First thing that we will must see is wake. What is the cause of wake? So, far we have seen that, when a ship is moving in water, if I draw the ship like this, there is a boundary layer which develops around the ship and goes behind it. Here, if I draw a velocity profile along the y axis, then the water velocity will be constant, because there is no disturbance to flow in front of the ship or very near the front because there is no boundary layer developed in the front of the ship. Let us consider a submerge part, no wave effect.
If I draw a velocity profile here, how will it look? The velocity will, will, be 0 here and will increase till the boundary layer and then it will become equal to the free stream velocity, but what about at the boundary layer itself? What will happen at the boundary or the boundary layer? Will it be equal to the free stream velocity or slightly more than or slightly less than?
Velocity will be more, because if you recall, there will be a pressure developed due to potential flow. There nothing to do with viscous flow. If I draw the pressure around this body, we have seen pressure will rise at the front, then drop in the middle, rise again at the aft and go like this, is not it? On around a stream lined body, when there is no