Flow induced noise and vibration modelling in the transportation industry

Development of industrial numerical simulation packages for flow induced noise and vibrations in the transportation industry.

The proposed project concerns the scientific fields of fluid dynamics and acoustics and, in particular, deals with the numerical simulation of the interaction between these areas. Computational Fluid Dynamics (CFD) is well established for steady complex flows, but in the case of time-dependent real turbulent flows, CFD remains limited due to computer resources. Computational Acoustics (CA) for fluids at rest and predicting the vibro-acoustic behaviour between a structure and an acoustic fluid at rest is state-of-the-art in Noise and Vibration Computer Aided Engineering (CAE). However, when this fluid (and/or structure) starts to move, and when this flow shows unsteady low or high frequency phenomena, flow noise is generated. These time dependent flows play a crucial role in many industrial acoustical problems in fields such as aerospace, automotive, architecture and medicine and the standard FEM (Finite Element Method) / BEM (Boundary Element Method) acoustic software cannot cope with these problems. Exploratory research has already been carried out by LMS INTERNATIONAL in the ESPRIT project ALESSIA, with the main objective being the Application of Large Eddy Simulation (LES) to the Solution of Industrial Problems including flow-induced noise generation. Within ALESSIA, the CFD code CFX5 developed by AEA TECHNOLOGY has been coupled with SYSNOISE Rev5.5 to model flow-induced noise problems. The methodology used in ALESSIA is the Aero-acoustic Analogy methodology developed by LIGHTHILL and FFOWCS WILLIAMS- HAWKINGS, where Navier Stokes equations are rearranged to yield the wave operator with aero-acoustic sources on the right hand side that are the converted outcome of CFD simulation. Therefore, the noise due to the interaction of bodies with an unsteady flow can be considered as the sound emanating from distributed aero-acoustic sources radiating in a medium at rest. This is a very attractive point of view that replaces the resolution of a very complex aero-acoustic problem by the derivation of equivalent sources. Therefore, the LES model of CFX has first been used for the prediction of the flow; next the FEM/BEM approach of SYSNOISE rev5.5 has been used for the acoustic calculations. The crucial issues were the derivation of the acoustic sources from the flow data, and the interface between CFX code and SYSNOISE. When applied to academic test cases such as the prediction of flow-induced noise from free or ducted cylinders, the aero-acoustic analogy within CFX/SYSNOISE coupling has lead to good results. However, the accuracy of this methodology to handle realistic situations has not been proven yet. The first objective of the proposed work is to go beyond the academic research project ALESSIA and explore the applicability of the aero-acoustic analogy to industrial cases. Only low Mach number flows will be considered. Interfaces to major leading CFD codes such as Fluent and STAR-CD will be built. This task is necessary to achieve the CFD/SYSNOISE coupling and apply the methodology. A number of industrial test cases, ranging from wing mirrors to rotating fans, will be considered. These applications constitute a crucial task that will help us understand the physics of the problems and the flow-induced noise generation mechanisms in real life situations. Confrontations of the numerical results obtained from the CFD/SYSNOISE coupling with the measurements will help validate the methodology and identify its limits. The second objective of the proposed project is to extend and validate the aero-acoustic analogy methodology to include the broadband noise components in rotating machinery and to include the effects of flow-induced vibrations in the noise generation and noise propagation mechanisms in confined flows. For the latter extension, a new methodology will be developed, using a unique approach that first models the flow-structure interaction and then couples the CFD models with vibro-acoustic simulations. The approach will be evaluated for a comprehensive set of relevant test cases where flow-induced noise and vibration play an important role in the overall sound pressure level and the numerical results will be compared with the measurements. The final objective of the proposed project is to focus, in addition to the theory and the derivation of the relevant equations, on gaining an insight in the physics of flow-noise and the complex link between the flow unsteadiness and the noise generation in real-life applications: HVAC (Heating, Ventilation and Air Conditioning), fans, ducts, mufflers and exhaust systems, which are of utmost relevance for the transportation industry. Keywords: aero-acoustics, aerodynamics, vibration.
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Project Duration: 
Project costs: 
1 070 000.00€
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