ff3d-users
[Top][All Lists]

## Re: [ff3d-users] Problem with setting Boundary condition

 From: Stephane Del Pino Subject: Re: [ff3d-users] Problem with setting Boundary condition Date: Sat, 17 Apr 2010 17:55:37 +0200 User-agent: KMail/1.12.4 (Linux/2.6.32-3-amd64; KDE/4.3.4; x86_64; ; )

```Le vendredi 16 avril 2010, Juzar Thingna a écrit :
>
> I want to set the derivative of w along the y-direction to be equal to wb
>  at ymin. I thought that setting dnu(w)=wb would do the trick, but
>  apparently I don't get the value of the slope at ymin = wb.
> Please could someone guide me as in where I'm going wrong?
>
> The foll is my geometry file:
>
> box {<0,7,0>,<20,37,20> pigment{color rgb <1,0,0>}}
>
> Regards,
> Juzar Thingna
> Center for Computation Science and Engineering
> National University of Singapore
>

Hello.

dnu(u) is not the normal derivative of "u" but the co-normal derivative as
described in remark 14 of the user documentation (p50).
so the co-normal derivative is :
dnu(w) = -L*dn(u)
where I noted here dn(u) to be the normal derivative. So, to get
dn(w)=wb
you need to specify
dnu(w) = -wb/L

This is quite tricky ... To really understand how to set dnu(w) you need to
understand variational formulas ...

Best regards,
Stéphane.

```

reply via email to