Large eddy simulations of decaying rotating turbulence

Abstract

Large eddy simulations of homogeneous isotropic turbulence subjected to system rotation were performed using the truncated Navier-Stokes method. In the method the Navier-Stokes equations are solved through a sequence of direct numerical simulation runs and a periodic processing of small scales to provide the necessary dissipation. The method is evaluated by comparing simulation results with theoretical analysis, direct numerical simulations, as well as with other large eddy simulation results. Obtained results demonstrate several advantages of the method over traditional large eddy simulations models. The method captures important features of rotating turbulence: the energy decay is inhibited, the energy spectrum departs from the classical k −5/3 form, and initially isotropic turbulence becomes anisotropic. For increasing rotation rate three distinct regimes are observed. At low rotation rates, the influence of rotation is weak and flow behaves like for nonrotating cases. At intermediate rotation rates strong coupling between rotation and nonlinear interactions has a significant influence on turbulence. At high rotation rates viscous effects dominate over nonlinear effects. Furthermore, for high Reynolds numbers, small Rossby numbers, and large elapsed time, the k −3 energy spectrum is observed due to the anisotropy identified by various indicators, rather than the k −2 form found under the assumption of isotropy.

Study of Some Key Issues for Applying LES to Real Engineering Problems

“…4.3. The physical filter provides the best result compared to the DNS data as also observed in paper ( (Domaradzki et al 2002;Yang & Domaradzki 2004). The main reason is that the physical filter keeps a small part of the small scales which facilitates the energy transfer.…”

“…The definitions for the first three can be easily found in some books (Pope 2000). The main problem for the Tophat and Gaussian filters is that they remove too much energy of the large scales (Domaradzki et al 2002;Yang & Domaradzki 2004). The spectral filter is thought as the best among these three for LES because it keeps all the large scales while removes all the small scales.…”

“…So one may think: if we can get the full velocity from the experiment data or DNS directly, can we just skip the filtering and defiltering steps? Based on that concept, Domaradzki et al (Domaradzki et al 2002;Domaradzki & Yang 2004) developed a new TNS approach from VEM model. TNS uses the full velocity.…”

“…It should be noticed that the filtering time interval plays a critical role in TNS. In order to avoid underdissipating or over-dissipating, appropriate interval must be carefully chosen (Domaradzki & Yang 2004). The suitable interval depends on the filter type, grid resolution and flow condition.…”

Small-scale intermittency and local anisotropy in turbulent mixing with rotation

“…The cyclonic vorticity component develops a positive skewness in rotating turbulence. The skewness is the strongest at intermediate rotation rates [4,5,7,8]. In a DNS study of the mixing of passive scalars in rotating turbulence, [9] reports that the small-scale intermittency in the gradients of the passive scalar is also reduced.…”