Modeling coherent structures in the atmosphere and assessing their impact on aircraft

2021 ◽  
Author(s):  
V.V. Vyshinsky ◽  
K.T. Zoan
Keyword(s):  
Stokes Equations ◽  
Grid Method ◽  
Computer Code ◽  
Light Transport ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Large Structures ◽  
Glide Path ◽  
Coherent Vortex ◽  
Coherent Vortex Structure

The paper introduces an engineering method for assessing the aerodynamic effect of disturbed atmosphere on an aircraft. As a source of vortex structures, we can consider vortex wind wakes that arise when the atmospheric wind flows around the landscape, large structures, moving or stationary aircraft-carrying platforms, vortex wakes behind aircraft, etc. In this study, we consider the situation when a light transport aircraft and an aircraft of the MC-21 type get into the vortex wake behind the super-heavy aircraft A-380 when flying along the glide path. A coherent vortex structure behind the A-380 is formed by the grid method within the framework of the boundary value problem for the Reynolds-averaged Navier —Stokes equations. The evolution and stochastics of the far wake are carried out using the author’s computer code written in the MATLAB system, within the framework of discrete vortices with a Rankine core. The assessment of the increment of forces and moments from the effect of the vortex system on the aircraft was carried out using the panel method.

scholarly journals Application of Through-Flow Calculation to Design and Performance Prediction of Centrifugal Compressor

1999 ◽  
Vol 5 (1) ◽  
pp. 17-33 ◽  
Author(s):  
Y. S. Choi ◽  
S. H. Kang
Keyword(s):  
Centrifugal Compressor ◽  
Performance Prediction ◽  
Stokes Equations ◽  
Control Volume ◽  
Computer Code ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Simpler Algorithm ◽  
And Performance

A computer code predicting the flows through the centrifugal compressor with the radial vaneless diffuser was developed and applied to investigate the detailed flowfields, i.e., secondary flows and jet-wake type flow pattern in design and off-design conditions. Various parameters such as slip factors, aerodynamic blockages, entropy generation and two-zone modeling which are widely used in design and performance prediction, were discussed.A control volume method based on a general curvilinear coordinate system was used to solve the time-averaged Navier–Stokes equations and SIMPLER algorithm was used to solve the pressure linked continuity equation. The standardk-εturbulence model was used to obtain the eddy viscosity. Performance of the code was verified using the measured data for the Eckardt impeller.

Magnetic field effects on the slip velocity and temperature jump of nanofluid forced convection in a microchannel

2015 ◽  
Vol 230 (11) ◽  
pp. 1921-1936 ◽  
Author(s):  
Arash Karimipour ◽  
Masoud Afrand
Keyword(s):  
Magnetic Field ◽  
Forced Convection ◽  
Slip Velocity ◽  
Temperature Jump ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Computer Code ◽  
Navier Stokes ◽  
Magnetic Field Effects ◽  
Navier Stokes Equations

Forced convection of water–Cu nanofluid in a two-dimensional microchannel is studied numerically. The microchannel wall is divided into three parts. The entry and exit ones are kept insulated while the middle one has more temperature than the inlet fluid. The whole of microchannel is under the influence of a magnetic field with uniform strength of B0. Slip velocity and temperature jump are involved along the microchannel walls for different values of slip coefficient such as B = 0.001, B = 0.01, and B = 0.1 for Re = 10, Re = 50, and Re = 100. Navier–Stokes equations are discretized and numerically solved by a developed computer code in FORTRAN. Results are presented as the velocity, temperature, and Nusselt number profiles. Moreover, the effect of magnetic field on slip velocity and temperature jump is investigated for the first time in the present work. Larger Hartmann number, Reynolds number, and volume fraction correspond to more heat transfer rate; however, the effects of Ha and ϕ are more significant at higher Re.

scholarly journals NUMERICAL SIMULATION OF DUST POLLUTION OF WORKING PLACE NEAR COAL DUMP

2021 ◽  
Vol 1 (4(68)) ◽  
pp. 40-45
Author(s):  
M. Biliaiev ◽  
V. Biliaieva ◽  
O. Berlov ◽  
V. Kozachyna
Keyword(s):  
Stokes Equations ◽  
Coal Dust ◽  
Computer Code ◽  
Navier Stokes ◽  
Finite Difference Schemes ◽  
Cfd Model ◽  
Surface Wetting ◽  
Dust Pollution ◽  
Mass Transfer Equation ◽  
Navier Stokes Equations

The problem of estimating the level of air pollution in the working areas near the coal pile is considered. The task is to develop a CFD model that allows to predict the level of air dust pollution, taking into account the process of wetting the surface of the coal pile. To model the process of coal dust transfer in the air, a twodimensional mass transfer equation is used, which takes into account coal dust transfer due to convection and diffusion. The Navier-Stokes equations are used to calculate the air flow field near the coal pile. Finite-difference schemes of splitting are used for numerical integration of modeling equations. Computer code is developed on the basis of created CFD model. The developed code can be used to analyze the effectiveness of the coal surface wetting to reduce dust pollution of work areas near coal piles. The results of a computational experiment are presented.

scholarly journals Analysis of Gas Turbine Rotor Blade Tip and Shroud Heat Transfer

1996 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Stokes Equations ◽  
Computer Code ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbine Rotor Blade ◽  
Blade Tip

Predictions of the rate of heat transfer to the tip and shroud of a gas turbine rotor blade are presented. The simulations are performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations. The effect of inlet boundary layer thickness as well as rotation rate on the tip and shroud heat transfer is examined. The predictions of the blade tip and shroud heat transfer are in reasonable agreement with the experimental measurements. Areas of large heat transfer rates are identified and physical reasoning for the phenomena presented.

