Authors:Kirill V. Belyaev, Andrey V. Garbaruk, Sergey V. Kravchenko, Michael K. Strelets Pages: 4 - 17 Abstract: A comparative study is performed on three different approaches for prediction of transonic buffet onset on infinite swept wings. All three approaches are based on the unsteady Reynolds-averaged Navier–Stokes (URANS) equations, and include: quasi-3D and fully-3D global stability analysis of the corresponding steady 2.5D RANS solutions and direct numerical solution of the 3D URANS equations. The results are presented for an infinite swept wing based on the ONERA OAT15A airfoil section. The quasi-3D stability analysis is shown to be accurate and most efficient and, thus, is best suited for this spanwise-uniform flow. The fully-3D stability analysis ensures the same accuracy, provided that the grid-step in the spanwise direction is sufficiently small. It is much more demanding in terms of computer memory but can be extended to more-general wing configurations. Good agreement is observed between the three approaches in terms of critical conditions for buffet onset and the instability growth characteristics, providing a cross-validation of the methods and an assessment of their computational demands. PubDate: 2022-12-30 DOI: 10.14529/jsfi220401 Issue No:Vol. 9, No. 4 (2022)

Authors:Dmitry E. Khazov Pages: 18 - 27 Abstract: Air flows with supersonic speeds are used in many cases, for example, as aircraft air intakes, wind tunnels, and energy separation devices. In many cases it is necessary to decelerate the flow to sonic speeds. Traditionally the deceleration realized through the shocks system, which leads to total pressure losses. The article considers the method of deceleration of supersonic flows using permeable surfaces. In this case, the deceleration process occurs without shocks and, therefore, with lower total pressure losses. We have considered the flow in a tube with permeable wall located behind a supersonic nozzle. One-dimensional and axisymmetric mathematical models of such a device are developed. The calculation results are compared with experimental data. It is shown that, depending on the ratio of pressure inside the tube and the ambient pressure, different flow regimes inside the tube are possible: pure subsonic, transitional from supersonic to subsonic, and pure supersonic. The transition from supersonic to subsonic flow occurs without shocks due to the suction and friction combined effects. PubDate: 2022-12-30 DOI: 10.14529/jsfi220402 Issue No:Vol. 9, No. 4 (2022)

Authors:Mikhail M. Krasnov, Olga B. Feodoritova Pages: 28 - 37 Abstract: Modern graphics accelerators (GPUs) can significantly speed up the execution of numerical tasks. However, porting programs to graphics accelerators is not an easy task, sometimes requiring their almost complete rewriting. CUDA graphics accelerators, thanks to the technology developed by NVIDIA, allow you to have a single source code for both conventional processors (CPUs) and graphics accelerators (CUDA). However, parallelization on shared memory is done differently and still must be specified explicitly. The use of the functional programming library developed by the authors makes it possible to hide the use of one or another parallelization mechanism on shared memory inside the library and make the user source code independent of the computing device used (CPU or CUDA). Functional programming is based on the modern mathematical theory, namely the Category Theory, in which the notions of Functors and Monads are widely used. Our work intensively utilizes these notions and extends them to grid expressions used in solving numerical problems. PubDate: 2022-12-30 DOI: 10.14529/jsfi220403 Issue No:Vol. 9, No. 4 (2022)

Authors:Andrey A. Savelyev, Innokentiy A. Kursakov, Evgeniy S. Matyash, Evgeny V. Streltsov, Ruslan A. Shtin Pages: 38 - 48 Abstract: The application of the nonlinear SST turbulence model (SST NL) for the calculation of flows with turbulence anisotropy is considered. The results of the following validation test cases are presented: the flow in a square duct, the corner flow separation at a wing-body junction (NASA Juncture Flow) and the transonic wing flow (NASA CRM). The nonlinear model has been found to significantly improve the quality of simulating the anisotropic flows as compared to models based on the Boussinesq hypothesis. It is shown that the model prevents false corner separation at the wing-body junction and thereby achieves a qualitative improvement in simulation results. The test case of the transonic wing flow revealed an upstream displacement of the shock wave on the upper side of the wing which leads to an underestimation of the lift force when using the SST NL model. In all the tests considered, the SST NL model required an increase in computational cost of at most 5 % compared to the conventional SST model. PubDate: 2022-12-30 DOI: 10.14529/jsfi220404 Issue No:Vol. 9, No. 4 (2022)

Authors:Andrey V. Gorobets Pages: 49 - 54 Abstract: The NOISEtte heterogeneous parallel code for simulating turbulent flow and aerodynamic noise is considered. In our previous works, high acceleration and parallel efficiency in scientific scale-resolving simulations using GPUs were reported. For parallelization, the MPI, OpenMP and OpenCL standards are used, the latter allows using GPUs from different vendors. However, the further transition to industrial-oriented applications brought more trouble. Instead of discussing the parallel algorithm, this work will focus on the problems that are not so obvious at first glance, which arise when developing a heterogeneous simulation code. How to deal with numerous simulation algorithm components, all those bells and whistles like wall functions, mixing plane and sliding interfaces, synthetic turbulence generators, a variety of boundary conditions, etc., that either need to be ported to the GPU side or incorporated directly from the CPU side' How to maintain and modify the OpenCL code in a growing number of source files' How to arrange the modularity of a complex heterogeneous software package' How to preserve reliability and fault tolerance, especially in the case of numerical schemes of increased accuracy, but reduced social responsibility' These issues are discussed here and some solutions will be proposed. PubDate: 2022-12-30 DOI: 10.14529/jsfi220405 Issue No:Vol. 9, No. 4 (2022)

