The influence of instantaneous velocity gradients on turbulence properties measured with multi-sensor hot-wire probes

Park, Seong‐Ryong; Wallace, J. M.

doi:10.1007/bf00188501

Cited by 25 publications

(14 citation statements)

References 10 publications

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“…It is assumed that each X-probe measures two velocity fluctuations at the centre of the probe. For each X-probe, the binormal velocity effect is assumed to be negligible compared with the other two components (e.g., [24,39]). Park and Wallace [24] also found that the effect of the velocity gradient across each X-probe on the rms values of velocity components is within 3% even when the mean velocity gradient is large, e.g., at y+ = 30, in a turbulent boundary layer.…”

Section: Methodsmentioning

confidence: 99%

“…For each X-probe, the binormal velocity effect is assumed to be negligible compared with the other two components (e.g., [24,39]). Park and Wallace [24] also found that the effect of the velocity gradient across each X-probe on the rms values of velocity components is within 3% even when the mean velocity gradient is large, e.g., at y+ = 30, in a turbulent boundary layer. In the present flow, the mean velocity gradient is smaller and this effect should be negligible, Since each X-probe is considered independently, the calibration procedure is the same as that for a standard X-probe.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

On the correlation between enstrophy and energy dissipation rate in a turbulent wake

Zhu

Antonia

1996

Appl. Sci. Res.

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Abstract. All three components of the vorticity fluctuation have been measured simultaneously in a turbulent wake using a new eight-sensor vorticity probe. The vorticity fluctuation spectra agree reasonably well with those from a direct numerical simulation of a turbulent channel flow at high wavenumbers. The similarity between the instantaneous energy dissipation rate e and the instantaneous enstrophy ~O 2 is examined using spectra and probability density functions. The correlation between w z and e is evaluated in some detail. The homogeneous value of e is strongly correlated with w E. The full value of e and, more especially its isotropic value, are less well correlated with the enstrophy. Conditional averaging indicates that high enstrophy regions are associated with high energy dissipation rate regions.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

On the correlation between enstrophy and energy dissipation rate in a turbulent wake

Zhu

Antonia

1996

Appl. Sci. Res.

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“…In a turbulent flow, the flow detected by a multiple-sensor probe is not uniform across the sensing volume. The effects of the velocity gradients on multiple-sensor probe performances have been demonstrated by Vukoslav~evi6 and Wallace (1981) and Park and Wallace (1992). Vukoslav6evi6 et al (1991) used a nine-sensor probe to measure the spanwise and cross-stream velocity gradients in addition to the three components of the instantaneous velocity vector in a turbulent boundary-layer.…”

Section: Nonuniform Velocity In the Sensing Volumethe Twelve-sensor Pmentioning

confidence: 99%

A calibration technique for multiple-sensor hot-wire probes and its application to vorticity measurements in the wake of a circular cylinder

Marasli

Nguyen

Wallace

1993

Experiments in Fluids

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A calibration technique for multiple-sensor hot-wire probes is presented. The technique, which requires minimal information about the probe geometry, is tested using a four-sensor and a twelve-sensor probe. Two data reduction algorithms are introduced. The first one assumes a uniform velocity over the probe sensingvolume and is applied to the four-sensor probe measurements. The second one assumes a uniform velocity gradient over the sensing volume of the probe. The procedure, when applied to the twelvesensor probe, is shown to measure the velocity gradient components successfully. In both algorithms, the unknowns (velocity and velocity gradient components) are obtained by solving the resulting systems of nonlinear algebraic equations in a least-squares sense. The performances of the probes and the algorithms are tested with measurements in the wake of a circular cylinder. The statistics and spectra show that the twelve-sensor probe is successful in the simultaneous measurement of all three components of the velocity and all three components of the vorticity vectors.

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“…While measured velocity components can be significantly in error when the velocity gradients are large, 16,21,22 the mean velocity gradient is not significant in the present flow. Using a range of hot-wire yaw factors corresponding to these experimental conditions, errors in neglecting the fluctuating instantaneous velocity gradients are estimated to be about 3% and 4% for u rms and v rms (or w rms ), respectively, where u, v, and w are the velocity fluctuations in the x, y, and z directions, respectively.…”

Section: Methodsmentioning

confidence: 78%

Reynolds Number Effects on Three-Dimensiional Vorticity in a Turbulent Wake

Yiu

Zhou

et al. 2004

AIAA Journal

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When Reynolds number Re (≡ U ∞ d/ν, where U ∞ is the free stream velocity, d is the cylinder diameter, and ν is the kinematic viscosity of fluid) varies from 10 3 to 10 4 , there is a large change in the turbulent near-wake dynamics (e.g., the base pressure coefficient, fluctuating lift coefficient, and vortex formation length) of a circular cylinder, which has previously been connected to the generation of small-scale Kelvin-Helmholtz vortices. This work aims to investigate how this Re variation affects the three components of the vorticity vector and to provide a relatively complete set of three-dimensional vorticity data. All three components of vorticity were simultaneously measured in the intermediate region of a turbulent circular-cylinder wake using a multiwire vorticity probe. It is observed that the root-mean-square values of the three vorticity components increase with Re, especially the streamwise component, which shows a large jump from Re = 5 × × 10 3 to Re = 10 4 . At Re = 2.5 × × 10 3 , the maximum phase-averaged spanwise vorticity variance ω 2 z * , normalized by d and U ∞ , is twice as large as its counterpart for the streamwise component, ω 2x * , or the lateral component, ω 2 y * . However, at Re = 10 4 , the maximum ω 2 z * is only 55% larger than the maximum ω 2x * or 47% larger than the maximum ω 2 y * . The observation is consistent with the perception that the three-dimensionality of the flow is enhanced at higher Re due to the occurrence of Kelvin-Helmholtz vortices. The effect of Re on vorticity signals, spectra, and coherent and incoherent vorticity fields is also examined.

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The influence of instantaneous velocity gradients on turbulence properties measured with multi-sensor hot-wire probes

Cited by 25 publications

References 10 publications

On the correlation between enstrophy and energy dissipation rate in a turbulent wake

On the correlation between enstrophy and energy dissipation rate in a turbulent wake

A calibration technique for multiple-sensor hot-wire probes and its application to vorticity measurements in the wake of a circular cylinder

Reynolds Number Effects on Three-Dimensiional Vorticity in a Turbulent Wake

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