Rotameters drag force

THEORY AND CALIBRATION OF ROTAMETERS. For a given flow rate, the equilibrium position of the float in a rotameter is established by a balance of three forces (1) the weight of the float, (2) the buoyant force of the fluid on the float, and (3) the drag force on the float Force 1 acts downward, and forces 2 and 3 act upward. For equilibrium... 

Diameter, m or ft D, of pipe of venturi throat Dj-, of rotameter float Dg, of orifice D, of rotameter tube Drag force, N or lb ... 

Correlations, dimensionless numbers, and regime maps have been developed for many of these applications. The Reynolds number was introduced in Chapter 5 to differentiate flow regimes in pipes—laminar versus transition versus turbulent. In Chapter 6, the notion of particle Reynolds number was mentioned with respect to drag force and rotameters. 

Fig. 12.15. Flow measurement with float (rotameter), a Conical flow pipe b float F gravity force Fe buoyancy force Fo- drag force [1].

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