Browsing by Author "Jones, R. I."
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Item Open Access Experimental investigation of attachment line transition on a large swept cylinder(Cranfield University, 1997-01) Flynn, G. A.; Jones, R. I.Transition of the attachment fine boundary layer was investigated using a large swept cylinder. Results for natural transition and transition tripping with two-dimensional trip wires were simila to those obtained by Poll using a similar, but smaller, model. ]Lower displacement thickness Reynolds numbers but larger trip sizes, than for the flat-plate boundary layer, were required for transition. The investigation of transition tripping was then extended to involve three-dimensional trips. The attachment line boundary layer was less susceptible to three-dimensional trips than to two-dimensional trips but upper and lower bounds of attachment line Reynolds number for transition were identical. It was also found that the roughness Reynolds numbers for fully effective three-dimensional trips were similar for the attachment line and flat-plate boundary layers. Another common feature was the more abrupt upstream movement of the transition front with increasing Reynolds number for three-dimensional trips than for two-dimensional trips. Turbulence spreading downstream of a three-dimensional trip was also examined and, as in the flat-plate boundary layer, was found to be heavily dependent on Reynolds number (varying from 3* at low Reynolds number to a value approaching 10* as Reynolds number exceeded the value for natural transition), but was also dependent on either the trip size or the initial conditions at which the trip first introduced turbulent spots. The effects of higher levels of freestrearn turbulence were then investigated for both two-dimensional and three-dimensional trips. With a small increase in freestrea turbulence the conditions for transition with twodimensional trips were affected far more than those for three-dimensional trips, for which only the transition completion conditions were affected signfficantly, resulting in a reduced extent ofthe transition region. Larger levels of turbulence appeared to have similar effects on the two trip types. Restrictions in model length and windspeed for the higher turbulence tests prevented an accurate investigation of the effects of turbulence,on the upper and lower bounds for transition tripping and on the influence of spanwise distance at higher levels of turbulence. Finally, the interaction between two trips positioned on the attachment line was examined. The effect of the second trip on the transition Reynolds number was found to a function of the streamwise separation distance between the two trips.Item Open Access Hydrogen aircraft concepts and ground support(Cranfield University, 2005-11) Sefain, Michael J.; Jones, R. I.As worldwide petroleum supplies diminish and prices escalate, the aviation industry will be forced to consider relying on energy resources other than kerosene for its aviation fuel needs. Additionally, there is growing environmental concern regarding greenhouse emissions particularly as aircraft cause pollution in sensitive layers of the atmosphere. These are serious implications necessitating prudence in seeking alternative fuels sooner rather than later. Liquid Hydrogen (LH2) combustion produces zero CO2 emissions, very little NOx, and water providing a solution to sustain air traffic growth whilst preventing further atmospheric pollution. Hydrogen itself is abundant and can be produced from renewable sources meaning worldwide availability and sustainability permitting sustainable growth of aviation at high rates (typically 4-5% per year). Despite these major advantages, there are compromises to be made. The low density fuel means ingenuity must be exercised to design an aircraft configuration which will accommodate a fuel volume more than four times that which would normally be required. Practical unconventional aircraft conceptual designs providing solutions to this problem are presented including estimates of performance, mass, and relative cost- and energy-effectiveness. To provide a means to produce, store and transport the fuel safely and efficiently, ground support operations have been systematically checked and the required airport infrastructure defined. Technical issues such as safety, airworthiness certification, environmental issues and system synergies are also discussed, and an outline plan is presented providing the R&D necessary to introduce LH2-fuelled civil aircraft into service. This Thesis proves that LH2 has sufficient long term promise to justify more substantial R&D offering possible improvement in performance and engine reliability. The overall cost for a LH2 aircraft are within reasonable values, and the requirement for new equipment to maintain and support LH2-fuelled aircraft is not extensive. Importantly LH2 is at least as safe.Item Open Access The introduction of laminar flow to the design and optimisation of transport aircraft(Cranfield University, 1997-03) Wilson, R. A. L.; Jones, R. I.A methodology has been developed to model the direct consequences of laminar flow technology on wing, empennage and nacelle surfaces. In particular two concepts were considered, namely Natural Laminar Flow (NLF) and Hybrid Laminar Flow Control (HLFC). The methodology was introduced into an existing numerical design synthesis for commercial transport aircraft, which was linked to a non-linear constrained optimisation code. This permitted the impact of laminar flow technology on the optimum aircraft configuration and Direct Operating Costs (DOC) to be assessed. Cont/d.Item Open Access Investigation of improvements in aircraft braking design(Cranfield University, 2004-10) Bailey, David A.; Jones, R. I.This work investigates and provides a methodology that enables better prediction of brake performance. Aircraft brake performance depends on the tribological properties of the friction couple used in the brake design. The behaviour of this couple combines both surface and bulk characteristics of the material. The increase in aircraft performance requirements has led to the development of new brake designs and new friction materials. The development of brakes for large commercial aircraft has stabilised to that of a carbon-carbon composite multi-disk brake design. The results of this investigation established a relationship between mean mass loading and the mean friction radius of the brake. This relationship provides a statistically good description of the results and will provide the brake performance engineer with a useful tool. In addition, the variance within the results of the 100 Normals aircraft qualification programme was also studied. In this case the relationship is not particularly good at describing the results. A case study has been included to promote further understanding of the developed methodology and to illustrate some of the trade-offs required when designing a carbon brake. The design of a multi-disk brake is a complex engineering task that requires many specialist engineering disciplines such as structural analysis and dynamic analysis etc. The wider context of aircraft braking is even broader and requires not only mechanical engineering skills but also electronic and software engineering. This research addresses all aspects of system integration and provides a framework of understanding on the interaction and dependencies of the various components.Item Open Access Novel ice protection system suitable for UAV composite wings(2005-02) Bhakta, Besant; Jones, R. I.The existence o f an atmospheric icing th re a t to a irc ra ft operating in moist, low altitudes at temperatures below freezing is well known. The objective o f this study was to develop an a irc ra ft ice protection system suitable fo r a UAV composite wing. Conventional wing leading edge ice protection systems were examined and found to either, necessitate significant electrical power, or were costly with respect to system mass. A low cost and low power technology capable o f protecting the UAV wing leading edge was identified. I t was proposed th a t a commercial magnetostrictive actuator fitte d to and in direct contact with the non-airflow wing surface would provide mechanical impulses to break the ice-wing surface bond. Assuming the accreted ice was o f a form expected o f te s t points in the FAR/ JAR Appendix C flight-icing envelope. Computational simulations demonstrated th a t pairs o f magnetostrictive actuators acting in unison a t a 0.3m span spacing, and deployed along the upper and lower wing leading edge surfaces a t around the 7% chord coordinate, would successfully break the ice-surface bond. I t was estimated th a t fo r a medium endurance UAV o f Predator B class, the proposed system power requirements is 500W at a 45kg total system mass. The proposed system would be more competitive than conventional systems if the use o f consumer grade electronics and control systems, harnessing etc. were permitted, together with the removal o f system redundancy and fail-safe provision requirements necessary fo r manned aircraft. Further work would require the demonstration o f a physical de-icing installation in the icing wind tunnel.