Peridynamic (PD) theories have become widespread in various research areas due to the ability of modeling discontinuity formation and evolution in materials. Bond-based peridynamics (BB-PD), notwithstanding some modeling limitations, is widely employed in numerical simulations due to its easy implementation combined with physical intuitiveness and stability. In this paper, we review and investigate several aspects of bond-based peridynamic models. We present a detailed description of peridynamics theory, applications, and numerical models. We display the employed BB-PD integral kernels together with their differences and commonalities; then we discuss some consequences of their mathematical structure. We critically analyze and comment on the kinematic role of nonlocality, the relation between kernel structure and material impenetrability, and the role of PD kernel nonlinearity in crack formation prediction. Finally, we propose and present the idea of extending BB-PD to fluids in the framework of fading memory material, drawing some perspectives for a deeper and more comprehensive understanding of the peridynamics in fluids.

Given the current practice to perform lean-premixed combustion to decrease NOx emissions, thermoacoustic instabilities have become one of the major drawbacks in gas turbine combustors. The necessity to control and limit such a deleterious phenomenon is mandatory to avoid structural damage of the burner. It has been demonstrated that perforated liners, if conveniently designed, can be very effective in reducing acoustic oscillations inside gas turbine combustors. Studying perforated plates traversed by bias flow can give a useful insight on sound absorption properties of liners, rather than investigate complex geometries. The present paper aims to carry out a numerically cost-effective, but reliable, CFD analysis to predict the acoustic impedance of perforated plates traversed by bias flow, and to grasp the details of the sound dissipation process. 2D axisymmetric simulations have been carried out and the governing equations solved by using the commercial code ANSYS Fluent®. Hypotheses, boundaries and operating conditions are described, focusing on the role of the Non-Reflecting-Boundary-Condition (NRBC) and the Transparent-Flow-Forcing condition (TFF) in treating acoustic waves. Numerical results are compared both with linear analytical models and experimental data from a case study, by proving a fast and reliable prediction of the acoustic response. Furthermore, effects of increasing bias flow temperature on the sound absorption property have been investigated, showing an increase in acoustic power losses as temperature rises. The proposed CFD model (2D-axisymmetric) proved to be a valid and versatile tool in evaluating the acoustic response of perforated plates under different operating conditions.