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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.
In most contexts a mention of rate of fluid flow is likely to refer to the volumetric rate. In hydrometry, the volumetric flow rate is known as discharge. Volumetric flow rate should not be confused with volumetric flux, as defined by Darcy's law and represented by the symbol q, with units of m 3 /(m 2 ·s), that is, m·s −1.
Isaac Newton's sine-squared law of air resistance is a formula that implies the force on a flat plate immersed in a moving fluid is proportional to the square of the sine of the angle of attack. Although Newton did not analyze the force on a flat plate himself, the techniques he used for spheres, cylinders, and conical bodies were later applied ...
The Newton's constitutive law for a compressible flow results from the following assumptions on the Cauchy stress tensor: [5] the stress is Galilean invariant: it does not depend directly on the flow velocity, but only on spatial derivatives of the
Airflow, or air flow, is the movement of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric air pressure is directly related to altitude , temperature , and composition.
In fluid dynamics, the volumetric flux is the rate of volume flow across a unit area (m 3 ·s −1 ·m −2), and has dimensions of distance/time (volume/(time*area)) - equivalent to mean velocity. The density of a particular property in a fluid's volume, multiplied with the volumetric flux of the fluid, thus defines the advective flux of that ...
where u is the flow velocity of the fluid, n is the outward-pointing unit normal vector, and s represents the sources and sinks in the flow, taking the sinks as positive. The divergence theorem may be applied to the surface integral , changing it into a volume integral :
It can be successfully applied to air flow in lung alveoli, or the flow through a drinking straw or through a hypodermic needle. It was experimentally derived independently by Jean Léonard Marie Poiseuille in 1838 [ 1 ] and Gotthilf Heinrich Ludwig Hagen , [ 2 ] and published by Hagen in 1839 [ 1 ] and then by Poiseuille in 1840–41 and 1846 ...