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kish April 5, 2013 21:06

Pressure recovery length
 
Dear all
For the group assignment, We are simulating pulsatile flow( Pulsatile velocity) through venturi. Our question is, How we can find out pressure recovery length from the divergent.

we did in the following way.

We found the average value of pulsatile flow and found the time that the average takes place.
After completion of simulation we draw a line along the axis. we have selected the the average time and plot the graph

Is the way correct or any other way should we follow?


Thank you

Regards
Kish

ghorrocks April 6, 2013 05:15

Are you looking for the time averaged pressure recovery, the time history of pressure recovery, or the pressure recovery at a specific instant in time? You would take quite different approaches for all these questions.

kish April 6, 2013 15:40

Quote:

Originally Posted by ghorrocks (Post 418719)
Are you looking for the time averaged pressure recovery, the time history of pressure recovery, or the pressure recovery at a specific instant in time? You would take quite different approaches for all these questions.

we are looking for time avraged pressure recovery length from the divergent.

we are also so confused about the Reynolds number. Since the flow is oscillatory, Re value changes from time to time. How do we find the mean Re number?

One of my team members has given the two way. We don't know which one is correct. The cfx users please help us.


1. create a point and find the time averaged velocity and use the diameter of the pipe and other parameters to calculate Re.

2. create a plane in the cfx pre and use a function calculator to find the areaAve velocity then find Re ( In this case we cannot find time averaged Re, I hope I am correct if anything wrong please correct us)

Thank you

ghorrocks April 7, 2013 06:32

* Re can be defined any way which makes sense. So for an oscilliatory flow then a tiem average of varying variables makes sense. But be careful about using this to estimate flow properties - turbulence, transition, friction will all be affected by the oscillations so the textbook relations probably do not apply (which is why you are modelling it in the first place).
* define a monitor point with the CEL expression massFlow()@cross section. Then you will get the full time history of the mass flow at that cross section.


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