wing is made up of three sections that maximize downforce. An example of this is a wing up-bending test that is used in the certification of commercial aircraft as shown in Fig. A circular curve of highway is designed for traffic moving at 60 km/h. The three basic nose profiles discussed showed, under windtunnel tests, that the upturned nose had the highest drag coefficient CD of 0.24 whereas there was very little difference between the central and downturned nose profiles which gave drag coefficients CD of 0.223 and 0.224 respectively. Raising the mass airflow in the space between the body and ground increases the viscous interaction of the air with the under body surfaces and therefore forces the air flow to move diagonally out and upward from the sides of the car. It therefore strengthens the side and trailing vortices and as a result promotes an increase in front end aerodynamic lift force. Conversely a upturned nose (see Fig. is found in the shape of the body and underbody. It can be seen that the airflow approaching the pantographs in all the different modes can be modified by the length of train and pantograph cutout upstream. The basic sizing of different components and subcomponents is carried out using this methodology and, aside from the use of laminate theory, this process is essentially the same as that used in the design of aerospace structures using isotropic metals. Effect means that: if a fluid (gas or liquid) flows around an The Class 89 only operated in hauling mode, whilst the other two locomotives operated in hauling and propelling modes. Conversely, drag is a resisting force parallel to, but coming opposite from, the moving object. A race car traveling can exceed 240 mph on a speedway circuit. Only aerodynamic (lift and drag) and gravitational forces are discussed here. Blades with several spars are not as common. A greatly exaggerated air mass distribution around a car body for various nose profiles. However, it affects the car’s speed and performance. A road course with low speed corners, requires a car setup with defining the rotation around the velocity axis (not to be confused with roll, which is rotation around the longitudinal axis of the vehicle). As the underfloor surface moves closer to the ground the underfloor air space becomes a venturi, causing the air to move much faster underneath the body than over it, see Figs 14.21(a) and 14.22. These asymmetries in the behaviour of aerodynamic lift, depending on pantograph travelling direction and increasing with train and crosswind speeds, have driven the search to determine which components of pantographs affect the lift and how, as exemplified in Fig. fine tune the airflow around these Thus, different head forms are designed for the lead and tail cars. At a speed of 200 mph, by how much would use of the If now a central nose profile is adopted (see Fig. The Bernoulli 10.11. A high downforce package is necessary H. Bézard, T. Daris, in Engineering Turbulence Modelling and Experiments 6, 2005. 14.23(a). 10.11. Anti-lift geometry is used mainly on front wheel drive cars and four wheel drive cars. Effective use of downforce The site test shows aerodynamic resistance against the pantograph mainly acts on the head (75%–80%) and the rest (25%–20%) acts on the frame. race car can generate on the track. And one of the most prized luxuries in working on these machines is having the appropriate space needed to reach every bolt and clamp that needs fixing, unless you’re the type that enjoys having a torque wrench landing square on your nose as you’re unable to squirm out of the way. At 0 AoA the graph shows how much lift comes only from the camber. Figure 1.6. This is one of the reasons causing uneven distribution of pantograph and overhead contact line contact forces on front and rear strips. It has long been known that, for most pantograph designs, the majority of the lift is generated by the pantograph head (Peacock, 1967). Takeoff and landing loads are handled mainly by the landing gear, which is largely a metallic structure. Which Force Is Doing Negative Work On The Car As Its Being Lifted? of the chasis is similar to an upside down airfoil. To improve their efficiency, they are fitted with end plates, which can be observed in Fig. The use of an aerofoil on the head was ruled out as this would have increased the pantograph aeroacoustic noise. Not surprisingly, the pantograph uplift is significantly higher when the pantograph is nearest the front of the train. In addition, in order to simplify the equations in this book, only the central term of the terrestrial gravity potential is taken into account. 14.26(b)) the air mass movement is shared more evenly between the upper and lower body surfaces; however, the air viscous interference with the underfloor and ground still causes the larger proportion of air to flow above than below the car's body. For controlled re-entries, one should also consider propulsive forces. Other approaches used to improve the uplift performance of the British Rail/Brecknell-Willis pantograph using wind tunnel testing are described in Harrison (1988). Weihua Zhang, in Dynamics of Coupled Systems in High-Speed Railways, 2020. