REVIEW—Review of Flow Interference Between Two Circular Cylinders in Various Arrangements

1977 ◽  
Vol 99 (4) ◽  
pp. 618-633 ◽  
Author(s):  
M. M. Zdravkovich
Keyword(s):  
Flow Pattern ◽  
Drag Force ◽  
Lift Force ◽  
Flow Direction ◽  
Critical Survey ◽  
Tandem Arrangement ◽  
Critical Spacing ◽  
Gap Flow ◽  
Lift Forces ◽  
Drag And Lift

There are infinite numbers of possible arrangements of two parallel cylinders positioned at right angles to the approaching flow direction. Of the infinite arrangements, two distinct groups may be identified: in one group, the cylinders are in a tandem arrangement, one behind the other at any longitudinal spacing; and in the second group, the cylinders face the flow side by side at any transverse spacing. All other combinations of longitudinal and transverse spacings represent staggered arrangements. The tandem arrangement will be treated first. A critical survey of previous research revealed some “odd” features which had been observed and overlooked by various authors. The discontinuity of vortex shedding implies that a similar discontinuity should be expected for the drag force on both cylinders. The measurements of the front (gap) pressures of the downstream cylinder and the base pressures of both cylinders at various spacings reveal a discontinuous “jump” at some critical spacing. The discontinuity is caused by the abrupt change from one stable flow pattern to another at the critical spacing. A new interpretation is given for the existing data on the drag force for both cylinders. The effects of Reynolds number and surface roughness are treated in some detail. Following this, two cylinders arranged side by side to the approaching flow are considered. All the available data on measured forces are compiled together with additional measurements in the range of intermittent changes of drag and lift forces. The bistable nature of the asymmetric flow pattern around each cylinder produces two alternative values of the drag force coupled with two alternative values of the lift force. The introduction of the interference force coefficient exposes the physical origin of two different forces experienced by the cylinders when arranged side by side. Finally, the least reported arrangement of two staggered cylinders is reviewed. The various arrangements are grouped into classes according to the sign of the lift force, or whether the drag force is greater or less than that for a single cylinder. The measurements of drag and lift forces for various arrangements reveal two different regimes for the lift force. In one regime, the lift force directed toward the wake of the upstream cylinder is due to the entrainment of the flow into the fully developed wake of the upstream cylinder. The lift force in this regime reaches a maximum value when the downstream cylinder is near to the upstream wake boundary. In the second regime, at very small spacings, the lift force becomes very large due to an intense gap flow which displaces the wake of the upstream cylinder. The maximum lift force occurs with the downstream cylinder near to the horizontal axis of the upstream cylinder. A discontinuity in the lift force for some staggered arrangements is found and attributed to the bistable nature of the gap flow.

scholarly journals Numerical Analysis of Fairings for Bicycles

2021 ◽  
Author(s):  
Polamarasetty Teja Bhavani ◽  
P. Teja Bhavani ◽  
Y. Seetharama Rao ◽  
B. V. Ramana Murthy
Keyword(s):  
Numerical Analysis ◽  
Drag Force ◽  
Atmospheric Pressure ◽  
Lift Force ◽  
Flow Direction ◽  
Comfort Level ◽  
Oncoming Flow ◽  
Pressure Drag ◽  
Air Resistance ◽  
Drag And Lift

Abstract Aerodynamics is the study of moving air's properties and the interactions between moving air and solids. Rider gets slammed into air particles while riding that gets compressed once rider hit them and then become spaced out once they flow over the rider. The distinction in atmospheric pressure from your front to your back creates a retardant force. The force that's perpendicular to the oncoming flow direction is the lift force. It contrasts with the drag force. Aerodynamic shapes reduce this pressure drag and lift by minimizing that difference in pressure and allowing the air to flow more smoothly over your front, reducing the low-pressure wake behind the cyclist and reducing this drag, and increasing speed in this paper; fairings designed. NACA airfoil as a base, fairings are designed using CATIA.CFD analysis is carried out on the bicycle with a fairing to calculate drag and lift force. As the position of cyclists isn't modified and due to fairing, the air resistance reduces, which may increase the comfort level of cyclists. From this analysis, the economical fairing can be determined, facilitating additional drag and producing less lift.

