The force on a boundary is similar to taking the integral of the solution variable “Pressure” over the boundary (although it is not calculated this way). Therefore the Reference Pressure does not directly affect the force calculation. However, if you change your boundary conditions to reflect a change in Reference Pressure then the pressure level in the domain may change and this will alter the force computed on a boundary. Hydrostatic contributions are included in the force since they are included in the variable “Pressure”. If you want to include the Reference Pressure in the forces, then you can set the Expert Parameter “include pref in forces = t”. The forces are then similar to the integral of the solution variable “Absolute Pressure” over the boundary. Note that forces calculations in CFX will generally also include viscous forces.