Velocity derivative skewness in isotropic turbulence and its measurement with hot wires

Abstract

We investigate the effect of the hot wire resolution on measurements of the velocity derivative skewness in homogeneous isotropic turbulence. A single wire configuration (with different lengths and temporal sampling resolutions) is considered. Estimates of the attenuation, based on numerical data in box turbulence, are applied to experimental data taken in grid turbulence. It is found that the sampling resolution has a sizeable attenuation effect, while the length of the wire has a relatively minor impact. The corrected experimental values support the conclusion that the skewness is constant with the Reynolds number, in agreement with Kolmogorov's 41 theory.

Lattice Boltzmann model for three-dimensional decaying homogeneous isotropic turbulence

“…It is clear that the skewness S of the velocity derivative is close to 0.5. The up-to-date results of the velocity derivative skewness are shown experimentally by Burattini et al [21]. The current simulated results agree with the experimental results very well.…”

“…The current simulated results agree with the experimental results very well. The deviation of the current simulation is about ±1% and the deviation of literature [21] is about ±5%.…”

Influence of an Extended Non-equilibrium Region on the Far-Field of Grid Turbulence

“…spatial resolution of the NSTAP for the secondary contraction case; accurate gradient estimation is highly dependent on spatial resolution [2,6]. When corrections [2] for resolution are applied to the measurements without the secondary contraction, then the far-field value becomes ∼ −0.43, which is in better agreement with contemporary estimates of S(∂ u/∂ x) in grid turbulence [9,11].…”

“…When corrections [2] for resolution are applied to the measurements without the secondary contraction, then the far-field value becomes ∼ −0.43, which is in better agreement with contemporary estimates of S(∂ u/∂ x) in grid turbulence [9,11].…”

“…Hearst and Lavoie [7] discriminated between the regions by identifying where the flow became homogeneous in transverse planes and noting this coincided with a change in the decay rate, n. Later, these same authors used the scale-by-scale kinetic energy budget to determine the difference between the flow regions [8]. The scale-by-scale kinetic energy budget for grid turbulence is given by [4], 2 , and s is a dummy integration variable. Equation (2) may be represented simply as G + D + I = C. G represents energy transfer through advection.…”