scholarly journals Redchyts Numerical simulation of the viscous incompressible flow around of the group of two bodies

2019 ◽  
Vol 3 (122) ◽  
pp. 117-132
Author(s):  
Serhii Serhiiovych Myrnyi ◽  
Dmytro Oleksandrovych Redchyts
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Steady State ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Aerodynamic Characteristics ◽  
Tandem Arrangement ◽  
Cylinders And Spheres ◽  
Two Bodies

Analysis of recent research and publications. It is known that the presence near the body of another body or a solid wall in a flow can significantly change both the overall flow pattern and the aerodynamic characteristics of bodies in a group. Studies of the interaction of bodies in the flow are conducted for a long time. In [6], the results of a study of changes in the overall flow pattern and the form of interaction of vortices behind tandem-arranged circular cylinders are presented. Further, experimental studies of the flow around a group consisting of two cylinders were aimed at classifying flow patterns depending on the position of the group in the flow, the distance between the cylinders and the Reynolds number [1, 2, 9]. A rather complete identification and classification of the pattern of flow was performed in [6, 7]. Studies on the classification and analysis of flow patterns are still being conducted [1]. Studies on the classification of patterns of the flow around group of spheres are currently performed mainly with the help of numerical simulation. In [3, 4, 5], simulation of the flow around spheres on the side-by-side position was performed. In [8], the classification of typical patterns of the flow around two spheres (Re = 300) with considering of different positions of the spheres relative to the flow direction was made. The authors of [8] describe nine typical patterns of the flow around two spheres in analogy with the patterns of the flow of the two cylinders.The purpose of the study. The main goal of this work is study the mutual influence of two bodies in a flow of a viscous incompressible fluid and a change in the flow structure with a change in the position of the bodies in the group relative to the incoming flow. Also, the aim of the work was to study the influence of the mutual arrangement of bodies in a group on the non-stationary and time-averaged aerodynamic characteristics of bodies in a group.Modeling of the flow around groups of cylinders and spheres. Numerical simulation of the flow around the group of cylinders was carried out with the values of the angle θ = 0°, 15°, 30°, 45°, 60°, 75°, 90° and the gap between the cylinders h = 0.2D, 0.4D, 0.6D, 0.8D, 1.0D, 2.0D, 3.0D, 4.0D, 5.0D. The flow parameters was corresponded to the flow around a circular cylinder at Re = 80 and 1.66 105. Eight patterns (regimes) of flow around a group of two cylinders at Re = 80 were found. Regimes 1 and 2 are steady state flows. In regime 1, the drag coefficient is Cx2 <0, and for regime 2, Cx2> 0. Regimes 3-8 are unsteady flows. Regime 8 is an aperiodic change in Cx, Cy. Regimes 3 - 7 are periodic, characterized by different values of the coefficients Cx, Cy, as well as those oscillations of Cx and Cy that occur in phase or antiphase. Simulation of the turbulent flow around a group of two cylinders took place at the tandem and the side-by-side positions at distances between cylinders centers 1.435D and 3.7D.Similarly, in this work, was performed the parametric study of the flow around two spheres for Reynolds number 750 with the distances between the centers of the spheres along axis Δx = 0.0, 1.0, 2.0, 3.0 and Δy = 0.0, 1.0, 2.0, 3.0. The drag and lift coefficients were obtained, as well as the patterns of flow around two spheres were analyzed.Conclusions. Depending on the position of the group relative to the flow, the average drag coefficient of the cylinders and spheres in the group can be both smaller and larger than the drag coefficient of a single body with the same parameters of the free flow. With a tandem arrangement, the second cylinder has a stabilizing effect and with a decrease in the gap of less than three diameters, the flow becomes steady state. For all cases with staggered arrangement of spheres the symmetry restoration of vortex structures is observed. In the case of the tandem arrangement of spheres, the separation of loop-shaped vortex structures is realized as in the case of a flow around a single sphere.

Direct numerical simulation of flow past a transversely rotating sphere up to a Reynolds number of 300 in compressible flow

2018 ◽  
Vol 857 ◽  
pp. 878-906 ◽  
Author(s):  
T. Nagata ◽  
T. Nonomura ◽  
S. Takahashi ◽  
Y. Mizuno ◽  
K. Fukuda
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Mach Number ◽  
Direct Numerical Simulation ◽  
Drag Coefficient ◽  
Rotation Rate ◽  
Free Stream ◽  
Rotating Sphere ◽  
Free Stream Mach Number ◽  
Low Reynolds

In this study, direct numerical simulation of the flow around a rotating sphere at high Mach and low Reynolds numbers is conducted to investigate the effects of rotation rate and Mach number upon aerodynamic force coefficients and wake structures. The simulation is carried out by solving the three-dimensional compressible Navier–Stokes equations. A free-stream Reynolds number (based on the free-stream velocity, density and viscosity coefficient and the diameter of the sphere) is set to be between 100 and 300, the free-stream Mach number is set to be between 0.2 and 2.0, and the dimensionless rotation rate defined by the ratio of the free-stream and surface velocities above the equator is set between 0.0 and 1.0. Thus, we have clarified the following points: (1) as free-stream Mach number increased, the increment of the lift coefficient due to rotation was reduced; (2) under subsonic conditions, the drag coefficient increased with increase of the rotation rate, whereas under supersonic conditions, the increment of the drag coefficient was reduced with increasing Mach number; and (3) the mode of the wake structure becomes low-Reynolds-number-like as the Mach number is increased.

