High resolution DNS studies of long-time behavior of homogeneous turbulent shear flow
Abstract
As discussed in Isaza & Collins [J. Fluid Mech. 678:14-40, 2011], the shear parameter S* has a pronounced effect on velocity gradient statistics for homogeneous turbulent shear flow (HTSF). Due to the importance of this effect, especially for higher S*, we extended those studies to higher resolution using a new direct numerical simulation (DNS) code based on a pseudospectral algorithm that avoids remeshing [Brucker et al., J. Comp. Phys. 225:20-32, 2007], and decomposes the domain into ``pencils''. We present DNS with 2048 × 1024 × 1024 grid points, achieving a maximum Taylor microscale Reynolds number of 300. The peak in the initial energy spectrum, viscosity, and box configuration also have been optimized to maximize the time window for well-resolved simulations (up to St = 20), ensuring we are well into the asymptotic regime. The DNS runs confirm the sensitivity of the large- and small-scale statistics to S*, as was found by Isaza & Collins. We also investigated the interaction between the fluctuating vorticity vector and rate-of-strain tensor as a function of scale, and find alignments vary dramatically, suggesting the primary source of enstrophy is at large scales, followed by a forward cascade to small scales. This helps explain the persistent sensitivity of the velocity gradient statistics to S*. The combination of results suggests a new framework for modeling HTSF at high values of S*.
- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2011
- Bibcode:
- 2011APS..DFDE12002S