Throttle is the general term used for a physical flow resistance. Throttle is therefore the generic term for orifice and nozzle. Flow resistances with a largely linear dependence of the flow rate on the pressure difference (capillary tube) (Figure D 43) are often termed laminar throttles. Hydraulic resistances that occur in practice are often a mixture of an orifice, nozzle and laminar flow resistance (Figure D 44), i.e. apart from the pressure difference, the flow rate is also dependent to some extent on the viscosity of the pressure fluid.
Figure D 43: Laminar throttle
Figure D 44: Common throttle forms