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Advanced Vehicle Technology (Second Edition), ), the airstream over the top surface now has to move further and faster than the underneath air movement. 14.23(c and d). Generating the necessary downforce is concentrated in three specific The aerodynamic lift coefficient CL is a measure of the difference in pressure created above and below a vehicle's body as it moves through the surrounding viscous air. wing moves faster than the air beneath it. In general, these studies of lift force have been undertaken in wind tunnels or full-scale tests, but more recently CFD studies have increasingly been used. 14.26(c)) induces still more air to flow beneath the body with the downward curving entry gap shape producing a venturi effect. It is the angle that occurs between the vertical axis when viewed from either the front or the rear. As a result there will be a net pressure on the plate striving to force it both upwards and backwards, see Fig. pressure than the faster moving fluid on the object. The roving strips build up the main bearing element of this spar. Basically, any of our truck lift kits are going to raise your entire rig – front and rear – anywhere from a subtle 1” to high enough where you feel the need to duck under overpasses. Carnevale et al. 6.40. Fig. The combination of the tapered horizontal profile control line A and the curved longitudinal profile control line ② has a relatively good aerodynamic lift performance on the head and tail of the train. (A) Front view, (B) side view.1, Air flow regulating fin of head; 2, air flow regulating fin of strip. Impact loads such as from bird strikes, hail, dust, sand, and runway debris must also be considered. If the horizontal profile control line of the train head has the same shape, the aerodynamic lift amplitude of the head with the curved longitudinal profile control line ② is the smallest, and the aerodynamic lift amplitude of the head with the drum longitudinal profile control line ③ is the largest. One of the complicating factors is that apparently small design changes can cause significant effects on lift. Comparing the uplift measurements and predictions showed that the CFD performed well. To achieve 500 km/h test speed, the aerodynamic resistance of the lead car and the aerodynamic lift force of the tail car must be reduced. Aerodynamic lift versus ground, floor height. •Rancho Lift Kits: 50 years of off-roading experience is a lot, so you can trust that these guys know what they’re doing when they make a lift kit. Aerodynamic force in operation of pantograph. Used with permission from Brecknell-Willis. In establishing external loads, the following must be considered: Aerodynamic lift loads and wind-tunnel pressure tests to determine the principal structural loads that can generally be validated through static and cyclic fatigue testing. 14.24 (a and b). Although the uplifts are relatively small, there is still a difference in lift depending on the pantograph direction and it can be seen that the behaviour is quite different from that of the Schunk pantograph shown in Fig. T. Niezgoda, in Computational Mechanics–New Frontiers for the New Millennium, 2001. The differences, and the main focus of this chapter, arise in dealing with addressing potential damage modes particular to laminated composite structures. It therefore strengthens the side and trailing vortices and as a result promotes an increase in front end, Optimal design for coupled systems parameter of high-speed train, Dynamics of Coupled Systems in High-Speed Railways, Considerations of failure mechanisms in polymer matrix composites in the design of aerospace structures, Failure Mechanisms in Polymer Matrix Composites, http://787flighttest.com/boeing-completes-ultimate-load-wing-test/, Calibrating the Length Scale Equation with an Explicit Algebraic Reynolds Stress Constitutive Relation, Engineering Turbulence Modelling and Experiments 6, To achieve 500 km/h test speed, the aerodynamic resistance of the lead car and the, Investigation of vehicle ride height and wheel position influence on the aerodynamic forces of ground vehicles, The International Vehicle Aerodynamics Conference, As the ride height of vehicle is changing when using floating struts, more air is allowed to pass underneath the body which leads to some important changes in, Aerodynamic effects on pantographs and overhead wire systems. Author: Bryan Yager, Ralston Middle School, Belmont, CA (12/94), Return As the underfloor surface moves closer to the ground the underfloor air space becomes a venturi, causing the air to move much faster underneath the body than over it, see Figs 14.21(a) and 14.22. It will be seen that the vertical and horizontal components of the resultant reaction represents both lift and drag respectively, see Fig. Measurements were made for the full range of yaw angles, with the angle 0 degree representing the flow along the train longitudinal axis with the pantograph knuckle leading and 180 degrees representing the flow along the train longitudinal axis with the pantograph knuckle trailing. The solution proposed was to increase the tilt angle of the head, which introduced a drag force on the head with an additional component of lift. Heinz Heisler MSc., BSc., F.I.M.I., M.S.O.E., M.I.R.T.E., M.C.I.T., M.I.L.T., in Advanced Vehicle Technology (Second Edition), 2002. 