Measurements of Secondary Flows in a Rotating Duct

Abstract

The paper presents a review of analytical and experimental work which has been done on flows in rotating ducts. It presents the results of an experimental study to measure the secondary flows predicted by the previous analytical work. A duct of approximately 3 ft in length with a cross section of 2 × 5 in. was rotated up to speeds of 300 rpm. Air was used as the working fluid. Static pressures, total pressures, and yaw angles were measured at selected points along the channel. The flow regime examined was the developing flow from the entrance to the exit of the channel. Examination of the data revealed the presence of two longitudinal vortices which extended the length of the channel. Pressure distribution across the height of the channel and across the width of the channel was obtained. The magnitude of the cross-flow velocities in the channel were determined and mapped. It was found that the data for various rotational speeds could be collapsed upon a single curve by dividing all data by the rotational speeds. The results of the experimental study provide solid verification for the hypothesis of longitudinal vortices in rotating ducts.