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.

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.

Ground Effect on the Vortex Flow and Aerodynamics of a Slender Delta Wing

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
T. Lee ◽  
L. S. Ko
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Leading Edge ◽  
Ground Effect ◽  
Drag Forces ◽  
Wing Chord ◽  
Ground Distance ◽  
Lift And Drag ◽  
Wing Stall ◽  
Wing In Ground Effect

The ground effect on the aerodynamic loading and leading-edge vortex (LEV) flow generated by a slender delta wing was investigated experimentally. Both the lift and drag forces were found to increase with reducing ground distance (up to 50% of the wing chord). The lift increment was also found to be the greatest at low angles of attack α and decreased rapidly with increasing ground distance and α. The ground effect-caused earlier wing stall was also accompanied by a strengthened LEV with an increased rotational speed and size compared to the baseline wing. The smaller the ground distance, the stronger the LEV and the earlier vortex breakdown became. Meanwhile, the vortex trajectory was also found to be located further inboard and above the delta wing in ground effect compared to its baseline-wing counterpart. Finally, for wing-in-ground effect (WIG) craft with delta-wing planform the most effective in-ground-effect flight should be kept within 10% of the wing chord.

Simulation of Viscous Diffusion for Extension of the Surface Vorticity Method to Boundary Layer and Separated Flows

1981 ◽  
Vol 23 (3) ◽  
pp. 157-167 ◽  
Author(s):  
D. T. C. Porthouse ◽  
R. I. Lewis
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Point Vortex ◽  
Fluid Flows ◽  
Reynolds Numbers ◽  
Separated Flows ◽  
Two Dimensional ◽  
Drag Forces ◽  
Boundary Layer Parameter ◽  
Lift And Drag

A numerical method for two-dimensional incompressible viscous fluid flows is tested on the diffusion of a point vortex. It is then applied to the boundary layer to reconstruct the Blasius profile, to demonstrate flow separation, and to simulate turbulence. The significance of Thwaites' boundary layer parameter for flow separation is explained. The Kelvin-Helmholtz instability, which is responsible for two-dimensional turbulence, is represented by the motion of an array of point vortices after an initial disturbance. The formation of the Von Karman vortex street downstream of a circular cylinder is described by computer simulation, and the influence of viscous diffusion is shown. For two different cylinder Reynolds numbers the vortex shedding frequencies and oscillating lift and drag forces are evaluated.

scholarly journals Numerical Investigation of Turbine Blades with Leading-Edge Tubercles in Uniform Current

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2205
Author(s):  
Shuling Chen ◽  
Yan Liu ◽  
Changzhi Han ◽  
Shiqiang Yan ◽  
Zhichao Hong
Keyword(s):  
Flow Separation ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Hydrodynamic Performance ◽  
Micro Scale ◽  
Drag Forces ◽  
Uniform Current ◽  
Naca0018 Airfoil ◽  
Lift And Drag

Inspired by the tubercles on humpback whale flippers, leading-edge tubercles have been incorporated into the design of wings and turbine blades in an attempt to improve their hydrodynamic performance. Although promising improvements, especially in terms of the stall performance, have been demonstrated in the limited research that exists to date, the effectiveness of the leading-edge tubercles seems to be influenced by the base blade. This paper focuses on the introduction of sinusoidal leading-edge tubercles to a base blade developed from the classic NACA0018 airfoil, and numerically investigates the effectiveness of leading-edge tubercles on the hydrodynamics associated with the blade in uniform current with different attack angles. Both the macroscopic parameters, such as the lift and drag forces, and the micro-scale flow characteristics, including the vortex and flow separation, are analyzed. The results indicate that the leading-edge tubercles brings a significant influence on the hydrodynamic forces acting on the blade when subjected to an attack angle greater than 15°. This study also reveals the important role of the turbulence and flow separation on hydrodynamic loading on the blade and the considerable influence of the tubercles on such micro-scale flow characteristics. Although the conditions applied in this work are relatively ideal (e.g., the blade is fixed in a uniform flow and the end effect is ignored), the satisfactory agreement between the numerical and corresponding experimental data implies that the results are acceptable. This work builds a good reference for our future work on the hydrodynamic performance of tidal turbines which adopt this kind of blade for operating in both uniform and shearing currents.

