Novel turbulence control strategy for simultaneously achieving friction drag reduction and heat transfer augmentation

An attempt is made for simultaneous, but independent control of skin friction reduction and heat transfer enhancement in a turbulent channel flow. First, a mathematical relation is derived of the contribution of turbulent heat flux to the Nusselt number. Two different thermal boundary conditions are considered: (1) isothermal condition, where two walls are kept at constant, but different temperatures; (2) isoflux condition, where both walls are heated at a given wall heat flux. By utilizing the difference between the derived relation and the similar relation for the skin friction (Fukagata et al., 2002), a strategy for the simultaneous control is proposed. The effects of the control strategy are examined by means of direct numerical simulation.