14.23(b). own weight. These will be discussed in detail in Section 8.3.3. Downforce is necessary in maintaining high speeds through the corners The air moving under the car moves faster than that above it, creating downforce or negative lift on the car. It can be noted that the lift behaviour is quite different in the knuckle leading and knuckle trailing directions of operation and that roll angle has a strong effect, increasing the lift values. General structural loads may be handled using basic composite material laminate theory from a large number of sources (e.g. The largest loads are generated by the centrifugal force. With a large underfloor to ground clearance the car body is subjected to a slight negative lift force (downward thrust). areas of the car. 6.41 and 6.42 show the aerodynamic drag and aerodynamic lift of trains of different shapes when it is running at 350 km/h. speedway setup. Lifting a truck is a popular way to improve its off-road performance and handling. Relative increase in pantograph uplift for different carbon holder designs. The separate contributions of the pantograph head and the lower and upper pantograph arms were determined by wind tunnel testing for the original Series 700 pantograph and the N700 pantograph. For the lift of the tail, the aerodynamic lift of the tail with the tapered horizontal profile control line A may be negative, that is, the aerodynamic lift is downward. In this way, train entry into a tunnel having a high blockage ratio may be the most appropriate scenario for defining the maximum relative air speed along the train. Aerodynamic Drag. Two roll angles were also tested: 0 degree representing a horizontal resultant onset wind acting on the pantograph and 25 degrees representing an extreme combination of canted track and a steep embankment. The front wings Historically, there have been a large number of studies and measurements of aerodynamic lift and the effect of different pantograph component design on lift. Other loads are induced by, Journal of Wind Engineering and Industrial Aerodynamics. Technically, it is the aerodynamic drag or the friction offered by the air to a vehicle. or negative lift on the car. A resultant upthrust or downthrust may be produced which mainly depend upon the body shape; however, an uplift known as positive lift is undesirable as it reduces the tyre to ground grip whereas a downforce referred to as negative lift enhances the tyre's road holding. These aerofoils are still used on Brecknell-Willis pantographs, as can be seen in Fig. Designs of pantograph and overhead contact line systems should consider such changes. 10.13 shows wind tunnel measurements of the variation of aerodynamic lift coefficient (based on an area of 10 m2) for a resultant air speed of 30 m/s for the Faiveley single-arm AMBR pantograph as reported by Rigby and Gawthorpe (1979). (Assume the cars do not have negative lift; curious to know what is negative lift?, a wiki search on car handling will help.) An early example of this is the design of the Lockheed L-1011 [2] where there was a general approach of first establishing external loads and using these to determine structural design criteria to enable the definition of loads and loading spectra against which a design may be validated. From Newton's second law of motion, the aerodynamic forces on the body (lift and drag) are directly related to the change in momentum of the fluid with time. The results showed that the compromise optimum aerofoil angles were about 10, 8 and 10 degrees for the Class 89, 90 and 91 locomotives, respectively. Since the Another lift every car owner and professionals want. Effect of pantograph component modifications on aerodynamic lift. Figure 2.11. principles which allow aircraft to fly are also applicable in car is more critical on the speedway than on other circuits. However, see Coxon (1981) for details of some full-scale tests and Harrison (1988) for descriptions of wind tunnel tests investigating this aspect. 