Computation of broadband mixing noise from turbomachinery
Abstract
Broadband mixing noise is generated by a number of sources inside a turbomachine. The most important sources are the turbulent boundary layers (on the casing walls or on the blades), the turbulent free shear layers (separated flows) and turbulent wakes (from blades). High quality noise data are currently not available. A set of reliable near and far field mixing noise data from the free shear layers of a low speed jet was obtained. Work concentrated on broadband mixing noise theory on free shear flows. One began the theory by adopting the KappaEpsilon turbulence modelling equations as the basis. Although at this stage the formalism is the same yet a slightly different interpretation of the physical variables is needed. The averaging process is to be a volume average. On assuming there is a distinct separation of scales between the large turbulence structures and fine scale turbulence a closed set of governing equations can be derived in the usual way by using a volume average. The volume is to be small compared with the large turbulence structures but large compared to the fine scale turbulence. The semiempirical constants used in turbulence calculation will be adopted. The next stage of work is to develop ways of solving the time dependent equations and to determine the radiated noise intensity and spectrum.
 Publication:

Semiannual Progress Report
 Pub Date:
 August 1989
 Bibcode:
 1989fsu..rept.....T
 Keywords:

 Boundary Layer Separation;
 Broadband;
 Noise (Sound);
 Shear Layers;
 Turbomachinery;
 Turbulent Boundary Layer;
 Turbulent Wakes;
 Walls;
 Computation;
 Constants;
 Mixing;
 Rates (Per Time);
 Acoustics