@Rob, I tried to enabled the proximity function but then I found some non-conforming issue at the mesh around it. The thing is whenever I make the cad model in the spaceclaim i choose the share topology to none, if I choose the share topology to merge or share, the mesh becoming conforming but then one of the body becomes the non-sweepable and we cannot use the hex mesh for that part. I think hex mesh is quite stucture mesh I can get for my application. You can see fluid domain A and C are not conforming both have separate pattern for the meshing element.  In fact, I tried to match them by creating less number of division on the A side and they look as this below which is closest I can get. Later I tried to check the pressure contours it was just showing diffusion toward B side only there was no diffusion on A side.