Browsing by Author "Di Pasquale, Davide"
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Item Open Access Aerodynamic and cost modelling for aircraft in a multi-disciplinary design context.(Cranfield University, 2015-12) Di Pasquale, Davide; Savill, Mark A.; Kipouros, Timoleon; Holden, CarrenA 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.Item Open Access Aircraft cost modelling, integrated in a multidisciplinary design context(Science Publishing Group, 2019-12-17) Di Pasquale, Davide; Gore, David; Savill, Mark A.; Kipouros, Timoleon; Holden, CarrenMost 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.Item Open Access Analysis of triangular cross-section slender bodies in supersonic regime using RANS simulations(AIAA, 2023-06-08) Bourny, Quentin; Proenca, Anderson; Di Pasquale, Davide; Prince, Simon A.This paper presents an investigation on the ability of RANS simulations to capture the aerodynamic forces and the flow topology of triangular cross-section slender bodies. At Cranfield University’s Transonic and Supersonic Wind Tunnel, force measurements and Schlieren images were obtained at zero incidence, Mach number equals to 2.5, and Reynolds number of 2.38 · 10^5 (based on section width). Tests were performed for three bodies of different nose geometries, but constant nose fineness ratio of 1.732. Tests were compared with RANS simulations for three turbulence models: Spalart-Allmaras, k− epsilon Realizable and k − omega SST using the ANSYS Computational Fluid Dynamics software Fluent. In addition, simulations for a configuration presented in the literature which investigated several angles of attack were also conducted. At Mach 2.5, the normal force was predicted accurately by all turbulence models. The axial force, however, was clearly predicted more accurately with the k − epsilon Realizable model. At the other hand, this turbulence model showed inferior ability to capture the flow features, particularly the leeside vortices. Spalart-Allmaras and k − omega SST gave similar results.Item Open Access Application of a semi-empirical method to model subsonic vortex lift over sharp leading-edge delta wings(AIAA, 2023-01-19) Huynh, Daniel; Di Pasquale, Davide; Prince, Simon A.; Ahuja, VivekA semi-empirical method is applied as a complement to the FlightStream solver, to more accurately model subsonic vortex lift over a sharp leading-edge delta wing. The method, based on the prediction of flow patterns and the application of the Polhamus method, is particularly well-adapted to a preliminary aerodynamic design phase. Within a few minutes, it can accurately predict the aerodynamic forces generated by the flow over a delta wing, which are strongly affected by the presence of a leading-edge vortex. This study presents a detailed analysis where computed results are compared against experimental data. Those were obtained from a test case of a 65° subsonic delta wing experiment (case 1), along with a sensitivity analysis against sweep angle and aspect ratio where multiple subsonic delta wings were tested (case 2). A good agreement is observed between computed data and experimental results, within pre-stall, before the vortex bursts. Analysed results demonstrate the validity of the method, for multiple wing configurations associated with different flow conditions.Item Open Access Assessment of Turbulence Models for Transonic / Supersonic Smooth Surface Separation(Cranfield University, 2021-06-21 13:14) Prince, Simon; González caballero, Roberto; Di Pasquale, DavideA systematic comparison of the principle modern turbulence prediction methods for the solution of the Navier-Stokes equations for the calculation of high speed flows about slender forebodies at low to moderate angle of attack is presented. This class of flow involves smooth surface turbulent boundary layer separation resulting in steady symmetric leeside vortices, and also the formation of embedded shock waves from the displacement effect of the large vortices in supersonic flow. As such this flow is both complex and highly sensitive to the state of the boundary layers on the body. This study revealed that the method which most consistently provides accurate predictions of the overall forces and moments on the body, the most accurate distribution of surface pressure and can most accurately resolve the flow features, including leeside vortices and embedded shock wave features, is the Solution Adaptive Simulation method. Detached Eddy Simulation and the Reynold Stress Model, which would be expected to provide superior accuracy over the RANS based linear eddy viscosity models, on the whole, failed to provide better