The corresponding unit in the centimeter gram second system of units (cgs) is the poise (P) and 1P = g The SI unit for dynamic viscosity is the Pascal-second, denoted "Pa s" or Pa Dynamic viscosity unitsĭynamic viscosity (or simply "viscosity") is the resistance to movement of one layer of a fluid over another for both shearing and non-shearing flows. This formula is the one we use to perform the math in this calculator. The experiment was described in his 1883 paper: he used dyed water and studied its under different flow velocities when it mixed with clear water flow in a see-through pipe. The formula was famously derived and demonstrated experimentally by Osborne Reynolds who studied the conditions in which the flow of fluid in pipes transitions from laminar flow to turbulent flow. Where ρ (Greek lower-case letter rho) is the density of the liquid (kg/m 3), u is the velocity of the fluid relative to the object (m/s), μ (Greek lower-case letter mu) is the dynamic viscosity, v is the kinematic viscosity and finally L is the characteristic length (by convention - inner diameter of a pipe, diameter of a sphere in liquid, length of plate, etc.). Since the Reynolds equation describes the ratio between inertial forces and viscous forces acting on a flow it can be expressed both in terms of the kinematic viscosity or the dynamic viscosity and density of the substance: While two flows with approximately equal Re can behave quite differently in practice due to their chaotic nature in which even small differences in shape and surface roughness can produce very different flows, the Reynolds number is still a useful and widely used guide to flow similarity. Edgy currents, in turn, use up energy and may produce cavitation. Turbulence also leads to edgy currents in which different sub-flows intersect or even move counter to the overall flow direction. One interprets the Reynolds number as such: a low Reynolds number suggest the flow should be dominated by laminar (sheet-like) flow at high Reynolds numbers one expects significant turbulence due to the differences in the fluid's speed and direction. At larger scale it has uses in meteorology and climatology. In practical applications the ability to predict when a turbulent flow will appear is important in designing piping systems, airplane wings, aerodynamic vehicles, including for scaling from study models to actual aircraft/vehicle. It can also be used to study and predict hot gases as in a flame in air.
The number sees uses in fluid mechanics where it is used to predict flow patterns in different fluid flow scenarios.
Knowing Re one can anticipate the transition from laminar to turbulent flow which is the main utility of a Reynolds Number calculator. The Reynolds number (Re) is a dimensionless quantity for dynamic similarity and is calculated as the ratio of inertial forces to viscous forces of a flow of liquid. The Reynolds Number calculator will then apply the relevant equation and produce the Reynolds Number (Re) as result. compressible gases) and fluids of variable viscosity (non-Newtonian fluids).
Special consideration should be taken for fluids of variable density (e.g. the inner diameter of a pipe, the diameter of a sphere moving in liquid, or the length of a plate over which the substance is flowing. Finally, enter the characteristic length, e.g. Then enter the velocity at which the substance is moving. m 2/s, Stokes and centiStokes for kinematic viscosity, imperial and metric/scientific units for density, velocity and length).įirst, select whether you know the substance's kinematic viscosity or the dynamic viscosity and density and then enter the quantities you know. It supports a wide range of input and output measurement units (e.g. With the help of this calculator you can compute the Reynolds Number of a liquid or gas.
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