scholarly journals An Improved Third-order HWCNS for Compressible Flow Simulation on Curvilinear Grids

2021 ◽  
Author(s):  
Mingyang Cheng ◽  
Lingyan Tang ◽  
Yu Liu ◽  
Huajun Zhu
Keyword(s):  
Hybrid Cell ◽  
Flow Simulation ◽  
Computational Grids ◽  
Complex Flow ◽  
Third Order ◽  
High Order Schemes ◽  
Curvilinear Grids ◽  
Smooth Region ◽  
Convergence Of The Scheme

Abstract Due to the very high requirements on the quality of computational grids, stability property and computational efficiency, the application of high-order schemes to complex flow simulation is greatly constrained. In order to solve these problems, the third-order hybrid cell-edge and cell-node weighted compact nonlinear scheme(HWCNS3) is improved by introducing a new nonlinear weighting mechanism. The new scheme uses only the central stencil to reconstruct the cell boundary value, which makes the convergence of the scheme more stable. The application of the scheme to Euler equation on curvilinear grids is also discussed. Numerical results show that the new HWCNS3 achieves the expected order in smooth region, captures discontinuities sharply without obvious oscillation, has higher resolution than the original one and preserves freestream and vortex on curvilinear grids.

scholarly journals An improved third-order HWCNS for compressible flow simulation on curvilinear grids

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Mingyang Cheng ◽  
Lingyan Tang ◽  
Yu Liu ◽  
Huajun Zhu
Keyword(s):  
Hybrid Cell ◽  
Flow Simulation ◽  
Computational Grids ◽  
Complex Flow ◽  
Third Order ◽  
High Order Schemes ◽  
Curvilinear Grids ◽  
Very High ◽  
Convergence Of The Scheme

AbstractDue to the very high requirements on the quality of computational grids, stability property and computational efficiency, the application of high-order schemes to complex flow simulation is greatly constrained. In order to solve these problems, the third-order hybrid cell-edge and cell-node weighted compact nonlinear scheme (HWCNS3) is improved by introducing a new nonlinear weighting mechanism. The new scheme uses only the central stencil to reconstruct the cell boundary value, which makes the convergence of the scheme more stable. The application of the scheme to Euler equations on curvilinear grids is also discussed. Numerical results show that the new HWCNS3 achieves the expected order in smooth regions, captures discontinuities sharply without obvious oscillation, has higher resolution than the original one and preserves freestream and vortex on curvilinear grids.

Aero-Thermodynamic Loss Analysis in Cases of Normal Shock Wave-Turbulent Shear Layer Interaction

1997 ◽  
Vol 119 (2) ◽  
pp. 297-303 ◽  
Author(s):  
J. K. Kaldellis
Keyword(s):  
Shear Layer ◽  
Practical Interest ◽  
Flow Simulation ◽  
Strong Shock ◽  
Turbulent Shear ◽  
Complex Flow ◽  
Loss Model ◽  
Layer Interaction ◽  
Loss Analysis ◽  
Shock Loss

Transonic-supersonic decelerating flow cases appearing in modern turbomachines are some of the most complex flow cases in fluid mechanics which also present practical interest. In the present work, a closed and coherent shock loss model is proposed based on the complete viscous flow simulation using some fast and reliable computational tools. The resulting model describes accurately the entropy rise and the total pressure loss in cases of strong shock-shear layer interaction and cancels the need to use low speed correlations modified for compressibility effects and extrapolated to transonic-supersonic flow cases. The accuracy and the reliability of the proposed shock-loss model are verified using detailed experimental data concerning various flow cases which present either flow separation or industrial interest.

scholarly journals Aerodynamic characteristics of detachable fairing shells in a subsonic incompressible flow

2019 ◽  
Author(s):  
Yu.V. Grebeneva ◽  
A.Yu. Lutsenko ◽  
A.V. Nazarova
Keyword(s):  
Flow Simulation ◽  
Aerodynamic Characteristics ◽  
Simulation Software ◽  
Stream Velocity ◽  
Normal Forces ◽  
Pitch Moment ◽  
Lift Off ◽  
Windward Surface ◽  
Aerodynamic Quality

