The problem of 2D incompressible flow simulation around airfoils using vortex methods is considered. An exact solution for the boundary integral equation with respect to a free vortex sheet intensity at the airfoil su...
The problem of 2D incompressible flow simulation around airfoils using vortex methods is considered. An exact solution for the boundary integral equation with respect to a free vortex sheet intensity at the airfoil surface line that arises in such problems is obtained. The exact solution is constructed for flows around elliptical and Zhukovsky airfoils using the theory of complex potentials and conformal mappings technique. It is possible to take into account the influence of singularities in the flow domain — point vortices which simulate vortex wake. The obtained exact solutions can be used to verify and estimate the accuracy of numerical schemes for the boundary integral equation solution: such procedure is also described in details.
The problem of the flow simulation around airfoils using Lagrangian vortex methods is considered. Numerical schemes of the second order of accuracy for free vortex sheet intensity distribution along the airfoil are de...
The problem of the flow simulation around airfoils using Lagrangian vortex methods is considered. Numerical schemes of the second order of accuracy for free vortex sheet intensity distribution along the airfoil are developed for smooth and non-smooth airfoils. The schemes are based on the Galerkin approach with piecewise-constant and piecewise-linear basis functions. The finite element method ideas are used and the resulting piecewise-linear scheme has the same numerical complexity as the scheme with piecewise-constant numerical solution. The modification of a FEM-type scheme is developed for non-smooth airfoils which permits to take into account the discontinuity of the solution at the specified points; its computational cost increases insignificantly.
We present the results of 3D-hydrodynamical simulations of accretion disk in close binary star system. The model includes the optical star filling its Roche lobe, a gas stream emanating from the inner Lagrangian point...
We present the results of 3D-hydrodynamical simulations of accretion disk in close binary star system. The model includes the optical star filling its Roche lobe, a gas stream emanating from the inner Lagrangian point of the binary system, and the accretion disc structure. A cold hydrogen gas stream is initially emitted towards a point-like gravitational centre. A stationary accretion disc is formed in about 5 orbital periods after the beginning of accretion. The model uses realistic cooling function for hydrogen. The simulation of accreting gas dynamics is performed using second order Runge — Kutta discontinuous Galerkin CFD solver for unstructured tetrahedral meshes. The monotonicity technique based on Hermite WENO solution reconstruction is implemented. Utilizing the hydrodynamical simulations the sinthetic light curves of the system are calculated as the volume emission of optically thin layers along the line of sight. The simulations results are in a good agreement with observations.
This paper is devoted to a numerical simulation of 2D gas dynamics flows on uniform rectangular meshes using the Runge - Kutta - Discontinuous - Galerkin (RKDG) method. The RKDG algorithm was implemented with in-house...
This paper is devoted to a numerical simulation of 2D gas dynamics flows on uniform rectangular meshes using the Runge - Kutta - Discontinuous - Galerkin (RKDG) method. The RKDG algorithm was implemented with in-house C++ code based on the experience in the investigation of 1D case. The advantage of the RKDG method over the most popular finite volume method (FVM) is discussed: three basis functions being applied in the framework of the RKDG approach lead to a considerable decrease of the numerical dissipation rate with respect to FVM. The results of the acoustic pulse simulation on a sufficiently coarse mesh with the piecewise-linear approximation show a good agreement with the analytical solution in contrast to the FVM numerical solution. For the Sod problem, the results of the discontinuities propagation illustrate the dependence of the scheme resolution on the numerical fluxes, troubled cell indicator and the limitation technique choice. The possibility to resolve strong shocks is demonstrated with the Sedov cylindrical explosion test.
Open Source C++ code is developed for 2D incompressible flow simulation by using vortex methods. The code has modular structure, it permits users to simulate flow around airfoils (as well as around system of airfoils)...
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Open Source C++ code is developed for 2D incompressible flow simulation by using vortex methods. The code has modular structure, it permits users to simulate flow around airfoils (as well as around system of airfoils) and compute unsteady hydrodynamic loads acting the airfoils. It is also possible to simulate hydroelastic regimes of airfoil motion in the flow by using weakly coupled and strongly coupled algorithms. Well known vortex methods algorithms as well as original numerical schemes developed by authors are implemented, which makes it possible to raise the accuracy of simulation significantly in comparison to traditional algorithms of vortex methods. It is possible to run simulations in parallel mode, OpenMP and MPI technologies are supported. The source code of VM2D is available on GitHub under GNU GPL license (https://***/vortexmethods/VM2D).
The next phase of LHC Operations – High Luminosity LHC (HL-LHC), which is aimed at ten-fold increase in the luminosity of proton-proton collisions at the energy of 14 TeV, is expected to start operation in 2027-2028 ...
The next phase of LHC Operations – High Luminosity LHC (HL-LHC), which is aimed at ten-fold increase in the luminosity of proton-proton collisions at the energy of 14 TeV, is expected to start operation in 2027-2028 and will deliver an unprecedented scientific data volume of multi-exabyte scale. This amount of data has to be stored and the corresponding storage system should ensure fast and reliable data delivery for processing by scientific groups distributed all over the world. The present LHC computing and data processing model will not be able to provide the required infrastructure growth even taking into account the expected hardware technology evolution. To address this challenge the new state-of-the-art computing infrastructure technologies are now being developed and are presented here. The possibilities of application of the HL-LHC distributed data handling technique for other particle and astro-particle physics experiments dealing with large-scale data volumes like DUNE, LSST, Belle-II, JUNO, SKAO etc. are also discussed.
The LS-STAG immersed boundary cut-cell method modification for viscoelastic flow computations is presented. Rate type viscoelastic flow models (linear and quasilinear) are considered. Rate type viscoelastic flow model...
The LS-STAG immersed boundary cut-cell method modification for viscoelastic flow computations is presented. Rate type viscoelastic flow models (linear and quasilinear) are considered. Rate type viscoelastic flow models (linear and quasilinear) are considered. The obtained numerical method is implemented in the LS-STAG software package developed by the author. This software allows to simulate viscous incompressible flows by using the LS-STAG method and it modifications. The LS-STAG-discretization of extra-stress equations for viscoelastic Maxwell, Jeffreys, upper-convected Maxwell, Maxwell-A, Oldroyd-B, Oldroyd-A, Johnson Segalman fluids was developed. Formulae for differential types of convected time derivatives (Oldroyd, Cotter — Rivlin, Jaumann — Zaremba — Noll derivatives) the LS-STAG discretization was obtained. Normal non-newtonian stresses are computed at the centers of base LS-STAG mesh cells and shear non-newtonian stresses are computed at the cell corners. Time-stepping algorithm is based on the first order predictor-corrector scheme. To validate developed numerical method the test problem about viscoelastic Oldroyd-B flow past a circular airfoil was used. Computational experiments were carried out at Weissenberg number in the range from 0 to 4. The computed values of the drag coefficients and the wake length are in good agreement with the experimental data.
Dynamic taint analysis is a well-known technique. This article describes some difficulties that have to be dealt with when using dynamic taint analysis with full-system emulation. A new method is proposed to evaluate ...
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Dynamic taint analysis is a well-known technique. This article describes some difficulties that have to be dealt with when using dynamic taint analysis with full-system emulation. A new method is proposed to evaluate the risk of a detected policy violation. The method is called Diluted Taint: each tainted byte has an assigned integer value that shows how much taint resides in this byte. High value represents fresh taint, that possesses more threat, low value means that many operations occurred with this fragment of data and it is not that dangerous. When a policy violation occurs, these values are used by an expert to quickly evaluate the potential threat and prioritize fixing dangerous ones first.
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