Impulse Propagation and Backscattering in Granular Beds
Surajit Sen Principal Investigator
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Name of PI: Surajit Sen, Dept. of Physics, State University of New York at Buffalo<br/>Proposal Number: 0070055<br/>Proposal Title: Impulse Propagation and Backscattering in Granular Beds<br/><br/>Project Abstract<br/><br/>Sound propagation in granular beds, such as in soil, has been studied for more than a century. However, little is known about the propagation impulses and of large amplitude, low frequency (less than 1 kHz) sound waves in granular beds. The propagation of impulses and of low frequency sound waves can only be described by taking into account the strongly nonlinear Hertzian forces, which make the grains repel nonlinearly upon intimate contact. The mathematical difficulties associated with such studies have hindered progress in studying impulse and low frequency wave propagation in granular beds. The proposed research will exploit recently developed theoretical advances and particle dynamics simulations to focus upon studying the dynamics of impulse and low frequency sound propagation in polydisperse granular assemblies. The possibility of exploiting backscattered impulses and low frequency acoustic waves to detect buried objects in granular beds will be addressed in this study. The effects of the presence of water in the inter-granular space on impulse propagation will also be analyzed. The studies will lead to the development of an algorithm to reconstruct a computer image of a buried object using surface based analyses of the backscattered acoustic impulses from such an object. An important application of the study will be for purposes of detecting buried antipersonnel landmines in nominally dry soils that are buried at depths of less than a foot in soil and kills nearly 2000 civilians each year.