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In fluid dynamics, the entrance length is the distance a flow travels after entering a pipe before the flow becomes fully developed. [1] Entrance length refers to the length of the entry region, the area following the pipe entrance where effects originating from the interior wall of the pipe propagate into the flow as an expanding boundary layer.
L is the length Re is the Reynolds number and Pr is the Prandtl number. This number is useful in determining the thermally developing flow entrance length in ducts. A Graetz number of approximately 1000 or less is the point at which flow would be considered thermally fully developed. [2]
The flow is axisymmetric ( ∂... / ∂θ = 0). The flow is fully developed ( ∂u x / ∂x = 0). Here however, this can be proved via mass conservation, and the above assumptions. Then the angular equation in the momentum equations and the continuity equation are identically satisfied.
In this state, the entrance length is 20% to 50% shorter in comparison with the straight tube. In the case of turbulent flow, the flow becomes fully developed during the first half-turn of the helically coiled tube. For this reason, the entrance region can be neglected in many engineering calculations.
For flow in a pipe of diameter D, experimental observations show that for "fully developed" flow, [n 2] laminar flow occurs when Re D < 2300 and turbulent flow occurs when Re D > 2900. [ 15 ] [ 16 ] At the lower end of this range, a continuous turbulent-flow will form, but only at a very long distance from the inlet of the pipe.
Entrance length (fluid dynamics) – Distance a flow travels after entering a pipe before fully developed Modon (fluid dynamics) – Sea eddies Shock (fluid dynamics) – term in fluid dynamics Pages displaying wikidata descriptions as a fallback
Hydrodynamic entrance length is that part of the tube in which the momentum boundary layer grows and the velocity distribution changes with length. The fixed velocity distribution in the fully developed region is called fully developed velocity profile. The steady-state continuity and conservation of momentum equations in two-dimensional are
In engineering, the Moody chart or Moody diagram (also Stanton diagram) is a graph in non-dimensional form that relates the Darcy–Weisbach friction factor f D, Reynolds number Re, and surface roughness for fully developed flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe.