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ID  Project  Category  View Status  Date Submitted  Last Update 

0001313  OpenFOAM  [All Projects] Bug  public  20140604 10:00  20150501 16:41 
Reporter  user676  Assigned To  
Priority  normal  Severity  major  Reproducibility  always 
Status  new  Resolution  open  
Platform  Linux  OS  Ubuntu  OS Version  10.04 
Product Version  
Fixed in Version  
Summary  0001313: Pressure Jump Correction. Actuator Disc Model and numerical wiggles  
Description  Hi all, I am working over the rotorDisk model implemented over OpenFoam and I have found a critical issue related to the SIMPLE algorithm. The issue is described in the next paper: http://orbit.dtu.dk/fedora/objects/o...190785/content Quote: Discrete body forces are used in the present context to model the influence of wind turbines on the flow. In order to overcome the pressure wiggles introduced by discre te body forces, one approach is to smooth out the body forces by using a Gaussi an distri bution instead of a Dirac delta distribution ] I found the problem when simulating the same configuration with TI=10% and TI=1% keeping turbulent length scale and wind speed. The TI=10% simulation matches theoretical quite well but TI=1% underpredict the wind speed in the rotor plane and power extraction is even 30 % lower than expected. Here it a picture of what happens. In the report, he modifies the RhieChow/SIMPLE pressure correction algorithm, but it is possible to overcome this issue by distributing the force around the cell. I think that the amplitude of the oscillation near the rotor plane is aleatory but could depend on TI, mesh discretization, schemes.... With a TI = 10%, that wiggle is still there but the amplitude of the oscillation is not so high so the error when calculating the angle of attack is not high. Best Regards  
Tags  fvOptions  
20140604 10:00



It may be solved using a different approach about how to include body forces into the momentum equation, similar to what it is already made in interFoam solver. It seems like including body forces directly over momemtum equation is not correct and could affect dramatically in the case of rotorDiskSource http://www.cfdonline.com/Forums/openfoamsolving/90435interpolationpressure.html#post315788 IMPORTANT: I am running all simulations with simpleFoam 

I second this. A small testcase can be found here https://drive.google.com/file/d/0BxalvZxvzSEaHdGbWJtYS1pc3M/edit?usp=sharing 

Thanks for the report. I have been considering calculating forces on faces, applying these directly in the pressure equation and using reconstruct in the momentum equation for some time. For some simple forces it is possible to construct them directly on the faces but for more complex forces e.g. involving grad, curl etc. it is only possible to construct in the cells and interpolate the values to the faces. However, the reconstruction will not guarantee that the integral over the cells is equal to the integral of the original cell values; i.e. no conservation of force, which might be an issue. Maybe some kind of integral correction could be applied to ensure conservation of force but I haven't looked into this in detail. Have you tested the idea of interpolating the force and using reconstruct? Is the force distribution improved and integrated force correct? 

I am investigating this in conjunction with http://www.openfoam.org/mantisbt/view.php?id=1363 [^] as the issues relate. The basic principles are simple but in this case a significant rewrite of fvOptions will be required for an elegant implementation. However, the simple interpolation/reconstuction approach proposed will not necessarily conserve the volume integrated force, which for some force models may be important/critical. This is why I have not implemented the approach yet. I am now working on a special interpolation/reconstuction combination which will conserve the integrated force. 

Thank you henry. I have not tested that idea. Is that idea the presented by Alberto here? http://www.cfdonline.com/Forums/openfoamsolving/90435interpolationpressure.html#post315788 I will be waiting for your conservative approach because I need it asap. It I can help you, please tell me. Best Regards Marcelino 
Date Modified  Username  Field  Change 

20140604 10:00 

New Issue  
20140604 10:00 

File Added: rotor_detail.PNG  
20140604 12:54 

Note Added: 0003100  
20140604 12:54 

Note Edited: 0003100  View Revisions 
20140604 15:43 

Note Edited: 0003100  View Revisions 
20140604 17:35 

Tag Attached: fvOptions  
20140606 14:17  linnemann  Note Added: 0003110  
20141221 10:42  henry  Note Added: 0003349  
20141229 11:36  henry  Note Added: 0003381  
20150108 11:51 

Note Added: 0003516 