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PITHIA

In-house developed BEM software package


Nowadays, engineers solve industrial problems using software packages mainly based on Finite Element Method (FEM). However, FEM faces serious difficulties in solving effectively multi-cracking fracture mechanics problems as well as large-scale problems dealing with infinite/semi-infinite domains, such as outdoor & underwater acoustics (e.g. infrasound, noise pollution), soil mechanics (e.g. earthquake waves, foundations, vibration isolation), radiation and scattering (e.g. radar, antennas), etc.

FEAC proposes PITHIA, an in-house developed simulation software package based on accelerated Boundary Element Method (BEM). It is well known in the scientific community that BEM is ideal for providing accurate and reliable solutions to the aforementioned engineering problems. PITHIA fills the gap among existing software packages and reinforces the simulation toolbox of engineers and scientists.

Wave scattering problems
  • Particle sizing
  • Ultrasonics
Fluid Structure Interaction
  • Underater Acoustics
  • Noise prediction
  • Vibroacoustics
Electromagnetics
  • Electrostatic fields
  • Magnetostatic fields
  • Maxwell equations
  • Ship signature
  • Corrosion protection

Case

Wind turbine noise and microseismicity modeling


Introduction:

Nowadays, it is common sense, that there is a vital need for increasing contribution of the renewable energy sources to the continuously growing world-wide electricity production, mainly due to the energy resources limitation and the climate change and air pollution because of carbon dioxide emissions.

Among the various renewable energy sources, wind energy has made a remarkable progress in the last 20 years. However, a significant factor restricting the installation of wind farms is the generated significant levels of low frequency noise and vibrations (miroseismicity). Noise is created by the vortices of the rotating blades and soil vibrations by the waves generated as seismic waves by the dynamic behaviour of turbine’s foundation. These waves can be either continuous due to wind loading in a frequency range of 1Hz-10Hz or transient created usually by a sudden braking of turbine’s rotor. Both, the emitted noise and microseismicity are propagated through the air and soil, respectively and can highly disturb the nearby residents, threatening their health.

The Project:

In the present project we investigate numerically how the acoustic and elastic waves generated by a wind turbine, are propagated through the air and soil, respectively and affect a nearby residence, taking into account in the analysis the fluid-soil-structure interaction (FSI) phenomenon.

The Solution:

The numerical simulation of those waves and their propagation in the surrounding soil can be accurately performed by PITHIA. PITHIA, is ideal for treating that kind of problems, since it takes automatically into account the radiation conditions of the problem and thus only the surfaces of the considered structures are needed to be discretized. Foundation and soil are considered as linearly elastic materials with interfacial bonding.

Furthermore, PITHIA is unique for solving that kind of problems, since it treats large scale models with more than one million Degree of Freedoms (DoFs) in conventional desktops by employing Adaptive Cross Approximation (ACA) and H-matrices techniques and perform fluid-soil-structure interaction analyses.

Model Sketch
Soil air interface
Wind turbine's foundation
Residence
Residence's internal air
Displacement (m) distribution for a frequency f = 2.3e-2 Hz
Sound Pressure Level (dB) for a frequency f=2.3e-2 Hz
Displacement (m) inside building for a frequency f=2.3e-2 Hz
Sound Pressure Level (dB) inside building for a frequency f=2.3e-2 Hz