PowerACOUSTICS: State-of-the-Art Flow-Induced Noise Analysis Simulation

SEEKING QUIET

Assessing wind and industrial noise pollution levels is becoming increasingly important to transportation manufacturers. Consumers demand quieter vehicles while government regulations demand reduced community noise.

 

Wind noise is consistently the number one consumer complaint, directly impacting consumer brand loyalty and vehicle sales. Reducing interior noise levels to achieve occupant comfort is therefore at the forefront of acoustic engineers’ concerns.

 

Additionally, with increasing air, rail and highway traffic, the amount of noise propagated into the community neighborhoods also has escalated. In order to remain customer competitive and compliant with government regulations, today’s manufacturers need to be able to assess their designs’ acoustic impact early in the development process.

 

SEEING & HEARING NOISE BEFORE IT HAPPENS: A CHALLENGE

Interior and far-field noise levels are typically not assessed until late in the development process when prototypes are built. This is often too late to make significant changes to the product design—requiring late stage design re-work or sound package upgrades such as thicker and/or laminated glass, adding significant cost and weight.

 

Acoustics engineers face numerous challenges: acoustic wind tunnel tests are expensive, flow visualization and noise source identification are difficult, and testing is not possible until physical prototypes are available. A numerical simulation approach is highly desirable for early design assessment. However, most available numerical solvers do not provide accurate prediction of complex transient turbulent flow, required for effective acoustic simulation. PowerFLOW’s unique transient and compressible flow solver technology allows engineers to simulate and visualize the flow-induced sources of noise and resulting transient pressure loading on the external surfaces.

 

PowerACOUSTICS® is Exa’s flagship aeroacoustics product, providing leading edge aeroacoustic analysis for flow-induced noise. PowerACOUSTICS, paired with PowerFLOW, enables accurate pressure fluctuation prediction, noise source identification, wind noise transmission to interior, propagation to the far-field, and sound package parameter study capabilities.

 

PowerACOUSTICS provides a complete, extensively validated, digital solution, enabling aeroacoustics and noise control engineers to efficiently collaborate to optimize the exterior shape and sound package design to meet noise targets.

 

PowerACOUSTICS BENEFITS

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ASSESS WIND NOISE PERFORMANCE THROUGHOUT DEVELOPMENT LIFECYCLEExterior wind-generated pressure load data from PowerFLOW is seamlessly combined with PowerACOUSTICS’ structural-acoustics and far-field propagation solvers to provide the wind noise contribution to the sound at the occupant’s or receiver’s location. The ability to simulate noise early in the product development workflow enables acoustic engineers to analyze and address wind noise issues throughout the development process.REDUCE DEPENDENCE ON PROTOTYPE WIND TUNNEL TESTINGPowerFLOW coupled with PowerACOUSTICS provides a digital aeroacoustic facility which is extremely cost effective relative to physical test and provides enhanced capability through detailed visual insight into how design features and changes impact the noise sources.RELIABLE, VALIDATED SOLUTIONExa’s well-recognized aeroacoustics technology team has extensively validated PowerACOUSTICS predictions against experimental data, and has developed best practices embedded in application templates for ease-of-use.LISTEN TO YOUR SIMULATIONSRapidly evaluate the impact on interior noise of various sound package configuration options to help meet wind noise targets—at minimized cost and weight.EXPLORE POTENTIAL SOUND PACKAGE COST & WEIGHT SAVINGSRapidly evaluate the impact on interior noise of various sound package configuration options to help meet wind noise targets—at minimized cost and weight.PROVIDES CONFIDENCE THAT PRODUCTS WILL PASS REGULATORY TESTSAssess noise performance against regulatory requirements to improve ability to design products that pass physical tests the first time.x

 

 

 

EASILY INTEGRATE AEROACOUSTICS SIMULATION INTO YOUR PRODUCT DEVELOPMENT PROCESS

PowerACOUSTICS seamlessly integrates into the workflow throughout the product development life cycle. PowerACOUSTICS is a modular application for aeroacoustic post-processing of simulation measurements from PowerFLOW. PowerACOUSTICS is comprised of three modules: a signal processing base module for acoustic analysis; a Noise Transmission Module – an optional module for interior noise prediction; and a Far Field Noise Module – an optional module for community noise prediction.

