Abstract:

ESDU 11005 introduces a computer program for estimating the noise from an isolated single rotating propeller in uniform motion or stationary in a lossless atmosphere without temperature gradients or wind. Thickness noise and noise due to tangential and axial loading are treated. The airflow need not be parallel to the propeller axis. The observer may be stationary or on the aircraft which may be climbing or descending. Noise due to non-linear effects arises at tip relative Mach numbers exceeding 0.9 but is neglected in the program. Input required includes the radial distributions of chord, thickness, blade angle, coordinates of the mid-chord line, relative Mach number, air angle, and the steady and unsteady drag and lift coefficients. If unsteady lift and drag coefficient distributions are not available, an option is provided to have the lift distribution calculated within the program using the method of ESDU 96027. The omission of the drag coefficient distribution is thought to have a negligible effect on the noise calculation in comparison with the lift coefficient distribution. There is an option to output results in either reception coordinates (based on the location of the propeller when the noise reaches the observer) or emission coordinates (based on its location when the noise was emitted). Details of the input and output format are illustrated by a worked example.