Integrated system to perform surrogate based aerodynamic optimisation for high-lift airfoil

This work deals with the aerodynamics optimisation of a generic two-dimensional three element high-lift configuration. Although the high-lift system is applied only during take-off and landing in the low speed phase of the flight the cost efficiency of the airplane is strongly influenced by it [1]. The ultimate goal of an aircraft high lift system design team is to define the simplest configuration which, for prescribed constraints, will meet the take-off, climb, and landing requirements usually expressed in terms of maximum L/D and/or maximum CL. The ability of the calculation method to accurately predict changes in objective function value when gaps, overlaps and element deflections are varied is therefore critical. Despite advances in computer capacity, the enormous computational cost of running complex engineering simulations makes it impractical to rely exclusively on simulation for the purpose of design optimisation. To cut down the cost, surrogate models, also known as metamodels, are constructed from and then used in place of the actual simulation models. This work outlines the development of integrated systems to perform aerodynamics multi-objective optimisation for a three-element airfoil test case in high lift configuration, making use of surrogate models available in MACROS Generic Tools, which has been integrated in our design tool. Different metamodeling techniques have been compared based on multiple performance criteria. With MACROS is possible performing either optimisation of the model built with predefined training sample (GSO) or Iterative Surrogate-Based Optimization (SBO). In this first case the model is build independent from the optimisation and then use it as a black box in the optimisation process. In the second case is needed to provide the possibility to call CFD code from the optimisation process, and there is no need to build any model, it is being built internally during the optimisation process. Both approaches have been applied. A detailed analysis of the integrated design system, the methods as well as th

Aerodynamic and cost modelling for aircraft in a multi-disciplinary design context.

A challenge for the scientific community is to adapt to and exploit the trend towards greater multidisciplinary focus in research and technology. This work is concerned with multi-disciplinary design for whole aircraft configuration, including aero performance and financial considerations jointly for an aircraft program. A Multi-Disciplinary (MD) approach is required to increase the robustness of the preliminary design data and to realise the overall aircraft performance objectives within the required timescales. A pre-requisite for such an approach is the existence of efficient and fully integrated processes. For this purpose an automatic aero high-speed analysis framework has been developed and integrated using a commercial integration/building environment. Starting from the geometry input, it automatically generates aero data for loads in a timescale consistent with level requirement, which can afterwards be integrated into the overall multi-disciplinary process. A 3D Aero-solution chain has been implemented as a high-speed aerodynamic evaluation capability, and although there is not yet a complementary fully automated Aerodynamic design process, two integrated systems to perform multi-objective optimisation have been developed using different optimisation approaches. In addition to achieving good aircraft performance, reducing cost may be essential for manufacturer survival in today's competitive market. There is thus a strong need to understand the cost associated with different competing concepts and this could be addressed by incorporating cost estimation in the design process along with other analyses to achieve economic and efficient aircraft. For this reason a pre-existing cost model has been examined, tested, improved, and new features added. Afterwards, the cost suite has been integrated using an integration framework and automatically linked with external domains, providing a capability to take input from other domain tool sets. In this way the cost model could be implemented in a multi-disciplinary process allowing a trade-off between weight, aero performance and cost. Additionally, studies have been performed that link aerodynamic characteristics with cost figures and reinforce the importance of considering aerodynamic, structural and cost disciplines simultaneously. The proposed work therefore offers a strong basis for further development. The modularity of the aero optimisation framework already allows the application of such techniques to real engineering test cases, and, in future, could be combined with the 3D aero solution chain developed. In order to further reduce design wall-clock time the present multi- level parallelisation could also be deployed within a more rapid multi-fidelity approach. Finally the 3D aero-solution chain could be improved by directly incorporating a module to generate aero data for performance, and linking this to the cost suite informed by the same geometrical variables.Engineering and Physical Sciences (EPSRC)PhD in Aerospac

CFD study of shock bump roughness for transonic shock control and buffet alleviation

Shock induced separation is a serious problem in the transonic flow regime which leads tobuffet - unsteady aerodynamic loading on the wing, that can cause serious structural fatigueand failure. These phenomena compromise the flight envelope and structural integrity ofan aircraft, and consequently its operational safety. One possible solution is to control anddelay the boundary layer separation. The aim of this work was to numerically study whethersub-boundary layer scale distributed roughness, arranged in periodic strips, which locallyincreases the boundary layer displacement thickness, can act as a virtual shock bump withthe aim of bifurcating the foot of the shock wave to reduce the shock’s adverse effect on theboundary layer. A full span bump (upper surface aerofoil shape) model mounted on the floor ofa transonic wind tunnel was previously tested with several configurations of such shock-bumproughness. This study performed steady Navier-Stokes CFD analysis of the working section flowto match the experimental data for the smooth surface bump, and then to assess the affect ofsimulated shock bump roughness. The performance of several turbulence models was comparedwith experimental data (Mach 0.55 inflow, Reynolds number based on bump chord between 3.1 -3.6 million) - the−SST model being found to be the most accurate for this type of problem. Itwas predicted that shock-bump roughness tends to move the shock wave downstream and reduceits strength in cases where the roughness elements are located directly under the interaction,as in the solid shock bump case. This suggests that the virtual displacement effect of surfaceroughness can be designed to provide the same shock-bump effect as a solid protuberance butpotentially without the extra weight and pressure drag. Shock-bump roughness arranged instrips aligned with the streamwise flow were predicted to perform better than those arranged ata 30 degree skew angle to the flow. No conclusive evidence from the numerical models showsthat shock-bump roughness can improve the separated flows if placed upstream of the shock, incases where the shock wave moved downstream of the roughness location

