# Euler solver in BCs

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

 August 7, 2013, 08:35 Euler solver in BCs #1 Member   Join Date: Sep 2012 Posts: 51 Rep Power: 7 Hi, I'm trying to implement a boundary conditions that links pressure to outflow using a differential equation (Windkessel) and therefore need to solve it. A simple 1st order backward Euler solver should be enough and, fortunately, one is available in OF. I've never added a new BC but I tried a take an existing one, use the outflow on the selected patch to calculate the pressure and export it. I was wondering : what it the best existing BC to start from ? Has anyone an example a the use of a solver in a BC function ? Best regards, Florian

 August 8, 2013, 13:19 #2 Senior Member     Mohsen KiaMansouri Join Date: Jan 2010 Location: CFD Lab Posts: 118 Rep Power: 9 Dear Hiroshiman The following pdf by Håkan Nilsson in Chalmers University is so helpful. How to implement a new boundary conditions: http://www.tfd.chalmers.se/~hani/kur...yCondition.pdf Also, take a look at his homepage for more tutorials: http://www.tfd.chalmers.se/~hani/index.html http://www.tfd.chalmers.se/~hani/kurser/OS_CFD_2009/ Hiroshiman and ScarFace like this. __________________ “If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.”

 August 8, 2013, 13:37 #3 Member   Join Date: Sep 2012 Posts: 51 Rep Power: 7 Hi Kia, thank you for the links. Actually I've already read the Chalmers guide for the programmation of BCs. Currently I'm using the codedFixedValue BC with a code that calculates p from phi on the outlet. I still have a few problems : how can I access the mean value of the pressure on the patch ? I'm able to do it for phi but not for p (surfaceField vs volume Field). Code: ```const surfaceScalarField& phi = db().lookupObject("phi"); const fvsPatchField& phip = patch().patchField(phi);``` I must solve something like : d(p-phi*R)/dt=f(p,phi) to impose p on the outlet, is it possible to use the ddt solver of openfoam ? I coded an Euler solver but I'd like to use a maximum of integrated functions... Regards, Florian ScarFace likes this.

 April 19, 2016, 05:58 #4 New Member   United Kingdom Join Date: Jun 2014 Posts: 12 Rep Power: 5 Hi, Hiroshiman, did you manage to get it to work? Here is how you can access pressure. Code: ```const scalarField& press = patch().lookupPatchField("pressure");``` Did you have to solve the ode at every internal iteration in a timestep? I am using resistance boundary conditions, where the pressure outlet is simply the product of a resistance value and the flowrate at the outlet. I have coded it with codedFixedValue but am not getting the same results as those I find in Fluent. Any pointers would be appreciated, Kind regards, Andreas

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Smaras FLUENT 2 February 19, 2013 07:58 SamCanuck FLUENT 2 August 31, 2011 11:34 hadikhayyamian ANSYS Meshing & Geometry 5 December 21, 2010 13:28 suitup OpenFOAM Running, Solving & CFD 0 January 20, 2010 08:45 youngan CFX 0 July 1, 2003 23:32

All times are GMT -4. The time now is 07:41.