scholarly journals The Aerodynamics of a Cornering Inverted Wing in Ground Effect

2014 ◽  
Vol 553 ◽  
pp. 205-210 ◽  
Author(s):  
James Keogh ◽  
Graham Doig ◽  
Tracie J. Barber ◽  
Sammy Diasinos
Keyword(s):  
Ground Effect ◽  
Oncoming Flow ◽  
Primary Vortex ◽  
Side Force ◽  
Straight Line ◽  
Constant Radius ◽  
Flow Curvature ◽  
Wing Geometry ◽  
Yaw Angle ◽  
Line Condition

For racing car configurations an inverted wing produces negative lift that allows increased levels of acceleration to be maintained through corners. Routine aerodynamic analysis, however, will typically be in the straight-line condition. A numerical analysis of the inverted T026 wing geometry through the curved path of a constant radius corner was conducted. The asymmetrical properties of the oncoming flow resulted in the introduction of a rolling and yawing moment along the span, as well as side-force. Yaw angle, flow curvature and a velocity gradient resulted in changes to the pressure distribution over the wing surface. Primary vortex behaviour was observed to differ significantly in both direction and structure.

scholarly journals The Effect of Cornering on the Aerodynamics of a Multi-Element Wing in Ground Effect

Fluids ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 3
Author(s):  
Dipesh Patel ◽  
Andrew Garmory ◽  
Martin Passmore
Keyword(s):  
Numerical Data ◽  
Ground Effect ◽  
Force Balance ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Surface Pressure Distribution ◽  
Straight Line ◽  
Race Cars ◽  
Line Condition ◽  
Wing In Ground Effect

This research investigates the effects of cornering on a multi-element wing in ground effect with the aim to improve the understanding of such in the effort to improve the performance of open-wheel race cars. A numerical validation study was performed to confirm the validity of the Detached Eddy Simulation CFD methodology used. This involved comparing numerical data with wind tunnel experimental data using a force balance and PIV for the velocity field to reveal the trajectory of the trailing vortex system. Once validated, the CFD was used to test the wing within a cornering condition as well as fixed yaw condition and its aerodynamic performance relative to the straight-line condition was analysed. Asymmetry was the general theme concerning the on-surface pressure distribution with this most prominent under the cornering condition. Ultimately, minimal change was observed regarding the downforce generated whilst drag was found to increase in the cornering condition and decrease slightly in the fixed yaw condition. Asymmetry was also observed in the wake of the wing where alterations to the relative strengths of the vortices was observed as well as their downstream paths which was generally governed by the direction of the freestream flow.

Assessment of derailment risk in railway turnouts through quasi-static analysis and dynamic simulation

2021 ◽  
pp. 095440972110240
Author(s):  
Ping Wang ◽  
Jun Lai ◽  
Tao Liao ◽  
Jingmang Xu ◽  
Jian Wang ◽  
...  
Keyword(s):  
Static Analysis ◽  
Dynamic Simulation ◽  
Economic Losses ◽  
Derailment Coefficient ◽  
Straight Line ◽  
Main Track ◽  
Pass Through ◽  
Multi Body ◽  
Yaw Angle ◽  
Curve Radius

Train derailments in railway switches are becoming more and more common, which have caused serious casualties and economic losses. Most previous studies ignored the derailment mechanism when vehicles pass through the turnout. With this consideration, this work aims to research the 3D derailment coefficient limit and passing performance in turnouts through the quasi-static analysis and multi-body dynamic simulation. The proposed derailment criteria have considered the influence of creep force and wheelset yaw angle. Results show that there are two derailing stages in switch panel, which are climbing the switch rail and stock rail, respectively. The 3D derailment coefficient limit at the region of top width 5 mm to 20 mm is much lower than the main track rail, which shows that wheels are more likely to derail in this area. The curve radius before the switch rail is suggested to be set as 350 m. When the curve radius before turnout is 65 m, the length of the straight line between the curve and turnout needs to be larger than 3 m. This work can provide a good understanding of the derailment limit and give guidance to set safety criteria when vehicles pass through the turnout.

scholarly journals Numerical studies on aerodynamics of high-speed railway train subjected to strong crosswind

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988727
Author(s):  
Xu Wang ◽  
Yuanhao Qian ◽  
Zengshun Chen ◽  
Xiao Zhou ◽  
Huaqiang Li ◽  
...  
Keyword(s):  
Wind Speed ◽  
High Speed ◽  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Width Ratio ◽  
Force Coefficient ◽  
Rolling Moment ◽  
Side Force ◽  
Train Speed ◽  
Yaw Angle

Under the action of strong crosswind, the aerodynamic behavior of a rail vehicle at high speed will be changed significantly, which could directly affect the safe operation of the vehicle. With the help of the shape of train used in China, the aerodynamic characteristics of trains with scale of 1:1 is investigated using computational fluid dynamics numerical simulation method, which consists of the variation of aerodynamics force and moment with wind yaw angle, wind speed, train speed, and nose shape. After an initial validation against Baker’s results from wind tunnel test, the numerical model is then used to investigate the aerodynamic characteristics of the trains. The numerical results indicate that lift coefficient of the M train is slightly higher than TMC1 and TMC2 trains. Regardless of aerodynamics force coefficients, TMC1 reaches the maximum at a yaw angle of 75°. Aerodynamics force coefficient increases with both wind speed and train speed, but the change of which is not linear. Comparing aerodynamic force with different geometric dimensions of train nose, it is shown that height–width ratio is insensitive to side force and rolling moment, but sensitive to lift force from the yaw angle 0°–90°. The side force coefficient, as we most concern, is less than other results, when the length–width ratio is 1 and height–width is 0.87.

Detached-Eddy Simulation of Ground Effect on the Wake of a High-Speed Train

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Chao Xia ◽  
Xizhuang Shan ◽  
Zhigang Yang
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Vortex Pair ◽  
Ground Effect ◽  
Longitudinal Vortex ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

The influence of ground effect on the wake of a high-speed train (HST) is investigated by an improved delayed detached-eddy simulation. Aerodynamic forces, the time-averaged and instantaneous flow structure of the wake are explored for both the stationary ground and the moving ground. It shows that the lift force of the trailing car is overestimated, and the fluctuation of the lift and side force is much greater under the stationary ground, especially for the side force. The coexistence of multiscale vortex structures can be observed in the wake along with vortex stretching and pairing. Furthermore, the out-of-phase vortex shedding and oscillation of the longitudinal vortex pair in the wake are identified for both ground configurations. However, the dominant Strouhal number of the vortex shedding for the stationary and moving ground is 0.196 and 0.111, respectively, due to the different vorticity accumulation beneath the train. A conceptual model is proposed to interpret the mechanism of the interaction between the longitudinal vortex pair and the ground. Under the stationary ground, the vortex pair embedded in a turbulent boundary layer causes more rapid diffusion of the vorticity, leading to more intensive oscillation of the longitudinal vortex pair.

Design of Strait-Line Tracking Controller of Under-Actuated USV Based on Back-Stepping Method and Feedback Compensation

2011 ◽  
Vol 48-49 ◽  
pp. 391-396
Author(s):  
Yu Long Ma ◽  
Jian Da Han ◽  
Yu Qing He
Keyword(s):  
High Performance ◽  
Mobile Robotics ◽  
Path Following ◽  
Main Research ◽  
Path Following Control ◽  
Straight Line ◽  
Feedback Compensation ◽  
Line Tracking ◽  
Line Path ◽  
Yaw Angle

Unmanned surface vehicle (USV) system has been one of main research directions in mobile robotics because it can be used in many situations. However, high performance path following control, especially straight line tracking control, has been one of the difficult problems in autonomous control of USV system. In this paper, we propose a new straight line path following control algorithm by combining yaw angle feedback and back-stepping technique and show its closed loop stability. The most absorbing advantage of the proposed controller is that it not only reserve the good performance of back-stepping controller but also bring much faster convergent rate, which is very important in real applications. The simulation results with respect to a training ship model have shown the feasibility and validity of the proposed method.

scholarly journals Investigation on Derailment of Empty Wagons of Long Freight Train during Dynamic Braking

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Xin Ge ◽  
Kaiyun Wang ◽  
Lirong Guo ◽  
Min Yang ◽  
Kaikai Lv ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Field Investigation ◽  
Running Safety ◽  
The Poor ◽  
Straight Line ◽  
The World ◽  
Simulation Results ◽  
Dynamic Braking ◽  
Yaw Angle ◽  
Large Wheel

The derailments of empty wagons of long freight trains frequently occurred around the world, which caused tremendous losses every year. Aiming at an actual derailment of empty wagons on straight line during dynamic braking, the field investigation was conducted to find the reasons of the accident. According to the investigation results, the large coupler yaw angle and coupler force, the special connection mode by drawbars, as well as the poor conditions of wheel treads and flanges were supposed to be responsible for the accident. The simulaiton model composed of 3 C80-type gondolas, and two RFC-type drawbars is established, the accuracy of which is validated by the field experimental test. When the wheel-rail friction coefficient is set to be 0.7 and the coupler forces are set to be 350 kN with a coupler yaw angle of 7 degrees, the simulation results are consistent with the field investigation results. Simulation results indicate that the coupler yaw angle, coupler force, and wheel-rail friction coefficient have significant influences on the derailment. The increasing coupler yaw angle and coupler force will increase the risk of derailment. For the wagon units adopting the drawbars, the riskiest wagon changes from the middle wagon to the front one as the lateral components of the coupler forces increase. A large wheel-rail friction coefficient can raise the risk of derailment. However, an overlarge friction coefficient will decrease the derailment risk. According to the field investigation and simulation results, the wheel-rail friction coefficients should be limited below 0.5 to ensure the running safety of empty wagons. Besides, the operations of the train should be optimized to avoid large coupler yaw angle and coupler force.

scholarly journals Aerodynamics of an aerofoil in transonic ground effect: Methods for blowdown windtunnel scale testing