Experimental Aerodynamic Characteristics of a Compound Wing in Ground Effect

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Saeed Jamei ◽  
Adi Maimun Abdul Malek ◽  
Shuhaimi Mansor ◽  
Nor Azwadi Che Sidik ◽  
Agoes Priyanto
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Center Of Pressure ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Ground Effect ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Ground Clearance

Wing configuration is a parameter that affects the performance of wing-in-ground effect (WIG) craft. In this study, the aerodynamic characteristics of a new compound wing were investigated during ground effect. The compound wing was divided into three parts with a rectangular wing in the middle and two reverse taper wings with anhedral angle at the sides. The sectional profile of the wing model is NACA6409. The experiments on the compound wing and the rectangular wing were carried to examine different ground clearances, angles of attack, and Reynolds numbers. The aerodynamic coefficients of the compound wing were compared with those of the rectangular wing, which had an acceptable increase in its lift coefficient at small ground clearances, and its drag coefficient decreased compared to rectangular wing at a wide range of ground clearances, angles of attack, and Reynolds numbers. Furthermore, the lift to drag ratio of the compound wing improved considerably at small ground clearances. However, this improvement decreased at higher ground clearance. The drag polar of the compound wing showed the increment of lift coefficient versus drag coefficient was higher especially at small ground clearances. The Reynolds number had a gradual effect on lift and drag coefficients and also lift to drag of both wings. Generally, the nose down pitching moment of the compound wing was found smaller, but it was greater at high angle of attack and Reynolds number for all ground clearance. The center of pressure was closer to the leading edge of the wing in contrast to the rectangular wing. However, the center of pressure of the compound wing was later to the leading edge at high ground clearance, angle of attack, and Reynolds number.

scholarly journals Numerical Analysis of the Aerodynamic Characteristics of NACA-4312 Airfoil

2020 ◽  
Vol 01 (02) ◽  
pp. 29-36
Author(s):  
Md Rhyhanul Islam Pranto ◽  
Mohammad Ilias Inam
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Numerical Results ◽  
Ansys Fluent ◽  
Coefficient Increase ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5×10^5 . These simulations were solved using two different turbulence models, one was the Standard k-ε model with enhanced wall treatment and other was the SST k-ω model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.

Three-Dimensional Wing Design Towards the Future Mars Airplane

2011 ◽  
Author(s):  
Ryoji Kojima ◽  
Donghi Lee ◽  
Tomoaki Tatsukawa ◽  
Taku Nonomura ◽  
Akira Oyama ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Viscous Drag ◽  
Stream Velocity ◽  
Main Stream ◽  
Lower Reynolds Number

The effects of aspect ratio and Reynolds number on aerodynamic characteristics of three-dimensional rectangular wing at low Reynolds number of 103 to 105, are investigated with Reynolds-averaged Navier-Stokes solver with the Baldwin-Lomax model. Present results show that lift coefficient decreases drastically at lower aspect ratio than 4. Besides, the much larger viscous drag coefficient is obtained at the lower Reynolds number, especially lower than 104. In order to focus on designing practical wings, the particular cases under the condition of fixed wing-surface area and fixed main stream velocity are conducted. The results show that there is trade-off between the decrease in viscous drag coefficient with increasing Reynolds number and the increase in lift coefficient with increasing aspect ratio. At the lower Reynolds number condition, as the former effect is stronger than the latter one, maximum lift-to-drag ratio is obtained at lower aspect ratio.

The Drag on Spheres and Cylinders in a Stream of Dust-Laden Air

1959 ◽  
Vol 26 (4) ◽  
pp. 584-586
Author(s):  
Thomas Gillespie ◽  
A. W. Gunter
Keyword(s):  
Particle Size ◽  
Reynolds Number ◽  
Kinetic Energy ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Reynolds Numbers ◽  
Dust Concentration ◽  
Phase System ◽  
Two Phase ◽  
Coefficient Versus

Abstract A system has been developed for measuring the drag on small spheres and cylinders in a stream of dust-laden air. The drag was found to be proportional to the kinetic energy of the air plus the kinetic energy of the dust, and to be independent of particle size for particles having diameters in the range of 50 to 400μ. The well-known drag-coefficient versus Reynolds-number plots are the same for dust-free and dust-laden air provided the drag coefficient is calculated using the density of the two-phase system and the Reynolds numbers are calculated using the density of air alone. This suggests that the dust has little effect on the flow pattern. The results indicate that an instrument utilizing the drag principle to measure dust concentration could be developed.