Authors:Natalia S. Zhdanova, Oleg V. Vasilyev Pages: 55 - 68 Abstract: A novel penalized wall function method for simulations of wall-bounded compressible turbulent flows is proposed. The new approach is based on the Reynolds-averaged Navier–Stokes (RANS) equations to model the outer region of the turbulent boundary layer, while the inner part is approximated by the equilibrium wall function model. The differential formulation to match the external and the wall function solutions is reformulated in a form of the generalized characteristic-based volume penalization method to model the transfer of the shear stress from the outer region of the boundary layer to the wall and to impose the wall-stress boundary conditions on the RANS solution. The exchange location is specified implicitly through a localized source term in the boundary layer equation, written as a function of the normalized distance from the wall. The wall-stress condition is determined by solving an auxiliary equation for the wall-stress, ensuring the correct matching of the RANS and the wall function solutions at the exchange layer. The proposed method noticeably reduces the near-wall mesh resolution requirements without significant modification of the RANS solver and removes the ill-defined explicit matching procedure, commonly used by traditional wall function-based methods. The penalized wall function approach is implemented using the vertex-centered control volume method on unstructured computational grids. The effectiveness of the developed penalized wall function method is demonstrated for twodimensional bump-in-channel flow for the Spalart–Allmaras turbulence model. PubDate: 2022-12-30 DOI: 10.14529/jsfi220406 Issue No:Vol. 9, No. 4 (2022)

Authors:Vladimir G. Bobkov, Tatiana K. Kozubskaya, Liudmila N. Kudryavtseva, Valeriia O. Tsvetkova Pages: 69 - 84 Abstract: A novel hybrid dynamic mesh redistribution – immersed boundary method for simulation of turbulent flows around rotating obstacles of complex geometry and analysis of tonal acoustics is proposed. The feasibility of the approach is demonstrated by considering a drone propeller problem. The results of three-dimensional Reynolds-averaged Navier–Stokes simulations using the proposed approach are compared to the results of body-fitted unstructured simulations in noninertial reference frame. The dynamic mesh redistribution method allows the reposition of mesh points taking into account the shape of the moving body while retaining the mesh topology. The cell size and quality of the dynamically redistributed mesh strongly depend on the curvature of the body surface. The position and shape of the moving obstacle is prescribed by a distance function defined on an adaptive octree. The results of simulations using the proposed method are in good agreement with both the results of body-fitted simulations and the experimental data. PubDate: 2022-12-30 DOI: 10.14529/jsfi220407 Issue No:Vol. 9, No. 4 (2022)

Authors:Anton A. Shershnev, Alexey N. Kudryavtsev, Alexander V. Kashkovsky, Georgy V. Shoev, Semyon P. Borisov, Timofey Yu. Shkredov, Danila P. Polevshchikov, Alexey A. Korolev, Dmitry V. Khotyanovsky, Yulia V. Kratova Pages: 85 - 99 Abstract: The major points in the development of the parallel multiplatform multipurpose numerical code solving the full unsteady Navier–Stokes equations are presented. The developed code is primarily designed for running on multi-GPU computational devices but can also be used on traditional multicore CPUs and even on manycore processors such as Intel Xeon Phi. Physical models include calorically perfect inert gas, single- and multi-temperature approaches for chemically reactive flows and an Euler–Euler model for gas-particle suspensions. Main details of the implementation are described. Shock capturing TVD and WENO schemes in general curvilinear coordinates are used for spatial approximation. Explicit, semi-implicit and fully implicit schemes are employed for advancing solution in time. The code is written in C++ with CUDA API and opensource libraries, such as MPI, zlib and VTK. A few examples of numerical simulations are briefly described to provide general idea of the numerical code capabilities. They include a supersonic flow past a wedge, a jet exhausting from a square nozzle, a heavy gas bubble descending in a lighter medium and a heterogeneous detonation in gas-particle suspension. PubDate: 2022-12-30 DOI: 10.14529/jsfi220408 Issue No:Vol. 9, No. 4 (2022)

Authors:Ilya A. Abalakin, Vladimir G. Bobkov, Tatiana K. Kozubskaya Pages: 100 - 113 Abstract: The paper presents the results of the simulation of unsteady turbulent flow generated by helicopter main rotor in the presence of the fuselage with an emphasis on the analysis of the influence of the fuselage on the rotor-induced flow and the rotor-generated acoustic field. The Reynolds-averaged Navier–Stokes equations with the Spalart–Allmaras turbulence model are used to simulate the Caradonna–Tung rotor and ROBIN fuselage interaction in hovering flight. The governing equations are discretized using the vertex-centered control volume method on mixedelement unstructured meshes with the sliding mesh technology to treat the rotor. The acoustic field generated by the rotor+fuselage interaction is comparatively analyzed against the case of an isolated rotor. It is found that the presence of fuselage significantly changes the rotor-generated acoustics. In particular, the presence of the fuselage noticeably distorts the directivity of acoustic radiation and increases the overall sound pressure level under the fuselage up to 20 dB, emphasizing the importance of the influence of fuselage on the helicopter acoustics. PubDate: 2022-12-30 DOI: 10.14529/jsfi220409 Issue No:Vol. 9, No. 4 (2022)