Experiments on swirling turbulent flows. I - Similarity in swirling flows

The effects of swirl on internal turbulent flows are studied by conducting experiments on turbulent pipe flow with variable initial swirl. This first part of the study is primarily concerned with similarity laws. The mean velocity profiles, both away from and close to the wall, are found to admit similarity representations at sufficiently large Reynolds numbers, provided that flow reversal does not take place near the entrance. While the wall law is not sensibly dependent on swirl, the velocity defect law in its extended form is sensitive to swirl. Further, a logarithmic skin-friction law is obtained in which only the additive coefficient depends on swirl. This coefficient is found to vary linearly with the swirl angle in the range of the present experiments

On the representation of the drag polar of a fighter aircraft

The values of lift coefficient encountered during manoeuvres13; of a fighter aircraft are known to be wel1 beyond the range where the classical representation CD = CDo + k ci is a good approximation. Examination of available test data on several configurations showed that the drag polars can be approximately represented as CD = CDo + k ci + a C with a suitable choice of a and n.13; A simpler representation with the value of n equal to 413; was carefully tested against detailed test data on two configurations for Mach numbers ranging from 0.5 to 1.5 and angles of attack from -4xB0; to 20xB0;. Agreement was generally better than 5% in transonic and supersonic range. The agreement was satisfactory in the subsonic range, although the departures were occasionally larger in magnitude. It is suggested that the representation with n = 4 can be advantageously used in the turn calculations of fighter aircrafts