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<br /> <br />Section 3.02. State of Flow <br /> <br />Effect of Velocity <br /> <br />In both open channel and pressure flow three states of behavior <br />can exist--laminar, transitional and turbulent. The ratio of viscous <br />to inertial forces. called Reynoldsnuntler. indicates which state pre- <br />vails and is defined by: <br /> <br />R = <br />e <br /> <br />VL <br /> <br />(3-1) <br /> <br />- <br />v <br /> <br />where: <br /> <br />R = Reynolds number <br />e <br /> <br />V = velocity of flow <br /> <br />L c characteristic length <br /> <br />v . kinematic viscosity <br /> <br />In open channel flow the hydraulic radius is the characteristic <br />length, L. For Reynolds numbers less than 500, laminar flow exists; <br />and for Reynolds numbers greater than 2000, the flow is usually con- <br />sidered turbulent. A transitional state exists between Reynolds <br /> <br />numbers of 500 and 2000. However, there is really no definite upper <br />limit for the transitional range for all flow conditions. In pipe <br />flow, pipe diameter is the characteristic length and the limiting <br />values of Re are 2000 and 8000 for the transitional zone. subject to <br />the same qualifications as discussed above for open channel flow. <br /> <br />The state of flow is important because of its influence on the <br /> <br />friction loss coefficients. Flow in natural channels is almost always <br />highly turbulent; and. therefore. the friction loss coefficients depend <br /> <br />3.02 <br />