Author : James Harold Stephenson
Publisher :
ISBN 13 :
Total Pages : 68 pages
Book Rating : 4.:/5 (794 download)
Book Synopsis Experimental Investigation of the Far-field Rotorcraft Wake Structure by : James Harold Stephenson
Download or read book Experimental Investigation of the Far-field Rotorcraft Wake Structure written by James Harold Stephenson and published by . This book was released on 2012 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: The tumbling tip vortex effect of a reduced-scale, 1 m diameter, four-bladed rotor during hover is studied using vortex methods, combined with a center of mass analysis approach. Measurements of all three components of the velocity field are acquired using a stereo PIV system synchronized to capture up to 500 degrees of vortex age, with 10 degree wake age offsets, during hover conditions. The nominal operating condition of the rotor is at a rotational rate of 1520RPM, corresponding to ReC = 248,000 with a chord length of 58.5mm. The rotor is operated with a pitch of 7.2± 0.5 degrees and a CT/sigma of 0.045. The far wake vortex tumbling phenomenon is captured and described. It is shown that tip vortices from two blades tumble through approximately 90 degrees of rotation before they coalesce. It is also seen that the constituent parent vortices do not combine to create a stronger daughter vortex as was previously thought to happen. Instead, the merged vortex has a lower large-radius circulation than either of its parent vortices. An accurate characterization and prediction of the trajectory of the far wake vortex tumbling can enhance the ability to predict and alleviate the resuspension of particles during brownout as well as provide a database for far wake validation of CFD codes.