along the last wave in the test section. Profiles at the center of the test section showed three dimensionality, but exhibited high turbulence intensities in the outer layer.Profiles off the test section centerline are highly three dimensional with multiple peaks in the normal stress profiles. The flow also reaches a state where all the normal stresses have equal magnitudes while the shear stresses are non-zero. A turbulent kinetic energy transport budget is performed for all profiles and the turbulence kinetic energy dissipation rate is estimated. Spectral measurements were also made and an independent estimate of the kinetic energy dissipation rate is made. These estimates agree very well with those estimates made by balancing the turbulence kinetic energy transport equation.Multiple turbulent diffusion models are compared to measured quantities. The models varied in agreement with experimental data. However, fair agreement with turbulence kinetic energy turbulent diffusion is observed. A model for the dissipation rate tensor anisotropy is used to extract estimates of the pressure-strain tensor from the Reynolds stress transport equations. The pressure-strain estimates are compared with some of the models in the literature. The comparison showed poor agreement with estimated pr...

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“…All work presented in this thesis is on nominally two-dimensional turbulent boundary layers. High free-stream turbulence studies on three-dimensional boundary layers will be done in the future and may be found in Lowe (2006).…”

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confidence: 99%

An Experimental Study of Turbulent Boundary Layers Subjected to High Free-Stream Turbulence Effects

Orsi¹

2005

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The work presented in this thesis was on nominally two-dimensional turbulent boundary layers at zero pressure gradient subjected to high free-stream turbulent intensities of up to 7.9% in preparations for high free-stream turbulence studies on three-dimensional boundary layers, which will be done in the future in the Aerospace and Ocean Engineering Boundary Layer Wind Tunnel at Virginia Tech. The two-dimensional turbulent flow that will impinge three-dimensional bodies needed to be characterized, before the three-dimensional studies can be made. An active turbulence generator designed to create high free-stream turbulence intensities in the wind tunnel was tested and modified in order to obtain the lowest possible mean flow non-uniformities. A sevenhole pressure probe was used to obtain planes of mean velocity measurements. A threecomponent state of the art laser-Doppler velocimeter (LDV) was used to obtain mean and fluctuating velocities. Previous high free-stream turbulence studies have been reviewed and are discussed, and some of the previously published data of other authors have been corrected. Based on the measurements obtained with the LDV, it was also determined that the semi-log law of the wall is valid for high free-stream turbulence cases, but with different constants than the ones proposed by Coles, where the constants for the high free-stream cases may be dependent on the turbulence intensity. For the first time, the skin friction coefficient (C f ) was deduced from the viscous sublayer. The difference between the U τ obtained in the viscous sublayer mean velocity profile and the U τ obtained in the semi-log layer from 2 τ U uv = − was 1.5%. The skin friction coefficient was determined to increase by 10.5% when the two-dimensional turbulent boundary layer was subjected to high free-stream turbulence effects. Spectral data obtained with the LDV, were compared to the von Kármán model spectrum and to the Pope's model spectrum, where the von Kármán spectrum was proven to fit the spectral data slightly better than the Pope's spectrum. Finally, the Hancock-Bradshaw-Blair parameter obtained for this experiment agreed very well with previously published data.

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Application of a Novel Laser-Doppler Velocimeter for Turbulence: Structural Measurements in Turbulent Boundary Layers

Cited by 16 publications

References 70 publications

Application of Particle Image Velocimetry (PIV) for Measuring Water Velocity in Laboratory Sedimentation Tank

Application of Particle Image Velocimetry (PIV) for Measuring Water Velocity in Laboratory Sedimentation Tank

A Basic Three-Dimensional Turbulent Boundary Layer Experiment to Test Second-Moment Closure Models

An Experimental Study of Turbulent Boundary Layers Subjected to High Free-Stream Turbulence Effects

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