Flow Simulations for Acoustic Applications

Numerical flow simulation in the field of aeroacoustics contribute a lot in early development phases to design a low-noise product. This helps with saving time and money.

Acoutic calculations deal with the sound formation, sound optimiziation and sound prevention.

The output of the simulation is the sound pressure level response on a desired receptor point. That signal is afterwards analyzed concering sound pressure level and frequencies. Through that the most important noise sources of the application can be identified and in consequence be optimized or prevented. If necessary it is possible to do on-site measurements  and to evaluate them in combination with the simulations.

bionic surface technologies has years of experience in different fields of application.

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Possible Simulation Methods

 

  • Aeroacoustics

Noise generation through inflows, boundary layers, vortex shedding
Main occurence in fans, rotors, barriers, channels, sound absorbers, clefts

  • Vibroacoustics

Noise generation through vibrations or stimulations with natural frequencies and their multiples

  • Underwater Acoustics

Noise generation through hydrodynamic stimulation

Possible Calculation Methods

Resolution of the acoustic pressure variation directly in the CFD simulation

Acoustic sources are taken from the CFD simulation
Analytic calculations of the sound propagation from the source to a desired reception point

Applications of Acoustic Simulations

Acoustic Simulations for Turbomachines

Flow through a low pressure turbine

Scope for Simulations

  • Fans
  • Enginges
  • Wind power plants
  • Blower
  • Compressor

Application: Simulation of a low-pressure turbine stage

  • Analysis of the noise emissions in the turbine
  • Resolution of the acoustic pressure variations
  • Examinations of the blade repetition rate and the broad band noise
  • Calculations with FW-H – acoustic analogy

Pressure variations in the wake of a low-pressure turbine stage

ISO-Q-Criterion

Acoustic Simulations for Vehicles

Scope for Simulations

  • Attachments like antenna, wing mirror, windshield wiper, roof girder, sun roof
  • Air conditioning and fans
  • Side window booming
  • Outlet noises
  • Interior acoustics
  • Engine flow
  • Total vehicle simulation

Applications: Simulation of the engine flow

  • Analysis of the noise sources in the engine flow
  • Total vehicle simulations
  • Calculation with CAA – direct acoustic

Acoustic Simulations for Lawn Mowers

  • Aeroacoustic analysis of the sound emitters and their optimization
  • Comparison of the measurements and development of a vitual blade and case test bench

The acoustic calculation is carried out with the calculation method FW-H acoustic analogy. The acoustic sources were taken from the CFD simulation and analytic calculations were carried out of the sound propagation from the source to the desired reception point (see scheme on the right side).

Output

  • BPF – Blade-Passing-Frequency
  • OASPL (Overall-Sound-Pressure-Level)
  • Broadband noise
  • SPL (Sound-Pressure-Level)

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