To resolve fluid flow problems, the Navier-Stokes equation can be utilized. Using the Navier-Stokes Equation to Solve Fluid Flow Problems Turbulent flow occurs at a relatively high value of Reynolds number, which means the kinematic viscosity of the turbulent fluid flow is less, and such fluids transport low momentum. Highly viscous fluids and low-density liquids are good examples of high momentum diffusion with low Reynolds number values. The increase in momentum transport or momentum diffusion in fluids accounts for more laminar flow regimes. The higher the kinematic viscosity, the more efficient the fluid becomes at transporting momentum. As the kinematic viscosity increases, the Reynolds number decreases and vice versa. Reynolds number is negatively influenced by kinematic viscosity. It describes the momentum the fluid in motion can transfer per volume. The kinematic viscosity is the normalized dynamic viscosity to density.

There is a strong relationship between Reynolds number and kinematic viscosity, which we will examine next. When the kinematic viscosity value is known, the Reynolds number can be calculated using the equation in the middle. When the density and absolute or dynamic viscosity is known, the first equation on the right hand side of the above equation can be used. In the above equation, it is shown that both absolute or dynamic viscosity and kinematic viscosity are involved in the calculation of the Reynolds number. Commonly used units of kinematic viscosity are ft2/s and Stoke (St). The SI unit of kinematic viscosity is m2/s. Kinematic viscosity - The ratio of absolute or dynamic viscosity to density is called kinematic viscosity. It is an indicator of a fluid’s internal resistance to flow. Viscosity is the fluid’s resistance to flow, and expresses the measure of a fluid’s resistance to the slow deformation caused by shear or tensile stress.Ībsolute or dynamic viscosity - The absolute or dynamic viscosity measures the tangential force per unit area required to slide one horizontal layer with respect to another layer that is spaced at a unit distance in the fluid at a unit velocity. When a fluid is in motion, it experiences a resistance called shear resistance due to the inter-molecular friction between the layers of the fluid. In fluid dependent systems, viscosity influences the fluid behavior and fluid motion. Reynolds Number and the Viscosity of a Fluid Note that is the density of the fluid, is the velocity of the fluid, l is the characteristic length or hydraulic diameter of the fluid flow, is the dynamic or absolute viscosity of the fluid, and v is the kinematic viscosity of the fluid. Mathematically, the Reynolds number can be given by the following equation: It reveals the effect of fluid viscosity in controlling the flow pattern or velocity of the fluid. It can also be interpreted as the ratio of dynamic pressure to shearing stress. Reynolds number is the ratio of inertial forces to viscous forces, and this number categorizes fluid systems. Reynolds numbers with a value of less than 2300 indicate a laminar flow of the fluid. As the Reynolds number increases above 4000, the fluid flow becomes turbulent. When the Reynolds number is between 23, the fluid flow is transitional. Fluid can be gas or liquid, and the value of the Reynolds number determines whether the flow is laminar or turbulent. Generally, the Reynolds number is a dimensionless measurement that describes the degree of laminar or turbulent fluid flow. In this article, we will explore the relationship between the Reynolds number and the kinematic viscosity. Reynolds number is dependent on several fluid properties such as density, velocity, and viscosity, and this number shares an inversely proportional relationship with the kinematic and dynamic viscosity. The range of Reynolds numbers indicate the degree of laminar or turbulent flow. To identify the flow type, engineers depend on a dimensionless quantity called the Reynolds number. With these simulations, a clear understanding of the flow regime as well as its paths and velocities can be obtained. The flow behavior of such systems can be analyzed using computational fluid dynamics (CFD) simulations. In systems influenced by fluid flow, it is important to analyze the fluid dynamics in order to quantify their effect. The range of Reynolds numbers indicate the degree of laminar or turbulent flow Reynolds number is a dimensionless measurement that describes the degree of laminar or turbulent fluid flow.įluid viscosity can be measured as absolute or dynamic viscosity and kinematic viscosity.Īs the kinematic viscosity increases, the Reynolds number decreases and vice versa.

Kinematic viscosity formula