Sentence:  The actual change * * f caused by a shear field is calculated by multiplying the pressure differential times the volume , just as it is for any gravitational or <WSD>osmotic</WSD> pressure head . 
Meaning of the word marked with <WSD> tags:  (physical chemistry) the pressure exerted by a solution necessary to prevent osmosis into that solution when it is separated from the pure solvent by a semipermeable membrane