(清华大学2006--2007学年春季学期期中考试试题)Consider incompressible flow in the entrance of a circular tube,as in Fig.6-39.The inlet flow is uniform,u1=U0.The flow at section 2 is developed pipe flow.Find the wall drag force F as a function of(p1,p2,ρ,Uo,R)if the flow at section 2 is: