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In fluid dynamics, the entrance length is the distance a flow travels after entering a pipe before the flow becomes fully developed. [1] Entrance length refers to the length of the entry region, the area following the pipe entrance where effects originating from the interior wall of the pipe propagate into the flow as an expanding boundary layer.
θ is the contact angle of the liquid on the tube wall; ρ is the mass density (mass per unit volume); r 0 is the tube radius; g is the gravitational acceleration. It is only valid if the tube is cylindrical and has a radius (r 0) smaller than the capillary length (= / ()). In terms of the capillary length, the law can be written as
A tube and pipe may be specified by standard pipe size designations, e.g., nominal pipe size, or by nominal outside or inside diameter and/or wall thickness. The actual dimensions of pipe are usually not the nominal dimensions: A 1-inch pipe will not actually measure 1 inch in either outside or inside diameter, whereas many types of tubing are ...
The hydraulic diameter, D H, is a commonly used term when handling flow in non-circular tubes and channels. Using this term, one can calculate many things in the same way as for a round tube. When the cross-section is uniform along the tube or channel length, it is defined as [1] [2] =, where
The pressure force pushing the liquid through the tube is the change in pressure multiplied by the area: F = −A Δp. This force is in the direction of the motion of the liquid. The negative sign comes from the conventional way we define Δp = p end − p top < 0. Viscosity effects will pull from the faster lamina immediately closer to the ...
The experiment uses a simple barometer to measure the pressure of air, filling it with mercury up until 75% of the tube. Any air bubbles in the tube must be removed by inverting several times. After that, a clean mercury is filled once again until the tube is completely full. The barometer is then placed inverted on the dish full of mercury.
The capillary length or capillary constant is a length scaling factor that relates gravity and surface tension. It is a fundamental physical property that governs the behavior of menisci, and is found when body forces (gravity) and surface forces ( Laplace pressure ) are in equilibrium.
In the cardiovascular system, the pulsation frequency, density, and dynamic viscosity are constant, however the Characteristic length, which in the case of blood flow is the vessel diameter, changes by three orders of magnitudes (OoM) between the aorta and fine capillaries. The Womersley number thus changes due to the variations in vessel size ...