Aero-Acoustic Projects
pioneerSOLUTIONS has developed an aero-acoustic approach for accurately predicting the noise level generated by HVAC blowers, axial fans or other rotating devices. It is based on a two steps procedure. In the first 
step, an unsteady flow is computed by a precise CFD solver, e.g. AcuSolve™. This first step serves to predict aerodynamic sources of noise. In the second step, an acoustic computation is performed using Actran/LA™. The variational formulation of Lighthill’s analogy, extended to allow handling control surfaces, is used. This is a key ingredient for treating blower problems as precise as possible.
So why are two steps necessary? Although the acoustic field is truly based on compressible waves, the unsteady flow patterns, i.e., the acoustic source terms, can be adequately represented by a pseudo-compressible flow solution. The acoustic wave propagation predicted by most Navier-Stokes flow solvers (including the solutions obtained here) are not sufficiently accurate to directly predict sound pressure level at a distance, therefore the “noise” must be propagated by an auxiliary method. In other words, the flow solution predicts the source terms, but not sound propagation, well enough.
Using different solvers for the two steps requires data exchange between the products; for accurate results the transfer “losses” need to be minimized. Together with our partners, Pioneer has developed a highly accurate solution. Experimental validations performed by our customers have demonstrated the reliability of this method.
