Turning moment

In fluid mechanics, it is customary to express the torque requirement in terms of a turning moment coefficient CM defined as... 

Fig. 4 shows a comparison between the experimental measurements of Sawatzki [53] and theoretical predictions for the turning moment coefficient, over a wide range of Reynolds numbers from 1 to 107. Eq. (26) for turbulent flow agrees with the data to within 4% for Re > 105. Eq. (19) for laminar flow agrees with the measurements of Sawatzki (53) and Bowden and Lord [7] to within 4 10% in the regime of... 

Fig. 4. Comparison between the theory and experimental data [53] for the turning moment coefficient.

This condition can be met by choosing either a RHSE of a sufficiently large radius, or by maintaining a high speed of rotation. From the results of the turning moment measurements shown in Fig. 4, one may take Re = 200 as the lower limit where the boundary layer approximation is valid. Thus the useful flow regime for electrochemical application is ... 

We consider a diatomic molecule the axis of which is at an angle 6 with respect to the electric field direction. The electric field Phas two effects a turning moment on the molecule, which we ignore here because it is presumably taken account of in the orientation polarization, and a stretching or compression of the H—Cl bond due to interaction of the field with the charge distribntion in the molecule. As the intemuclear distance r changes from the eqnilibrinm valne that it has in the absence of an applied electric... 

Precession— What happens when a turning moment (torque) is applied to a body with angular momentum. Instead of turning in the direction of the turning moment, the body s angular momentum will turn in a plane perpendicular to the one in which the turning moment acts. 

An important feature of the rotation of a rod-like particle is that the turning moment depends on its orientation relative to the direction of the shear field. The moment, and hence the angular velocity, is greatest when the particle is at 90° to the shear field and least when it is parallel to it [Figure 8.9(a)]. As the axial ratio increases, this variation of angular velocity with orientation increases dramatically until, although particles continue to rotate, they spend most of their time in a near-parallel orientation... 

In the parallel orientation the turning moment is zero, so one might expect rotation to cease. However, Brownian motion will ensure that from time to time the particle will rotate slightly and then be subjected to forces causing it to rotate further. 

Figure 8.9 Behaviour oj anisotropic particles in a shear field, (a) Rotation induced by a shear field the turning moment, and hence the angular velocity, is greatest when the major axis is at 90° to the field (lit).

If both cylinders have the same height A, the turning moment /x necessary to maintain continuous motion is given by... 

This formula can perhaps better be understood by referring to Fig. 2.3. A small effort at a long distance from the fulcrum can balance a large load at a short distance from the fulcrum. Thus a turning force or turning moment depends upon the distance from the fulcrum and the magnitude of the force. 

For a body to move in the direction of the force applied to it, the line of that force must pass through the centre of gravity of the body. If the line of the force does not pass through the body s centre of gravity, the force will apply a turning moment to the body. Two equal and opposite forces acting on a body will apply a turning couple. 

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