Experimental Study of Automotive Aerodynamics in Headlamp Effect

2011 ◽  
Vol 279 ◽  
pp. 339-344
Author(s):  
Lan Fang Jiang ◽  
Hong Liu ◽  
Ai Qi Li
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Experimental Study ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Surface Pressure ◽  
Symmetry Plane ◽  
Automotive Aerodynamics ◽  
Inlet Boundary Condition

The effect of headlamp modeling on automotive aerodynamics was studied by wind tunnel tests. Firstly, the effect of Reynolds number on drag coefficient of automotive scaled down models was studied under different velocity of flow to verify the rationality of selecting scale for scaled down model and setting inlet boundary condition. Secondly, drag coefficient of automotive scaled down models with different headlamp modeling design were measured. Thirdly, the distribution of surface pressure on central symmetry plane and headlamp was measured and analyzed. It also validated the validity of preceding numerical simulation. It is of importance to guide the headlamp modeling design and automotive modeling design.

Effect of Sunroofs and Side Windows on Aerodynamic Characteristics of Transit Bus

2012 ◽  
Vol 224 ◽  
pp. 333-337 ◽  
Author(s):  
Xing Jun Hu ◽  
Feng Tao Ren ◽  
Bo Yang ◽  
Peng Guo
Keyword(s):  
Numerical Simulation ◽  
Drag Coefficient ◽  
Turbulence Model ◽  
Working Conditions ◽  
Working Condition ◽  
Aerodynamic Characteristics ◽  
Rear Side ◽  
Front Side ◽  
Side Window ◽  
Transit Bus

In this paper, k-Omega turbulence model is applied in the numerical simulation of the transit bus, several typical working conditions of the transit bus with windows open at a speed of 10m/s are investigated, and a custom function Q is introduced to characterize the amount of ventilation of each window. The results show that, when the transit bus travels with windows open, the air always flows into the carriage through the middle and rear side windows of the transit bus, and circulates in the carriage and then flows out of the carriage through the front side window. When the bus travels with sunroofs open in leeward mode and side windows open, the amount of ventilation is the maximum. This working condition is the best one when taking both drag coefficient and the amount of ventilation.

Numerical Simulation and Modelling of the Forces Acting on Single and Multiple Non-Spherical Particles

2014 ◽  
Author(s):  
Rafik Ouchene ◽  
Amine Chadil ◽  
Pascal Fede ◽  
Mohammed Khalij ◽  
Anne Tanière ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Coefficient ◽  
Turbulent Flows ◽  
Large Range ◽  
Direct Numerical Simulations ◽  
Particle Orientation ◽  
Spherical Particles ◽  
Ellipsoidal Particle ◽  
Particle Shapes

The paper deals with gas-solid turbulent flows carrying non-spherical particles. The main objective of the present paper is to compute the hydrodynamics forces on non-spherical particles as a function of the particle orientation, for different particle shapes and a large range of particle Reynolds number. Two Direct Numerical Simulations at the scale of the particle are used, i.e. a body-fitted approach and a viscous penalty approach, in the case of a uniform flow with a single ellipsoidal particle. Results are compared with several correlations from the literature and a new proposal for the drag coefficient is given. The study is then extended to the case of a lattice of non-spherical particles to measure the pressure drop and to connect it with the drag coefficient.

Gravity currents propagating into shear

2015 ◽  
Vol 778 ◽  
pp. 552-585 ◽  
Author(s):  
M. M. Nasr-Azadani ◽  
E. Meiburg
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Steady State ◽  
High Reynolds Number ◽  
Gravity Current ◽  
Gravity Currents ◽  
Maximum Energy ◽  
Channel Height ◽  
High Reynolds ◽  
The Given

An analytical vorticity-based model is introduced for steady-state inviscid Boussinesq gravity currents in sheared ambients. The model enforces the conservation of mass and horizontal and vertical momentum, and it does not require any empirical closure assumptions. As a function of the given gravity current height, upstream ambient shear and upstream ambient layer thicknesses, the model predicts the current velocity as well as the downstream ambient layer thicknesses and velocities. In particular, it predicts the existence of gravity currents with a thickness greater than half the channel height, which is confirmed by direct numerical simulation (DNS) results and by an analysis of the energy loss in the flow. For high-Reynolds-number gravity currents exhibiting Kelvin–Helmholtz instabilities along the current/ambient interface, the DNS simulations suggest that for a given shear magnitude, the current height adjusts itself such as to allow for maximum energy dissipation.

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