1,721,078 research outputs found
Custer channel wings for short takeoff and landing of unmanned aircraft
No full textThe channel wing is a lift-enhancement concept pioneered by Willard Ray Custer in the late 1940s in an effort to provide a fixed-wing aircraft with short takeoff and landing (STOL) capabilities. This paper experimentally investigates the possibility of using Custer channel wings for slow flight and STOL of small (under 35 kg) fixed-wing unmanned aerial vehicles. The Custer unmanned aircraft developed at the University of Southampton is introduced in this paper, including details of the installed channel wings and other systems necessary for slow-flight operation. Results from wind-tunnel tests are presented, showing a significant lift increase due to the channel wings in the range of airspeeds of interest. Flight tests are carried out to demonstrate the slow flight and STOL capabilities of the aircraft, showing superior stall characteristics and a two-thirds reduction of the runway length required when using the channel wings. Flight-test comparisons to a conventional wing–propeller configuration show superior slow-flight performance and 7–9% lower cruise speed of the channel-wing aircraft
Comparison of several optimisation strategies for robust turbine blade design
No full textThis paper addresses the problem of turbine blade shape optimization in the presence of geometric uncertainties. Several strategies are tested and compared on a two-dimensional compressor blade optimization process for which performance is assessed using a commercial Reynolds-averaged Navier-Stokes computational fluid dynamics code. In each case, a range of shape errors are considered that attempt to simulate foreign object damage, erosion damage, and manufacturing errors. These lead to stochastic performance measures that, in turn, are considered in a multi-objective optimization framework. Because of the long run times associated with Reynolds-averaged Navier-Stokes codes, use is also made of surrogate or response surface-based optimization methods to speed up the search processes. The paper shows that a range of techniques can be used to tackle this problem, but that no one method is clearly best overall. The practitioner is therefore cautioned against favoring a single approach for such design problems. Further research may help clarify these issue
Computational approaches for aerospace design: the pursuit of excellence
No full textOver the last fifty years, the ability to carry out analysis as a precursor to decision making in engineering design has increased dramatically. In particular, the advent of modern computing systems and the development of advanced numerical methods have made computational modelling a vital tool for producing optimized designs.
This text explores how computer-aided analysis has revolutionized aerospace engineering, providing a comprehensive coverage of the latest technologies underpinning advanced computational design. Worked case studies and over 500 references to the primary research literature allow the reader to gain a full understanding of the technology, giving a valuable insight into the world’s most complex engineering systems
Parameter screening using impact factors and surrogate-based ANOVA techniques
No full textThis paper introduces the concept of parameter impact factors in order to screen important parameters in high dimensional design optimization problems which make use of computationally expensive high fidelity simulation models. Based on a snapshot dataset obtained by evaluating design points produced by Design of Experiments techniques, a simple concept of parameter impact factors is introduced and calculated to obtain preliminary estimates on the importance of parameters in the simulation results. Combined with parallel tuning of hyperparameters used in Gaussian process surrogate models and ANOVA techniques using the progressively built surrogate models, a more accurate estimation on the impact of different parameters can be achieved. Less important parameters can then be fixed in order to reduce the dimensionality of the problem to make the problem more tractable within given computational budget and time constraints
Genetic programming, logic design and case-based reasoning for obstacle avoidance
No full textThis paper draws on three different sets of ideas from computer science to develop a self-learning system capable of delivering an obstacle avoidance decision tree for simple mobile robots. All three topic areas have received considerable attention in the literature but their combination in the fashion reported here is new. This work is part of a wider initiative on problems where human reasoning is currently the most commonly used form of control. Typical examples are in sense and avoid studies for vehicles – for example the current lack of regulator approved sense and avoid systems is a key road-block to the wider deployment of uninhabited aerial vehicles (UAVs) in civil airspaces.The paper shows that by using well established ideas from logic circuit design (the “espresso” algorithm) to influence genetic programming (GP), it is possible to evolve well-structured case-based reasoning (CBR) decision trees that can be used to control a mobile robot. The enhanced search works faster than a standard GP search while also providing improvements in best and average results. The resulting programs are non-intuitive yet solve difficult obstacle avoidance and exploration tasks using a parsimonious and unambiguous set of rules. They are based on studying sensor inputs to decide on simple robot movement control over a set of random maze navigation problems
