Vascular resistance recent results showing the sheath flow surrounding the plug flow in a vessel, the sheath flow size is not neglectible in the real blood flow velocity profile in a vessel. The velocity profile is directly linked to flow resistance in a vessel. The viscosity variations, according to Thurston, are also balanced by the sheath flow size around the plug flow. The secondary regulators of vascular resistance, after vessel radius, is the sheath flow size and its viscosity. Thurston, as well, shows that the resistance R is constant, where, for a defined vessel radius, the value η(δ)/δ is constant in the
Knudsen flow Knudsen flow Knudsen flow describes the movement of fluids with a high Knudsen number, that is, where the characteristic length in the flow space is of the same or smaller order of magnitude as the mean free path. For a gas passing through small holes in a thin wall in the Knudsen-flow regime, the number of molecules that pass through a hole is proportional to the pressure of the gas and inversely proportional to its molecular mass. It is therefore possible to effect a partial separation of a mixture of gases if the components have different molecular masses. The technique