Abstract
We propose a new direct coupling scheme based on the overset technique to tackle moving boundary problems within the lattice Boltzmann framework. The scheme is based on the interpolation of distribution functions rather than moments, that is, macroscopic variables, and includes an additional hypothesis ensuring mass and momentum conservation at the interface nodes between fixed and moving grids. The method is assessed considering four test cases and considering both the vortical and the acoustic fields. It is shown that the direct coupling method results are in very good agreement with reference results on a configuration without any moving subdomain. Moreover, it is demonstrated that the direct coupling method provides an improvement of the accuracy of the lattice Boltzmann overset algorithm for aeroacoustics. In particular, a convected vortex test case is studied and reveals that the direct coupling approach leads to a better ability to conserve the vortex structure over time, as well as a reduction in spurious acoustic distorsions at the fixed/moving interface.
Highlights
We propose a new direct coupling scheme based on the overset technique to tackle moving boundary problems within the lattice Boltzmann framework
We present a new direct coupling scheme based on the overset technique to tackle moving boundary problems within the lattice Boltzmann framework
It has been shown that the direct coupling method results compare very well with the original overset method results as well as the reference computation results
Summary
Fluid flows around rotating systems are nowadays found in numerous industrial applications, for example, fans, pumps, propellers, turbomachinery components, wind turbines, and blades. The ALE approach has been extended in several works to LB methods, see, for example, Meldi et al (2013) for the simulation of immersed moving solids in low-speed incompressible flows, or more recently Saadat and Karlin (2020) for LB compressible flow simulations on unstructured moving meshes In addition to this nonexhaustive list of methods, one can mention the so-called overset technique, on which the present paper is based. Even though the present work does not entirely address this issue in the sense that it still makes use of an overset framework, it is worth noting that one of the final aims of the direct coupling approach is to completely eliminate the existent overlapping area, thereby helping minimize the effort for parallelization as duplication of points would be prevented In this regard, the present work can be seen as a first step toward this objective by providing a tighter link between moving and fixed grids, as will be further detailed over Secs. IV presents a numerical validation of the direct coupling overset method with three aerodynamic test cases (an uniform flow, a Poiseuille flow, and an uniform flow past a rotating cylinder) and two aeroacoustic test cases (an acoustic pulse and a convected vortex)
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