DESIGN AND PRELIMINARY TESTS OF A BLADE TIP AIR MASS INJECTION SYSTEM FOR VORTEX MODIFICATION AND POSSIBLE NOISE REDUCTION ON A FULL-SCALE HELICOPTER ROTOR

摘要

Full-scale tests were conducted on the Langley helicopter rotor test facility as part of a study to evaluate the effectiveness of a turbulent blade tip air mass injection system in alleviating the impulsive noise (blade slap) caused by blade-vortex interaction. Although blade-slap conditions could not be induced during these tests, qualitative results from flow visualization studies using smoke showed that the differential velocity between the jet veloc¬ity and the rotor tip speed was a primary parameter controlling the vortex modification.