Always-On 674uW @ 4GOP/s Error Resilient Binary Neural Networks with Aggressive SRAM Voltage Scaling on a 22nm IoT End-Node

Binary Neural Networks (BNNs) have been shown to be robust to random bit-level noise, making aggressive voltage scaling attractive as a power-saving technique for both logic and SRAMs. In this work, we introduce the first fully programmable IoT end-node system-on-chip (SoC) capable of executing software-defined, hardware-accelerated BNNs at ultra-low voltage. Our SoC exploits a hybrid memory scheme where error-vulnerable SRAMs are complemented by reliable standard-cell memories to safely store critical data under aggressive voltage scaling. On a prototype in 22nm FDX technology, we demonstrate that both the logic and SRAM voltage can be dropped to 0.5Vwithout any accuracy penalty on a BNN trained for the CIFAR-10 dataset, improving energy efficiency by 2.2X w.r.t. nominal conditions. Furthermore, we show that the supply voltage can be dropped to 0.42V (50% of nominal) while keeping more than99% of the nominal accuracy (with a bit error rate ~1/1000). In this operating point, our prototype performs 4Gop/s (15.4Inference/s on the CIFAR-10 dataset) by computing up to 13binary ops per pJ, achieving 22.8 Inference/s/mW while keeping within a peak power envelope of 674uW - low enough to enable always-on operation in ultra-low power smart cameras, long-lifetime environmental sensors, and insect-sized pico-drones.Comment: Submitted to ISICAS2020 journal special issu

Validating surrogate models and incorporating uncertainty quantification in multi-element airfoil design optimisation

This work deals with the aerodynamics optimisation of a generic two-dimensional three element high-lift configuration. Specifically, it focuses on the development and validation of surrogate models, as well as their integration with optimisation algorithms, uncertainty quantification method, and other computational design tools in order to define and develop a better design methodology for high-lift systems. Special emphasis is put into the process itself to make it fast and highly automated yet keeping accuracy uncompromised. Although the high-lift system is applied only during take-off and landing in the low speed phase of the flight the cost efficiency of the airplane is greatly influenced by it. The ultimate goal of an aircraft high-lift system design team is to define the simplest configuration which, for prescribed constraints, will meet the take-off, climb, and landing requirements usually expressed in terms of maximum L/D and/or maximum CL. The ability of the calculation method to accurately predict changes in objective function value when gaps, overlaps and element deflections are varied is therefore critical. Despite advances in computer capacity, the enormous computational cost of running complex engineering simulations makes it impractical to rely exclusively on simulation for the purpose of design optimisation. To cut down the cost, surrogate models, also known as metamodels, are constructed from and then used in place of the actual simulation models. A detailed analysis of the integrated design system, the methods as well as the optimisation results are provided

A rapid aerodynamic prediction method for unconventional transonic aircraft configurations

This paper presents some results comparing the use of the Full Potential equations, coupled with the turbulent integral boundary layer equations for aircraft transonic cruise analysis. Use of such a method in the conceptual design stage is shown to be capable of yielding accurate enough data in a few minutes on a single processor, where Navier - Stokes simulations on 100+ processors take several days

Open Source Interactive Map of Albania Cultural Heritage

AbstractICTs represent strategic resources for Cultural Heritage (CH) projects. Anyway, several conditions put the success of promotion projects at risk, especially if carried out at the local level. Firstly, local scale amplifies the weight of budget constraints on the priorities of public administrations, compelled to allocate funds to the physical conservation of heritage rather than to software and training. Secondly, proprietary SW, often sophisticated and complex in procedures, fails to integrate precious unformalized knowledge from local stakeholders and communities, particularly in the field of cultural tourism. Finally, a changing demand for cultural tourism, with potential visitors frequently searching for information directly on the Web before moving, requires a higher interactivity in tools and systems. The paper illustrates the work carried out at the Construction Technologies Institute for delivering procedures and SW specifically designed to simplify the publication of geo-referenced information and reduce the need for specialized skills and equipments. The described results were achieved along different research programs focusing on the Albanian CH with a learning-by-doing approach

Aircraft cost modelling, integrated in a multidisciplinary design context

Most of the current cost models focus on a particular manufacturing process or a specific maintenance aspect, therefore not providing the whole picture. The main challenge in modelling the manufacturing cost, associated to a new aircraft at the initial design stage, is to examine all the cost features and the way to link them into the decision making process. It is important to understand the cost related to different competing designs, and this can be tackled by including cost estimation in the design process. Estimating the cost at the early design stage is paramount to reduce the life cycle cost of the aircraft. This paper presents the development of a new methodology for the generation of a cost estimation approach for preliminary aircraft design in a multidisciplinary environment. The framework is able to capture the design attributes that drive the cost allowing a designer to assess cost changes with respect to different design configurations. The cost model is built in Excel using a Visual Basic interface and it is integrated within Model Centre platform, where it can be treated as a component of a computational design process. The paper concludes by presenting the results from a real wing trade-off study that includes all the components of a complete design system