Direct numerical simulation of coherent structure in turbulent open-channel flows with heat transfer

In the present study, turbulent heat transfer in open-channel flows. has been numerically investigated by means of a Direct Numerical Simulations (DNSs) with a constant temperature at both free surface and bottom wall. The DNSs were conducted for two Prandtl number, 1.0 and 5.0 with a neutral (i.e., zero gravity) or stable stratification (Richardson number; 27.6), while a Reynolds number of 200, based on the friction velocity and flow depth. As the results, the coherent turbulent structures of fluid motion and thermal mixing, and the influence of Pr change for heat transfer, buoyancy effect for turbulent structures and hear transfer, and relationship among them, are revealed and discussed.