Its flow condition, velocity of flow often must understand to distributing when measuring flow of the fluid inside the canal etc. Reynolds number is a of character of token fluid flow important parameter.

The force F when the fluid flows_GWith agglutinant force (inside attrition force) F_Mcount than calling Reynolds. Express with symbolic Re. Re is a zero dimension quantity.

The dynamical viscosity η in type is replaced with athletic viscosity υ , because of η ＝ ρυ , criterion

In type:

L The average rate of υ—— fluid;

L L—— flows bundle finalize the design dimension;

L ρ , η is working one by one condition; The athletic viscosity of the fluid and dynamical viscosity

L ρ—— is measured fluid density;

By go up type is knowable, the size of Reynolds number Re depends on 3 parameter, namely the speed of the fluid, stream bundle finalize the design the viscosity below dimension and working status.

The canal that use a circle transmits a fluid, when computational Reynolds is counted, finalize the design dimension takes conduit diameter commonly (D) , criterion

Transmit a fluid with quadrate canal, conduit finalizes the design dimension takes equivalent diameter (D_D) . What equivalent diameter is equal to hydraulic radius is fourfold. To the conduit of aleatoric and sectional appearance, its are hydraulic radius is equal to conduit jab area and circumference than. Grow so and wide it is A and B respectively

rectangular conduit, its equivalent diameter To conduit of aleatoric and sectional appearance

equivalent diameter, what can press cut area is fourfold with sectional circumference than computation, accordingly, the computational formula that Reynolds counts is

Reynolds number is small, the between each particle agglutinant force when meaning a fluid to flow takes main place, fluid each particle parallel flows regularly at pipeline wall, show laminar flow flow condition. Reynolds number is large, mean force to take main place, the fluid shows turbulence flow condition, general conduit Reynolds counts Re ＜ 2000 for laminar flow condition, re ＞ 4000 for turbulence condition, 2000 ～ of Re ＝ 4000 to transfer condition. Below different flow condition, the motion curve of the fluid. Of velocity of flow distributing etc is different, consequently the ratio of the υ of average velocity of flow of the fluid inside conduit and υmax of the largest velocity of flow also is different. The volume that counts because of this Reynolds decided the flow of agglutinant fluid is characteristic. The Reynolds that issues chart to show smooth conduit counts ReD and speed to compare the relation of V/Vmax.
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