Dear Prof. Sherwin,<div><br><div>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 ?</div><div><br></div><div>Best</div><div><br></div><div>Jian Yu<br><br><br><blockquote name="replyContent" style="padding-left:5px;margin-left:5px;border-left:#b6b6b6 2px solid;margin-right:0">-----原始邮件-----<br>
<b>发件人:</b> "Sherwin, Spencer J" &lt;s.sherwin@imperial.ac.uk&gt;<br>
<b>发送时间:</b> 2015年9月28日 星期一<br>
<b>收件人:</b> "Jian Yu" &lt;yuj@buaa.edu.cn&gt;<br>
<b>抄送:</b> nektar-users &lt;nektar-users@imperial.ac.uk&gt;<br>
<b>主题:</b> Re: [Nektar-users] Adding Body force for the Channel flow<br><br>




Dear Jian,
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<div>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?</div>
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<div>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.&nbsp;</div>
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<div>Depending on what you want to achieve I would initially consider calculating it with a fixed body force.</div>
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<div>Cheers,</div>
<div>Spencer.</div>
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<div>On 25 Sep 2015, at 01:43, Jian Yu &lt;<a href="mailto:yuj@buaa.edu.cn" target="_blank">yuj@buaa.edu.cn</a>&gt; wrote:</div>
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<div><span style="line-height: 1.2;">Dear all,</span></div>
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<div>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.</div>
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<div>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</div>
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<div>f=-tw/h, where tw is the wall friction containing velocity derivatives, h is the channel scale.</div>
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<div>Can anybody tell me how to perform this flow in Nektar? Thank you very much!</div>
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<div>Best</div>
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<div>Jian Yu</div>
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<div>Spencer &nbsp;Sherwin</div>
<div>McLaren Racing/Royal Academy of Engineering Research Chair,&nbsp;</div>
<div>Professor of Computational Fluid Mechanics,</div>
<div>Department of Aeronautics,</div>
<div>Imperial College London</div>
<div>South Kensington Campus</div>
<div>London SW7 2AZ</div>
<div><br>
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<div><a href="mailto:s.sherwin@imperial.ac.uk" target="_blank">s.sherwin@imperial.ac.uk</a></div>
<div>+44 (0) 20 759 45052</div>
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