Ram pressure

In physics, ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as In physics, ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as P ram = ρ u i u j {displaystyle P_{ ext{ram}}= ho u_{i}u_{j}} , where ρ {displaystyle ho } is the density of the fluid; this is the momentum flux per second in the i {displaystyle i} direction through a surface with normal in the j {displaystyle j} direction. u i , u j {displaystyle u_{i},u_{j}} are the components of the fluid velocity in these directions. The total Cauchy stress tensor σ i j {displaystyle sigma _{ij}} is the sum of this ram pressure and the isotropic thermal pressure (in the absence of viscosity).