Vätskelagar

Vätskelagar refers to the physical principles that describe the behavior of fluids, including liquids and gases, in physics. They are studied in fluid mechanics and cover both statics (hydrostatics) and dynamics (hydrodynamics). The laws apply to incompressible and compressible fluids across a wide range of scales and conditions.

Key principles include Pascal's principle, which states that pressure applied to a confined fluid is transmitted undiminished in all directions and throughout the fluid and container. Hydrostatic pressure describes how pressure increases with depth, P = P0 + ρgh. Archimedes’ principle explains buoyancy: a body submerged in a fluid experiences a buoyant force equal to the weight of the displaced fluid. Bernoulli’s principle relates pressure, velocity, and height along a streamline for steady, incompressible, inviscid flow, expressed as P + 0.5ρv^2 + ρgz = constant.

The motion of fluids is governed by the Navier–Stokes equations, which express conservation of momentum for viscous fluids: ρ(Dv/Dt) = −∇p + μ∇^2v + ρg, together with the continuity equation for mass conservation. Boundary conditions include the no-slip condition at solid boundaries and appropriate conditions at inlets and outlets.

Fluid properties such as density, viscosity, and surface tension, as well as compressibility and turbulence, determine fluid behavior. In practice, Vätskelagar are applied in hydraulics, aerodynamics, meteorology, oceanography, and biomedical flows, often using simplifications or numerical methods when exact solutions are not feasible.