[edersonj1995]

Hello everyone,

I am fairly new to CFD and I am working on a simulation that has a rather unique geometry with no inlets or outlets. The only way to create flow inside this test loop to flow is through natural convection with a heat source and sink.

My goal with the initial velocity is to start the simulation as if the natural convection had already created a somewhat steady-state flow, meaning that the velocity would could not be described in a simple XYZ fashion. I have been trying to use swak4Foam to create a custom condition but have not had any success there. I am using OpenFOAM-v2012 and buoyantPimpleFoam to run these simulations.

Any help regarding using swak4Foam or any other method that can yield this initial U case would be very appreciated.

Thank you all for your time.

[sbaffini]

Originally Posted by edersonj1995

Hello everyone,

I am fairly new to CFD and I am working on a simulation that has a rather unique geometry with no inlets or outlets. The only way to create flow inside this test loop to flow is through natural convection with a heat source and sink.

My goal with the initial velocity is to start the simulation as if the natural convection had already created a somewhat steady-state flow, meaning that the velocity would could not be described in a simple XYZ fashion. I have been trying to use swak4Foam to create a custom condition but have not had any success there. I am using OpenFOAM-v2012 and buoyantPimpleFoam to run these simulations.

Any help regarding using swak4Foam or any other method that can yield this initial U case would be very appreciated.

Thank you all for your time.

Can't help on OF and related issues but, could you elaborate more? Because, as a matter of fact, actually solving the flow field is indeed one of your best shots at this, at least for general commercial solvers (I don't know if OF has specific issues with this kind of flows).

What, instead, you really need to account for in such flows is the fact that the system mass won't change, so your initial density specification will fix it (can't say if OF is broken on that in any way). So, if you use Boussinesq, your constant density will be it, otherwise the suggestion is to proceed with a transient, non constant density, calculation where the initial density field comes from your initial pressure and temperature (if that actually makes sense with any OF solver... hopefully it does).

[edersonj1995]

Thank you, that makes sense for what I should be calculating for. However, my biggest problem is implementing this calculated velocity/equation on the OF solver.

As far as the model itself, I unfortunately cannot go too in-depth on its geometry. Essentially the problem stems from the lack of inlets and outlets to drive flow and an initial condition velocity that is acting in many directions in different parts of the test loop simultaneously. I believe the only way to model this would be with a custom field where I can input these initial velocity conditions. My biggest problem is understanding if that is possible on OF and how I would implement this solution.

[sbaffini]

Ok, I now probably see better what your concern might be. In these problems the driving force must be thermal, of course.

You either have thermal bcs that will set some kind of motion (i.e., different walls at different temperatures) or some heat source/sink or, eventually, an initial temperarure distribution in case you are interested in its transient to equilibrium.

Excluding the latter case, you don't need to worry about initial conditions.

[LuckyTran]

It would of course be helpful to actually describe the issue!


funkySetFields and swap4Foam is obsolete. Does it even compile? in v2012? Probably not


Newer foam versions should be using setExprFields, which is setFields with expressions and conditions, which is exactly what funkySetFields allowed you to do before setExprFields became a built-in tool