计算报错: incompatible dimensions

OpenFOAM
1 
--> FOAM FATAL ERROR: 
incompatible dimensions for operation 
    [U[0 1 -2 0 0 0 0] ] - [U[-1 -1 -1 0 0 0 0] ]

    From function checkMethod(const fvMatrix<Type>&, const fvMatrix<Type>&)
    in file /home/zay/foam/foam-extend-3.1/src/finiteVolume/lnInclude/fvMatrix.C at line 1292.

FOAM aborting
2

不清楚你这个是在什么条件下产生的？