Pressure-gradient

\[\dmompre{2}\]

src/fluid/predict/uy.c

  BEGIN
    src[cnt] -= 1. / HYXC(i  ) * (
#if NDIMS == 2
        - P(i  , j-1)
        + P(i  , j  )
#else
        - P(i  , j-1, k  )
        + P(i  , j  , k  )
#endif
    );
  END