Drag Reduction for Blunt Body With Cross Flow by Extremum-Seeking Control

2008 ◽  
Author(s):  
Nobuhiko Kamagata ◽  
Susumu Horio ◽  
Koichi Hishida
Keyword(s):  
Control System ◽  
Drag Reduction ◽  
Shear Layer ◽  
Flow Velocity ◽  
Drag Force ◽  
Lift Force ◽  
Flow Direction ◽  
Extremum Seeking ◽  
Extremum Seeking Control ◽  
Separated Shear Layer

The active flow control, which can adapt to variation of flow velocity and/or direction, is an effective technique to achieve drag reduction. The present study has investigated a separated shear layer and established two control systems; the system reduces drag force and lift force by controlling the separated shear layer to reattachment for variation of flow velocity and /or direction. The adaptive control system to the variation of flow velocity was constructed by using a hot wire anemometer as a sensor to detect flow separation. The system to flow direction was constructed by using pressure transducers as a sensor to estimate drag force and lift force. The extremum-seeking control was introduced as a controller of the both systems. It is indicated from the experimental results that adaptive drag/lift control system to various flow velocity ranging from 3 to 7 m/s and various flow direction ranging from 0 to 30 deg. was established.

Analysis of lift and drag coefficients of a GT2 racing car at various speeds with movable wheels and ground

2015 ◽  
Vol 12 (3) ◽  
pp. 261-270
Author(s):  
Albert Boretti
Keyword(s):  
Wind Tunnel ◽  
Drag Force ◽  
Computational Fluid Dynamic ◽  
Lift Force ◽  
Fluid Dynamic ◽  
Time Simulation ◽  
Rear Wing ◽  
Speed Range ◽  
Drag And Lift ◽  
Lift And Drag

The paper proposes a study of a GT2 racing car with a computational fluid dynamic (CFD) tool. Results of STAR-CCM+ simulations of the flow around the car in a wind tunnel with movable ground and wheels are presented for different air speeds to assess the different contributions of pressure and shear to lift and drag over the speed range. The rear wing contributes more than 85% of the lift force and 7-8% of the drag force for this particular class of racing cars. When reference is made to the low speed drag and lift coefficients, increasing the speed from 25 to 100 m/s produces an increase of CD of more than 3% and a reduction of CL of more than 2%. The resultsuggests modifying the constant CD and CL values used in lap time simulation toolsintroducing the tabulated values to interpolate vs. the speed of the car.

scholarly journals Effect of turbulent fluctuations on the drag and lift forces on a towed sphere and its boundary layer

2013 ◽  
Vol 721 ◽  
pp. 155-179 ◽  
Author(s):  
Holger Homann ◽  
Jérémie Bec ◽  
Rainer Grauer
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Spherical Particle ◽  
Drag Force ◽  
Turbulent Regime ◽  
Mean Velocity ◽  
Turbulent Fluctuations ◽  
The Mean ◽  
Lift Forces ◽  
Drag And Lift

AbstractThe impact of turbulent fluctuations on the forces exerted by a fluid on a towed spherical particle is investigated by means of high-resolution direct numerical simulations. The measurements are carried out using a novel scheme to integrate the two-way coupling between the particle and the incompressible surrounding fluid flow maintained in a high-Reynolds-number turbulent regime. The main idea consists of combining a Fourier pseudo-spectral method for the fluid with an immersed-boundary technique to impose the no-slip boundary condition on the surface of the particle. This scheme is shown to converge as the power $3/ 2$ of the spatial resolution. This behaviour is explained by the ${L}_{2} $ convergence of the Fourier representation of a velocity field displaying discontinuities of its derivative. Benchmarking of the code is performed by measuring the drag and lift coefficients and the torque-free rotation rate of a spherical particle in various configurations of an upstream-laminar carrier flow. Such studies show a good agreement with experimental and numerical measurements from other groups. A study of the turbulent wake downstream of the sphere is also reported. The mean velocity deficit is shown to behave as the inverse of the distance from the particle, as predicted from classical similarity analysis. This law is reinterpreted in terms of the principle of ‘permanence of large eddies’ that relates infrared asymptotic self-similarity to the law of decay of energy in homogeneous turbulence. The developed method is then used to attack the problem of an upstream flow that is in a developed turbulent regime. It is shown that the average drag force increases as a function of the turbulent intensity and the particle Reynolds number. This increase is significantly larger than predicted by standard drag correlations based on laminar upstream flows. It is found that the relevant parameter is the ratio of the viscous boundary layer thickness to the dissipation scale of the ambient turbulent flow. The drag enhancement can be motivated by the modification of the mean velocity and pressure profile around the sphere by small-scale turbulent fluctuations. It is demonstrated that the variance of the drag force fluctuations can be modelled by means of standard drag correlations. Temporal correlations of the drag and lift forces are also presented.

