[CIG-MC] computation of div/v in CitcomS

[Dan Bower]

OK - thanks Shijie.  In that case, I'll divide the output of
assemble_div_u() by the volume of each element to give me the divergence
for each element.

Thanks,

Dan


On Fri, Mar 8, 2013 at 3:13 PM, Shijie Zhong <shijie.zhong at colorado.edu>wrote:

>
> Eh did this change which I agree.
>
> In "temp += A[m][i] * A[m][i] / E->eco[m][i].area;",
>
> A[m][i] already had E->eco[m][i].area multiplied once, before
> global_div_norm2() call.
>
> Shijie
>
>
> Shijie Zhong, Professor
> Department of Physics
> University of Colorado at Boulder
> Boulder, CO 80309
> Tel: 303-735-5095; Fax: 303-492-7935
> Web: http://anquetil.colorado.edu/szhong
> ________________________________________
> From: cig-mc-bounces at geodynamics.org [cig-mc-bounces at geodynamics.org] On
> Behalf Of Dan Bower [dan at caltech.edu]
> Sent: Friday, March 08, 2013 3:06 PM
> To: cig-mc at geodynamics.org
> Subject: [CIG-MC] computation of div/v in CitcomS
>
> Hi CIG-MC,
>
> I don't understand global_div_norm2() in Global_operations.c in CitcomS.
>
> Why does the function divide by each element volume in the loop over caps
> and elements?
>
> temp += A[m][i] * A[m][i] / E->eco[m][i].area;
>
> Whereas, in other functions, such as global_p_norm2(), the expression is
> what I would expect:
>
> temp += P[m][i] * P[m][i] * E->eco[m][i].area;
>
> In both cases, the sums are divided by the mesh volume to give a
> volumetric average.  Presumably assemble_div_u() in Element_calculations.c
> is computing the divergence for each element?
>
> Thanks,
>
> Dan
>
>
>
> +2008-10-29 23:22  tan2
> +
> +       * lib/global_defs.h: (for r13196) Fixing convergence criterion for
> +         Stokes solver.
> +
> +         * New functions global_v_norm2(), global_p_norm2(),
> +         global_div_norm2() compute the L2 norm of velocity, pressure, and
> +         divergence. * The L2 norm of the vector f is defined as:
> +         \sum_{all elements} ( \int_{element} (f*f dA) ) / A where A is
> +         the volume of the domain. * The convergence criterion is
> +         controlled by parameter "accuracy" under
> +         "[CitcomS.solver.vsolver]". The iteration stops if
> +         (norm(div(rho*V))/norm(V) < accuracy) or ( (norm(dV)/norm(V) <
> +         accuracy) and (norm(dP)/norm(P) < accuracy) for the last two
> +         iterations ) * The default value of "accuracy" becomes 1e-4. *
> +         The input parameters "tole_compressibility" and
> +         "relative_err_accuracy" under "[CitcomS.solver.vsolver]" are
> +         gone. * The mass matrix E->MASS becomes double precision (was
> +         single precision).
> _______________________________________________
> CIG-MC mailing list
> CIG-MC at geodynamics.org
> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-mc
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://geodynamics.org/pipermail/cig-mc/attachments/20130309/445bc458/attachment.htm