arXiv subjects

Xinliang Li

Publications and source records attributed to Xinliang Li.

22 records · Page 2Linked to original sources

arXiv2023

An MPI-OpenMP mixing parallel open source FW-H code for aeroacoustics calculation

In this paper, a permeable surface nondimensional FW-H (Ffowcs Williams-Hawkings) acoustics analogy post-processing code with convective effect and AoA (angle of attack) corrections, OpenCFD-FWH, has been eveloped. OpenCFD-FWH is now used as post processing code of our finite volume CFD solver OpenCFD-EC (Open Computational Fluid Dynamic code for Engineering Computation). However, OpenCFD-FWH can also be used by other CFD solvers with the specified data interface. The convective effect is taken into account by using Garrick Triangle to switch the wind tunnel casesoordinate system to a moving model with fluid at rest coordinate system, which simplifies the FW-H integration formulation and improves the computationalfficiency of the code. The AoA effect is also taken into account by coordinate transformation. In order to validate the code, three cases have been implemented. The first two cases are a monopole and aipole in a mean flow with AoA, and the results of the code and the analytical solution are practically identical. The third case is theell-known 30P30N configuration with a Reynolds number of 1.71$\times10^6$ and an AoA of $5.5^\circ$. OpenCFD-EC with IDDES (Improved Delayedetached-eddy simulation) is utilized to obtain the flow field, and the result shows relative good agreement when compared to JAXA experiments oreover, the code is implemented in a hybrid parallel way with MPI and OpenMP to speed up computing processes (up to 538.5 times faster in the0P30N validation case) and avoid an out-of-memory situation. The code is now freely available on \url{https://github.com/Z-K-LpenCFD-FWH}.

physics.flu-dyn↗

arXiv2022

Direct numerical simulation of compressible turbulence accelerated by graphics processing unit. Part 1: An open-source high accuracy accelerated computational fluid dynamic software

This paper introduces open-source computational fluid dynamics software named open computational fluid dynamic code for scientific computation with graphics processing unit (GPU) system (OpenCFD-SCU), developed by the authors for direct numerical simulation (DNS) of compressible wall-bounded turbulence. This software is based on the finite difference method and is accelerated by the use of a GPU, which provides an acceleration by a factor of more than 200 compared with central processing unit (CPU) software based on the same algorithm and number of message passing interface (MPI) processes, and the running speed of OpenCFD-SCU with just 512 GPUs exceed that of CPU software with 130\,000 CPUs. GPU-Stream technology is used to implement overlap of computing and communication, achieving 98.7\% parallel weak scalability with 24\,576 GPUs. The software includes a variety of high-precision finite difference schemes, and supports a hybrid finite difference scheme, enabling it to provide both robustness and high precision when simulating complex supersonic and hypersonic flows. When used with the wide range of supercomputers currently available, the software should able to improve the performance of large-scale simulations by up to two orders on the computational scale. Then, OpenCFD-SCU is applied to a validation and verification case of a Mach 2.9 compression ramp with mesh numbers up to 31.2 billion. More challenging cases using hybrid finite schemes are shown in Part 2(Dang, Li et al. 2022). The code is available and supported at \url{http://developer.hpccube.com/codes/danggl/opencfd-scu.git}.

physics.flu-dyn↗

arXiv2019

New methodology based on energy flux similarity for large-eddy simulation of transitional and turbulent flows

A new methodology based on energy flux similarity is suggested in this paper for large eddy simulation (LES) of transitional and turbulent flows. Existing knowledge reveals that the energy cascade generally exists in transitional and turbulent flows with different distributions, and the characteristic quantity of scale interaction in energy cascade processes is energy flux. Therefore, energy flux similarity is selected as the basic criterion to secure the flow field getting from LES highly similar to the real flow field. Through a priori tests, we find that the energy flux from the tensor-diffusivity (TD) model has high similarity with the real energy flux. Then, we modify the modelled energy flux from the TD model and obtain uniform formulas of energy flux similarity corresponding to different filter widths and locations in the wall-bounded turbulence. To secure the robustness of simulation and the LES results similar to the real flow, we apply the energy flux similarity method (EFSM) to the Smagorinsky model in the LES of compressible turbulent channel flow, compressible flat-plate flow, and flow over a compressible ramp. The a posteriori tests show that, overall, EFSM can better predict these flows than other subgrid-scale models. In the simulation of turbulent channel flow, EFSM can accurately predict the mean stream-wise velocity, Reynolds stress, and affluent coherent structures. In LES of compressible flat-plate flow, EFSM could provide accurate simulation results of the onset of transition and transition peak, skin friction, and mean stream-wise velocity in cases with three different grid scales. Meanwhile, for flow over a compressible ramp, EFSM could correctly describe the process of bypass transition, locations of separation and reattachment in the corner region, and abundant coherent vortex structures, etc.

physics.flu-dyn↗

arXiv2019

Dual channels of helicity cascade in turbulent flows

Helicity, as one of only two inviscid invariants in three-dimensional turbulence, plays an important role in the generation and evolution of turbulence. From the traditional viewpoint, there exists only one channel of helicity cascade similar to that of kinetic energy cascade. Through theoretical analysis, we find that there are two channels in helicity cascade process. The first channel mainly originates from vortex twisting process, and the second channel mainly originates from vortex stretching process. By analysing the data of direct numerical simulations of typical turbulent flows, we find that these two channels behave differently. The ensemble averages of helicity flux in different channels are equal in homogeneous and isotropic turbulence, while they are different in other type of turbulent flows. The second channel is more intermittent and acts more like a scalar, especially on small scales. Besides, we find a novel mechanism of hindered even inverse energy cascade, which could be attributed to the second-channel helicity flux with large amplitude.

physics.flu-dyn↗