scholarly journals Numerical Investigation of Flow around Two Tandem Identical Trapezoidal Cylinders

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yupu Wang ◽  
Wenming Cheng ◽  
Run Du ◽  
Shubiao Wang ◽  
Yong Deng
Keyword(s):  
Flow Instability ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Streamwise Velocity ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Mode Iii ◽  
Extended Body ◽  
Spacing Ratio ◽  
Volume Method

The trapezoidal beam structure is ubiquitous in giant engineering equipment, while their aerodynamic characteristics have not been clearly understood. Numerical simulation method was adopted to investigate the flow around two tandem identical trapezoidal cylinders. The study was conducted using a Reynolds number of 2.2 × 104, and with a spacing ratio varying from 0.5 to 10. The incompressible two-dimensional finite volume method was used for solving Reynolds-Averaged Navier–Stokes (RANS) equations with realizable k−ε model. The effects of cylinder geometry and spacing between the cylinders on aerodynamic characteristics, unsteady flow patterns, time-averaged flow characteristics, and flow instability was studied. The results show that the flow around the two tandem trapezoidal cylinders is highly dependent on the spacing ratio. The flow modes can be classified into: extended-body regime (Mode I, S∗ ≤ 1), reattachment regime (Mode II, 2 ≤ S∗ ≤ 3), and binary regime (Mode III, S∗ ≥ 4). We explored their respective flow characteristics and distinctions through the force/pressure coefficients, time-average streamwise velocity, and the flow field evolution.

Numerical Study of Wave Slamming on an Oscillating Flap

2014 ◽  
Author(s):  
Yanji Wei ◽  
Alan Henry ◽  
Olivier Kimmoun ◽  
Frederic Dias
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Studies ◽  
Wave Slamming ◽  
Volume Method

Bottom hinged Oscillating Wave Surge Converters (OWSCs) are efficient devices for extracting power from ocean waves. There is limited knowledge about wave slamming on such devices. This paper deals with numerical studies of wave slamming on an oscillating flap to investigate the mechanism of slamming events. In our model, the Navier–Stokes equations are discretized using the Finite Volume method with the Volume of Fluid (VOF) approach for interface capturing. Waves are generated by a flap-type wave maker in the numerical wave tank, and the dynamic mesh method is applied to model the motion of the oscillating flap. Basic mesh and time step refinement studies are performed. The flow characteristics in a slamming event are analysed based on numerical results. Various simulations with different flap densities, water depths and wave amplitudes are performed for a better understanding of the slamming.

Aerodynamic Simulation of Road Vehicle in Steady Crosswind

2013 ◽  
Vol 376 ◽  
pp. 341-344
Author(s):  
Shan Ling Han ◽  
Ru Xing Yu ◽  
Yu Yue Wang ◽  
Gui Shen Wang
Keyword(s):  
Flow Field ◽  
Wind Direction ◽  
Motor Vehicle ◽  
Aerodynamic Force ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
External Flow ◽  
Slant Angle ◽  
Ahmed Body

Because crosswind affects drivers to control their vehicles safely, the research on flow characteristics in automotive crosswind has a great significance to improve the crosswind stability of the vehicle. By the steady state numerical simulation method, the aerodynamic characteristics of external flow field of Ahmed body in crosswind was investigated. The Ahmed body with 25° slant angle is built in UG NX. The external flow field of the Ahmed body in the wind direction of 0°, 15º, 30° angle is simulated in XFlow software. According to the map of the pressure and velocity distribution, the flow field both before and after, as well as left and right has significant change as the wind direction angle increased, and the trail turbulence intensity also changes. The changes of aerodynamic force and moment affect the driving stability of a motor vehicle.

Numerical Study of Wing Aerodynamics in Ground Proximity

2008 ◽  
Author(s):  
Alex E. Ockfen ◽  
Konstantin I. Matveev
Keyword(s):  
Iterative Process ◽  
Stokes Equations ◽  
Numerical Study ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Design And Optimization ◽  
Volume Method ◽  
Experimental Design And Optimization

Experimental design and optimization of innovative ground-effect transportation means is an iterative process which requires a large amount of time and resources. To avoid the large experimental expense, numerical modeling can be used to investigate Wing-in-Ground (WIG) vehicle flight. In this paper, modeling technique is applied for a two dimensional NACA 4412 airfoil in viscous flow in and out of ground effect. The numerical method consists of a steady state, incompressible, finite volume method utilizing the Spalart-Allmaras turbulence model. Grid generation and solution of the Navier-Stokes equations are completed using FLUENT 6.3. The modeling procedures are first validated against published experimental data for unbounded flow around an airfoil. Wing section aerodynamic characteristics are then studied for varying ground heights and two separate boundary conditions: fixed ground and moving ground. Ground effect calculations are compared to several previous studies, and our results are found to correlate with published aerodynamic trends in ground effect, although all studies appear to predict different magnitudes of aerodynamic forces.

