# Accelerating Reference Frame

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

 July 1, 2014, 12:11 Accelerating Reference Frame #1 New Member   Jakob Join Date: May 2014 Posts: 2 Rep Power: 0 Hello everyone! my name is Jakob and this is my first thread in the forum. I have been working with OpenFOAM for a couple of months now and so far found the forum to be extremely help full! However I spend multiple days now searching through the forum and the internet to find a solution to my problem and was not able to find an answer to it: I would like to simulate the free fall of an object in a axisymmetric mesh (it is a wedge mesh). To minimize the mesh motion my idea was to use the 6-dof solver on the object with pimpleDymFoam and have an accelerating reference frame that moves with the object (for now the simulations didn't include the object yet but just show the moving reference frame), at an acceleration of g. My first thought to solve this issue was to just ramp the velocity at the inlet at a constant acceleration of g over my simulation time of 1.6 seconds. The velocity looks great: Here showing the velocity at time 0 and 1.5 seconds. Velocity_0_seconds.png Velocity_1.5_seconds.png However I ran into some issues with the pressure distribution. Namely the pressure should be constant in my whole domain (since the atmospheric pressure is constant), but in my simulations it decreases from the inlet to the outlet, as it can be seen in the picture. This pressure drop is constant over the 1.5 seconds: Pressure_0_seconds.png So here is my question: Could this be solved with different boundary conditions or is my approach just completely wrong? If it is wrong what would the solution be? Velocity BC: Code: ```#include "include/initialConditions" dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { //- Set patchGroups for constraint patches #include "\${WM_PROJECT_DIR}/etc/caseDicts/setConstraintTypes" inlet { type uniformFixedValue; uniformValue table ( (0 (0 0 0)) (1 (0 0 9.81)) (2 (0 0 19.62)) ); } outlet { type inletOutlet; inletValue uniform (0 0 0); } OuterWall { type slip; } front { type wedge; } back { type wedge; } }``` Pressure BC: Code: ```#include "include/initialConditions" dimensions [0 2 -2 0 0 0 0]; internalField uniform \$pressure; boundaryField { //- Set patchGroups for constraint patches #include "\${WM_PROJECT_DIR}/etc/caseDicts/setConstraintTypes" inlet { type zeroGradient; value \$internalField; } outlet { type fixedValue; value \$internalField; } OuterWall { type slip; } capsule { type zeroGradient; } front { type wedge; } back { type wedge; } }``` I hope I gave you all the information you need and was able to explain my problem in a somewhat understandable manner.... Thank you for your help! Jakob

 July 2, 2014, 18:25 #2 New Member   Jakob Join Date: May 2014 Posts: 2 Rep Power: 0 Does nobody have an idea? Is there any additional information I should supply?

 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 fu-ki-pa OpenFOAM 10 May 1, 2014 16:26 Attesz OpenFOAM Installation 45 January 13, 2012 13:38 skabilan OpenFOAM Installation 3 July 28, 2009 00:35 allenzhao OpenFOAM Installation 127 January 30, 2009 20:08 Bruno Main CFD Forum 1 January 30, 2007 01:34

All times are GMT -4. The time now is 03:21.