Press Room -

	Aeroacoustic analysis in STAR-CD v3.15
	Significant general interest is currently being shown in the use of CFD methods to capture and thereby understand aeroacoustic phenomena, aimed ultimately towards noise suppression. This is important for many reasons - comfort, safety, avoiding component failure and meeting noise regulations - and is relevant to most industry sectors of which automotive, rail, aerospace and marine are typical examples. STAR-CD offers two methods for aeroacoustic noise predictions. The first is aimed at the capture of intrinsically broad-band turbulence-based shear noise quadrupoles, for which a synthesization approach is used. Secondly, time-accurate calculations are intended to directly capture the acoustic pressure fluctuations which arise from coherent oscillating flow structures or resonance. The synthesization approach uses turbulence field data from a steady-state simulation to approximate the turbulent shear-noise distribution in the flow field. Figures 1 and 2 show the aeroacoustic source around a surface-mounted side mirror and a wing flap. The noise synthesization method is a new feature released in STAR-CD V3.15.
	The second method uses long-standing capabilities of STAR-CD that have been extensively exercised, mostly for the prediction of coherent flow noise (sometimes referred to as dipole noise, resonance, buffeting or wind-throb). This is mainly caused by the interaction of the fluid (convection and pressure-wave combined effects) with surfaces to produce oscillations in the flow. We have demonstrated highly usable simulations using standard features in STAR-CD, namely a standard RANS turbulence model and a transient solver. Figures 3, 4 and 5 illustrate the acoustic behaviour of a deep cavity in an aircraft structure with a free-stream Mach Number of 0.85. In another example, the benefit of a wind deflector can be seen in the sound pressure level (SPL) plot against frequency. Figure 6 shows that the STAR-CD predictions demonstrate a suppression of acoustic tonal modes and a reduction of the overall decibel level for a sunroof buffeting application. An important consideration is that run-times for three-dimensional calculations are reasonable. Analyses comprising half a million cells typically take less than 100 hours on eight 400MHz parallel nodes to produce many oscillations which are fully limit-cycled. In conclusion, whether your noise problem is broad-band based or resonant, we believe that STAR-CD can help you find a solution.