<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
In addition to last question, when I went through the manual it seems <b>DiffuseFluxBased</b> implementation only works with
<b>PPM</b> implementation of the Hydro unit. How is this done for unsplit hydro solver?</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Thanks,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Nitish </div>
<div id="appendonsend"></div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> flash-users-bounces@flash.uchicago.edu <flash-users-bounces@flash.uchicago.edu> on behalf of Acharya, Nitish <nachary2@ur.rochester.edu><br>
<b>Sent:</b> Thursday, June 18, 2020 10:56 PM<br>
<b>To:</b> Klaus Weide <klaus@flash.uchicago.edu><br>
<b>Cc:</b> flash-users@flash.uchicago.edu <flash-users@flash.uchicago.edu><br>
<b>Subject:</b> Re: [FLASH-USERS] [EXTERNAL] Re: Adding viscous term in the momentum equation</font>
<div> </div>
</div>
<style type="text/css" style="display:none">
<!--
p
{margin-top:0;
margin-bottom:0}
-->
</style>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-size:11pt">Hi Klaus,</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<br>
</div>
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:11pt">Thank you so much for your reply. </span></div>
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<br>
</div>
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:11pt">Does this work for a multi-fluid problem as well? Can i specify separate viscosities to each of the materials?</span></div>
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<br>
</div>
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:11pt">Best,</span></div>
<div style="margin:0px; font-size:12pt; font-family:Calibri,Arial,Helvetica,sans-serif; color:black; background-color:rgb(255,255,255)">
<span style="margin:0px; font-size:11pt">Nitish</span></div>
</div>
<div id="x_appendonsend"></div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Klaus Weide <klaus@flash.uchicago.edu><br>
<b>Sent:</b> Thursday, June 18, 2020 12:36 PM<br>
<b>To:</b> Acharya, Nitish <nachary2@ur.rochester.edu><br>
<b>Cc:</b> flash-users@flash.uchicago.edu <flash-users@flash.uchicago.edu><br>
<b>Subject:</b> [EXTERNAL] Re: [FLASH-USERS] Adding viscous term in the momentum equation</font>
<div> </div>
</div>
<div class="x_BodyFragment"><font size="2"><span style="font-size:11pt">
<div class="x_PlainText">On Fri, 12 Jun 2020, Acharya, Nitish wrote:<br>
<br>
> I figured FLASH solves only the non-viscous Euler equations for <br>
> simulating HED experiments. I plan to solve a complete Navier Stokes <br>
> Equation for a Laserslab problem by explicitly defining a constant <br>
> viscosity coefficient for materials. From what I understand, I might <br>
> have to add a viscous term in the momentum equation and modify the hydro <br>
> unit in FLASH. How convenient is it to implement this? What should be <br>
> the general approach to add this extra term in the hydro solver? I would <br>
> really appreciate any sort of help here?<br>
<br>
As Rodrigo Fernandez already pointed out, you can use the "flux-based" <br>
part of the "Diffuse" unit for your purpose. You will need to include<br>
<br>
physics/Diffuse/DiffuseFluxBased<br>
<br>
in your configuration, as well as an implementation of the Viscosity unit, <br>
and set appropriate runtime parameters. Hopefully the User's Guide can <br>
help you further.<br>
<br>
Keep in mind that this is an explicit implementation; FLASH currently does <br>
not provide an implicit (or semi-implicit) solver for viscosity. So your <br>
time step may have to become significantly smaller than what you are used <br>
to.<br>
<br>
Klaus<br>
</div>
</span></font></div>
</div>
</body>
</html>