CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Pre-Processing

Boundary condition to simulate a compliant volume

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   November 11, 2020, 03:25
Lightbulb Boundary condition to simulate a compliant volume
New Member
Join Date: Jul 2020
Posts: 2
Rep Power: 0
fromanza is on a distinguished road
Hello world from sunny South Africa,

I am looking for help to solve what seems should be a relatively simple problem. I am new to openFOAM and have googled this particular thought but not come up with many results other than programming a new BC which seems quite daunting.

I would like to define a BC that essentially acts as a compliant isentropic volume. In other words, consider the boundary as a gas balloon/accumulator/lung etc that expands and as it expands its pressure rises as the volume expands/stretches. The pressure will rise (compressing the gas) because of the compliance of the volume walls. I am not interested at this point to consider thermal effects as the process happens slowly and at low pressures (5cmH20 to 40cmH20). I define the volumes compliance as (change in volume/change in pressure). EG if the volume changes by 50ml then the pressure goes up by 5cm.

The hope is to model a lung without the computational overhead of:
-Modelling the actual volume as a 'static' mesh and running a compressible solver
-Modelling a moving mesh system like a piston in a cylinder

The following BC's showed potential but thought I would reach out and see if im missing something simpler:
- codedFixedValue (not sure this has the ability to look at dV/dT)
- externalCoupled (seems most likely to work)
- Possibly using an energy BC like gradientEnergy (doubt this will work)
- plenumPressure (too defined for my use)
- syringePressure (too defiend for my use)

I think the most likely is attempting a pseudo-custom BC and emplying externalCoupled which I assume will involve a Python script to pull data from the OF results, make a calculation and then return/apply the boundary pressure based on the volume of air that has moved through the boundary.

Would appreciate some insight!
fromanza is offline   Reply With Quote

Old   January 19, 2021, 03:09
Cool Any thoughts?
New Member
Join Date: Jul 2020
Posts: 2
Rep Power: 0
fromanza is on a distinguished road
Bump? Any thoughts?
fromanza is offline   Reply With Quote


balloon, boundary condition, lungs

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Wind turbine simulation Saturn CFX 58 July 3, 2020 01:13
CFD analaysis of Pelton turbine amodpanthee CFX 31 April 19, 2018 18:02
Question about adaptive timestepping Guille1811 CFX 25 November 12, 2017 17:38
Question about heat transfer coefficient setting for CFX Anna Tian CFX 1 June 16, 2013 06:28
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 15:55

All times are GMT -4. The time now is 02:02.