Acoustic submodeling

The submodeling capability is applied to an acoustic model of a duct. The global model is represented by either 20 linear elements or 10 quadratic elements along the lengthwise direction of the duct. An absorbing boundary condition is applied at one end of the duct; loads are applied to the other end. The submodel models the part of the duct close to the absorbing end and has a finer mesh than the global model. The driven nodes of the submodel lie along the global model element boundaries. Two-dimensional, three-dimensional, and axisymmetric models are tested for the driven nodes' acoustic pressure; the direct solution steady-state dynamic and direct-integration implicit dynamic procedures are used in Abaqus/Standard, and the explicit dynamic procedure is used in Abaqus/Explicit. The transient simulations are performed for period of time long enough to allow the wave to propagate past the end of the duct. Each element type used in the global model can be tested against each other element type of similar dimensionality in the submodel.