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<p>Dear Prof. Federrath,</p>

<p><span>Thank you very much for providing <span>the reason for subtracting the bulk momentum</span>. At present, I have opted to maintain this term activated in my simulations. If it prove effective, excellent. However, if any issues arise, I will not hesitate

 to seek your help.</span></p>

<p><span><br>

</span></p>

I also thank you for sharing the link for your TurbGen code. I am sure it will be helpful. If I am not wrong, I believe it is the same code in 'StirFromFile' directory of Flash code.

<br>

</span></p>

<p><span><br>

</span></p>

In my simulations, ensuring a fixed and known energy supply rate is crucial. Could you provide insight into whether achieving this is feasible and, if so, what parameters would need to be controlled?

</span><span>Any guidance on this matter would be highly appreciated.</span> <br>

</span></p>

<p><span><br>

</span></p>

<p><span><br>

</span></p>

<p><span>Best regards,</span></p>

<p><span>Shadab<br>

</span></p>

<p><span><br>

</span></p>

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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Christoph Federrath <christoph.federrath@gmail.com><br>

<b>Sent:</b> Tuesday, May 14, 2024 4:50:32 AM<br>

<b>To:</b> Alam Shadab TU Ilmenau<br>

<b>Cc:</b> flash-users@flash.rochester.edu<br>

<b>Subject:</b> Re: [FLASH-USERS] Question regarding velocity update in Stir.F90</font>

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<div>Dear Shadab,</div>

<div><br>

</div>

<div>I implemented this. The reason for subtracting the bulk momentum is that we normally use continuous turbulence driving in periodic box simulations, such that the gas remains in the zero-momentum rest frame. It is usually a tiny correction, so switching

 this off mostly likely wouldn’t matter, but I chose to do it to make the momentum perfectly zero in x, y, z. If you have a different application in mind that would require you to keep the momentum, I’d be happy to chat further or make this a user parameter,

 for instance. Btw: the most recent TurbGen code is available here (which includes some extra features, such as automatic amplitude adjustment, etc.):</div>

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<div>Best regards,</div>

<div>Christoph</div>

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<div style=""><span style="font-size:11px"><i>—</i></span></div>

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<font color="#696567" style="font-size:11px"><b><i><span style="margin:0px"><span style="margin:0px"><span style="margin:0px">Professor </span></span></span>Christoph Federrath</i></b></font></div>

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<span style="margin:0px; font-size:11px"><i><font color="#696567">Research School of Astronomy & Astrophysics</font></i></span></div>

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<font color="#696567"><span style="margin:0px"><i><span style="font-size:11px; margin:0px">Australian National University, Canberra, ACT, Australia</span><br>

<span style="margin:0px; font-size:11px"><i>Tel: </i></span></i></span><a href="tel:+61-2-6125-0217" style="font-size:11px"><i>+61-2-6125-0217</i></a></font></div>

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<div><span style="font-size:11px"><i><font color="#696567">Web: <a href="https://www.mso.anu.edu.au/~chfeder">https://www.mso.anu.edu.au/~chfeder</a></font></i></span></div>

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<blockquote type="cite">

<div>On 13 May 2024, at 10:08 PM, Alam Shadab TU Ilmenau <shadab.alam@tu-ilmenau.de> wrote:</div>

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<div style="margin-top:0px; margin-bottom:0px">Hi,</div>

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<span>I have a query about why the 'momentum/mass' is subtracted during the velocity update in the forcing unit. Here's the snippet from Stir.F90 for reference.</span>

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<div style="margin-top:0px; margin-bottom:0px"><span id="cid:b6991838-bdab-48cb-aa19-8d0e87f6c5c6"><Screenshot from 2024-05-13 13-51-41.png></span><br>

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<div style="margin-top:0px; margin-bottom:0px">Could anyone please clarify this?<br>

</div>

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<div style="margin-top:0px; margin-bottom:0px">Best regards,</div>

<div style="margin-top:0px; margin-bottom:0px">Shadab<br>

</div>

</div>

<span style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:400; letter-spacing:normal; text-align:start; text-indent:0px; text-transform:none; white-space:normal; word-spacing:0px; text-decoration:none; float:none; display:inline!important">_______________________________________________</span><br style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:400; letter-spacing:normal; text-align:start; text-indent:0px; text-transform:none; white-space:normal; word-spacing:0px; text-decoration:none">

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