Search results

The purpose of this paper is to examine the aerodynamic effects of rear spoiler geometry on a sports car. Today, due to economical, safety and even environmental concerns, vehicle aerodynamics play a much more significant role in design considerations and rear spoilers play a major role in this area.

A 2-D vehicle geometry of a race car is created and solved using the computational fluid dynamics (CFD) solver FLUENT version 6.3. The aerodynamic effects are analyzed under various vehicle speeds with and without a rear spoiler. The main results are compared to a wind tunnel experiment conducted with 1/18 replica of a Nascar.

By the CFD analysis, the drag coefficient without the spoiler is calculated to be 0.31. When the spoiler is added to the geometry, the drag coefficient increases to 0.36. The computational results with the spoiler are compared with the experimental data, and a good agreement is obtained within a 5.8 percent error band. The uncertainty associated with the experimental results of the drag coefficient is calculated to be 6.1 percent for the wind tunnel testing. The sources of discrepancies between the experimental and numerical results are identified and potential improvements on the model and experiments are provided in the paper. Furthermore, in the CFD model, it is found that the addition of the spoiler caused a decrease in the lift coefficient from 0.26 to 0.05.

This paper examines the effects of rear spoiler geometry on vehicle aerodynamic drag by comparing the CFD analysis with wind tunnel experimentation and conducting an uncertainty analysis to assess the reliability of the obtained results.

This study aims to predict dynamic responses of aileron and spoiler control surfaces in subsonic flight via the use of surrogate models. The prepared reduced order models prove useful when quick estimations for a large number of variations are required.

The linear frequency domain (LFD) method was used for the simulation study. Each surrogate contained a database of 100 control surface dynamic responses over a spectrum of 200 harmonics computed with LFD. To interpolate new results, the DLR surrogate modelling toolbox, SMARTy, was used. The database’s samples were prepared in a Halton sequence, making interpolation reliable. The surrogate’s parameter space was the Mach number, Reynold’s number, angle of attack, control surface deflection angle and the control surface chord length.

The LFD method proved effective for the mentioned purpose: the surrogates were accurate, up to 15% of relative error, in reproducing dynamic responses of aileron and spoiler deflections at low speed, within the limitations of flow field linearity, as well as surrogate prediction capability. The restrictions of the surrogate, and the reasoning thereof, are also presented in detail in the study. Future load alleviation studies are a potential of the findings here.

LFD is an innovative technique for load prediction and alleviation studies. This paper provides a reference for engineers wishing to use the method for the two mentioned control surfaces, or the like.

Apparatus, for the lateral control of aeroplanes, comprises spoiler vanes adapted to be projected from the upper surface of the wings by the operation of a manual control device which operates so that a uniform increase in the displacement of the control device through substantially its full range of movement is arranged to effect a continuously decreasing increase in the effective extent of the projection of the spoiler vanes, whereby the rolling moment of the aeroplane is continuously increased during the displacement of the control device. The spoiler vane may be divided into two or more unequal sections in the direction of the wing span and the control device constructed so that in its initial movement it projects the smaller vane at a rapid rate and subsequently raises the larger vane or vanes at a reduced rate. In Fig. 7 (not shown), the spoiler vane is projected by a rotatable bell‐crank lever positioned so that rapid regular movement of the vane is attained during the initial movement of the bell‐crank lever. In an alternative construction Fig. 8 (not shown), a roller on the arm of a bell‐crank lever engages a cam‐shaped surface on the underside of the spoiler vane. As shown in Figs. 9, 10 the initial rapid movement may be effected by a shaped cam It and where the spoiler vane is divided into two unequal portions, the smaller part is projected by a cam k as shown in Fig. 9, whilst the slower movement of the larger vane is effected by a differently‐shaped cam k as shown in Fig. 10. In a modification Figs. 11, 12 the vane b is torsionally twisted, about an edge in the wing by a set of cams p1 . . p4 arranged along a rotatable shaft o and arranged to come into action successively with a decreasing rate of projection of the vane. In a further modified construction, Fig. 13, a vane b is projected from a slit in the wing d by a slider s formed with arms z1, z2 which engage lugs u2, u1 carried by the vane. The width of the vane may be varied along its length so that the area projected during the initial movement of the control member is additionally increased. The spoiler vanes may be held in their normal positions by springs arranged so that the spoiler vanes are automatically projected from their normal position when the pressure on the wing in the locality of the vanes is abnormally low, e.g., under high list conditions.

