Pressure

Pressure variations in fluids are reviewed, with a particular emphasis on water. Variations under both hydrostatic and flowing conditions are described, and impacts of density stratification on pressure distribution are discussed. Calculations of forces due to pressure acting on submerged objects are derived, both for static and moving fluids, and the relationship between buoyancy and pressure is shown. The role of pressure terms in the equations of motion (Navier-Stokes equations) is discussed, and the basis for incorporating density stratification in the momentum equations is described. Additionally, the assumption of hydrostatic pressure variation in the vertical direction is shown to be generally suitable for development of models of water motion in most natural systems. Several examples of the impact of pressure and buoyancy on biological processes are presented.