Any Help is deeply appreciated
 

Any Help is deeply appreciated;

I have these

volSymmTensorField R;
volSymmTensorField P = - twoSymm(R & fvc::grad(U_));
volScalarField G = 0.5 * tr(P);
solve (R == 2*I/3 - G*(P+2*I)) ;

written in foam file.
but in compile I recieve following error:

"invalid use of void funcion"

it seems that "solve" does not work in this way.

what can I do to solve an "implicit algebraic matrix equation" like this(i.e. without div,grad,laplacian,... )?

URGENT NEED PLS!!!!!!!!!!!!!!
 

URGENT NEED PLS!!!!!!!!!!!!!!!!!!!

ISn't there any one to help me
 

ISn't there any one to help me!!!!!