Large eddy simulations of decaying rotating turbulence

A new large eddy simulation (LES) model, the truncated Navier-Stokes Equation (TNS) method, is extended to simulate homogenous isotropic turbulence subjected to system rotation. The influence of rotation on the energy decay, spectra and anisotropy structures is investigated in details at both low and high Reynolds numbers.; The TNS with integrating factor technique and velocity estimation procedure is applied first to study the low Reynolds number rotating turbulence at various rotation rates. Very good results are obtained compared with theoretical analysis, direct numerical simulation (DNS) and other LES results. The energy decay is inhibited and the energy spectrum is modified by rotation, especially at moderate rotation rate a spectrum close to k-2 is observed. Due to the coupling effect between nonlinear interactions and rotation, anisotropy appears and is reflected in longitudinal integral length scales and directional stress tensors. We find this effect is strongest at moderate rotation rates. At low rotation rates, the influence of rotation is weak and flow behaviors like non-rotation cases. While at strong rotation rates, only pure viscous decay is obtained.; At high Reynolds numbers, we also observed all the most important features as at low Reynolds numbers. The rotation effect is stronger since there is no viscosity term. The energy decay is almost frozen at very strong rotation rate. By running simulation for long enough time, the Reynolds stress anisotropy tensors and their invariants also become anisotropic, which is different from the results for low Reynolds number short time runs. The anisotropy may be responsible for the energy spectrum behaving like k -3 (at final simulation time) instead of a k -2 form which will be found with the assumption of isotropy.; Finally, TNS was applied to other initial condition at high Reynolds numbers. For initial condition with Kolmogoroff k -5/3 spectrum, the k-5/3 form is preserved during time evolution without rotation. And for pulse initial condition, the k-5/3 spectrum is developed at non-rotation case.