Figure 8. Smoke flow around the scale football model showing: (a) laminar flow at Re=90,000; and (b) turbulent flow at Re=130,000.
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The drag forces measured during the spinning ball tests were used to examine the effect of spin on drag. The problem with these data was that the side supports were found to have a significant effect on the drag measured on the complete ball-support arrangement. The measurements of drag force with zero spin were compared with data from the experiments that used a rear mounted sting (see earlier section) to calculate the effect of the tare drag, due to the side supports. When all the data were adjusted for tare, there was found to be very little effect on the drag coefficient due to spin and the relationship was found to be very similar to that shown in Figure 6, for all values of spin parameter.