Bernoulli Forces

Fluid flow across a valve spool generates forces which are caused by pressure drop and change of flow direction. These are named Bernoulli Forces.

Bernoulli Forces tend to close the valve and limit the controllable hydraulic power over the valve. This is mainly a limitation with direct operated valves because of the low spool driving forces available from solenoids or linear force motors. Bernoulli Forces are often a critical factor for proportional or servovalve performance in closed-loop control applications.

With Moog’s advanced spool design it is possible to partially compensate for Bernoulli Forces to increase the controllable hydraulic power across a spool valve. Moog uses highly sophisticated CAE tools to find optimum solutions for Bernoulli Force compensation in its direct drive spool valves. This means that Moog can often provide the required level of hydraulic power with a single stage direct drive valve where other companies need a two stage pilot operated valve, thereby saving the customer money and improving reliability.