<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div><br></div><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><div><div style="display: block;"><div style="-webkit-user-select: all; -webkit-user-drag: element; display: inline-block;" class="apple-rich-link" draggable="true" role="link" data-url="https://www.mso.anu.edu.au/~chfeder/codes/turbgen/turbgen.html"><a style="border-radius:10px;font-family:-apple-system, Helvetica, Arial, sans-serif;display:block;-webkit-user-select:none;width:300px;user-select:none;-webkit-user-modify:read-only;user-modify:read-only;overflow:hidden;text-decoration:none;" class="lp-rich-link" rel="nofollow" href="https://www.mso.anu.edu.au/~chfeder/codes/turbgen/turbgen.html" dir="ltr" role="button" draggable="false" width="300"><table style="table-layout:fixed;border-collapse:collapse;width:300px;background-color:#E5E6E9;font-family:-apple-system, Helvetica, Arial, sans-serif;" class="lp-rich-link-emailBaseTable" cellpadding="0" cellspacing="0" border="0" width="300"><tbody><tr><td vertical-align="center"><table bgcolor="#E5E6E9" cellpadding="0" cellspacing="0" width="300" style="font-family:-apple-system, Helvetica, Arial, sans-serif;table-layout:fixed;background-color:rgba(229, 230, 233, 1);" class="lp-rich-link-captionBar"><tbody><tr><td style="padding:8px 0px 8px 0px;" class="lp-rich-link-captionBar-textStackItem"><div style="max-width:100%;margin:0px 16px 0px 16px;overflow:hidden;" class="lp-rich-link-captionBar-textStack"><div style="word-wrap:break-word;font-weight:500;font-size:12px;overflow:hidden;text-overflow:ellipsis;text-align:left;" class="lp-rich-link-captionBar-textStack-topCaption-leading"><a rel="nofollow" href="https://www.mso.anu.edu.au/~chfeder/codes/turbgen/turbgen.html" style="text-decoration: none" draggable="false"><font color="#272727" style="color: rgba(0, 0, 0, 0.847059);">Federrath - Codes</font></a></div><div style="word-wrap:break-word;font-weight:400;font-size:11px;overflow:hidden;text-overflow:ellipsis;text-align:left;" class="lp-rich-link-captionBar-textStack-bottomCaption-leading"><a rel="nofollow" href="https://www.mso.anu.edu.au/~chfeder/codes/turbgen/turbgen.html" style="text-decoration: none" draggable="false"><font color="#808080" style="color: rgba(0, 0, 0, 0.498039);">mso.anu.edu.au</font></a></div></div></td><td style="padding:6px 12px 6px 0px;" class="lp-rich-link-captionBar-rightIconItem" width="36"><a rel="nofollow" href="https://www.mso.anu.edu.au/~chfeder/codes/turbgen/turbgen.html" draggable="false"><img style="pointer-events:none !important;display:inline-block;width:36px;height:36px;border-radius:3px;" width="36" height="36" draggable="false" class="lp-rich-link-captionBar-rightIcon" alt="favicon.ico" src="cid:BD0484A3-9CB6-4620-A4CF-E2E9F39C2F3B"></a></td></tr></tbody></table></td></tr></tbody></table></a></div></div></div><div><br></div><div>Best regards,</div><div>Christoph</div><div><br></div><div style="font-variant-ligatures: normal; font-variant-east-asian: normal; font-variant-position: normal;"><span style="font-size: 11px;"><i>—</i></span></div><div style="font-variant-ligatures: normal; font-variant-east-asian: normal; font-variant-position: normal;"><div style="background-color: rgb(255, 255, 255); margin: 0px; line-break: after-white-space;"><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><div style="background-color: rgb(255, 255, 255); margin: 0px; line-break: after-white-space;"><span style="margin: 0px; font-size: 11px;"><i><font color="#696567">Research School of Astronomy & Astrophysics</font></i></span></div><div style="background-color: rgb(255, 255, 255); margin: 0px; line-break: after-white-space;"><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></div><div style="font-variant-ligatures: normal; font-variant-east-asian: normal; font-variant-position: normal;"><div style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><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></div></div><div><br><blockquote type="cite"><div>On 13 May 2024, at 10:08 PM, Alam Shadab TU Ilmenau <shadab.alam@tu-ilmenau.de> wrote:</div><br class="Apple-interchange-newline"><div><div id="divtagdefaultwrapper" dir="ltr" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-size: 12pt; font-family: Calibri, Helvetica, sans-serif;"><div style="margin-top: 0px; margin-bottom: 0px;">Hi,</div><div style="margin-top: 0px; margin-bottom: 0px;"><br></div><p style="margin-top: 0px; margin-bottom: 0px;"></p><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><div style="margin-top: 0px; margin-bottom: 0px;"><br></div><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></div><div style="margin-top: 0px; margin-bottom: 0px;">Could anyone please clarify this?<br></div><div style="margin-top: 0px; margin-bottom: 0px;"><br></div><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="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">_______________________________________________</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">flash-users mailing list</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><a href="mailto:flash-users@flash.rochester.edu" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">flash-users@flash.rochester.edu</a><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">For list info, including unsubscribe:</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><a href="https://flash.rochester.edu/mailman/listinfo/flash-users" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">https://flash.rochester.edu/mailman/listinfo/flash-users</a></div></blockquote></div><br></body></html>