In a body adapted to travel through a fluid medium, the combination comprising: a control surface; hinge means for hinging said control surface to said body for controlling the movement of said body; a tab connected to said control surface for up and down movement at the trailing edge of said control surface; spoiler means connected to said control surface for movement up and down to project respectively above and below said control surface at a given point spaced between said hinge means and said trailing edge to leave an area of said control surface aft of said spoiler means over which a negative pressure is developed establishing a hinge moment that overcomes the hinge moment established by positive pressure in front of said spoiler means and by drag forces caused by said spoiler means; and means inter‐connecting said tab to said spoiler means to move said tab down when said spoiler means is moved up, and to move said tab up when said spoiler means is moved down, whereby the net hinge force moment acting on said control surface as a result of fluid flow thereover is increased over a given range of control surface deflexions as compared to the hinge force moment available over said same given range in the absence of said spoiler means.

The nozzle 1 of the jet unit is extended by a diverging part 2. Between nozzle 1 and part 2, immediately behind the nozzle outlet 3, four segmental spoilers 4 are arranged. By operating the control bars 8 the spoilers can be pushed into the nozzle as shown in the diagram below. A ring chamber 9 is divided by radial walls 9a into four sectors opening into the diverging part 2 of the nozzle by an annular slot 10. Each sector may be provided with air pressure by opening a valve 12 in the tube 11. When all four spoilers project into the nozzle the jet leaves the nozzle in its axial direction. By retracting one of the spoilers 4 the jet is deflected to the side of this spoiler. This deflexion is increased by providing the adjacent chamber sector with air pressure. Each valve 12 is coupled to the corresponding spoiler control bar 8 by a lever 13.

In a rotary wing aircraft having a fuselage and two load‐carrying rotors turning in opposite directions and having rotor blades of aerofoil cross section, means for controlling the directional heading of the fuselage comprising spoilers on said rotor blades and movable between an active position in which they increase the drag of the respective rotors on which they are provided and an inactive position in which they do not materially increase said drag, said spoilers being located not less than 30 per cent of the length of the blade from the tip of the blade, and pilot‐controlled operating mechanism for moving said spoilers between active and inactive position, said operating mechanism including a movable pilot‐controlled member and being connected to said spoilers to move said spoilers of one rotor to active position by movement of the pilot‐controlled member in one direction and to move said spoilers of the other rotor to active position by movement of the pilot‐controlled member in the opposite direction.

WITH tailless aeroplanes, all known aerodynamic control devices possess the peculiarity of not only producing moments about one axis, but of also causing secondary moments about one or both of the other axes. Horizontal controllers forming part of the wing near the tips in wings having sweep‐back or sweep‐forward, for instance, do not produce rolling moments alone, when differ‐entially deflected; they also cause yawing and pitching moments. Similarly, wing‐tip disk rudders operated on such wings not only produce yawing moments, but may cause rolling and even pitching moments.

This paper seeks to address issues related to the development of a knowledge‐based engineering system for estimating manufacturing cost and weight of a composite structure at the conceptual stage of a design.

The system has been developed in the CATIA V5 knowledge environment and is applied to structures made of composite materials. At the conceptual stage of the design process, a structure is often represented by simple surfaces. The system adds the details necessary to accurately estimate weight and manufacturing cost using geometry and process‐based techniques. Knowledge captured from an expert was used to construct the knowledge base in the system.

It has been found that the system can provide continuous tracking of the weight and cost as the design evolves. Structural FEA and optimisation using MSC.NASTRAN have been integrated into the design process to enables the designer to conduct “what‐if” analyses to explore different design options involving geometry parameters such as the internal configuration of the structure.

The paper demonstrates that tools embedded in CAD systems can be expected to be able to facilitate the task of estimation of weight and manufacturing cost at the conceptual stage of the design process.

This paper describes and extends the game theoretic approach to network vulnerability assessment. The basic idea is to set up a game between the network users who are trying to minimise their expected travel time by choice of route and a network tester who is trying to penalise the users most by degrading a link through capacity reduction leading to congestion. The method therefore finds the worst possible location for a link degradation, taking re-routing options into account (an upper, lower bound of impact). The original game identifies the weakest link for routes between an OD pair in the network. Two variations are introduced in this paper in order to determine the weak links for a specific origin or a specific destination and for the whole network. All three game variations are tested on a small network in Leicester and the results are presented.