Actual vs Standard BC

rajcoep.88 · February 7, 2016, 19:20

Hi,

I tried to search about it before posting my doubt. But, I could not find anything which would clarify the things that are bugging me. It might seem like stupid question. But, I am new to CFD field.

When one does simulation of internal incompressible flow, then at inlet one should assign Mass flow rate or volume flow rate or velocity and gage pressure 0 at outlet. Lets say I want to assign Velocity at inlet. So this velocity is Standard or Actual Velocity

I have done test of pneumatic check valve. Flow meter gives reading of 6 Standard LPM (Standard Conditions written on flow meter are 20deg C and 1 Atm) and Pressure Drop across valve is 50 hPa. I want to verify same using Simulation. From Q=AV, I can calculate velocity. Pipe Internal Diameter is 4mm. But, people say standard and actual flow rates are different in case of air flow from what I have read. So which flow rate should I use to calculate Velocity so that I can give it as inlet boundary condition?

Thanks in advance!

Best Regards,
Rajdeep Rajput

fisichel · February 12, 2016, 23:11

Hi,

So you did a test where you sent through air at nonstandard temperature and pressure and the meter reported flow rate in terms of standard temperature and pressure.

If you apply the standard atmospheric boundary conditions, then you should get nearly the same reading as the meter.

Matching test data requires some finesse. If you are comfortable using the adaptive meshing feature, I would turn it on.

Good luck,
Chris

February 7, 2016, 19:20	Actual vs Standard BC	#1
rajcoep.88 New Member E-Joker Join Date: Nov 2015 Posts: 7 Rep Power: 11	Hi, I tried to search about it before posting my doubt. But, I could not find anything which would clarify the things that are bugging me. It might seem like stupid question. But, I am new to CFD field. When one does simulation of internal incompressible flow, then at inlet one should assign Mass flow rate or volume flow rate or velocity and gage pressure 0 at outlet. Lets say I want to assign Velocity at inlet. So this velocity is Standard or Actual Velocity I have done test of pneumatic check valve. Flow meter gives reading of 6 Standard LPM (Standard Conditions written on flow meter are 20deg C and 1 Atm) and Pressure Drop across valve is 50 hPa. I want to verify same using Simulation. From Q=AV, I can calculate velocity. Pipe Internal Diameter is 4mm. But, people say standard and actual flow rates are different in case of air flow from what I have read. So which flow rate should I use to calculate Velocity so that I can give it as inlet boundary condition? Thanks in advance! Best Regards, Rajdeep Rajput

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February 12, 2016, 23:11		#2
fisichel New Member Chris Fisichella Join Date: Oct 2012 Posts: 28 Rep Power: 14	Hi, So you did a test where you sent through air at nonstandard temperature and pressure and the meter reported flow rate in terms of standard temperature and pressure. If you apply the standard atmospheric boundary conditions, then you should get nearly the same reading as the meter. Matching test data requires some finesse. If you are comfortable using the adaptive meshing feature, I would turn it on. Good luck, Chris