Viscoelastic material similitude for predicting underwater acoustic scattering performances

Underwater acoustic scattering experiments of full-size submarines entail considerable complexity and expense. Acoustic scattering similitude laws provide a practical means to extrapolate full-scale prototype properties from scaled-down models for laboratory testing. However, including viscoelastic materials, vital for enhancing acoustic stealth, introduces notable inaccuracies in the predicted outcomes based on existing similitude laws. This discrepancy stems from the frequency-dependent complex modulus of viscoelastic materials, leading to distorted material similitude. This study proposes a similitude concept, termed viscoelastic material similitude, to tackle this issue. We establish the conditions for achieving viscoelastic material similitude and explore two approaches for satisfying these conditions. Experimental data from references validate the effectiveness of both approaches. Moreover, we evaluate the impact of viscoelastic material similitude and distorted viscoelastic material similitude on underwater target strength similitude of simple shells and the Benchmark Target Strength Simulator II submarine coated with viscoelastic materials. Our findings demonstrate that viscoelastic material similitude significantly enhances the predictive accuracy of scaled models for underwater acoustic scattering performance compared to distorted viscoelastic material similitude.