Impedance is an important issue in the design of acoustic lenses because mismatched impedance detrimental to real focusing applications. Here, we report two designs that focus waves water and air, respectively. They are tailored by meta-surfaces, which rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks constructed from coiling-up spaces layered structures air. Analytic analysis based on coupled-mode theory transfer matrix reveals...

A second-order topological insulator is designed on a platform of two-dimensional (2D) square lattice with all coupling coefficients having the same sign. Simulated results show existence two types nontrivial corner states in this system, one type being identified as bound continuum (BIC). The non-BIC are also found by surrounding sample trivial one, and interestingly, these perfectly confined can be gradually delocalized merge into edge tuning intersystem coefficient. Both BIC originate...

The leakage of sound waves in a resonance based rainbow trapping device prevents the wave being trapped specific location. In this study, we report design on coupled Helmholtz resonators, loaded to an air waveguide, which can effectively tackle issue. We show that resonators structure generate dips transmission spectrum by analytical model derived from Newton's second law and numerical analysis finite-element method. An effective medium theory is derived, shows cause negative bulk modulus...

Abstract We propose to achieve efficient emission of highly directional sound beams from multiple monopole sources embedded in a subwavelength enclosure. Without the enclosure, emitted fields have an indistinguishable or omnidirectional radiation directivity far fields. The strong formed presence enclosure is attributed interference under degenerate Mie resonances anisotropic property. Our numerical simulations demonstrate directed beam unidirectional bidirectional patterns, depending on how...

Industrially relevant computational fluid dynamics simulations frequently require vast resources that are only available to governments, wealthy corporations, and institutions. Thus, in many contexts realities, high-performance computing grids cloud on demand should be evaluated as viable alternatives conventional clusters. In this work, we present the analysis of time-to-solution cost an entropy stable collocated discontinuous Galerkin (SSDC) compressible framework Ibex, on-premises cluster...

In compressible computational fluid dynamics, the step size of explicit time integration schemes is often constrained by stability when high-order accurate spatial discretizations are used. We report a set new optimized Runge–Kutta for systems ordinary differential equations arising from discretization wave propagation problems with entropy stable collocated discontinuous Galerkin methods. The eigenvalues discrete operator advection equation and an isentropic vortex Euler various values...

Convection-diffusion-reaction equations are a class of second-order partial differential widely used to model phenomena involving the change concentration/population one or more substances/species distributed in space. Understanding and preserving their stability properties numerical simulation is crucial for accurate predictions, system analysis, decision-making. This work presents comprehensive framework constructing fully discrete Lyapunov-consistent discretizations any order...

View Video Presentation: https://doi.org/10.2514/6.2021-0633.vid In this work, we design a new set of optimized explicit Runge--Kutta schemes for the integration systems ordinary differential equations arising from spatial discretization wave propagation problems with entropy stable collocated discontinuous Galerkin methods. The optimization time is based on spectrum discrete operator advection equation. To demonstrate efficiency and accuracy compared to some widely used classic methods,...