Drag and lift forces on a rotating sphere in a linear shear flow

1999 ◽  
Vol 384 ◽  
pp. 183-206 ◽  
Author(s):  
RYOICHI KUROSE ◽  
SATORU KOMORI
Keyword(s):  
Shear Flow ◽  
Lift Force ◽  
Fluid Velocity ◽  
Reynolds Numbers ◽  
Fluid Shear ◽  
Rotating Sphere ◽  
High Particle ◽  
Linear Shear ◽  
Lift Forces ◽  
Drag And Lift

The drag and lift forces acting on a rotating rigid sphere in a homogeneous linear shear flow are numerically studied by means of a three-dimensional numerical simulation. The effects of both the fluid shear and rotational speed of the sphere on the drag and lift forces are estimated for particle Reynolds numbers of 1[les ]Rep[les ]500.The results show that the drag forces both on a stationary sphere in a linear shear flow and on a rotating sphere in a uniform unsheared flow increase with increasing the fluid shear and rotational speed. The lift force on a stationary sphere in a linear shear flow acts from the low-fluid-velocity side to the high-fluid-velocity side for low particle Reynolds numbers of Rep<60, whereas it acts from the high-velocity side to the low-velocity side for high particle Reynolds numbers of Rep>60. The change of the direction of the lift force can be explained well by considering the contributions of pressure and viscous forces to the total lift in terms of flow separation. The predicted direction of the lift force for high particle Reynolds numbers is also examined through a visualization experiment of an iron particle falling in a linear shear flow of a glycerin solution. On the other hand, the lift force on a rotating sphere in a uniform unsheared flow acts in the same direction independent of particle Reynolds numbers. Approximate expressions for the drag and lift coefficients for a rotating sphere in a linear shear flow are proposed over the wide range of 1[les ]Rep[les ]500.

scholarly journals NUMERICAL SIMULATION ON REAR SPOILER ANGLE OF MINI MPV CAR FOR CONDUCTING STABILITY AND SAFETY

SINERGI ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 23
Author(s):  
Alief Avicenna Luthfie ◽  
Dedik Romahadi ◽  
Hanif Ghufron ◽  
Solli Dwi Murtyas
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Drag Force ◽  
Lift Force ◽  
Lift Coefficient ◽  
Air Resistance ◽  
Rear Part ◽  
Rear Spoiler ◽  
Computational Fluid Dynamics Cfd ◽  
Drag And Lift

Spoiler attached on the rear part of a car can generate drag force and negative lift force, called downforce. This drag force can increase air resistance to the car, meanwhile, a negative lift force can improve the car’s stability and safety. Refer to many researchers, the shape and the angle of the spoiler give different aerodynamic effects and therefore give a different value of drag force and lift force. Based on these facts, this study was focused on the analysis of different spoiler angle attached to a mini MPV car to drag and lift force generated by the spoiler. The method used in this study is a numerical simulation using the Computational Fluid Dynamics (CFD) technique. The analysis was carried out at different spoiler angle and car’s speed. The spoiler angles are -20o, -10o, 0o, 10o, and 20o. The car’s speeds are 40 km/h, 60 km/h, 80 km/h, 100 km/h, and 120 km/h. Then the drag and lift force and their coefficient generated by different spoiler angles were being investigated at specified speeds. The result shows that higher spoiler angles generate higher drag and lower lift. Spoiler angles higher than 0o generate negative lift force, otherwise generate positive lift force. Therefore, to increase a car’s stability and safety, it is recommended to use a spoiler angle higher than 0o. Based on the result, it is best to use spoiler angle 10o because it generates negative lift force with -0.05 lift coefficient and 0,68 drag coefficient.

scholarly journals Investigation of Drag and Lift Forces over the Profile of Car with Rearspoiler using CFD

2015 ◽  
Vol 1 (8) ◽  
pp. 331
Author(s):  
Naveen Kumar Velagapudi ◽  
Lalit Narayan K. ◽  
L. N. V. Narasimha Rao ◽  
Sri Ram Y.
Keyword(s):  
Drag Force ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Fuel Utilization ◽  
Ansys Fluent ◽  
Total Drag ◽  
Rear Spoiler ◽  
Computational Fluid Dynamics Cfd ◽  
Lift Forces ◽  
Drag And Lift

