Field Function script for varying Mass Flow Rate based on LOCAL Pressure

Aeromidd · August 9, 2017, 12:07

Hi,

I'm simulating a 'clapper' valve, but I need it to be a mass flow inlet that essentially only opens and emits fuel mass when pressure near the inlet is below a certain value.

I'm attempting to write a conditional field function along the lines of this logic:

---
IF (local pressure) is greater than [specified value]
Then output [zero] for mass flow rate.
ELSE
output [specified value] for mass flow rate.
---

I'm having technical trouble putting this into Star-CCM+'s code.

How do I specify pressure specifically near the inlet, as opposed to pressure overall? I can't find a 'local pressure' variable available on the list of functions. Is there a way to do this?

me3840 · August 9, 2017, 19:17

Yeah, sure, but I don't know how stable this would be.

Worth noting you could just make an overset simulation and actually close the valve.

Anyway, to do this you're doing to need to make a threshold/constrained plane of the area you want. You might need to make a few nested thresholds depending on the geometry. Or maybe a few point probes if you want.

After you build that derived part make an average pressure report on it. The report can be accessed by any field function via its name. For example a report named pressureNearValve can be accessed by $pressureNearValveReport.

Then you can make your field function as you stated there.

Also you will probably need to add in a limiter or use the alternateValue function in the case that the pressure is unphysically high or the solution is not yet stable. Or perhaps only turn this field function on at a specific time.

August 9, 2017, 12:07	Field Function script for varying Mass Flow Rate based on LOCAL Pressure	#1
Aeromidd New Member Michael Join Date: Jul 2017 Posts: 7 Rep Power: 8	Hi, I'm simulating a 'clapper' valve, but I need it to be a mass flow inlet that essentially only opens and emits fuel mass when pressure near the inlet is below a certain value. I'm attempting to write a conditional field function along the lines of this logic: --- IF (local pressure) is greater than [specified value] Then output [zero] for mass flow rate. ELSE output [specified value] for mass flow rate. --- I'm having technical trouble putting this into Star-CCM+'s code. How do I specify pressure specifically near the inlet, as opposed to pressure overall? I can't find a 'local pressure' variable available on the list of functions. Is there a way to do this?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Specifying a Flow's Mass Flow Rate and Inlet Pressure	Jayhawk	STAR-CCM+	16	March 20, 2015 16:03
Mass flow rate prediction of Purge control valve using set pressure drop	enr_venkat	CFX	11	February 27, 2014 11:30
Mass Flow Rate Field Function	RonBon	STAR-CCM+	0	February 19, 2013 08:58
Could anybody help me see this error and give help	liugx212	OpenFOAM Running, Solving & CFD	3	January 4, 2006 18:07
Hydrostatic pressure in 2-phase flow modeling (long)	DS & HB	Main CFD Forum	0	January 8, 2000 15:00

August 9, 2017, 19:17		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	Yeah, sure, but I don't know how stable this would be. Worth noting you could just make an overset simulation and actually close the valve. Anyway, to do this you're doing to need to make a threshold/constrained plane of the area you want. You might need to make a few nested thresholds depending on the geometry. Or maybe a few point probes if you want. After you build that derived part make an average pressure report on it. The report can be accessed by any field function via its name. For example a report named pressureNearValve can be accessed by $pressureNearValveReport. Then you can make your field function as you stated there. Also you will probably need to add in a limiter or use the alternateValue function in the case that the pressure is unphysically high or the solution is not yet stable. Or perhaps only turn this field function on at a specific time.