Hidden Flow Patterns in Reservoirs

The fluids around us - water and air - are almost always stratified according to their density. For many ordinary engineering problems dealing with strong motions on a relatively small scale (such as flow of water in a pipe, or the flow of air around the wing of an airplane) we may easily neglect the density stratification; the ordinary mechanics of homogeneous fluids apply. But when we consider weak motions in large bodies of fluid, the slight variation in fluid weight with depth (due to gradients of temperature or salinity) may profoundly alter the fluid motion