Motion of 2D buoyant clouds downslope

The motion of conservative 2D thermals on beds with slope angles theta ranging from 5 to 90 degrees is investigated theoretically and experimentally. Using a large number of experimental data, important flow characteristics, including the shape factors, spatial growth rate, propagation speed, and entrainment coefficient, are quantified as functions of bottom slope angles. A thermal model, which includes a resistance term, is developed. It is found semiempirically that resistance coefficients C-d are almost independent of a and the values of C-d are in the range of 0.4-0.6. Capability of the model is demonstrated by comparing numerical results with theoretical as well as experimental results.