Abstract
This paper presents the development of a fourth-order finite difference computational aeroacoustics solver. The solver works with a structured multi-block grid domain strategy, and it has been parallelized efficiently by using an interface treatment based on the method of characteristics. More importantly, it extends the characteristic boundary condition developments of previous researchers by introducing a characteristic-based treatment at the multi-block interfaces. In addition, most characteristic methods do not satisfy Pfaff’s condition, which is a requirement for any mathematical relation to be valid. A mathematically-consistent and valid method is used in this work to derive the characteristic interface conditions. Furthermore, a robust and efficient approach for the matching of turbulence quantities at the multi-block interfaces is developed. Finally, the implementation of grid metric relations to minimise grid-induced errors has been adopted. The code was validated against a number of benchmark cases, which demonstrated its accuracy and robustness across a range of problem types.
Highlights
Aerodynamically-generated noise is an often undesirable by-product of unsteady fluid motion.From ground vehicles to commercial and military aircraft, unwanted aerodynamic noise generation imposes significant problems
The finite difference method allows the formulation of accurate high-order schemes relatively because the high-order accuracy can be maintained for complex geometries through the use of a curvilinear coordinate system
If the cells in the attached boundary layer are designed such that CDES ∆ < d, a local grid spacing will be used as the length scale rather than the standard SA Reynolds-averaged Navier–Stokes (RANS) length scale required in the boundary layer
Summary
Aerodynamically-generated noise is an often undesirable by-product of unsteady fluid motion. The emergence of computational aeroacoustics (CAA) as a viable research tool is a testament, to the proliferation of powerful computer resources, and the development and improvement of high-order accurate schemes, available in a variety of forms Both explicit and implicit finite difference spatial discretization schemes are widely used [3,4,5]. Characteristic boundary conditions for Navier–Stokes equations (NSCBC) are widely used, for example, in reacting flows and high temperature mixtures [11,12,13] Another important advantage of this method is that it can be used to efficiently parallelize the solver in multi-block domains because it avoids the excessive communication at multi-block interfaces required by other inter-block treatments, for example overlapping grids. The work presented here outlines the implementation of metric cancellation errors to extend the use of the CAA code to complex geometries with curvilinear grids
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