No description available.

The effect of sweep on separation bubbles as occurring in the subsonic flows past thin flat plates with rectangular leading edges has been studied experimentally. The distance between separation and reattachment, at high Reynolds number, was about 5.5 times the plate thickness in the flow region undisturbed by end effects. This distance was independent of sweepback for sweep angles up to and including 45<SUP>o</SUP>. The chordwise distribution of a static-pressure coefficient and a coefficient of the intensity of the static-pressure fluctuations, both measured on the surface of the plate and based upon the free-stream velocity component normal to the leading edge, were independent of the sweep angle up to and including 30<SUP>o</SUP> to a first approximation. The spectra of the static-pressure fluctuations, however, displayed some qualitative changes with increasing sweep angle. The distribution of a coefficient of the chordwise skin-friction component, based upon the free-stream velocity component normal to the leading edge, was independent of sweep up to and including 30<SUP>o</SUP> to a crude first approximation. The chordwise velocity profiles non-dimensionalised by the local external chordwise velocity component, were independent of sweep up to and including 45<SUP>o</SUP> in the separation bubble but downstream of reattachment small but persistent changes occurred with increasing sweep angle. Smoke-flow visualisations in the swept and the unswept flow at low Reynolds number displayed the presence of typical vortex loops in the reattachment region, many of which broke up and were partially entrained into the separation bubble.

No description available.

No description available.

No description available.

The flow at incidence to a slender delta wing with leading edge and secondary separation is considered. A potential flow model is constructed in which the spiral vortex sheets of the actual flow are replaced by concentrated vortices and flat vortex feeding sheets connecting them with the separation lines. The problem is then reduced to a two-dimensional one by the use of slender body theory and the assumptions of conical flow. The method of conformal mapping is employed to obtain the potential solution. The auxiliary boundary condition on each of the vortex systems is that it is force free. The resulting non-linear algebraic equations are solved numerically by means of an iterative method, and values for lift are obtained as a function of incidence. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The use of periodic structures to reduce interference from large reflecting surfaces is proposed. Instrument landing system (ILS) interference from large hangars and terminal buildings is cited as a typical problem. An analytical and numerical investigation of an infinite fin-corrugated surface composed of infinitely thin fins of spacing λ/2<a<λ under TM polarized plane wave illumination is described. Specular reflection from this surface can be completely converted to back-scatter in a direction opposite to the incident wave when the angle of incidence from the normal to the surface and the fin height are properly chosen. Experiments were performed at 35 and 37 GHz. using finite size fin-corrugated surfaces with fins of finite thickness under non-plane wave illumination and the results indicate that these surfaces behave essentially as predicted. In addition, the experimental surfaces remain completely effective for small oblique angles of incidence and have sufficient bandwidth for ILS applications. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The development work of a race car revolves around numerous goals such as drag reduction, maximizing downforce and side force, and maintaining balance. Commonly, these goals are to be met at the same time thus increasing the level of difficulty to achieve them. The methods for data acquisitions available to a race team during the season is mostly limited to wind tunnel testing and computational fluid dynamics, both of which are being heavily regulated by sanctioning bodies. While these methods enable data collection on a regular basis with repeat-ability they are still only a simulation, and as such they come with some margin of error due to a number of factors. A significant factor for correlation error is the effect of tires on the flow field around the vehicle. This error is a product of a number of deficiencies in the simulations such as inability to capture loaded radius, contact patch deformation in Y direction, sidewall deformation and overall shifts in tire dimensions. These deficiencies are evident in most WT testing yet can be captured in CFD. It is unknown just how much they do affect the aerodynamics performance of the car. That aside, it is very difficult to correlate those findings as most correlation work is done at WT which has been said to be insufficient with regards to tire effect modeling. Some work had been published on the effect of tire deformation on race car aerodynamics, showing a large contribution to performance as the wake from the front tires moves downstream to interact with body components. Yet the work done so far focuses mostly on open wheel race cars where the tire and wheel assembly is completely exposed in all directions, suggesting a large effect on aerodynamics. This study bridges the gap between understanding the effects of tire deformation on race car aerodynamics on open wheel race cars and closed wheel race cars. The vehicle in question is a hybrid of the two, exhibiting flow features that are common to closed wheel race cars due to each tire being fully enclosed from front and top. At the same time the vehicle is presenting the downstream wake effect similar to the one in open wheel race cars as the rear of the wheelhouse is open. This is done by introducing a deformable tire model using FEA commercial code. A methodology for quick and accurate model generation is presented to properly represent true tire dimensions, contact patch size and shape, and deformed dimension, all while maintaining design flexibility as the model allows for different inflation pressures to be simulated. A file system is offered to produce CFD watertight STL files that can easily be imported to a CFD analysis, while the analysis itself presents the forces and flow structures effected by incorporating tire deformation to the model. An inflation pressure sweep is added to the study in order to evaluate the influence of tire stiffness on deformation and how this results in aerodynamic gain or loss. A comparison between wind tunnel correlation domain to a curved domain is done to describe the sensitivity each domain has with regards to tire deformation, as each of them provides a different approach to simulating a cornering condition. The Study suggests introducing tire deformation has a substantial effect on the flow field increasing both drag and downforce.In addition, flow patterns are revealed that can be capitalized by designing for specific cornering condition tire geometry. A deformed tire model offers more stable results under curved and yawed flow. Moreover, the curved domain presents a completely different side force value for both deformed and rigid tires with some downforce distribution sensitivity due to inflation pressure.

A literature survey was conducted to determine the factors which affect aerodynamic drag of spheres. Graphs are presented which show the effect of each variable where such information was available. Equipment was designed and built for the purpose of studying the effects of acceleration on the aerodynamic drag of spheres. Special emphasis was placed on the measurement and control of each of the other variables which can affect the drag. Tests were conducted using large spheres in air and water to show that the method presented can produce a valid determination of the drag coefficients. The numerical values of the measured data cannot be considered accurate because of known discrepancies in the test equipment. Information is also presented on the use of this equipment for tests with small diameter spheres. Recommendations are made for further testing on the aerodynamic drag of spheres and for needed changes and additions to the test equipment.

The object of this investigation was to obtain a reliable technique for finding the drag coefficient for a sphere falling at a non-constant velocity through air. And then to apply this technique to the data collected by R. G. Lunnon in 1925^(4)*.