How do i calculate reynolds number

The friction factor is then used in the Darcy-Weisbach formula to calculate the fluid frictional loss in a pipe. Search 0 items. Friday 12th November Reynolds Numbers Fluid flow in a pipe encounters frictional resistance due to the internal roughness e of the pipe wall, which can create local eddy currents within the fluid.

Pipes that have a smooth wall such as glass, copper, brass and polyethylene cause less fritional resistance and hence they produce a smaller frictional loss than those pipes with a greater internal roughness, such as concrete, cast iron and steel.

The velocity profile of fluid flow in a pipe shows that the fluid at the centre of the stream moves more quickly than the fluid flow towards the edge of the stream. Therefore friction occurs between layers within the fluid. Fluids with a high viscosity flow more slowly and generally not produce eddy currents, thus the internal roughness of the pipe has little or no effect on the frictional resistance to flow in the pipe. This condition is known as laminar flow.

Reynolds Number Calculation The Reynolds number Re of a flowing fluid is calculated by multiplying the fluid velocity by the internal pipe diameter to obtain the inertia force of the fluid and then dividing the result by the kinematic viscosity viscous force per unit length. Turbulent Flow in a Pipe Turbulent flow occurs when the Reynolds number calculation exceeds Pipe Flow Software. Inside the reactor pressure vessel RPV , the coolant first flows down outside the reactor core through the downcomer.

The flow is reversed up through the core from the bottom of the pressure vessel, where the coolant temperature increases as it passes through the fuel rods and the assemblies formed by them. See also: Example: Flow rate through a reactor core. The Reynolds number describes the external flow naturally as well. In general, when a fluid flows over a stationary surface , e.

The boundary layer is the region in which flow adjusts from zero velocity at the wall to a maximum in the mainstream of the flow. Basic characteristics of all laminar and turbulent boundary layers are shown in the developing flow over a flat plate.

The stages of the formation of the boundary layer are shown in the figure below:. Boundary layers may be either laminar or turbulent, depending on the value of the Reynolds number. Also, here the Reynolds number represents the ratio of inertia forces to viscous forces and is a convenient parameter for predicting if a flow condition will be laminar or turbulent. The boundary layer is laminar for lower Reynolds numbers, and the streamwise velocity uniformly changes as one moves away from the wall, as shown on the left side of the figure.

As the Reynolds number increases with x , the flow becomes unstable. Finally, the boundary layer is turbulent for higher Reynolds numbers, and the streamwise velocity is characterized by unsteady changing with time swirling flows inside the boundary layer. The transition may occur earlier, but it is dependent especially on the surface roughness. The turbulent boundary layer thickens more rapidly than the laminar boundary layer due to increased shear stress at the body surface.

The external flow reacts to the edge of the boundary layer just as it would to the physical surface of an object. This happens because the flow in the boundary has very low energy relative to the free stream and is more easily driven by changes in pressure.

See also: Boundary layer thickness. See also: Tube in crossflow — external flow. Special reference: Schlichting Herrmann, Gersten Klaus. At what distance x from the leading edge will be the transition from laminar to turbulent boundary layer i. Fluid Dynamics.

Search Search. How is Reynolds number calculated? How is the Reynolds number calculated? Determine the type of flow internal, external, steady-state, etc. Choose or calculate the characteristic linear dimension From tables, determine the viscosity and the density of the fluid. Forgiven flow velocity, calculate the Reynolds number. It is defined as: where: V is the flow velocity, D is a characteristic linear dimension , travelled length of the fluid; hydraulic diameter etc.

At what Reynolds number is turbulent flow? What is the critical Reynolds number? What are applications of the Reynolds number? What are the applications of the Reynolds number? It is essential to calculate the friction factor in a few of the equations of fluid mechanics, including the Darcy-Weisbach equation. It is essential for heat transfer calculations since many other characteristic numbers e.

It is used when modeling the movement of organisms swimming through water. Atmospheric air is considered to be fluid. History of Reynolds Number The concept was introduced by George Stokes in , but Arnold Sommerfeld named the Reynolds number in after Osborne Reynolds — , who performed exhaustive experiments in the s.

Osborne Reynolds discovered that the flow regime depends mainly on the ratio of the inertia forces to viscous forces in the fluid. Please read AddThis Privacy for more information. If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords.

Make Shortcut to Home Screen? Reynolds Number Introduction and definition of the dimensionless Reynolds Number - online calculators Sponsored Links. Online Reynolds Calculator Density and absolute dynamic viscosity is Known This calculator can be used if density and absolute dynamic viscosity of the fluid is known.

Privacy We don't collect information from our users. Citation This page can be cited as Engineering ToolBox, Reynolds Number. On one hand, inertial forces generate fluid friction which is a factor in developing turbulent flow. On the other hand, viscous forces counteract this effect and progressively inhibit turbulence. The Reynolds number definition generally includes the velocity of a fluid, the characteristic length or characteristic dimension and the properties of the fluid, such as density and viscosity.

If you want to learn more about fluid viscosity , you should check out Stokes' law calculator , where you can find, among others, viscosity definition. Although the Reynolds number can be defined in several different ways, it remains a non-dimensional factor. Now, you probably want to know what Reynolds number means at all. Reynolds number is used to predict whether the fluid flow will be laminar or turbulent. In this situation, the flow will begin to change from laminar to turbulent flow and then back to laminar flow.

It is so-called intermittent or transitional flow. Therefore, the choice of laminar vs turbulent flow isn't always easy and possible. The Reynolds number formula depends on viscosity. We generally distinguish two types of viscosity:. The Reynolds number calculator simultaneously uses two different Reynolds number equations, as below:. In this calculator you can choose a particular substance from some examples we have prepared or enter your own fluid parameters. Characteristic linear dimension L or characteristic length in the above formulas is a matter of convention.