DIRECT SIMULATIONS OF LOW-REYNOLDS-NUMBER TURBULENT-FLOW IN A ROTATING CHANNEL

Direct numerical simulations of fully developed pressure-driven turbul ent flow in a rotating channel have been performed. The unsteady Navie r-Stokes equations were written for flow in a constantly rotating fram e of reference and solved numerically by means of a finite-difference technique on a 128 x 128 x 128 computational mesh. The Reynolds number , based on the bulk mean velocity U(m) and the channel half-width h, w as about 2900, while the rotation number Ro = 2 \OMEGA\h/U(m) varied f rom 0 to 0.5. Without system rotation, results of the simulation were in good agreement with the accurate reference simulation of Kim, Moin & Moser (1987) and available experimental data. The simulated flow fie lds subject to rotation revealed fascinating effects exerted by the Co riolis force on channel flow turbulence. With weak rotation (Ro = 0.01 ) the turbulence statistics across the channel varied only slightly co mpared with the non-rotating case, and opposite effects were observed near the pressure and suction sides of the channel. With increasing ro tation the augmentation and damping of the turbulence along the pressu re and suction sides, respectively, became more significant, resulting in highly asymmetric profiles of mean velocity and turbulent Reynolds stresses. In accordance with the experimental observations of Johnsto n, Halleen & Lezius (1972), the mean velocity profile exhibited an app reciable region with slope 2OMEGA. At Ro = 0.50 the Reynolds stresses vanished in the vicinity of the stabilized side, and the nearly comple te suppression of the turbulent agitation was confirmed by marker part icle trackings and two-point velocity correlations. Rotational-induced Taylor-Gortler-like counter-rotating streamwise vortices have been id entified, and the simulations suggest that the vortices are shifted sl ightly towards the pressure side with increasing rotation rates, and t he number of vortex pairs therefore tend to increase with Ro.