6.1 Principle of operation LDO F=rwd The resistance to the movement of the globule depends on its size and the viscosity of the fluid For small particles moving under streamline flow the relationship between these properties is expressed by stokes LawFs D ( )g 6 0 3    =  − Fr = 3 vd 6.1 Principle of operation • The resistance to the movement of the globule depends on its size and the viscosity of the fluid. For small particles moving under streamline flow the relationship between these properties is expressed by Stoke’s Law: