Abstract: CFD (Computational Fluids Dynamic) is an important branch of fluid dynamics. It applies various kinds of discrete mathematical method to analyze and simulate problems in fluid mechanics with the use of computer. During the computation, huge computational tasks on a single CPU often makes it very inefficient to get the result, so there is an increasing number of application of parallel computation in CFD. With more powerful computing capability and lower price, GPU (Graphic Processing Unit) has become a better solution for parallel computing than CPU in recent years. In this paper, we implemented the HSMAC and SIMPLE algorithms on GPU. For the simulation of 2D lid-driven cavity flow, the GPU version could get a speedup up to 58x and 21x respectively with double precision, and 78x and 32x with single precision, compared to the sequential CPU version. It demonstrates a good prospects of GPU acceleration of CFD algorithms.

Abstract: Numerical modeling of gas and liquid flows and, in particular, multiphase mediums, is a promising direction of scientific investigations and development of industrial apparatus. Experimental approach in the field of multiphase flows is not always capable of obtaining required information about the flow structure due to the excessive amount of physical phenomena involved. Numerical simulations of real flows with inclusion of all processes and phenomena or on real-scale geometries are very resource-demanding and are not feasible on stand-alone personal working stations. Thus, applying parallelization techniques at the existing solution algorithms with the means of OpenMP library alongside with supercomputer technologies can reduce computational time and can help with simulations of complex flows on the systems with shared memory. The study presents the description of the previously developed mathematical model of polydisperse multiphase flows, numerical algorithm for the solution of governed equations of the model and description of the numerical method. Simulations by the means of the proposed algorithm were carried out for the case of polydisperse bubbly flow inside water-filled rectangular column. Results presented in the paper, which are obtained during numerical experiments carried out on the “SC Politechnichesky”, comprise of the obtained flow field and bubble distributions and of the dependencies of program working time on the amount of threads and model parameters.

Abstract: In this work, a hybrid particle-grid method coupled with a penalization technique is introduced in order to compute Direct Numerical Simulations in three dimensions. The method is validated with the litterature for the flow past a sphere and a hemisphere. The approach is extented to solid-porous-fluid media and applied to passive flow control for the hemisphere using porous coatings.

Abstract: This paper presents a numerical study of the gravity-driven motion of single bubbles and bubble swarms through a vertical channel, using High Performance Computing (HPC) and Direct Numerical Simulation (DNS) of the Navier-Stokes equations. A systematic study of the wall effect on the motion of single deformable bubbles is carried out for confinement ratios CR={2,4,6}. Then, the rising motion of a swarm of deformable bubbles in a vertical channel is researched, for void fractions alpha={8.33%,12.5%}. These simulations are carried out in the framework of a novel multiple marker interface capturing approach, where each bubble is represented by a conservative level-set function. This method has the ability to avoid the numerical and potentially unphysical coalescence of the bubbles, allowing for the collision of the fluid particles as well as long time simulations of bubbly flows. Present simulations are performed in a periodic vertical domain discretized by 2e6 control volumes (CVs) up to 21e6 CVs, distributed in 128 up to 2048 processors. Collective and individual behaviour of the bubbles are characterized and compared against previous results from the literature.

Abstract: This work deals with an extension of the Path Tubes method for the solution of the timedependent Navier-Stokes equations for an incompressible Newtonian fluid. The resulting technique Departing from a physically intuitive methodology based on the theoretical basis of the mechanics of continuous media, a robust numerical technique is obtained. This version of the Path Tubes method draws on a semi-Lagrangian time-discretization employs the Reynolds’ transport theorem, and a localization approach, to establish an implicit semi-Lagrangian algorithm that allows the use of classical schemes for spatial discretization, such as central-difference formulas, without the need to use upwind techniques, or high-order corrections for time derivatives. Some of the extensive numerical tests are shown herein, in particular for Reynolds’ numbers typical of advection dominated flows. The tests are shown to be accurate and perform well even for coarse grids.

Abstract: A new second-order numerical scheme based on an operator splitting is proposed for the Godunov-Peshkov-Romenski model of continuum mechanics. The homogeneous part of the system is solved with a finite volume method based on a WENO reconstruction, and the temporal ODEs are solved using some analytic results presented here. Whilst it is not possible to attain arbitrary-order accuracy with this scheme (as with ADER-WENO schemes used previously), the attainable order of accuracy is often sufficient, and solutions are computationally cheap when compared with other available schemes. The new scheme is compared with a second-order ADER-WENO scheme for various test cases, and a convergence study is undertaken to demonstrate its order of accuracy.