Your title goes here Aeroacoustics Methodologies, Validations and Continuing Outlook Your subtitle goes here Fred Mendonça
Some Characteristic Flow Noise Issues Automotive external, sunroof buffeting, HVAC Aerospace airframe noise, jets, ECS
Industry and Expert Collaborations DESTINY Aeroacoustics Projects (2002-2005) German Auto manufacturers Aeroacoustics Working Group (2005-7 and 2009-11)» Daimler, BMW, Audi, VW, Porsche Acoustic partner collaborations» LMS through BEM codes SYSNOISE and V.Lab.Acoustics» FFT s FEA code, ACTRAN» ESI s SEA code, VA-One Aero-Vibroacoustics» External flow excitation, internal structural noise transmission» Internal flow excitation, external structural noise transmission» One of the originators in the field, Paul Bremner, expert advisor to CD-adapco LES for Acoustics, Cambridge University Press http://www.cambridge.org/us/catalogue/catalogue.asp?isbn=0521871441
Introduction CFD, with the correct physical models.» Is very capable of simulating the sources of aeroacoustic noise - Directly (LES) for applications in the low Reynolds number range - Indirectly (RANS) using broadband syntesization models» Also possible to propagate the noise STAR-CCM+ provides the software tools to extract the maximum value from the CFD process in Aeroacoustics CAE» Dedicated Training programme for Aeroacoustics CD-adapco sees as its responsibility to deliver the validated tools, with the best-practice advice; stating value and limitations
Aeroacoustics Overview: v6.04 and beyond Aeroacoustics Simulations Options Steady state Transient Broadband Correlations CURLE surface PROUDMAN volume GOLDSTEIN 2D-axi Synthesized Fluctuations SNGR LEE Lilley Export to Propagation codes LES DES Transient RANS Point and Surface FFTs Auto and Cross Spectra coherence and phase Mesh Frequency Cut-off FW-H Direct Export to ACTRAN / V.Lab.Acoustics / VA-One Direct Noise Propagation Direct Export to SEA for internal noise characterisation
Process Steady-state: Model Optimisation» Source Locations (Broadband correlations, Lilley, Curle, Proudman)» Mesh requirements (Mesh frequency cut-off estimator)» Assess time-step requirements Transient: Direct Source Capture» Advanced turbulence models» Advanced boundary conditions» Compressible solutions Direct Propagation (in STAR-CCM+) Propagation via coupling to:» SYSNOISE / V.Lab.Acoustics» FFT-ACTRAN» VA-One VibroAcoustics transmission via SEA, FEA 250 Hz 500 Hz 1000 Hz 2000 Hz
Steady-state: Broadband correlations for AAC sources Quadrupole-like sources re-synthesized from steady-state RANS result STAR 1 st commercial CFD code to introduce Lilley source visualisation (2000) Curle surface noise correlation Proudman volume correlation Locates maximum noise sources quickly Adds value for» Parametric design changes» Locates regions for mesh refinement» Locates regions for data output
Steady-state: Broadband correlations - Examples Surface (Curle) Volume (Proudman)
Steady-state: Mesh Frequency Cut-off Estimator Unique to STAR Estimates the resolvable frequency from steady-state results Informs user of CFD grid suitability early in the process E.g. Frequency of up to1000hz in mirror wake example
Transient capabilities LES-type turbulence model» DES (options of Spalart-Allmaras, k-ε, k-ωsst)» DES advection scheme blending» Full LES (wall resolved or unresolved) Advanced wall treatment» y+ insensitive Non-reflecting conditions for» Inflow and outflow boundaries Full Compressibility» Interaction between the flow and acoustics - Especially for cavity resonance Most efficient commercial transient solver» 2 nd order space and time discretisation Spectral Analysis» FFT at points and surfaces» Auto and Cross spectra coherence and phase» Frequency and Wave Number Fourier analysis
Validated Methodology Monitor point in mirror wake STAR Experiment Tail-off in predicted spectrum at mesh cut-off frequency of ~1000 Hz
Validated Methodology (bottom) Surface FFT (db) at 500Hz (top) and 1000Hz
Direct Propagation in STAR-CCM+ Mesh requirement» 20 cells per acoustic wavelength ( λ= c / f ) - In ambient conditions, you need cells of ~15mm to propagate a signal at 1000Hz - Domain size = 1000D, (~10 λ ) Non-reflective in/outflow boundaries
Propagation FW-H and 3 rd party code export STAR results capture the acoustic sources for propagation via» Ffowcs Williams-Hawkings (far-field propagation of compact sources without internal reflections) STAR offers coupling to 3 rd party propagation codes:» FFT, ACTRAN 100 Hz 500 Hz» LMS, Virtual.Lab.Acoustics» ESI, VA-One VibroAcoustics» Using FVS in STAR-CCM+» Export to SEA and FEA 3150 Hz Overall
Industrial examples with Validations Resonance Effects Slat / Cavity /Flap HVAC duct: Dipole Sources Fan Noise Side-view mirror: External Aero AIAA Aeroacoustics Benchmarks (2009)
Thank you Aeroacoustics Validated methodologies and Outlook