Spatial resolution of a 4-X-wire vorticity probe

Zhu, Yonggang; Antonia, R. A.

doi:10.1088/0957-0233/7/10/019

Cited by 30 publications

(13 citation statements)

References 20 publications

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“…For the present flow conditions, the separation between X-probes in either the z2 or z3 direction is approximately 47/. Our previous spatial resolution analysis of this probe [40] indicated that the high wavenumber part ofvorticity spectra could be attenuated by 70% for i = 2, 3 and 40% for i = 1. The smaller attenuation is r predicted by the analysis is consistent with the smaller discrepancy between the measured and DNS r (Figure 2a).…”

Section: Resultsmentioning

confidence: 71%

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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: Resultsmentioning

confidence: 71%

“…A detailed analysis of the response equation of this probe was given in [40]. The 2.5 #m diameter Wollaston Pt-10% R_h wires were used for all the probes and were etched to an active length of about 0.5 mm.…”

Section: Oui Auimentioning

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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“…The exact and discrete derivatives are used to estimate the error associated with direct calculations of turbulent kinetic energy dissipation. The concept of using a specified turbulent spectrum to estimate bias error and correct measurements lacking sufficient resolution has been applied by others [ Wyngaard , 1968; Zhu and Antonia , 1996; Lavoie et al , 2007]. For the parameters of this experimental setup, direct calculation of the dissipation rate from velocity gradients using the derivative stencil suggested by Raffel et al [1998] and Rosman [2007] underestimates the actual dissipation rate by an order of magnitude for the range of dissipation rates in this study.…”

Section: Methodsmentioning

confidence: 88%

The mixing efficiency of interfacial waves breaking at a ridge: 2. Local mixing processes

2011

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[1] The efficiency with which internal wave energy is converted irreversibly to diapycnal mixing in bathymetry-induced mixing events is of great importance to larger-scale ocean modeling efforts. High-resolution laboratory measurements are used to investigate the spatial and temporal variability of interfacial wave breaking events at a submerged bathymetric ridge. From high spatial resolution measurements, it appears the local efficiency can vary significantly. Parameterizations based on the turbulent Reynolds number and Froude number suggest that the local mixing efficiency within the overturning patch at the interface is 10-17% but the local efficiency is near zero within the relatively homogenous layers. When the local mixing efficiency is integrated over the entire event, the resulting overall efficiency is consistent with the result from Part 1 that the overall event efficiency is 3-8%. This spatial variation in the mixing efficiency reinforces the importance of dynamic mixing efficiency parameterizations based on local stratified turbulence parameters.

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“…The result agrees with previous reports. 18,21 The maxi- mum concentration ofω * z impairs for a larger x/d. Table 2 lists the maximum magnitude ofω * z at x/d = 10, along with previous reports.…”

Section: B Extract Of Coherent Structurementioning

confidence: 99%

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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Spatial resolution of a 4-X-wire vorticity probe

Cited by 30 publications

References 20 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

The mixing efficiency of interfacial waves breaking at a ridge: 2. Local mixing processes

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

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