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DNS OF STOCHASTICALLY FORCED LAMINAR PLANE COUETTE FLOW: PECULIARITIES OF HYDRODYNAMIC FLUCTUATIONS

George Chagelishvili
Abastumani Astrophysical Observatory Ilia State University & Nodia Institute of Geophysics Tbilisi State University Tbilisi, 0160, Georgia

Martin Oberlack
Chair of Fluid Dynamics, Dept. Mech. Eng., TU Darmstadt, Otto-Berndt-Str. 2, 64287 Darmstadt, Germany; Center of Smart Interfaces, TU Darmstadt, Germany; GS Computational Engineering, TU Darmstadt, Germany

George Khujadze
Universitat Siegen, Chair of Fluid Mechanics Paul-Bonatz-Str. 9-11, 57068 Siegen, Germany & Abastumani Astrophysical Observatory Ilia State University, Tbilisi 0160, Georgia

Abstract

The background of three dimensional (3D) hydrodynamic/vortical fluctuations in a stochastically forced, laminar, incompressible, plane Couette flow is simulated numerically. The fluctuating field is anisotropic and has well pronounced peculiarities: (i) the hydrodynamic fluctuations exhibits non-exponential, transient growth; (ii) fluctuations with the streamwise characteristic length-scale about two times larger than the channel width are predominant in the fluctuating spectrum instead of streamwise constant ones; (iii) nonzero cross-correlations of velocity (even streamwise-spanwise) components appear; (iv) stochastic forcing destroys the spanwise reflection symmetry (inherent to the linear and full Navier-stokes equations in a case of the Couette flow) and causes an asymmetry of the dynamical processes. The wavelet analysis was used for post-processing of the DNS data. Coherent vortex extraction method was used to split the velocity and vorticity fields in coherent and incoherent parts. The wavelet analysis confirmes the existence of the non-constant streamwise coherent structures in the flow.