Dear all, I am now trying to compute the channel flow using the Compressible Flow Solver. I have found the body force with derivatives non-trivial to add. Once the flow in a channel has reached a fully developed state, inertial forces in the channel, which are related to the mean favourable streamwise pressure gradient (pressure drop in a duct), are balanced with the wall friction forces. In this case, the body force f would be in the following form f=-tw/h, where tw is the wall friction containing velocity derivatives, h is the channel scale. Can anybody tell me how to perform this flow in Nektar? Thank you very much! Best Jian Yu
Dear Jian, We do a similar think for the body force in the incompressible flow case but using a fixed body force. In this case we typically fix the body force and then let the flow setting down to a steady state. Have you considered doing this? There are more complex ways to implement forcing terms and this has been done in the Incompressible Navier Stokes solver with a solver specific forcing term which can access the flow velocity. You would then have to look at the routines to evaluate the shear stress (for example in the FilterAeroForces.cpp) at the boundaries to get the shear stress. However this would still be a distributed value along the walls and so is not exactly a body force. Depending on what you want to achieve I would initially consider calculating it with a fixed body force. Cheers, Spencer. On 25 Sep 2015, at 01:43, Jian Yu <yuj@buaa.edu.cn<mailto:yuj@buaa.edu.cn>> wrote: Dear all, I am now trying to compute the channel flow using the Compressible Flow Solver. I have found the body force with derivatives non-trivial to add. Once the flow in a channel has reached a fully developed state, inertial forces in the channel, which are related to the mean favourable streamwise pressure gradient (pressure drop in a duct), are balanced with the wall friction forces. In this case, the body force f would be in the following form f=-tw/h, where tw is the wall friction containing velocity derivatives, h is the channel scale. Can anybody tell me how to perform this flow in Nektar? Thank you very much! Best Jian Yu _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> +44 (0) 20 759 45052
Dear Prof. Sherwin, Thank you for your response. I guess I would do this with a fixed body force. Where can I find the implementation of the fixed body force you mentioned? Or is there any more detailed information or example that I can follow ? Best Jian Yu -----原始邮件----- 发件人: "Sherwin, Spencer J" <s.sherwin@imperial.ac.uk> 发送时间: 2015年9月28日 星期一 收件人: "Jian Yu" <yuj@buaa.edu.cn> 抄送: nektar-users <nektar-users@imperial.ac.uk> 主题: Re: [Nektar-users] Adding Body force for the Channel flow Dear Jian, We do a similar think for the body force in the incompressible flow case but using a fixed body force. In this case we typically fix the body force and then let the flow setting down to a steady state. Have you considered doing this? There are more complex ways to implement forcing terms and this has been done in the Incompressible Navier Stokes solver with a solver specific forcing term which can access the flow velocity. You would then have to look at the routines to evaluate the shear stress (for example in the FilterAeroForces.cpp) at the boundaries to get the shear stress. However this would still be a distributed value along the walls and so is not exactly a body force. Depending on what you want to achieve I would initially consider calculating it with a fixed body force. Cheers, Spencer. On 25 Sep 2015, at 01:43, Jian Yu <yuj@buaa.edu.cn> wrote: Dear all, I am now trying to compute the channel flow using the Compressible Flow Solver. I have found the body force with derivatives non-trivial to add. Once the flow in a channel has reached a fully developed state, inertial forces in the channel, which are related to the mean favourable streamwise pressure gradient (pressure drop in a duct), are balanced with the wall friction forces. In this case, the body force f would be in the following form f=-tw/h, where tw is the wall friction containing velocity derivatives, h is the channel scale. Can anybody tell me how to perform this flow in Nektar? Thank you very much! Best Jian Yu _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk +44 (0) 20 759 45052
Hi Jian, I believe that in master (and the recently-released 4.2), the compressible solver has the support for generic forcing terms, including a body force. You can find an example of how this is enabled for a periodic channel flow in the incompressible solver here: solvers/IncNavierStokesSolver/Tests/ChanFlow_Standard_BodyForce.xml Note that, for the compressible solver, you are evolving the conserved variables so the derivation might be a little more convoluted. Cheers, Dave
On 6 Oct 2015, at 02:43, Jian Yu <yuj@buaa.edu.cn> wrote:
Dear Prof. Sherwin,
Thank you for your response. I guess I would do this with a fixed body force. Where can I find the implementation of the fixed body force you mentioned? Or is there any more detailed information or example that I can follow ?
Best
Jian Yu
-----原始邮件----- 发件人: "Sherwin, Spencer J" <s.sherwin@imperial.ac.uk> 发送时间: 2015年9月28日 星期一 收件人: "Jian Yu" <yuj@buaa.edu.cn> 抄送: nektar-users <nektar-users@imperial.ac.uk> 主题: Re: [Nektar-users] Adding Body force for the Channel flow
Dear Jian,
We do a similar think for the body force in the incompressible flow case but using a fixed body force. In this case we typically fix the body force and then let the flow setting down to a steady state. Have you considered doing this?
There are more complex ways to implement forcing terms and this has been done in the Incompressible Navier Stokes solver with a solver specific forcing term which can access the flow velocity. You would then have to look at the routines to evaluate the shear stress (for example in the FilterAeroForces.cpp) at the boundaries to get the shear stress. However this would still be a distributed value along the walls and so is not exactly a body force.
Depending on what you want to achieve I would initially consider calculating it with a fixed body force.
Cheers, Spencer.
On 25 Sep 2015, at 01:43, Jian Yu <yuj@buaa.edu.cn> wrote:
Dear all,
I am now trying to compute the channel flow using the Compressible Flow Solver. I have found the body force with derivatives non-trivial to add.
Once the flow in a channel has reached a fully developed state, inertial forces in the channel, which are related to the mean favourable streamwise pressure gradient (pressure drop in a duct), are balanced with the wall friction forces. In this case, the body force f would be in the following form
f=-tw/h, where tw is the wall friction containing velocity derivatives, h is the channel scale.
Can anybody tell me how to perform this flow in Nektar? Thank you very much!
Best
Jian Yu
_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ
s.sherwin@imperial.ac.uk +44 (0) 20 759 45052
_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
-- David Moxey (Research Associate) d.moxey@imperial.ac.uk | www.imperial.ac.uk/people/d.moxey Room 363, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK.
participants (3)
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David Moxey
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Jian Yu
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Sherwin, Spencer J