<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style id="owaParaStyle" type="text/css">P {margin-top:0;margin-bottom:0;}</style>
</head>
<body ocsi="0" fpstyle="1">
<div style="direction: ltr; font-family: Tahoma; color: rgb(0, 0, 0); font-size: 13px;">
<div style=""> Hi,<br>
<br>
My objective is to write a primitive variable CFD solver based on SNES and TS. As a new user, I plan to start with the tutorial code snes/ex19.c by removing the temperature term. Then I can implement its equations and boundary conditions (BC) into the tutorial
code ts/ex7.c for pseudo-transient. Finally I can switch to primitive variables.
<br>
<br>
But I could not fully understand the BC setup in the tutorial codes and could not get a correct result by simply imitating the tutorial codes or my own attempts.
<br>
<br>
PETSc usually defines F as the function vector and X as solution vector. In snes/ex19.c, the BC are setup by manipulating arrays pointing to F and X, such as:<br>
<br>
f[j][i].u = x[j][i].u - lid; (line 297)<br>
<br>
in which x[j][i].u is initialized as zero by other function. Why it's here " - lid" rather than "+ lid"? How about if we use " f[j][i].u = - lid " or " x[j][i].u = - lid "? And in my test runs with a modified ts/ex7.c with equations and BC from snes/ex19.c
, only BC with " x[j][i] = some numerical value " can give a convergent result. <br>
<br>
<br>
I also found that in TS codes an initial condition at the boundary will overwrite the BC setup if they are of different values. Is this a bug?
<br>
<br>
I think TS is something like a structure, but I cannot find descriptions of its members like "step","ptime" and "v" in any document. To run a TS simulation successfully, does it require a NORM_2 of "v" converge?
<br>
<br>
<br>
Thank you very much.<br>
<br>
<br>
<br>
Best regards,<br>
<br>
Zhisong Li<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
</div>
</div>
</body>
</html>