Computational Aerodynamics of a Winston-Cup-Series Race Car

2002 ◽  
Author(s):  
Oktay Baysal ◽  
Terry L. Meek
Keyword(s):  
Present Model ◽  
Pressure Coefficient ◽  
The Body ◽  
Race Car ◽  
Drag Forces ◽  
Surface Pressure Distribution ◽  
Computational Aerodynamics ◽  
Baseline Case ◽  
Quantitative Results ◽  
Lift And Drag

Since the goal of racing is to win and since drag is a force that the vehicle must overcome, a thorough understanding of the drag generating airflow around and through a race car is greatly desired. The external airflow contributes to most of the drag that a car experiences and most of the downforce the vehicle produces. Therefore, an estimate of the vehicle’s performance may be evaluated using a computational fluid dynamics model. First, a computer model of the race car was created from the measurements of the car obtained by using a laser triangulation system. After a computer-aided drafting model of the actual car was developed, the model was simplified by removing the tires, roof strakes, and modification of the spoiler. A mesh refinement study was performed by exploring five cases with different mesh densities. By monitoring the convergence of the computed drag coefficient, the case with 2 million elements was selected as being the baseline case. Results included flow visualization of the pressure and velocity fields and the wake in the form of streamlines and vector plots. Quantitative results included lift and drag, and the body surface pressure distribution to determine the centerline pressure coefficient. When compared with the experimental results, the computed drag forces were comparable but expectedly lower than the experimental data mainly attributable to the differences between the present model and the actual car.

Dragonfly flight. I. Gliding flight and steady-state aerodynamic forces.

1997 ◽  
Vol 200 (3) ◽  
pp. 543-556 ◽  
Author(s):  
JM Wakeling ◽  
CP Ellington
Keyword(s):  
Steady State ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
The Body ◽  
Flat Plates ◽  
Viscous Forces ◽  
Drag Forces ◽  
Aerodynamic Properties ◽  
Gliding Flight ◽  
Lift And Drag

The free gliding flight of the dragonfly Sympetrum sanguineum was filmed in a large flight enclosure. Reconstruction of the glide paths showed the flights to involve accelerations. Where the acceleration could be considered constant, the lift and drag forces acting on the dragonfly were calculated. The maximum lift coefficient (CL) recorded from these glides was 0.93; however, this is not necessarily the maximum possible from the wings. Lift and drag forces were additionally measured from isolated wings and bodies of S. sanguineum and the damselfly Calopteryx splendens in a steady air flow at Reynolds numbers of 700-2400 for the wings and 2500-15 000 for the bodies. The maximum lift coefficients (CL,max) were 1.07 for S. sanguineum and 1.15 for C. splendens, which are greater than those recorded for all other insects except the locust. The drag coefficient at zero angle of attack ranged between 0.07 and 0.14, being little more than the Blassius value predicted for flat plates. Dragonfly wings thus show exceptional steady-state aerodynamic properties in comparison with the wings of other insects. A resolved-flow model was tested on the body drag data. The parasite drag is significantly affected by viscous forces normal to the longitudinal body axis. The linear dependence of drag on velocity must thus be included in models to predict the parasite drag on dragonflies at non-zero body angles.

Controlling subterranean forces enables a fast, steerable, burrowing soft robot

2021 ◽  
Vol 6 (55) ◽  
pp. eabe2922
Author(s):  
Nicholas D. Naclerio ◽  
Andras Karsai ◽  
Mason Murray-Cooper ◽  
Yasemin Ozkan-Aydin ◽  
Enes Aydin ◽  
...  
Keyword(s):  
Granular Media ◽  
The Body ◽  
Nonlinear Dependence ◽  
Soft Robot ◽  
Flow Angle ◽  
Drag Forces ◽  
Tip Extension ◽  
Order Of Magnitude ◽  
Lift And Drag ◽  
And Control

Robotic navigation on land, through air, and in water is well researched; numerous robots have successfully demonstrated motion in these environments. However, one frontier for robotic locomotion remains largely unexplored—below ground. Subterranean navigation is simply hard to do, in part because the interaction forces of underground motion are higher than in air or water by orders of magnitude and because we lack for these interactions a robust fundamental physics understanding. We present and test three hypotheses, derived from biological observation and the physics of granular intrusion, and use the results to inform the design of our burrowing robot. These results reveal that (i) tip extension reduces total drag by an amount equal to the skin drag of the body, (ii) granular aeration via tip-based airflow reduces drag with a nonlinear dependence on depth and flow angle, and (iii) variation of the angle of the tip-based flow has a nonmonotonic effect on lift in granular media. Informed by these results, we realize a steerable, root-like soft robot that controls subterranean lift and drag forces to burrow faster than previous approaches by over an order of magnitude and does so through real sand. We also demonstrate that the robot can modulate its pullout force by an order of magnitude and control its direction of motion in both the horizontal and vertical planes to navigate around subterranean obstacles. Our results advance the understanding and capabilities of robotic subterranean locomotion.