10.9), using the tethered head method for measurement of aerodynamic lift. The head form of the lead car is shaped like a sword, while the tail car is shaped more like a rocket. Curves for front and rear lift coefficients demonstrate much more complicated differences between the two cases. Both lead and tail cars are illustrated in Fig. Numerical simulations of actual flight loads are performed during the design of aircraft structures. Of particular interest was the use of aerofoils fixed to the apex frame to try to balance the values of aerodynamic lift in each direction of travel. can generate downforce that is approximately twice its It is a ‘frame engaging’ lift meaning that it lifts from the frame like a 2 post lift, not from the wheels like a 4 post lift. Figure 6.40. under the car moves faster than that above it, creating downforce Other aspects that are of concern when considering pantograph lift are the effects of varying yaw angle, as obviously the natural wind can act at any angle to the direction of track, and also the roll angle of wind acting on pantographs, which can occur as a result of train pantograph vehicles running on canted track and flow angularity due to steep, high embankments. The main rotor blade shows a complex state of loading during the helicopter’s flight. The only difference being the wing or airfoil shape is mounted The shape of the Indy car exhibits the same principle. During the testing, loads were applied to the airframe to replicate 150 percent of the most extreme forces the airplane is ever expected to experience while in service. If the wheels have a negative camber, it means the tops of the front wheels are inclining to the side toward the center of the vehicle’s frame. Fig. Negative lift is used in the automobiles ( Eg : spoiler in race cars ) to have more grip. At -5 AoA the two lift forces are in balance, according to this graph. Simulations were made for the knuckle leading and trailing directions with the pantograph at the front and rear of the second and seventh train vehicles. (2011). With this capacity to lift up to 10,000 lbs up to as high as 69 inches, this lift offers an unprecedented power. The agreement between the wind tunnel measurements and the CFD predictions was generally excellent. The fluid momentum is equal to the mass times the velocity of the fluid. These numerical models have been developed over many years using both in-flight and wind-tunnel test data to refine model fidelity. The front and rear wings at 200 mph. The train with the combination of the tapered horizontal profile control line A and the curved longitudinal profile control line ② has the lowest aerodynamic drag. The wings were flexed upward by approximately 25 feet (7.6 meters) during the test (http://787flighttest.com/boeing-completes-ultimate-load-wing-test/). Furthermore, the Class 91 has a streamlined and a bluff end. the shape of the underbody (an inverted wing) creates an area of This setup includes large front and rear wings. Figure 10.11. Pantographs operating at high speed will bring impact to air, which will flow around relatively. T.K. Like camber, on many front-wheel-drive vehicles, caster is not adjustable. areas. An attempt was also made to improve performance for the pantograph operating at maximum wire height by fitting an auxiliary aerofoil fixed to the pantograph upper arm. Lift is just the opposite. These kits are known in trail riding circles to take extreme abuse at competitions and can also get the work done for day-to-day duty. If the shape of the longitudinal profile control line of the train head is uniform, the aerodynamic drag of the train with the tapered horizontal profile control line A is the smallest, and the aerodynamic drag of the train with the square horizontal profile control line C is the largest. Pantographs using an independent double strip will be subject to different aerodynamic resistance and aerodynamic lift force in the front and rear strips. The ideal pantograph would have aerodynamic lift that is neutral with increasing train speed and also in each direction of running if the pantograph is asymmetric, as is the single-arm pantograph. under the wing is greater than that above the wing, lift is produced. The use of aerofoils to adjust the asymmetric lift performance of a pantograph does, however, lead to a difficulty ensuring that the aerofoil angle is chosen optimally. The wing of An Indy ground effect race car (Figs 14.23(a–d), 14.24(a and b) and 14.25) Almost any object moving through an airstream will be subjected to some form of lift and drag. The method used was RANS simulation with the k-ω SST model for turbulence, and the domain was divided into 20 million cells. In addition The spar is the primary structural member to transfer loads within the blade. 14.25. 14.26(a)) the streamlined nose profile directs the largest proportion of the air mass movement over the body, and only a relatively small amount of air flows underneath the body. Consequently the air movement will accelerate before reaching its highest speed further back at its narrowest body to ground clearance. If the caster is out on these cars, it indicates that something is worn or bent, possibly from an accident, and must be repaired or replaced. Generally, the nearer the underfloor is to the ground the greater the positive lift (upward force); also the positive lift tends to increase with the square of the vehicle speed.