The purpose of the work was to mathematically simulate the flow around the fairing shell of the launch vehicle at a low subsonic free-stream velocity in the α = 0...360° angle-of-attack range. The calculations were performed using the SolidWorks Flow Simulation software package and the open source OpenFoam package based on the use of numerical methods for simulating the motion of liquid and gas. Within the research, we obtained the flow patterns and the aerodynamic coefficients of the longitudinal and normal forces, the pitch moment, and calculated the aerodynamic quality of the shell. Furthermore, we determined the positions of the stable equilibrium of the model and revealed the features of the flowing around the shell of the combined form at flow from the convex and concave sides. Next, we analyzed the leeward lift-off zones and the zones with increased pressure on the windward surface during flow from the concave side. Finally, we compared the obtained characteristics with the experimental data of TsAGI.

Complex Flow Simulation via Lattice Boltzmann Method

2016 ◽  
pp. 38-1-38-30 ◽  
Author(s):  
G Falcucci ◽  
S Melchionna ◽  
S Ubertini ◽  
Sauro Succi
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Flow Simulation ◽  
Complex Flow ◽  
Boltzmann Method

Effect of Dissipative Terms on the Quality of Two and Three-Dimensional Euler Flow Solutions

2008 ◽  
Author(s):  
Seyed Saied Bahrainian
Keyword(s):  
Euler Equations ◽  
Hyperbolic Conservation Laws ◽  
Three Dimensional ◽  
Strong Shock ◽  
Computational Domain ◽  
Third Order ◽  
First Order ◽  
Proper Values ◽  
Dissipative Terms

The Euler equations are a set of non-dissipative hyperbolic conservation laws that can become unstable near regions of severe pressure variation. To prevent oscillations near shockwaves, these equations require artificial dissipation terms to be added to the discretized equations. A combination of first-order and third-order dissipative terms control the stability of the flow solutions. The assigned magnitude of these dissipative terms can have a direct effect on the quality of the flow solution. To examine these effects, subsonic and transonic solutions of the Euler equations for a flow passed a circular cylinder has been investigated. Triangular and tetrahedral unstructured grids were employed to discretize the computational domain. Unsteady Euler equations are then marched through time to reach a steady solution using a modified Runge-Kutta scheme. Optimal values of the dissipative terms were investigated for several flow conditions. For example, at a free stream Mach number of 0.45 strong shock waves were captured on the cylinder by using values of 0.25 and 0.0039 for the first-order and third-order dissipative terms. In addition to the shock capturing effect, it has been shown that smooth pressure coefficients can be obtained with the proper values for the dissipative terms.

scholarly journals Validation Methods of Geometric 3D-CityGML Data for Urban Wind Simulations

2019 ◽  
Vol 128 ◽  
pp. 10006 ◽  
Author(s):  
Younis Saida Saeedrashed ◽  
Ali Cemal Benim
Keyword(s):  
Healing Process ◽  
Flow Simulation ◽  
Software Tools ◽  
Geometrical Structures ◽  
Geometric Data ◽  
3D City Model ◽  
City Model ◽  
Closed Shells

Validation of the geometric data such as 3D city model is quite crucial for simulation tasks, since the simulation process strongly correlates to the quality of geometric data being meshed. Validation methodology and healing of the 3D city models using different tools are presented. The most common inherited geometrical errors are checked and analyzed. Accordingly, an appropriate healing process to the case study is performed, which illustrates that the required closed solids and closed shells are obtained within the geometrical structures of the 3D city model being processed. Also, in this paper we compare some related open source and commercial software tools for the validation and healing process. It is noticed that they differ from each other in performing the required healing process. Some of them are quite good in healing specific errors, whereas not successful in healing the rest of errors. The goal of the paper is to obtain more understanding of the geometric validation and healing capabilities of various software tools, and the qualities of generated meshes, to lead to more effective and reliable simulations in the field of urban wind flow simulation.

Effects of production factors on germination responses of carrot seeds to temperature and oxygen

1995 ◽  
Vol 5 (3) ◽  
pp. 129-135 ◽  
Author(s):  
F. Corbineau ◽  
M. A. Picard ◽  
A. Bonnet ◽  
D. Côme
Keyword(s):  
Honey Bees ◽  
Large Range ◽  
Oxygen Deprivation ◽  
Hybrid Seed Production ◽  
Male Sterile ◽  
Third Order ◽  
Production Factors ◽  
Mother Plants ◽  
The Mean

AbstractVarious sources of germination heterogeneity of carrot (Daucus carota L.) seeds were investigated: germination conditions (temperature, oxygen tension), size of seeds, position of the umbels on the mother plants, and pollination conditions of male-sterile plants in hybrid seed production. All seeds tested germinated over a large range of temperatures (5–35°C). However, low temperatures (5–10°C) and temperatures above 30°C reduced germination. Seeds were also sensitive to oxygen deprivation, but their sensitivity to hypoxia depended on the cultivar. The germination responses of seeds to temperature and oxygen depended on their size, particularly at sub- and supra-optimal temperatures. The largest seeds (1.8–2.1 mm) of commercial lots usually germinated better at 5°C and were more sensitive to oxygen deprivation than the smallest ones (1.2–1.8 mm). Experiments performed with open pollinated plants showed that seeds produced by umbels of first and second orders germinated faster and at higher percentages than those collected on third-order umbels. Evidence for the involvement of pollination conditions in the germination quality of carrot seeds was given by pollination by honey bees of male-sterile plants cultivated at various distances from the pollen donors. The longer the distance of the mother plants from the pollinating plants, the lower the seed yield, the heavier the mean seed weight, the more difficult the germination of seeds, and the higher their sensitivity to oxygen deprivation.

scholarly journals Investigation of electric generator robust algorithm under measurement noises

2018 ◽  
pp. 204-209
Author(s):  
Igor B. Furtat ◽  
Artem N. Nekhoroshikh
Keyword(s):  
Control Algorithm ◽  
Nonlinear Differential Equations ◽  
Frequency Measurement ◽  
Unknown Parameters ◽  
Third Order ◽  
Electric Generator ◽  
Bounded Disturbances ◽  
Measurement Noises ◽  
Load Angle

The paper considers the investigation of a novel robust control algorithm of an electric generator with unknown parameters under bounded disturbances and high-frequency measurement noises. It is assumed that only the load angle is available for measurement, but not the rotor speed. The electric generator model is described by a system of third-order nonlinear differential equations with algebraic coupling ones. The proposed algorithm consisting of static and dynamical terms is based on the separation of the filtering and estimating properties. Differently from existing results the proposed scheme provides the opportunity to control independently the quality of filtering and stabilization. Investigations show that the proposed algorithm attenuates parametric uncertainties and disturbances with accuracy that can be reduced by tuning algorithm parameters.

scholarly journals Computational geometry as a tool for studying root-finding methods

Filomat ◽  
2019 ◽  
Vol 33 (4) ◽  
pp. 1019-1027 ◽  
Author(s):  
Ivan Petkovic ◽  
Lidija Rancic
Keyword(s):  
Computational Geometry ◽  
Basins Of Attraction ◽  
Dynamic Study ◽  
Third Order ◽  
Root Finding ◽  
Mathematical Visualization ◽  
Order Root ◽  
Insight Into ◽  
Basins Of Attractions

We present an efficient method from Computational geometry, a branch of computer science devoted to the study of algorithms, for mathematical visualization of a third order root solver. For many decades the quality of iterative methods for solving nonlinear equations were analyzed only by using numerical experiments. The disadvantage of this approach is the inconvenient fact that convergence behavior strictly depends on the choice of initial approximations and the structure of functions whose zeros are sought, which often makes the convergence analysis very hard and incomplete. For this reason in this paper we apply dynamic study of iterative processes relied on basins of attraction, a new and powerful methodology developed at the beginning of the 21th century. This approach provides graphic visualization of the behavior of convergent sequences and, consequently, offers considerably better insight into the quality of applied root solvers, especially into the domain of convergence. For demonstration, we present dynamic study of one parameter family of Halley?s type introduced in the first part of the paper. Characteristics of this family are discussed by basins of attractions for various values of the involved parameter. Special attention is devoted to clusters of polynomial roots, one of the most difficult problems in the topic. The analysis of the methods and presentation of basins of attractions are performed by the computer algebra system Mathematica.

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