Problem description
The problem considers steady-state and transient wave propagation in a rectangular duct. Figure 1 shows the two-dimensional test mesh. There are two unconnected regions: the lower region has the tie constraints, and the simpler upper region is used for comparison.
The lower region is made up of five subregions, totaling 5000 mm long by 1000 mm wide. In Abaqus/Standard the first (leftmost) subregion consists of AC2D6 elements, the second of AC2D3 elements, the third of AC2D4 elements, the fourth (far right, upper) of AC2D4 elements, and the last of AC2D8 elements. The nodes on the intersecting surfaces do not coincide. The upper reference domain is 5000 mm long by 80 mm wide and consists of AC2D4 elements. In Abaqus/Explicit the AC2D4 and AC2D8 elements defined above are replaced by AC2D4R elements, and the AC2D6 elements are replaced with AC2D3 elements. Both domains are made of an acoustic material with a bulk modulus of 0.142 MPa and a density of 1.21 kg per cubic meter. The subregions of the lower domain are connected with tie constraints. In each tie constraint pair, the more refined surface is defined as the secondary surface.