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

[Dan Bower]

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).
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