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In physics, a body force is a force that acts throughout the volume of a body. [1] Forces due to gravity, electric fields and magnetic fields are examples of body forces. Body forces contrast with contact forces or surface forces which are exerted to the surface of an object. Fictitious forces such as the centrifugal force, Euler force, and the ...
The derivation of the Navier–Stokes equation involves the consideration of forces acting on fluid elements, so that a quantity called the stress tensor appears naturally in the Cauchy momentum equation. Since the divergence of this tensor is taken, it is customary to write out the equation fully simplified, so that the original appearance of ...
The right side of the equation is in effect a summation of hydrostatic effects, the divergence of deviatoric stress and body forces (such as gravity). All non-relativistic balance equations, such as the Navier–Stokes equations, can be derived by beginning with the Cauchy equations and specifying the stress tensor through a constitutive relation .
In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of water and other liquids in motion).
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface.
Archimedes' principle (also spelled Archimedes's principle) states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces. [1] Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of ...
Fluid body forces are negligible. The variation of pressure across the fluid film is negligibly small (i.e. ∂ p ∂ z = 0 {\displaystyle {\frac {\partial p}{\partial z}}=0} ) The fluid film thickness is much less than the width and length and thus curvature effects are negligible.
There are two causes of aerodynamic force: [1]: §4.10 [2] [3]: 29 the normal force due to the pressure on the surface of the body; the shear force due to the viscosity of the gas, also known as skin friction. Pressure acts normal to the surface, and shear force acts parallel to the surface. Both forces act locally.