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of another system, especially a computer program designed for that purpose
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Automobile Shock Absorber
Analysis for Noise reduction
Noise due to flow through valve
In a shock absorber the fluid passes through the valves, which provides flow unsteadiness. This unsteadiness causes a harsh noise. Theoretical prediction of this noise was done using an accurate flow simulation of shock oil through the valves and then coupled simulation of flow along with acoustic simulation. This simulation result showed that prominent noise in the shock absorber is not created due to valve flow.
Noise due to structural resonance
Natural frequency analysis was conducted for all the components in the shock absorber. The natural frequencies were compared with experimental noise signature. It was found that none of the peaks in the noise signature occurred at any natural frequency, hence it was concluded that resonance of any of the shock absorber components is not the reason of observed noise.
Natural frequency analysis of piston &
base valve components
Experimental sound signature which was simulated
to determine the cause of noise
Conclusion
It was finally determined by experimental and analytical approach that noise is produced due to the formation of bubbles when the dissolved air in the shock oil gets separated. The other factors were found to be not contributing substantially in producing noise. Based on this analysis various options were suggested to the client to reduce the noise generated from the analyzed shock absorber.
Objective
The shock absorber produces noise during its operation. This phenomenon of noise produced in a shock absorber is an amalgamation of various physics research topics. The problem was to analyze these physical phenomena and identify the contribution of each of the phenomena in the noise and then reduce the noise produced by making design changes. These proposed design changes should be feasible and cost effective.
Oil flow path inside the piston valve of shock absorber
and CFD simulation of flow inside the piston valve
Background
Various phenomenon which were identified as the possible sources of noise are:
1) Noise due to fluid flow through the valves.
2) Noise due to fluid flow in the chambers.
3) Structural resonance.
These possible causes were analyzed in detail. Further, sound produced from one or more of these sources travels through various media to reach the human ear. The process of sound transmission was also analyzed to determine if there was a possibility of amplification during transmission.