Heat transfer from a rotating disk in a parallel air crossflow

The heat transfer from a rotating disk in an air stream parallel to the plane of rotation is of importance in the assessment of disk brake performance. Numerically determined heat transfer coefficients and correlations are accordingly presented for a large range of rotational and crossflow velocities. These were obtained by means of large-eddy-simulations (LES). The extreme conditions of a stationary disk in an air crossflow and a rotating disk in still air are also considered. It is found that a critical ratio between the rotational and the crossflow Reynolds numbers exists with respect to rotational heat transfer augmentation. Only above this critical value, rotational heat transfer augmentation sets on in case of laminar crossflow Reynolds numbers. This phenomenon is directly linked to a flow instability that leads to a periodic vortex generation, and which can be described by the classical Landau model. For higher angular velocities, the wake becomes fully turbulent, and the transition is very rapid.