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.

scholarly journals A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces

Lab on a Chip ◽  
2012 ◽  
Vol 12 (22) ◽  
pp. 4617 ◽  
Author(s):  
Peter Barkholt Muller ◽  
Rune Barnkob ◽  
Mads Jakob Herring Jensen ◽  
Henrik Bruus
Keyword(s):  
Acoustic Radiation ◽  
Numerical Study ◽  
Drag Forces ◽  
Induced Drag ◽  
Radiation Forces

Numerical Investigation of Cowl Lip Adjustments for a Rocket-Based Combined-Cycle Inlet in Takeoff Regime

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Lei Shi ◽  
Xiaowei Liu ◽  
Guoqiang He ◽  
Fei Qin ◽  
Xianggeng Wei ◽  
...  
Keyword(s):  
Numerical Integration ◽  
Numerical Investigation ◽  
Flow Separation ◽  
Static Condition ◽  
Combined Cycle ◽  
Variable Geometry ◽  
Overall Performance ◽  
Negative Impacts

AbstractNumerical integration simulations were performed on a ready-made central strut-based rocket-based combined-cycle (RBCC) engine operating in the ejector mode during the takeoff regime. The effective principles of various cowl lip positions and shapes on the inlet operation and the overall performance of the entire engine were investigated in detail. Under the static condition, reverse cowl lip rotation in a certain range was found to contribute comprehensive improvement to the RBCC inlet and the entire engine. However, the reverse rotation of the cowl lip contributed very little enhancement of the RBCC inlet under the low subsonic flight regime and induced extremely negative impacts in the high subsonic flight regime, especially in terms of a significant increase in the drag of the inlet. Changes to the cowl lip shape provided little improvement to the overall performance of the RBCC engine, merely shifting the location of the leeward area inside the RBCC inlet, as well as the flow separation and eddy, but not relieving or eliminating those phenomena. The results of this study indicate that proper cowl lip rotation offers an efficient variable geometry scheme for a RBCC inlet in the takeoff regime.

Vibration Excitation Forces in a Normal Triangular Tube Bundle Subjected to Two-Phase Cross Flow

2011 ◽  
Author(s):  
E. S. Perrot ◽  
N. W. Mureithi ◽  
M. J. Pettigrew ◽  
G. Ricciardi
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Random Excitation ◽  
Two Phase ◽  
Constant Frequency ◽  
Fluid Forces ◽  
Drag Forces ◽  
Wide Range ◽  
Drag And Lift ◽  
Lift And Drag

This paper presents test results of vibration forces in a normal triangular tube bundle subjected to air-water cross-flow. The dynamic lift and drag forces were measured with strain gage instrumented cylinders. The array has a pitch-to-diameter ratio of 1.5, and the tube diameter is 38 mm. A wide range of void fraction and fluid velocities were tested. The experiments revealed significant forces in both the drag and lift directions. Constant frequency and quasi-periodic fluid forces were found in addition to random excitation. These forces were analyzed and characterized to understand their origins. The forces were found to be dependent on the position of the cylinder within the bundle. The results are compared with those obtained with flexible cylinders in the same tube bundle and to those for a rotated triangular tube bundle. These comparisons reveal the influence of quasi-periodic forces on tube motions.

scholarly journals Measurement of Formula One Car Drag Forces on the Test Track

1996 ◽  
Author(s):  
C. M. Crewe ◽  
M. A. Passmore ◽  
P. Symonds
Keyword(s):  
Test Track ◽  
Formula One ◽  
Drag Forces
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