A Navier–Stokes Solver for Turbomachinery Applications

1993 ◽  
Vol 115 (2) ◽  
pp. 305-313 ◽  
Author(s):  
A. Arnone ◽  
R. C. Swanson
Keyword(s):  
Stokes Equations ◽  
Computer Code ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Eddy Viscosity Model ◽  
Local Time Stepping ◽  
Grid Independence ◽  
Full Multigrid Method ◽  
Transonic Rotor

A computer code for solving the Reynolds-averaged full Navier–Stokes equations has been developed and applied using H- and C-type grids. The Baldwin–Lomax eddy-viscosity model is used for turbulence closure. The integration in time is based on an explicit four-stage Runge–Kutta scheme. Local time stepping, variable coefficient implicit residual smoothing, and a full multigrid method have been implemented to accelerate steady-state calculations. A grid independence analysis is presented for a transonic rotor blade. Comparisons with experimental data show that the code is an accurate viscous solver and can give very good blade-to-blade predictions for engineering applications.

Generalization of the RANS Equations Using Mean Modal Decomposition of the Navier Stokes Equations

Volume 1 ◽  
2004 ◽  
Author(s):  
Fereydoun Sabetghadam
Keyword(s):  
Stokes Equations ◽  
Order System ◽  
Navier Stokes ◽  
Real Field ◽  
Navier Stokes Equations ◽  
Rans Equations ◽  
Zeroth Mode ◽  
Reynolds Decomposition ◽  
Coherent Vortex ◽  
Part Decomposition

A generalization in the Reynolds decomposition and averaging are proposed in this paper. The method is directly applied to the Navier Stokes (N-S) equations to construction of a generalized Reynolds Averaged Navier Stokes (RANS) equations. The formulation which is presented for the fields realized in a suitable ensemble, is based on a two part decomposition. One part is an approximate unique representation of the field and when reconstruction of the field, will repeat in all ensemble elements. The other part represents deviation of the real field from the approximate part and therefore is different in any mode and each ensemble element. The decomposition is applied in both spatial and temporal fashions. In the temporal decomposition, a system of Partial Differential Equations (PDEs) is obtained that is nonclosed, coupled and second order in space and its zeroth mode is the classical Reynolds averaged values of the field. In the spatial decomposition whereas, a first order system of nonclosed PDEs is obtained which could be seen as an alternative version of the Proper Orthogonal Decomposition (POD) or the Coherent Vortex Simulation (CVS) methods. In both fashions however, there are some terms that must be modeled just like as the classical closure problem in the RANS method. The method is applied on a one dimensional mixed random-nonrandom field and successfully extracted the coherent part of the field.

Vibrations of Circular Cylindrical Shells With Nonuniform Constraints, Elastic Bed and Added Mass Coupled to Internal, External and Annular Flow

2002 ◽  
Author(s):  
M. Amabili ◽  
R. Garziera
Keyword(s):  
Annular Flow ◽  
Stokes Equations ◽  
Computer Code ◽  
Inviscid Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Viscous Forces ◽  
Added Masses ◽  
Circular Cylindrical Shells ◽  
Lumped Masses

The effect of steady viscous forces on vibrations of shell with internal and annular flow has been considered by using the time-mean Navier-Stokes equations. The model developed by Amabili & Garziera (2000), capable of simulating shells with non-uniform boundary conditions, added masses and partial elastic bed, has been extended to include non-uniform prestress. The effect of steady viscous forces has been added to the inviscid flow formulation considered by Amabili & Garziera (2002). The computer code DIVA has been developed by using the model developed in the present study. It has been validated by comparison with available results for shells with uniform constraints and has been used to study shells with non-uniform constraints and added lumped masses.

scholarly journals Thresholds for the formation of satellites in two-dimensional vortices

2008 ◽  
Vol 614 ◽  
pp. 381-405 ◽  
Author(s):  
M. R. TURNER ◽  
A. D. GILBERT
Keyword(s):  
Normal Mode ◽  
Stokes Equations ◽  
Critical Layer ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Coherent Vortex ◽  
Neutral Mode ◽  
The Mean ◽  
Fourier Harmonics

This paper examines the evolution of a two-dimensional vortex which initially consists of an axisymmetric monopole vortex with a perturbation of azimuthal wavenumber m = 2 added to it. If the perturbation is weak, then the vortex returns to an axisymmetric state and the non-zero Fourier harmonics generated by the perturbation decay to zero. However, if a finite perturbation threshold is exceeded, then a persistent nonlinear vortex structure is formed. This structure consists of a coherent vortex core with two satellites rotating around it.The paper considers the formation of these satellites by taking an asymptotic limit in which a compact vortex is surrounded by a weak skirt of vorticity. The resulting equations match the behaviour of a normal mode riding on the vortex with the evolution of fine-scale vorticity in a critical layer inside the skirt. Three estimates of inviscid thresholds for the formation of satellites are computed and compared: two estimates use qualitative diagnostics, the appearance of an inflection point or neutral mode in the mean profile. The other is determined quantitatively by solving the normal mode/critical-layer equations numerically. These calculations are supported by simulations of the full Navier–Stokes equations using a family of profiles based on the tanh function.

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