GPU-Native Adaptive Mesh Refinement with Application to Lattice Boltzmann Simulations

The Lattice Boltzmann Method (LBM) has garnered significant interest in General-Purpose Graphics Processing Unit (GPGPU) programming for computational fluid dynamics due to its straightforward GPU parallelization and could benefit greatly from Adaptive Mesh Refinement (AMR). AMR can assist in efficiently resolving flows with regions of interest requiring a high degree of resolution. An AMR scheme that could manage a computational mesh entirely on the GPU without intermediate data transfers to/from the host device would provide a substantial speedup to GPU-accelerated solvers, however, implementations commonly employ CPU/hybrid frameworks instead, due to lack of a recursive data structure. A block-based GPU-native algorithm will be presented for AMR in the context of GPGPU programming and implemented in an open-source C++ code. The meshing code is equipped with a Lattice Boltzmann solver for assessing performance. Different AMR approaches and consequences in implementation are considered before careful selection of data structures enabling efficient refinement and coarsening compatible with single instruction multiple data architecture is detailed. Inter-level communication is achieved by tricubic interpolation and standard spatial averaging. Although the present open-source implementation is tailored for LBM simulations, the outlined grid refinement procedure is compatible with solvers for cell-centered block-structured grids. Link to repository: https://github.com/KhodrJ/AGALComment: 30 pages, 16 figure

LOW REYNOLDS NUMBER EFFECT ON OPEN CHANNEL FLOW OVER A RIB

ABSTRACT An experimental study was conducted to investigate low Reynolds number effects on open channel flow over a transverse square rib. Particle image velocimetry technique was used to perform detailed velocity measurement in the upstream and recirculation region of a square rib of height, h = 12 mm. The Reynolds number based on the freestream velocity and rib height, Re h = 1510, 2650 and 3950 and the ratio of the boundary layer thickness to step height, /h = 2.5 ± 0.2. The results showed that the reattachment length of Re h = 2650 and 3950 increased by 5.7% compared with corresponding value of Re h = 1510. The mean velocities were independent of Reynolds number in the recirculation region but at the reattachment point, Re h = 3650 reduced the streamwise mean velocity and enhanced the wall-normal mean velocity in the region adjacent to the wall. The turbulent kinetic energy beyond the center of the recirculation region increased with increasing Reynolds number