Propeller angular velocity

The simplest and most commonly used convection apparatus consists of a disc electrode rotating with a constant angular velocity u [1-5]. The disc sucks the solution toward its surface, much in the way a propeller would as the solution approaches the disc, it is swept away radially and tangentially (see Fig. 14.1). The transport of the reacting species to the disc occurs both by convection and diffusion. Though the mathematics are complicated, the rate of transport can be calculated exactly for an infinite disc. A particularly nice feature of this setup is the fact that the transport is uniform so that the surface concentration of any reacting species is constant over the surface of the electrode. 

Inferential meters include instruments in which the volumetric flow rate is inferred by the movement of a turbine, propeller, or impeller. The fluid impinging on a blade causes it to rotate at an angular velocity that is proportional to the flow rate. The early anemometers made with plates and cups are examples. These types of meters are becoming less and less common due to the need to calibrate and compensate for effects like viscosity. According to Crabtree (2009), the Coriolis and ultrasonic meters are replacing the turbine meters in most industrial applications. 

Fig. 7.6. Definition sketch for a propeiler-blade eiement [16]. Vr Velocity of fluid relative to propeller section. Fl Lift force normai to Vr. Fd- Drag force acting parallel to Vr. Vq Speed of airplane and propeller. Vj = ruj Tangential velocity resulting from propeller rotation, r Radiai position on propeller, cu Angular speed of propeller. 9 Angle between Vt and Vr. a and fS Angnlar measnres. Reproduced with permission from John Wiley Sons, Inc, 2006.

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