Is there a source for these equations? The Welty textbook: Fundamentals of momentum heat and mass transfer (6e) agrees with the laminar entrance length equation (eqn 13-20). This text also says on P-199 (chapter 13, description of equation 13-20) that there is no relation available to predict entrance length for turbulent flow?
The entrance region is where the velocity profile is still affected by the developing boundary layer and thus a function of both distance from the walls and distance along the pipe. It becomes difficult to predict velocity in this region whereas after the entrance region, the flow becomes fully developed and the velocity is only a function of distance from the walls. In this case, the flow is turbulent and the entrance length is determined for turbulent flow. We would use empirical relationships for turbulent flow in the fully developed region to examine the pressure and velocity profiles in that region. If the flow encounters any changes in the piping system (bends, tees, expansions, etc.) we would recalculate the flow regime and entrance region at that point due to this disturbance in flow.
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Is there a source for these equations? The Welty textbook: Fundamentals of momentum heat and mass transfer (6e) agrees with the laminar entrance length equation (eqn 13-20). This text also says on P-199 (chapter 13, description of equation 13-20) that there is no relation available to predict entrance length for turbulent flow?
Exactly what I needed to clarify and simplify the material for my midterm. Thanks!
Glad it helped. Thanks for the comment and please feel free to suggest other topics/problems for videos.
Very simple and useful explanation to understand the concept of FD flow, thanks!!!
thanks for the brief and very clear explanation.
How can I find the entry length if given the initial velocity instead of the flow rate?
Thanks! It’s easy to understand!
Does that mean that after 2.125 m the flow can be assumed to be laminar?
The entrance region is where the velocity profile is still affected by the developing boundary layer and thus a function of both distance from the walls and distance along the pipe. It becomes difficult to predict velocity in this region whereas after the entrance region, the flow becomes fully developed and the velocity is only a function of distance from the walls. In this case, the flow is turbulent and the entrance length is determined for turbulent flow. We would use empirical relationships for turbulent flow in the fully developed region to examine the pressure and velocity profiles in that region. If the flow encounters any changes in the piping system (bends, tees, expansions, etc.) we would recalculate the flow regime and entrance region at that point due to this disturbance in flow.
fantastic explanation. thank you!
I couldn't calculate the reynold's number
thank you :)
How can I find entrance length in case of open channel flow?