Question

What is the relative velocity term in drag and lift force in the following case?

Answer 1

When a stationary particle is introduced in a fluid moving with horizontal velocity Vfx, what is the relative velocity terms in the drag force (FD) and lift force (FL) equations. Am I correct to write the following:  FD=0.5ρCDA(Vfx−Vpx)2 FL=0.5ρCLA(Vfx−Vpy)2 where Vpx and Vpx is the particle's velocity in x and y direction respectively.  Also, what will be the force terms if the flow has a vertical component Vfy too?  Edit 1: The particle is completely submerged in water, and is lying at the bottom of a river bed (suppose) at t=0.