Application of Computional Fluid Dynamics for Study of the Occurrence of Aerodynamic Effect for its Application in the Construction of Electric Race Car

2015 ◽  
Vol 809-810 ◽  
pp. 956-961
Author(s):  
Łukasz Grabowski ◽  
Andrzej Baier ◽  
Andrzej Buchacz ◽  
Michał Majzner ◽  
Michał Sobek
Keyword(s):  
Fluid Dynamics ◽  
Aerodynamic Drag ◽  
The Body ◽  
Air Velocity ◽  
Race Car ◽  
Drag Forces ◽  
Graphic Analysis ◽  
Aerodynamic Effect ◽  
Air Streams ◽  
The Ideal

In this article the issues related to Computional Fluid Dynamics of the occurrence of innovative aerodynamic effect were presented. Analysis were performed to determine the occurrence of Kammback aerodynamic effect and its application in a shape of a body of the real racing car in order to minimize drag forces of the vehicle. For the analysis, ideal aerodynamic shapes were modeled, subsequently they were subjected to modifications which were used to determine the occurrence of effect. The basic modeled shape was the raindrop shape solid, which is generally regarded as the ideal shape in terms of aerodynamics. The result of analysis was compared with the drag values known from the literature. Afterwards changes in the shape of the base solid were made to verify and determine the optimum Kammback shape, selected from a set of possible solutions, in which the geometrical changes has the lowest difference of values of drag force and drag coefficientCx(Cd)in comparison to the basic raindrop shape. Results of the study were subjected to graphic analysis, especially the distribution of air pressure on the surface of a solid and in a virtual wind tunnel, distribution of the air velocity and the course of air streams around the shape. The results were used to design the body of electric race car. The main objective was to minimize the aerodynamic drag of the vehicle.

Vortex force map method for viscous flows of general airfoils

2017 ◽  
Vol 836 ◽  
pp. 145-166 ◽  
Author(s):  
Juan Li ◽  
Zi-Niu Wu
Keyword(s):  
Flat Plate ◽  
Normal Force ◽  
Viscous Flows ◽  
Reynolds Numbers ◽  
The Body ◽  
Drag Forces ◽  
Edge Force ◽  
Lift And Drag ◽  
Critical Regions ◽  
Map Approach

In a previous paper, an inviscid vortex force map approach was developed for the normal force of a flat plate at arbitrarily high angle of attack and leading/trailing edge force-producing critical regions were identified. In this paper, this vortex force map approach is extended to viscous flows and general airfoils, for both lift and drag forces due to vortices. The vortex force factors for the vortex force map are obtained here by using Howe’s integral force formula. A decomposed form of the force formula, ensuring vortices far away from the body have negligible effect on the force, is also derived. Using Joukowsky and NACA0012 airfoils for illustration, it is found that the vortex force map for general airfoils is similar to that of a flat plate, meaning that force-producing critical regions similar to those of a flat plate also exist for more general airfoils and for viscous flow. The vortex force approach is validated against NACA0012 at several angles of attack and Reynolds numbers, by using computational fluid dynamics.

Fluid forces on a body in shear-flow; experimental use of ‘stationary flow'

1974 ◽  
Vol 340 (1621) ◽  
pp. 147-171 ◽  
Keyword(s):  
Shear Flow ◽  
Lift Force ◽  
Force Measurement ◽  
Fluid Velocity ◽  
Stationary Flow ◽  
The Body ◽  
Fluid Forces ◽  
Drag Forces ◽  
Lift And Drag ◽  
Repulsive Forces

The lift and drag forces have been measured on a sphere and a transverse cylinder immersed in an open liquid shear-flow and situated close to the lower, frictional, boundary (the bed). Two conditions were investigated: ( a ) that of zero drag, when the body was drifting with the flow, and ( b ) that when it was held against the flow. In condition ( a ) the body could be either allowed to rotate about a transverse axis subject to unavoidable pivot friction, or prevented from rotating. Marked difference was found in the magnitude of the lift force according to the applied resistance to rotation. The lift force was a maximum when rotation was prevented and small or undetectable when free rotation was allowed. In the conditions ( a ) and ( b ) the lift force decreased with increasing clearance between body and boundary, to zero when the clearance exceeded approximately one body diameter. In condition ( b ) lift, i. e. normally repulsive, forces of approximately equal magnitudes to those below were exerted as the body approached the upper free liquid surface. In the drifting condition ( a ) the considerable difficulties of observation and force measurement when a body is moving with the flow were removed by the use of a backward-moving bed boundary. By thus superimposing a reverse velocity on the whole system, the mean fluid velocity at any desired distance from the boundary can be made zero relative to the observer without appreciably affecting the internal dynamics of the flow. This device also permitted the repetition of the measurements made by using liquids of greater viscosity than water available in limited quantities. The results are interpreted with an explanation in mind of certain aspects of the motions of unsuspended solids in saltation over a stream bed.

