The stream function psi (x, y) = Axy describes corner flow. Graph the streamlines in the first quadrant for A = 4 and describe the flow field. Fluid dynamics deals with the motion of materials that flow. For this reason, fluid dynamics provides the equations that describe the motion of oceans, hurricanes, lava flows, and air around the wing of a supersonic jet. The usual starting point for fluid dynamics is ideal flow. As the name implies, ideal flows are often not very realistic (the physicist Richard Feynman claimed that ideal flow applies only to "dry water"). However, ideal flow offer a good opportunity to apply the ideas of vector calculus.We consider two-dimensional flows in which the velocity vector describing the motion of the fluid at a point (x,y) is You can think of u as the east-west component of velocity and v as the north-south component two dimensional models describe either very shallow flows or flows in which there is no variation in depth.