1. The problem statement, all variables and given/known data In certain hydrodynamic flows the velocity of a liquid is given by v = -grad φ, where φ is referred to as the velocity potential. The potential given by: 'equation' corresponds to flow around a solid sphere of radius a. U is a constant. Determine the velocity of the fluid throughout the flow. Confirm that the radial component of velocity is zero on the surface of the sphere. I've successfully found the velocity of the fluid, as my answer is in agreement with the answer given. However, I'm not sure this part of the question means: ' Confirm that the radial component of velocity is zero on the surface of the sphere.' Could anyone help me?