img512.imageshack.us/img512/2985/42904009cw1.jpg Hey guys, I am a bit stuck on this prolbem. When it says identify the characteristic physical scales is this refering only to the lenght scales (l, h, b)? or is U, gravity, density and viscosity included as well? Now the only two dimenionless groups that I think are relevant is the reynolds number and the froude number. So I am thinking of using the buckingham Pi theorem to derive the reynolds and froude number for this problem, is that correct? *I have ignored the Mach number cos it says that the density and viscosity remains constant.