Hi, To give a precision, the variable coefficient only generate an error computing the diffusion term (u''(x)). In contrast, tests made with an X dependent coordinate coefficient on convection term and u(x) term gave a very powerful precision. Thus, the error can't be attributed to previous definitions in the code.
// ----------------------------------------------------------------------- // Taking the equation : x * u''(x) = 1 between [0.5 ; 1.0] with u[0.5] = 0.5 and u[1.0] = 1.0, we would expect a value of 0.88045 at the point 0.900391 but we obtain 0.900391. The corresponding code is : Ke(i,j) += JxW[qp]*(dphi[i][qp]*dphi[j][qp])*(-q_point[qp](0)); Fe(i) += JxW[qp]*phi[i][qp]*1.0; The correct result could be obtained computing " u''(x) = 1/x ", making disappear the variable coefficient on the diffusion term. The corresponding code is : Ke(i,j) += JxW[qp]*(dphi[i][qp]*dphi[j][qp])*(-1.0); Fe(i) += JxW[qp]*phi[i][qp]*1.0*q_point[qp](0); However this kind of solution is only available in an 1D equation. // ----------------------------------------------------------------------- // These results are obtained with the linear system presented in example 0. Furthermore, the problem only occurs with a non-constant diffusion term coefficient. Ideas and comments welcome, Best regards, Maxime ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