Aerodynamic Analysis and Design Numerical Simulation of the Vortex Flow over a Common Research Model with Flying-Wing Configuration

2014 ◽  
Vol 540 ◽  
pp. 138-142 ◽  
Author(s):  
Yong Hong Li ◽  
Yong Huang ◽  
Ji Chuan Su
Keyword(s):  
Stokes Equations ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Aerodynamic Characteristics ◽  
Rapid Expansion ◽  
Navier Stokes ◽  
Research Model ◽  
Analysis And Design ◽  
Dominant Feature

Previous wind tunnel study has found that the lift slope of a common research model with flying-wing configuration in a transonic freestream can experience a sudden drop as the angle of attack is increased. A numerical investigation of aerodynamic characteristics of the flying-wing configuration in transonic speed flow is presented with the intend to examine the changes of the flow characteristics in detail. As can been seen from the analysis, at sufficiently high angles of attack the dominant feature of flows over the leeside of the configuration is a pair of counter-rotating vortices. Solving the steady Reynolds-Averaged Navier-Stokes equations , the flow structures were exhibited in different angles and the analysis of total pressure, static pressure and axial velocity through wing vortex cores were presented in order to analyze the flow characteristics for the develop of the vortex. The investigation shows that the numerical method is accurate enough to capture the features of the flow especially the formation and breakdown of the leading-edge vortices. The rapid expansion of the vortex core and adverse pressure gradient the flow encounters in the chordwise direction affect the aerodynamic performance severely.

Numerical Simulation on Aerodynamic of the Wing in Ground Effect

2012 ◽  
Vol 546-547 ◽  
pp. 200-205
Author(s):  
Rong Wu ◽  
Feng Liang
Keyword(s):  
Numerical Simulation ◽  
Drag Coefficient ◽  
Finite Volume Method ◽  
Lift Coefficient ◽  
Ground Effect ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performances ◽  
Volume Method ◽  
Drag Ratio

Aerodynamic characteristics of the wing NACA5312 in ground effect are investigated with the numerical simulation method. The N-S equations and the k-ε turbulence model are solved by the finite volume method in CFD software. This paper computes the flying states under different clearances, steam velocities and angles of attack. Compared with results under the unbounded flow, it studies the relations between the aerodynamic performances and the angles of attack, the steam velocity, and the relative heights. The aerodynamic performances include the lift coefficient, drag coefficient, and lift-drag ratio.

scholarly journals Unsteady RANS Simulations of Flow around a Twin-Box Bridge Girder Cross Section

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2670 ◽  
Author(s):  
Wonmin Jeong ◽  
Shengnan Liu ◽  
Jasna Bogunovic Jakobsen ◽  
Muk Chen Ong
Keyword(s):  
Cross Section ◽  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Long Span Bridges ◽  
Long Span ◽  
Sst Turbulence Model ◽  
Bridge Girder ◽  
Drag And Lift

The aerodynamic performance of bridge deck girders requires a thorough assessment and optimization in the design of long-span bridges. The present paper describes a numerical investigation of the aerodynamic characteristics of a twin-box bridge girder cross section in the range of angles of attack between −10.0° and +10.2°. The simulations are performed by solving 2D unsteady Reynolds-averaged Navier–Stokes (URANS) equations together with the k–ω shear stress transport (SST) turbulence model. The investigated Reynolds number (Re) based on the free stream velocity ( U ∞ ) and the height of the deck (D) is 31,000. The predicted aerodynamic characteristics such as the mean drag, lift and moment coefficients, are generally in good agreement with the results from the wind tunnel tests. Changes of flow patterns and aerodynamic forces with different angles of attack are investigated. Flow characteristics during one vortex shedding period are highlighted. Relative contributions of each of the two bridge decks to the overall drag and lift coefficients, with respect to the angle of attack, are also discussed.

scholarly journals Numerical determination of aerodynamic characteristics of an airfoil in a ground effect

2021 ◽  
pp. 44-50
Author(s):  
М.А. Ливеринова ◽  
Н.В. Тряскин
Keyword(s):  
Pressure Coefficient ◽  
Independent Solution ◽  
Ground Effect ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Method Of Images ◽  
Reverse Motion ◽  
Continuity Equations ◽  
The Difference

