Measurement of the fluid flow, often must understand its flow, flow rate distribution. Reynolds number is the characterization of fluid flow characteristics of an important parameter.

Fluid flow when the inertial force F g and viscous forces (the friction) F m ratio known as the Reynolds number. Re said that using symbols. Re is a non-dimensional volume.

The driving force in the viscosity of kinematic viscosity used to replace, because = Ѧ, then

In the formula;

l The average speed of fluid;

l l Beam-size stereotypes;

l ѡ һһWork in the state of the movement of fluid viscosity and dynamic viscosity

l Measured fluid density;

By the on-we can see that Reynolds number Re depends on the size of three parameters, namely, the rate of fluid, the flow beam size stereotypes and work under the viscosity.

Pipe transmission fluid used to calculate Reynolds number, size stereotypes diameter pipeline from the general (D), while

With a square of the transmission fluid, the pipeline from stereotypes size equivalent diameter (D d).Hydraulic equivalent diameter equal to four times the radius. For any cross-section shape of the pipeline, its radius equal to the hydraulic pipes poke area and the ratio of circumference. Therefore, length and width of A and B, respectively

The rectangular channel, the equivalent diameter pipeline for any cross-section shape

The equivalent diameter, can the cross-sectional area four times and the ratio of circumference section, therefore, the Reynolds number is calculated as

Reynolds number of small means that the fluid flow when the viscosity of the particles hold a major position, the fluid particles parallel to the pipe wall regularly flows, a laminar flow state. Reynolds number, means that the inertia of the status of the principal, a turbulent fluid flow, the general pipeline Reynolds number Re <2000 for the state of flow, Re> 4000 for the turbulent state, Re = 2000 ~ 4000 for the transition state. In the different state of the movement, the movement of fluid. Velocity of the distribution is different and therefore channels, the average velocity of the fluid max maximum velocity and the ratio is different. So Reynolds number determines the size of the viscous fluid flow characteristics. The chart that the Reynolds number ReD smooth channels and faster than the V / Vmax relationship.

Smooth channels of the Reynolds number Re p and faster than the V / Vmax relations

Tests showed that when the external conditions similar to geometry (geometric similarity of the tubes, fluid flow through similar geometric objects, etc.), if they are equal to the Reynolds number, the fluid flow is similar to the geometric (similar to fluid dynamics). This law is similar to cutting expenditure flow measurement devices standardized basis. Clearly, Reynolds number accurately reflects the flow of fluid flow is commonly used in measuring the parameters.

Reynolds number flow expressions:

M Measured the mass flow medium kg h

Q The volume of traffic measured media m h

D Diameter pipeline mm

v Working under the dynamic viscosity measured media Pa S

p Working under a kinematic viscosity measured media m 2 /s

The often-value, in accordance with the parameters of the units vary. When the use of non-type specified in the flat, often numerical should be amended accordingly.