# Flow over a heated flat plate: non-physical solution

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 May 4, 2018, 23:43 Flow over a heated flat plate: non-physical solution #1 New Member   Sushobhan Sen Join Date: May 2018 Posts: 1 Rep Power: 0 Hello everyone, I've been using OpenFOAM for some months now and am fairly confident with the isothermal solver simpleFoam. Now, I'm trying to use buoyantBoussinesqSimpleFoam to solve a temperature field with the Boussinesq approximation, and I've seem to hit a dead end. I looked around the forum and Googled it, but I could not find an answer to this problem (most examples with the solver, including OpenFOAM's tutorial, are related to natural convection). Here is what I am trying to do: I have air flowing over a heated horizontal plate of length L = 1.0 m (solving a 2D problem). The value of Re_L was set to 3000 to make the flow turbulent. I set the height of the domain to 5*L i.e., the top far-field boundary is "far away". So I have these faces: an inlet, and outlet, the heated plated, the top atmosphere at 5*L (symmetry), and also the empty faces on the sides for 2D simulation. I created a structured mesh with a finer mesh size near the plate using Gmsh and imported that into an OpenFOAM case. It passes all the checkMesh checks. Here's what should happen: The air flows in at 0.03 m/s and 300 K from the inlet and, due to the noSlip condition and 310 K fixed temperature at the plate, develops a boundary layer for both velocity and temperature, whose thickness should grow over the length of the plate. Here's what is happening: I am using a realizable k-eps model for turbulence with wall functions applied at the plate. When I solve the case with just simpleFoam (i.e., only for the velocity and pressure fields), I get a very good solution in about 300 iterations (convergence set to 1e-6). However, when I use buoyantBoussinesqSimpleFoam, with the same 0/ files for U, k, epslion, and nut and adding files in 0/ for T and alphat (I use the same conditions for p_rgh as for p), I get a terrible solution after as much as 6000 iterations (20x the number as with simpleFoam). My velocity accelerates to non-physical values (something like 100x the boundary condition!), and p_rgh and temperature also increase non-physically, and at positions in the domain where nothing should be happening i.e., near the far-field boundary. Interestingly enough, if I set either g or beta to zero, the solutions looks fine, although obviously it is missing some of the physics. I was mostly following the settings from the hotRoom tutorial, so I'm surprised the solution is so poor despite the simpleFoam solution working very well! I've tried a finer mesh, lowering Re_L into the laminar range, and using the converged simpleFoam solution for U and p as my initial conditions for the buoyant flow problem - same problem every single time. Could anyone help me figure out what I am doing wrong? I've uploaded my case file here if you'd like to see - just run either simpleFoam or buoyantBoussinesqSimpleFoam. The names of the walls are pretty self-explanatory as well. I am using OpenFOAM-4.0. Thank you! samik108 likes this.

 Tags buoyancy force

 Thread Tools Search this Thread Search this Thread: Advanced Search 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 Off Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Bin STAR-CCM+ 19 June 26, 2017 11:03 Bin STAR-CCM+ 0 November 13, 2015 03:23 mb.pejvak Main CFD Forum 13 December 2, 2013 00:13 mb.pejvak Main CFD Forum 0 September 12, 2012 21:25 sarat FLUENT 4 September 9, 2005 18:35

All times are GMT -4. The time now is 01:00.

 Contact Us - CFD Online - Privacy Statement - Top