scholarly journals Cavities at atmospheric pressure behind two-dimensional bodies at an angle of attack

2005 ◽  
Vol 47 (1) ◽  
pp. 103-119
Author(s):  
P. M. Haese
Keyword(s):  
Atmospheric Pressure ◽  
Angle Of Attack ◽  
The Body ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Physical Conditions ◽  
Drag Forces ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

AbstractThis paper presents an interior source method for the calculation of semi-infinite cavities behind two-dimensional bluff bodies placed at an angle of attack in a uniform stream. Aspects under consideration include the pressure distribution along the body, especially just ahead of the separation point, lift and drag forces, and how these quantities vary with the angle of attack. We include discussion of the physical conditions of separation, and identify critical angles of attack for which the cavitating flow past an airfoil may (a) become unstable, or (b) yield the greatest lift to drag ratio.

scholarly journals A Perturbation Method to Analyze the Effect of Cross Section and Angle of Attack for Some Conical Bodies in Hypersonic Flow

2010 ◽  
Vol 3 (1) ◽  
pp. 52-58
Author(s):  
N. Talebanfard ◽  
A. B. Rahimi
Keyword(s):  
Perturbation Method ◽  
Cross Section ◽  
Cross Sections ◽  
Angle Of Attack ◽  
The Body ◽  
Drag Forces ◽  
Lift And Drag ◽  
Flow Variables ◽  
Drag Ratio ◽  
Lift To Drag Ratio

An analysis is performed to study the supersonic flow over conical bodies of three different cross sections circular, elliptic and squircle (square with rounded corners) shaped. Perturbation method is applied to find flow variables analytically. In order to find lift and drag forces the pressure force on the body is found, the component along x is drag and the component along z is lift. Three equations are obtained for lift to drag ratio of each cross section. The graphs for L/D show that for a particular cross section an increase in angle of attack, increases L/D. Comparing L/D in the three mentioned cross sections it is obtained that L/D is the greatest in squircle then in ellipse and the least in circle. The results have applications in design of flying objects such as airplanes where many more seats can be arranged in ellipse and or squircle cross section compared to regular circular case.

Magnetohydrodynamic wakes

1963 ◽  
Vol 15 (1) ◽  
pp. 1-12 ◽  
Author(s):  
M. B. Glauert
Keyword(s):  
Velocity Field ◽  
Electric Current ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Effective Diffusivity ◽  
The Body ◽  
Flow Perturbation ◽  
Drag Forces ◽  
Lift And Drag ◽  
Three Degrees Of Freedom

The most notable feature of the magnetohydrodynamic flow at large distances from a three-dimensional body is the formation of two wakes, within which vorticity and electric current are confined. In this paper results are obtained for the effective diffusivity and the relation between current and vorticity in each wake, for the balance between the strengths of the disturbances in the wakes and in the irrotational current-free flow outside, and for the lift and drag forces acting on the body. The final answers take the form of remarkably simple extensions of the corresponding formulae for non-conducting flow. In spite of the extra wake and the presence of a magnetic as well as a velocity field, the flow perturbation at large distances still has only three degrees of freedom.

scholarly journals Numerical Investigation of the Controllable Wing Stall Caused by the Air Injection

2013 ◽  
Vol 60 (2) ◽  
pp. 199-217 ◽  
Author(s):  
Paulina Pietrzak ◽  
Janusz Piechna
Keyword(s):  
Numerical Investigation ◽  
Flow Separation ◽  
Aerodynamic Drag ◽  
Formula One ◽  
Drag Forces ◽  
Surface Pressure Distribution ◽  
Induced Drag ◽  
Air Jet ◽  
Lift And Drag ◽  
Wing Stall

This paper presents results of numerical investigation on a controllable airfoil flow separation phenomena practically applied in Formula One racing by a device called the F-duct. Separation is forced by air jets from slots located at different positions on the profile of the dual element wing and is intended to reduce aerodynamic drag. Slot position and the air jet velocity are the main parameters controlling the flow separation. The flow structure, surface pressure distribution, and the generated downwards lift and drag forces were investigated in this study. Two different flow separation structures have been recognised. Typically, wing stall is correlated with an increase in aerodynamic drag force. However, in the case of the finite wing with low aspect ratio, the induced drag is dominant and is proportional to the downforce. Therefore, flow separation on the wing increases the profile drag while simultaneously reducing the induced drag, resulting in a decrease in the total aerodynamic drag.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

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