Now a days demand of a high speed car is increasing in which vehicle stability is of major concern. Forces like drag& lift,weight,side forces and thrust acts on a vehicle when moving on road which significantly effect the fuel consumption The drag force is produced by relative motion between air and vehicle and about 60% of total drag is produced at the rear end. Reduction of drag force at the rear end improves the fuel utilization. This work aims to reduce the drag force which improves fuel utilization and protects environment as well. In the stage of work a sedan car with different types of spoilers are used to reduce the aerodynamic drag force. The design of sedan car has been done on CATIA-2010 and the same is used for analysis in ANSYS-(fluent). The analysis is done for finding out drag and lift forces at different velocities, and spoilers. This study proposes an effective numerical model based on the computational fluid dynamics (CFD) approach to obtain the flow structure around a passenger car with a rear spoiler

scholarly journals Drag and lift forces acting on a spherical gas bubble in homogeneous shear liquid flow

2009 ◽  
Vol 629 ◽  
pp. 173-193 ◽  
Author(s):  
KEN-ICHI SUGIOKA ◽  
SATORU KOMORI
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Lift Force ◽  
Lift Coefficient ◽  
Gas Bubble ◽  
Fluid Shear ◽  
Air Bubble ◽  
Linear Shear ◽  
Lift Forces ◽  
Drag And Lift

Drag and lift forces acting on a spherical gas bubble in a homogeneous linear shear flow were numerically investigated by means of a three-dimensional direct numerical simulation (DNS) based on a marker and cell (MAC) method. The effects of fluid shear rate and particle Reynolds number on drag and lift forces acting on a spherical gas bubble were compared with those on a spherical inviscid bubble. The results show that the drag force acting on a spherical air bubble in a linear shear flow increases with fluid shear rate of ambient flow. The behaviour of the lift force on a spherical air bubble is quite similar to that on a spherical inviscid bubble, but the effects of fluid shear rate on the lift force acting on an air bubble in the linear shear flow become bigger than that acting on an inviscid bubble in the particle Reynolds number region of 1≤Rep≤300. The lift coefficient on a spherical gas bubble approaches the lift coefficient on a spherical water droplet in the linear shear air-flow with increase in the internal gas viscosity.

scholarly journals Numerical Investigation of M21 Aerofoil and Effect of Plain Flapper at Various Angle of Attack

2021 ◽  
Vol 2070 (1) ◽  
pp. 012153
Author(s):  
Vimal Patel ◽  
Vikram Rathod ◽  
Chirag Patel
Keyword(s):  
Drag Force ◽  
Lift Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Similar Work ◽  
Maximum Value ◽  
Different Types ◽  
Stall Angle ◽  
Drag And Lift ◽  
Plane Jet

Abstract The aerofoil plays an important role in any structure moving in a fluid-like in a passenger plane, jet plane, or helicopter. The aerofoils decide whether the lift force is appropriate to balance the weight of the plane or not and the amount of drag force is required on the vehicle. The purpose of this project is to simulate the M21 Aerofoil with the help of FLUENT and validate it with theory. This Project also includes the study of various Flapper designs and their simulation. Flappers are useful when the Airplane is about to take-off or landing. The Important parameters to be study are Lift Force, Drag Force, lift coefficient, and Drag coefficient. Simulation has been done for the different Angle of Attack which is useful for finding maximum Lift force and Stall Angle. The Work includes simulation of Plain Flapper for the Angle of Attack where CL/CD is maximum. Similar work can be done for different types of Flapper used in Airplane. The stall angle achieved for M21 was 24° and maximum value of CL/CD measured at 7° A.O.A. Investigation also shows that for the 10° plain flap angle highest drag and lift force was possible. It contains the study of the Adverse Yaw effect which rolls the Airplane while taking a turn. since the validity of any theoretical prediction can only be assessed in practice.

scholarly journals A Continuum Model of Drag and Lift Forces for Inclined Planes Dragged Through Granular Beds

2019 ◽  
Author(s):  
Hong Guo ◽  
Jiangtao Fu ◽  
Rui Guo ◽  
Hong Jiang ◽  
Nengyuan Chen
Keyword(s):  
Inclination Angle ◽  
Continuum Model ◽  
Lift Force ◽  
Friction Angle ◽  
Granular Bed ◽  
Coulomb Model ◽  
Lift Forces ◽  
Drag And Lift ◽  
Inclined Angle ◽  
Inclined Planes

Both drag and lift forces impact an inclined plane when it is dragged through a granular bed. In this paper, the following results have been obtained: the drag and lift forces grow with the velocity of motion; when the immersion depth is constant, the inclination angle has no effect on drag force, however, the lift force increases linearly with this inclination angle; the ratio of drag and lift forces is exactly equal to the tangent value of the inclined angle. In order to describe this physical process macroscopically, a continuum wedge model based on the Coulomb model is established to predict drag and lift forces. Particularly，the dynamic friction angle in the assumed shear band is predicted as a function of both inclined angle and moving velocity.

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