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Calculate Statistics and Spectra

Easily calculate single-point or two-point statistics and spectra: auto-correlation and auto-spectrum, cross-correlation and cross-spectrum, coherence functions and more

 

Fast Fourier Transforms

Selectable frequency resolution and time window functions

 

Advanced Capabilities for Flow-Induced Acoustic Visualization

Highlight sources of problematic frequencies. PowerACOUSTICS  includes ‘wavenumber filtering’ and time derivative calculations of pressure to provide enhanced visibility of the acoustic field, making it easier to assess and improve design related to the generation of acoustics.

 

Communicate your Results

Quickly and easily generate many types of technical graphs and/or choose to output to Exa PowerVIZ® for 3D visualizations

 

Synthesize Total Noise

Simulate complete vehicle interior noise, or complete far-field noise, including all sources. In addition to directly predicting the total wind noise contribution at a microphone location, other contributions can be directly included in order to easily plot and evaluate total SPL spectra and contribution by source.

 

Create Sound Files

With audio signal synthesis and SPL graphing, it is easy to generate sound files, convert spectra between different bandwidths and to calculate A-weighting or loudness in sones

 

Leverage your Hardware

Parallel computation for high performance

 

Enliven Presentations

With audio signal synthesis, spectrum conversion and sound quality metrics, accurate audio files may be added to presentations to enhance understanding and engineering collaboration

 

 

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Predict Interior Wind Noise

Fully embedded Statistical Energy Analysis [SEA] solver makes it easy to predict noise spectra at occupant’s head location generated by exterior wind pressure fluctuations. Fully integrated solution, complete with validated model templates.

 

Predict Total Wind Noise Contribution

PowerACOUSTICS’  Noise Transmission Module (NTM)  provides the option to include greenhouse and floor panels in the structural acoustics model of the vehicle, enabling prediction of the complete wind noise contribution to the overall noise heard at driver and passenger head locations.

 

Sound Package Parameter Studies

Allows acoustics engineers to rapidly set up glass and cabin properties for interior noise spectra

calculations—quantify the effect of changes to glass and interior absorption properties in seconds

 

Graph Interior Noise Spectra

Analyze panel contributions and variation of sound with microphone location

 

Reliable, Validated Solution

Based on extensive validation, PowerACOUSTICS’ users may confidently rely on results and proceed with design recommendations to reduce noise levels

 

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The cross plot (above,right) demonstrates excellent correlation of predicted interior wind noise from

PowerACOUSTICS versus experimental results for the 500 to 4000Hz octave bands from 30 test cases.

 

 

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Accurate Transient Flow Fluctuation Prediction

Leverage PowerFLOW’s proven accuracy for the prediction of aerodynamically induced noise: time-unsteady, very low dissipation, and the ability to handle complex detailed geometry.

 

Fully Coupled Far-Field Noise Solver

The fully-integrated Fowcs Williams and Hawkings (FW-H) based solver predicts time signals at receiver/microphone locations based on PowerFLOW transient simulations. Options for fly-over/pass-by vs. wind tunnel scenarios and solid vs. permeable configurations.

 

Simulate the Noise Rotating Parts Generate

PowerFLOW’s ability to simulate true rotating geometry coupled with the Far-Field Noise Module, provides an accurate solution for predicting fan and other rotating machinery noise propagation to the far field.

 

Noise Metrics and Digital Certification

The Far-Field Noise Module outputs time-domain pressure signals, to which any user specific post-processing can be applied.

 

Insight on Noise Source Locations

The Far-Field Noise Module provides a contribution analysis of the noise sources, highlighting the near-wall regions contributing the most to the far-field. Output far-field signals can be input to inverse methods such as beam forming or acoustic holography providing spatial noise source localizations.

 

 

 

 

References

PowerACOUSTICS Product Brief

 

The Physics Behind PowerFLOW

 

Technical Publications Highlighting the Exa PowerFLOW Suite

 

Acoustics Bibliography

 

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