Acoustic Assessment of 3 Meter Radius Rotor with Whirl Tower Test and Analysis

Acoustic characterization of the indigenously designed 3 meter radius main rotor, which is designed for light weight helicopters, at hover conditions is performed by tests and analyses. Tests are conducted on the in house designed whirl tower, TWT (TAI Whirl Tower), at various rotational speeds and collective pitch settings. Effect of varying rotational speed and collective setting on cumulative rotor noise and sound power level (SPL) - frequency spectrum are measured with vertically oriented microphone array. Ffowcs Williams-Hawkings (FW-H) equations are solved with in-house developed acoustic tool and by commercial computational fluid dynamics (CFD) solver using the blade surface as noise source. CFD analysis tools were already validated with literature and whirl tower test data. Collected test data from whirl tower tests and analysis outputs are compared and dominant noise sources, acoustic evaluation varying with rpm and collective setting as well as total noise of the designed rotor are assessed. Following acoustic assessment of the designed rotor by analysis and whirl tower tests, the rotor is installed on the built unmanned rotorcraft prototype. Main motivation behind this study is to develop noise measurement, assessment and test capability for the existing whirl tower.