[vvqf]

volVectorField A = (a, b, c)
volVectorField U = (u, v, w)

a*Ñu + b*Ñv + c*Ñw

How to describe this expression in OpenFoam?

I express it as A*grad(U), grad(U) is then a tensor. Is that right?
I tried many ways to denote it in the codes, well, each time i got errors like "no match ..."

ps:
in OpenFoam,(U . Ñ)U is expressed as div(phi,U), phi = rho*U?

[vvqf]

original form:

a¶xu + b¶<font size="-1">xv + c¶xw</font>
a¶yu + b¶<font size="-1">yv + c¶yw</font>
a¶zu + b¶<font size="-1">zv + c¶zw</font>

Thanks a lot.

[eugene]

http://foam.sourceforge.net/doc/Guid...mmersGuide.pdf

Check section one for a general overview of OpenFOAM tensor algebra and notation. Very useful document IMO.

[vvqf]

Thank you so much.

I mixed * and &.

and operator calculation order is the written/appearing order, *, /, ect, do not have precedence to +, -.

[grtabor]

Yes - the one thing you can't redefine (or one of the things you can't redefine) in c++ is the order of precedence for the various binary operators. Its probably worth adding lots of brackets into your expressions to compensate for this.

Gavin