1. Can a fluid which is accelerating down an inclined channel with constant acceleration still satisfy the continuity equation for a constant-density fluid? Since the acceleration will be down the slope, in the streamwise direction, then surely ∇⋅U > 0? 2. Assuming that continuity is satisfied above, then is the flow unsteady? I can't seem to agree with my textbook that it is, since I imagine if you used an accelerating reference frame (with acceleration equal to that of the accelerating fluid), then the flow would be steady. Am I misunderstanding something?