Data for: Control and performance of small Custer channel wing Unmanned Aircraft
No full textData supporting the thesis 'Control and performance of small Custer channel wing Unmanned Aircraft'.</span
Use of Custer Channel Wings–Wing Ducts on Small UAVs
No full textThe strong variations in lift that occur with changes in forward speed lead to one of the fundamental difficulties in aircraft design: how to provide sufficient lift at landing and take-off without having oversized wings for cruise conditions. This fundamental problem is generally tackled using two approaches. First, by providing flaps and other high-lift devices, extra lift can be generated during landing and take-off, albeit at the cost of extra drag and complexity. Second, by using long and smooth runways, higher landing and take-off speeds can be tolerated, closing the gap between these speeds and those of operational flight. Even so, it is common for aircraft flying in the cruise condition to be operating with rather small main wing angles of attack (AoAs) compared with those at stall, implying that smaller wings would be desirable if acceptable landing and take-off could be achieved. A number of designers have attempted to tackle this problem with various forms of powered lift augmentation. This paper re-examines the idea of the Custer wing duct, also known as a channel wing, here applied to small unmanned air vehicles (UAVs). Such aircraft are generally not operated from long smooth runways and rarely have complex high-lift systems in their wings. It is shown that by using suitable ducts around the propellers, startlingly good take-off and landing performance can be achieved, and that suitable ducts can be readily incorporated into small UAVs with the use of 3D printing (selective laser sintering) for their manufacture. Computational fluid dynamics (CFD) analysis, wind tunnel tests, and flight trials of a Custer channel wing UAV are described
Surrogate-based aerodynamic shape optimization of a civil aircraft engine nacelle
No full textIn this paper, we present a study on the aerodynamic shape optimization of a three-dimensional subsonic engine
nacelle using computational fluid dynamics simulations. Gaussian process-based surrogate modeling (kriging) and
parameter screening techniques are combined to tackle the high cost associated with both computational fluid
dynamics simulations and the large number of design variables involved, with a multi-objective genetic algorithm
being used to obtain the Pareto fronts. The primary goal of the study was to identify the tradeoff between
aerodynamic performance and noise effects associated with various geometric features within practical
computational costs. The fan face total pressure recovery is used to measure the aerodynamic performance, and the
scarf angle is used as an indicator of the noise impact on the ground. The geometry is modeled using a feature-based
parametric computer-aided design package. An unstructured tetrahedral mesh is generated for the subsequent
solution using the Reynolds averaged Navier–Stokes flow equations. Analyses of variance techniques are used to
identify the dominant geometry parameters, thereby reducing the number of design variables and computational
cost in the trade study. Multiple Pareto fronts are constructed using progressively built kriging models based on
simulation data with the reduced parameter set. A full-scale search was also carried out for comparison with the
results produced using the reduced parameter set. The procedures outlined can be further applied to other
optimization problems with significant numbers of parameters and high-fidelity analysis codes
Pattern search algorithm for Blackboard-based Multidisciplinary Design Optimisation frameworks
No full textPreliminary aircraft design necessitates the use of a range of analysis tools, which are often scattered among many departments in an organisation and require regular tuning from skilled operators. For this reason, a distributed Multidisciplinary Design Optimisation approach that permits individual organisational domains to use their preferred analysis and optimisation tools would be most suitable. This paper revisits a Blackboard framework, which uses simple heuristics to automatically guide organisational design domains to a single optimum by narrowing the bounds on the shared design variables. The authors present a newly developed rule base for this legacy framework, which has been given the title “Multidisciplinary Pattern Search”. Two examples, one of which is for conceptual transonic wing design, demonstrate the merit of the newly developed rule base, database and visualisation modules. They also serve as a means for comparisons with two established Multidisciplinary Design Optimisation architectures. The results indicate that the Blackboard performs better than the distributed Collaborative Optimisation approach, albeit worse than the monolithic Simultaneous Analysis and Design method that tends to be organisationally disruptive to implemen
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