Physical implementation of immersive boundary conditions in one dimension

Abstract

Immersive boundary conditions (IBCs) are a novel approach to target-oriented numerical wavefield modeling. When implemented physically, IBCs allow the construction of anechoic chambers that actively suppress the reflection of wavefields from the boundaries of a physical domain, such as a wave propagation laboratory. Moreover, IBCs can be used for immersive wave propagation experimentation by linking the wave propagation in the physical domain with the propagation in a virtual domain enclosing the physical domain. In this case, the IBCs correctly account for all wavefield interactions between the two domains. The physical implementation of IBCs is achieved by densely populating the boundary surrounding the physical domain with transducers that enforce the necessary boundary conditions. To estimate the signals that need to be emitted at the injection boundary, a second surface of transducers slightly inside the physical domain records the propagating wavefield. The recorded wavefield is extrapolated to the injection boundary by evaluating a Kirchhoff-Helmholtz integral in real-time using an FPGA-enabled data acquisition and control system. A recently constructed one-dimensional acoustic wave propagation laboratory provides an ideal setup for the physical installation of IBCs in one dimension. In this work, we demonstrate the implementation of IBCs on one side of this laboratory.