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Fan is generally used for cooling of alternator and an undesirable side effect of these fans is generation of flow induced noise. With stricter regulations and growing importance on acoustic comfort in present day market, it's very important to address flow induced noise problems early in product development stage. With physical testing, it would not be possible to get information on source strengths thus, limiting its usage. Whereas simulation on the other hand would be able to provide source strengths, directivity pattern and source ranking. This paper focuses on numerical simulation of alternator's fan for prediction of air- borne noise. For this purpose, Computational Fluid Dynamics (CFD) based transient analysis is performed with high fidelity turbulence model using commercial software package, ANSYS Fluent. Ffowcs Williams and Hawkings (FW-H) model is used for modeling sound propagation. Overall sound pressure level for fan (source) is calculated at various receiver locations.

In the present scenario wherein the cost of fuel is ever increasing, maximizing fuel efficiency of a vehicle is one of the prime areas of focus for all the OEM's. Aerodynamic drag forms a prominent portion of the resistive forces acting on a moving car. In the early design phase, engineers are interested to get insight into the flow field around the vehicle so as to take informed design decisions. It would be difficult to build different designs and physically test them. Thus it becomes necessary for all the OEM's to use simulation to predict resistive forces and also to develop a robust simulation procedure which would help them to predict with confidence. Reynolds Averaged Navier Stokes Equation (RANS) method is used to simulate external Aerodynamics, which is a steady state simulation methodology. The use of Large Eddy Simulation (LES) to model transient simulation is not feasible for production purpose because of huge mesh especially near the walls.