F

=

αρQ(V2-V 1)

Where: F—— the resultant force acting on the isolator water body (including the dead weight of the water body, the water pressure on the cross section and the reaction force of the solid side wall), vector; ρ-fluid density; Q flow; V2-velocity of outflow section, vector; V1-velocity of inflow section, vector. α-momentum correction coefficient.

All parts of the surface of the isolated water body are affected by atmospheric pressure, and the atmospheric pressure in different directions is self-balanced (the resultant force of atmospheric pressure on the isolator is equal to zero), so this pressure is gauge pressure.