Fig. 1. Energy dissipation rate P as a function of reduced velocity u along different directions in (a) high dissipation regime and (b) low dissipation regime. Discrete symbols are numerical results, and dashed lines in (a) and (b) correspond to the asymptotic expressions (8) and (9), respecti-vely. From up to bottom, the critical velocities for each line are given by v_c = 1.41c₀, 1.21c₀, 1.07c₀, 0.89c₀, and 0.71c₀. The two plots use the same legend. The relative strength of dipolar interaction is set as .