2012 ◽  
Vol 116 (1180) ◽  
pp. 599-620 ◽  
Author(s):  
G. Doig ◽  
T. J. Barber ◽  
A. J. Neely ◽  
D. D. Myre
Keyword(s):  
Wind Tunnel ◽  
Ground Plane ◽  
Ground Effect ◽  
Mirror Image ◽  
Navier Stokes ◽  
Oncoming Flow ◽  
Ground Clearance ◽  
Mach Numbers ◽  
Reynolds Averaged Navier Stokes ◽  
Symmetry Method

Abstract Experimental aerodynamic testing of objects in close ground proximity at high subsonic Mach numbers is difficult due to the construction of a transonic moving ground being largely unfeasible. Two simple, passive methods have been evaluated for their suitability for such testing in a small blowdown wind tunnel: an elevated ground plane, and a symmetry (or mirror-image) approach. The methods were examined using an unswept wing of RAE2822 section, with experiments and Reynolds-Averaged Navier Stokes CFD used synergistically to determine the relative merits of the techniques. The symmetry method was found to be a superior approximation of a moving ground in all cases, with mild discrepancies observed only at the lowest ground clearance. The elevated ground plane was generally found to influence the oncoming flow and distort the flowfield between the wing and ground, such that the method provided a less-satisfactory match to moving ground simulations compared to the symmetry technique.

Experimental and Theoretical Hydrodynamic Forces on a Mathematical Model in Confined Waters

1983 ◽  
Vol 27 (02) ◽  
pp. 75-89
Author(s):  
Stuart B. Cohen ◽  
Robert F. Beck
Keyword(s):  
Mathematical Model ◽  
Shallow Water ◽  
Hydrodynamic Forces ◽  
Experimental Results ◽  
Hull Form ◽  
Side Force ◽  
Yaw Angle ◽  
Yaw Moment

Experimental results are given for a mathematical hull form tested in shallow water. The side force and yaw moment acting on the model due to a yaw angle, the presence of canal walls, and the interaction with another stationary mathematical shape are presented. Comparisons with linearized theories are made and, in general, found to be good.

Aerodynamics of Fixed and Rotating Spoked Cycling Wheels

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
S. J. Karabelas ◽  
N. C. Markatos
Keyword(s):  
Aerodynamic Performance ◽  
Numerical Results ◽  
Vertical Force ◽  
Side Force ◽  
Magnus Effect ◽  
Angular Velocities ◽  
Ground Effects ◽  
Effects Of Rotation ◽  
Yaw Angle ◽  
Yaw Moment

The performance of a semiracing spoked wheel is numerically and experimentally studied at full size in a wind tunnel. The numerical investigation is divided into two parts. In the first part, the wheel is considered to be fixed (no rotation) and the numerical results are compared to the experimental measurements. The flow past the wheel is treated as stationary and turbulent. The effects of cross wind and the wheel’s speed on the drag, side force, and yaw moment are investigated. Numerical results are presented via diagrams and plots at various yaw angles. Both the measurements and predictions agree quite well and they show a considerable increase in the yaw moment and side force at medium and high yaw angles. The axial drag force initially increases with yaw angle (up to 7.5 deg) and eventually decreases. Ground effects did not affect the overall loads, except for the vertical force at high yaw angles. In the second part, the effects of rotation have been taken into account. The wheel rotates at constant angular velocities and the flow is modeled as nonstationary and turbulent. The aerodynamic performance of the wheel is strongly affected by the rotational speed. In most of the cases, as the latter parameter increases, the loads nonlinearly increase. The rotation generates asymmetrical loading, since the flow is accelerated in one side and decelerated in the other (the Magnus effect). A vertical force is produced, which is dependent on the ratio of the rotational to the free-stream speed. Moreover, in an attempt to assess the effects of the number of spokes to the aerodynamic performance, two other models with 8 and 32 spokes have been numerically tested and compared to the original one (16 spokes). The results revealed, as expected, an increase in the axial drag and vertical force with the number of spokes.

scholarly journals A Thrust Cooperative Control Strategy of Multiple Propulsion Motors for Distributed Electric Propulsion Aircraft

2021 ◽  
Vol 12 (4) ◽  
pp. 199
Author(s):  
Luhui Weng ◽  
Xuan Zhang ◽  
Taike Yao ◽  
Feifei Bu ◽  
Hang Li
Keyword(s):  
Experimental Verification ◽  
Control Strategy ◽  
Electric Propulsion ◽  
Cooperative Control ◽  
Straight Line ◽  
Yaw Angle ◽  
The Given ◽  
Yaw Moment

This paper presents a thrust cooperative control strategy of multiple propulsion motors for distributed electric propulsion aircraft. The control strategy can keep the propulsion motors running synchronously when the aircraft is flying in a straight line; at the same time, when the aircraft needs to turn, the yaw moment is generated by changing the speed of the propulsion motors on both sides, so as to achieve the given yaw angle of the aircraft. In order to verify the control strategy, the paper also carries out simulation and experimental verification, and the results show that the cooperative control strategy is feasible.

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