For hard spheres in shear flow, the function u(r) arises from the solution to the steady-state two-body Smoluchowski convection-diffusion equation or two-body Smoluchowski equation with shear flow.
The function u(r) is produced for hard spheres in shear flow; it comes from solving the steady-state two-body Smoluchowski convection-diffusion equation or two-body Smoluchowski equation under conditions of shear flow.