# MPPICInterFoam中的bug？

• 在ESI的版本中，MPPICInterFoam中的pEqn:

fvScalarMatrix p_rghEqn
(
fvm::laplacian(Dp, p_rgh)
==
fvc::ddt(alphac) + fvc::div(alphacf*phiHbyA)
);


其中的fvc::ddt(alphac)为0。 Jasak也表示：

Thus, if you try to evaluate the ddt the way it is written, it will recognise that the field does not have the oldTime() level stored and will use the current value to initialise it. Basically, fvc::ddt(magSqr(U)) will always give you zero, which is wrong.

是个bug？将fvc::ddt(alphac)去掉之后求解结果没变化。