Fluid-structure interaction effects for minimizing transmission in waveguides: Time and frequency domain approach

In many noise and vibration control applications, transmission loss in waveguides needs to be maximized. We propose a waveguide comprising of two different fluids with large impedance mismatch. The two dissimilar fluids are separated by two identical spring-mass combinations. An analytical model for such waveguide is undertaken using principles of one-dimensional linear wave propagation theory. Transmission loss for the waveguide across the frequency range is formulated in terms of (i) impedance mismatch of the fluids (ii) fluid-structure interaction parameter. It is shown that an appropriate choice of the above two parameters leads to a minimal transmission across the frequency range. The above inference is also corroborated through transient Finite Element Analysis. For transient simulation an initial condition is imposed on the system and the simulation is carried on till the first transmission is observed. The ratio of the maximum response in the transmitted pulse to the maximum response in the incident pulse is defined as the transmission ratio in time domain. It is observed that the transmission ratio computed in time domain correlate well with the transmission ratio formulated in the frequency domain.