There are two discs in the pipe but not at the same time. You can consider conditions with X but without Y, then with Y and without X.
I am pretty sure that disc X will feel less force from fluid than disc Y does. I am looking for its reason.
Total pressures (static + dynamic) are the same for both conditions, because it's the same flow. In R1 area, dynamic pressure is low, but static is high. In R2 area, dynamic is high, but static is low, but in conclusion, total pressure is the same.
If total pressure is the same but force on X and Y is not the same, then how to justify this observation?
Does it mean that discs feel only dynamic pressure, not total? When I go for momentum equations, I find that disc Y must feel more force than X does since flow has higher velocity in R2 than in R1, which means higher momentum.
So, in this case, discs feel only dynamic pressure, I think.
What's your comment?