The hydrodynamic pressure is determined entirely by the motion and density of the fluid as follows: Anyone familiar with aerodynamics will likely recognize this as the main contributor to quadratic drag. This is the pressure a fluid exerts on an object due to the object’s motion through a fluid. If the fluid is compressible, the same applies as long as the fluid density field can be determined, such as in an FEA/FEM simulation. Similarly, a denser fluid will have greater weight per unit volume, thus it should exert more pressure for a given depth.ĭetermining the hydrostatic pressure in any system is relatively simple as long as the density of the fluid is known simply measure the depth below the surface of the fluid and the hydrostatic pressure is easily calculated. This variation with depth makes sense-the deeper an object is below the surface of a fluid, the more fluid available to exert its weight on the object. Hydrostatic pressure has a simple definition based on the depth beneath the fluid surface h, acceleration of gravity g, and fluid density ⍴: This means a fluid will exert some force on an object depending on the depth of an object into the fluid, regardless of its motion. This is the pressure created by the weight of the fluid, or rather due to the force of gravity acting on the fluid. Each of these pressures is described as follows: Hydrostatic Pressure These two contributions to total pressure exerted by a fluid are exploited in applications like hydraulics, propulsion, and aerodynamics. Hydrostatic and hydrodynamic pressure are always present inside a moving fluid and will exert pressure on a nearby body, system wall, or surface of any other object. In this article, we will discuss how these two pressure components arise in real systems and how they can be analyzed from CFD simulation data. The two types of pressure that arise in any fluid are hydrostatic and hydrodynamic pressure, the latter of which relates to the flow characteristics of fluid during motion. However, we sometimes like to discuss flows in terms of the pressure they exert on a moving body, as this aids the design of many mechanical systems. These two pressures will occur together in real flows.įluid flow, as it is derived from the main equations of fluid dynamics, is often discussed in terms of flow rates or forces. Hydrodynamic pressure arises due to a fluid moving against an object and any pressure gradient in the system.
Hydrostatic pressure arises due to the weight of a fluid acting on an object.
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