В работе изучается движение профиля над экраном на различных относительных высотах. Рассмотрены следующие методы его моделирования: условие неподвижного экрана и метод зеркального отображения для моделирования обращённого движения и условие экрана, движущегося со скоростью профиля, что моделирует прямое движение. Целью работы является выбор метода моделирования экрана, при котором обтекание профиля соответствует действительности и оценка разницы между рассмотренными методами. Задача решена в открытом пакете OpenFOAM методом контрольного объёма, где совместно решены уравнения Навье-Стокса и неразрывности, осреднённые по Рейнольдсу. Произведена верификация и валидация математической модели и найдено сеточно-независимое решение. Выбраны два профиля в плане: сегментный и симметричный. Рассмотрены несколько относительных высот. В работе построены эпюры скоростей под профилем, представлены картины обтекания профилей, исследованы их основные эксплуатационные характеристики: коэффициент подъёмной силы и коэффициент сопротивления в зависимости от относительной высоты. Построено распределение коэффициента давления по поверхности рассматриваемых профилей в зависимости от граничных условий и относительных высот. В результате анализа показано различие происходящих физических процессов при обтекании профилей в прямом и обращённом движении. Данная работа позволяет сделать вывод о том, каким образом проводить физический эксперимент для различных профилей, показывает преимущество использования метода зеркальных отображений или подвижного экрана при проведении эксперимента. In this article the movement of the profile above the screen at different relative heights is reviewed. The following methods of its modeling are considered: the condition of a stationary screen and the method of images for simulating reverse motion and the condition of a screen moving with the profile speed that simulate forward motion are considered. The aim of the work is to select a screen simulation method for a physical experiment. An open-source packet OpenFOAM based on finite-volume method is used to solve the Navier-Stokes and continuity equations averaged by Reynolds method. The mathematical model is verified and validated, and a grid-independent solution is found. Two profiles are selected: segmental and symmetrical. Several relative heights are considered. The velocitiy profiles under the airfoil are constructed, the patterns of the flow around the airfoils are presented. The dependences of coefficients on the studied parameters and the distribution of the pressure coefficient over the profile are studied and analyzed. As a result of the analysis, the difference between the physical processes when flowing around the airfoils is in forward and reverse motion is shown. This work allows us to make a conclusion about how to conduct a model experiment for various profiles, shows the advantage of using the method of images or a movable screen in the experiment.

Compressible Flow Simulations Over Basic Reusable Rocket Configurations

2003 ◽  
Author(s):  
Keiichiro Fujimoto ◽  
Kozo Fujii
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Compressible Flow ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Pressure Level ◽  
The Body ◽  
Navier Stokes ◽  
Aerodynamic Coefficients ◽  
Flow Simulations

Compressible flow around the basic reusable rocket configurations are numerically simulated by Navier-Stokes computations. The study started with the simulations of Apollo configuration to validate the simulation method by the comparison of the aerodynamic data with NASA’s experiments, and the capability of CFD estimation are discussed. Computed aerodynamic coefficients for the Apollo agreed well with the experiments at subsonic to supersonic flow regime for whole angle of attack range. Then, the effects of the configuration parameters on the aerodynamic characteristics are numerically investigated and clarified in detail. It turns out that the aerodynamic characteristicsismainlyinfluenced by the separating position of the flow, shock wave on the surface and the pressure level behind the body. Large shoulder radius causes the strong Mach number dependency of the aerodynamic characteristics, and large fineness ratio strongly influences to the (CL)max.

A COUPLED MOLECULAR-CONTINUUM HYBRID MODEL FOR THE SIMULATION OF MACROMOLECULAR DYNAMICS

2007 ◽  
Vol 18 (04) ◽  
pp. 520-527 ◽  
Author(s):  
GIOVANNI GIUPPONI ◽  
GIANNI DE FABRITIIS ◽  
PETER V. COVENEY
Keyword(s):  
Stokes Equations ◽  
Simulation Method ◽  
Mass Range ◽  
Polymer Dynamics ◽  
Coarse Grained ◽  
Navier Stokes ◽  
Radius Of Gyration ◽  
Navier Stokes Equations ◽  
Self Diffusion ◽  
Volume Method

We describe a hybrid simulation method that captures the combined effects of molecular and hydrodynamic forces which influence macromolecules in solution. In this method, the solvent contribution is accounted for implicitly as the Navier-Stokes equations are solved on a grid using a finite volume method, while we use coarse-grained molecular dynamics to describe the macromolecule. The two systems are coupled by a dissipative Stokesian force. We show that our method correctly captures the hydrodynamically enhanced self-diffusion of a single monomer for different fluids and grid sizes. Moreover, the monomer diffusion does not depend on the monomer mass for the mass range used, as postulated by polymer dynamics theories. We also show that the dynamical properties of the chain do not depend on the grid size a when the chain radius of gyration Rg ≫ a.

Experimental and Numerical Study of a Pitching Blade

2010 ◽  
Author(s):  
M. R. Amiralaei ◽  
H. Alighanbari
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Hysteresis Loops ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Qualitative Behavior ◽  
Reduced Frequency ◽  
Lift Curve ◽  
High Turbulence ◽  
Volume Method

The objective of the present study is to investigate the effects of the reduced frequency on the aerodynamic characteristics of a three dimensional pitching blade. Experimental data are recorded at three sections of the blade model; tip, middle, and root sections at low and high turbulence intensities. A 2D numerical simulation is also conducted based on the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations and Finite Volume Method (FVM) and the results are compared with those of the experimental observations. The results show that 2D numerical simulations are useful in obtaining the qualitative behavior of the flow field. Moreover, it is shown experimentally that the reduced frequency is of great importance to the flow physics. It affects the maximum lift coefficients, hysteresis loops, lift curve slopes, and angles at which stall occurs.

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