Global Journal of Researches in Engineering, I: Numerical Methods, Volume 23 Issue 1

Figure 8: Sensitivity of thermal shape factor ' on the 1st and 2nd high-frequency reflected waves at an excitation frequency of 50 kHz Based on the results presented in Table 1 and Figures 3-8, we can classify the sensitivity of each parameter on the reflected signal in the order of decreasing influence as presented in Table 2. Table 1: Relative variation of the reflection coefficient ∆R R % corresponding to a variation of ± 20% of each physical parameter © 2023 Global Journals Global Journal of Researches in Engineering Volume XxXIII Issue I Version I 41 Year 2023 ( ) I Investigating the Effects of Physical Parameters on First and Second Reflected Waves in Air-Saturated Porous Media under Low-Frequency Ultrasound Excitation ∆ % 1st reflected wave 2nd reflected wave Parameters Variations 50 kHz 120 kHz 50 kHz 120 kHz Porosity ϕ +20% -66.84 -68.88 -65.06 -67.66 -20% 80.26 82.30 71.32 74.12 Tortuosity α ∞ +20% 33.16 34.02 10.82 5.82 -20% -40.98 -42.10 -27.47 -24.77 Viscous characteristic length Λ ( μ m) +20% -1.07 -0.61 42.76 58.54 -20% 1.77 0.93 -44.86 -52.95 Ratio thermal-viscous characteristic lengths ( Λ ’/ Λ ) +20% 0.17 0.11 3.29 4.63 -20% -0.26 -0.16 -4.89 -6.57 Viscous shape factor ξ +20% 0.10 0.19 -11.91 -12.16 -20% -0.97 -0.18 13.56 13.88 Ratio viscous-thermal shape factors ξ / ξ ’ +20% 0.16 0.25 0.35 0.34 -20% -0.25 -0.38 -0.52 -0.51