![]() It is used to predict the transition from laminar to turbulent flow and is used in the scaling of similar but different-sized flow situations, such as between an aircraft model in a wind tunnel and the full-size version. The Reynolds number has wide applications, ranging from liquid flow in a pipe to the passage of air over an aircraft wing. These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. The turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow ( eddy currents). At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers, flows tend to be turbulent. In fluid mechanics, the Reynolds number ( Re) is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. Osborne Reynolds popularised the concept. George Stokes introduced Reynolds numbers. This can occur around cylinders and spheres, for any fluid, cylinder size, and fluid speed provided that it has a Reynolds number between roughly. This also means that it can be used in many dimensionless numbers to compare ratios of diffusivities, and hence the relative importance of different physical processes.The transition from laminar (left) to turbulent (right) flow of water from a tap occurs as the Reynolds number increases. The transport of momentum is analogous to the transport of other properties of a fluid. The kinematic viscosity can also be called diffusivity of momentum since it has the same dimensions as the diffusivity of heat and diffusivity of mass concentration. It is also expressed in terms of centistokes (cSt or ctsk). The Stokes(St) is the cgs physical unit for kinematic viscosity, named after George Gabriel Stokes, where 1 St = 10 -4 m 2/s. Where ν = kinematic viscosity, μ = absolute or dynamic viscosity, ρ = density. Kinematic viscosity can be obtained by dividing the dynamic viscosity of a fluid by its density. ![]() Kinematic Viscosity is the ratio of absolute or dynamic viscosity to density - a quantity in which the force is external and independent of the mass of the fluid. a fluid with less viscosity will take less time to flow than a fluid with higher viscosity). The higher the viscosity, the longer it takes to flow through the tube (i.e. The liquid is placed in the container and allowed to flow by gravity. Kinematic viscosity can be measured using a device called a capillary viscometer which consists of a graduated canister with a narrow tube at the bottom. For example cream becomes butter if agitated. Such fluids can become solid when flowing within a pipe. Those fluids that increase their viscosity with the increase in agitation or pressure under constant temperature are called Shear Thickening Fluids or Dilatant Fluids. They appear to be thick or viscous but they can be pumped quite easily. Those fluids which reduce their viscosity, when agitation or pressure is increased, keeping temperature constant, are known as Shear Thinning Fluids or Thixotropic Fluids. Most common liquids and gases are Newtonian fluids, such as water, oil and air. Types Of Fluid Newtonian Fluidsįluids in which shearing stress is linearly related to rate of shearing strain are called Newtonian fluids or true liquids, since agitation or pumping at constant temperature does not affect their viscosity or consistency. The kinematic viscosity of a liquid usually decreases with increase in temperature whereas the kinematic viscosity of a gas increases. The kinematic viscosity is highly dependent on temperature. ![]() Usually a thin liquid like water has less viscosity as compared to a thick fluid like honey having high viscosity. ![]() It can be thought of as fluid friction or internal resistance of a fluid to flow, and specifically the kinematic viscosity measures the resistance to flow of a fluid under the influence of gravity (or some other body force acting on the mass of the fluid). In general it is the "thickness" of a fluid. The resistance of a fluid that is being deformed from shear stress or extensional stress is called viscosity.
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