Angular drag coefficient

In a recent work, Aiba (A2) studied the flow currents in water, in a mixing vessel 14 in. in diameter, using an axially-mounted two-bladed flat paddle 4.7 in. in diameter. Measurements were made both without baffles and with four baffles %2 tank diameter wide. A sphere about 6 mm. in diameter was suspended by a flexible wire, and its displacement from the equilibrium (no-flow) position was measured. To get the horizontal displacement, cobalt-60 was embedded in the sphere, and a Geiger-Mueller counter approximately 10 mm. in diameter was immersed in the tank 2-5 cm. from the sphere. The vertical movement of the sphere was measured with a cathetometer, and its angular position observed by eye. From the known components of displacement and the assumed drag coefficient of the sphere, values of the radial, tangential, and vertical components of the flow around the sphere were calculated. 

O or equivalently the drag coefficient becomes very large. (The noninertial limit typically corresponds to // 10 s.) In this limit the Maxwell-Boltzmann distribution for the angular velocities has set in so that orientation and angular velocity variables are decoupled from each other as far as the time behavior of the particle orientations is concerned. Thus on setting / = 0 in Eqs. (5.23)-(5.25), we have... 

The drag coefficient depends on the size of the bead. In the case of rods, the local flow field may not be uniform across the rod, which gives rise to moments on the object as well. Because the motion of a rod involves an additional angular acceleration, the computations are often more involved. 

Threat models define the fragment initial velocities relative to the point of detonation, masses, area coefficients, materials, drag coefficients, ricochet angles and distribution in angular bands along an axis of rotational symmetiy (Fig. 9.6). CASPER contains a database of predefined weapons that are based on arena fragmentation trials. There is also the facility to enter more threats to suit the particular operational scenario. 

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