Abstract
Bulk viscosity is an important factor in the damping properties of fluid systems and exhibits frequency dependent behaviour. A comparison between modal analysis in ANSYS Acoustics, custom code and experimental data is presented in this paper. The measured system consists of closed ended water-filled steel pipes of different lengths. The influence of a pipe wall, flanges on both ends and longitudinal waves in the structural part were included in measurement evaluation. Therefore, the obtained values of sound speed and bulk viscosity are parameters of the fluid. A numerical simulation was carried out only using fluid volume in a range of bulk viscosity. Damping characteristics in this range were compared to measured values. The results show a significant influence of sound speed and subsequently, the use of sound speed value regressed from experimental data yields a better fit between the measurement and the computation.
Highlights
Bulk viscosity is a parameter describing dissipation of energy in a fluid caused by compression and dilatation and can be defined as a resistance of fluid against change of volume
More information from studies focused on determination of bulk viscosity of different fluids is summarized in [2]
Acoustic simulation applied to a design of a muffler, design of a damper of pressure pulsations and modification of industrial fan after failure are described in mentioned references
Summary
Bulk viscosity is a parameter describing dissipation of energy in a fluid caused by compression and dilatation and can be defined as a resistance of fluid against change of volume. It is different from shear viscosity describing energy loss of flowing liquid. To degrees of freedom in mechanical solver the acoustic simulation solves degrees of freedom of acoustic pressure and velocity [7] Aim of this contribution is to discuss how commonly used acoustic analysis software treats bulk viscosity and compare simulation to experiment and theory used in evaluation process
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