predictions. In fact, the k-omega Realizable and k-omega SST turbulence models provided data which was almost as consistently accurate as the Solution Adaptive Simulation method. The standard k-omega turbulence model appears to be completely unsuitable for the computation of this class of high speed flow problem, and this may be associated with the poor initial / default prescription of the value of omega at the far-field boundary.Item Open Access Blended wing body (BWB) planform multidisciplinary optimisation (MDO) for early stage aircraft design using model based engineering(International Council of the Aeronautical Sciences, 2021-09-10) Di Pasquale, Davide; Verma, D.; Pagliuca, GiampaoloA model-based engineering (MBE) framework has been developed for Multi-Disciplinary Optimisation (MDO) of a Blended Wing Body (BWB) configuration during early design stages. Specifically, a planform optimisation has been performed by focusing on three objective functions, namely, aerodynamic efficiency (Eff), drag coefficient (CD) and Operational Empty Weight (OEW). Particle Swarm Optimisation (PSO) has been used as algorithm for the optimisation, an open-source Vortex Lattice Method (VLM), with empirical corrections for compressibility, as aerodynamic module, along with a mass estimation model with respect to BWB considerations. A successful multidisciplinary optimisation has been performed for the BWB-11 configuration flying at cruise condition, specifically at Mach 0.85 and at an altitude of 10 km. Increment in Eff and decrement in CD and OEW compared to the baseline BWB has been achieved. The OEW has been calculated from a newly developed mass estimation model and successfully validated via statistical methods. The paper presents a rapid MDO framework for efficient BWB planform optimisation to be used at the early design stage, providing useful guidance to the designers. A detailed analysis of the integrated design system, the methods as well as the optimisation results are provided. In addition, further research to the current framework is also presented.Item Open Access CFD study of shock bump roughness for transonic shock control and buffet alleviation(AIAA, 2024-01-04) Di Pasquale, DavideShock 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) - the𝜅−𝜔SST 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.Item Open Access Feasibility of a spinning cylinder on the leading and trailing edges of a flap for high lift(AIAA, 2023-01-19) Francannet, Antoine; Prince, Simon A.; Di Pasquale, Davide; Proenca, AndersonThis paper presents a numerical feasibility study of a spinning cylinder mounted on the leading edge and trailing edge of a flap to improve lift force generation. The baseline used in this study is a two-dimensional NLR 7301 airfoil with a single-slotted trailing-edge flap. For this configuration, experimental data is available in the literature. The Ansys computational fluid dynamics (CFD) simulation software has been used in this work to simulate the aerodynamic properties of several configurations. Firstly, a turbulence model dependency study over the existing geometry was conducted, providing lift, drag and pitching moment coefficients, as well as pressure distribution for three angles of attack. Data was then acquired using the Spalart-Allmaras turbulence model at Mach and (chord-based) Reynolds numbers 0.185 and 2.51×10^6, respectively. Three configurations with a leading-edge spinning cylinder and one with a trailing-edge spinning cylinder were investigated. Results suggest that the introduction of a cylinder in the baseline geometry decreased lift and drag performance by inducing flow separation. Nevertheless, for the leading edge configurations, the rotation of the cylinder allowed recovery of the original flapped airfoil performance by re-energizing the flow around the flap and reattaching the boundary layer. For the trailing edge configuration, the spinning cylinder generated additional lift due to Magnus and suction effects at high rotation speed of the cylinder, and by modifying the flow circulation around the flap’s trailing edge. Overall, no benefit over the lift-to-drag ratio could be derived from this preliminary study.Item Open Access The importance of coupling aerodynamic and cost analysis in aircraft design(Springer, 2022-08-03) Di Pasquale, Davide; Savill, MarkCompanies are increasingly required to improve their quality, flexibility and innovation while maintaining or reducing their costs. However, engineering and finance are often handled by different staff groups at different times in the manufacturing process, and by uncoupling engineering and finance, a company runs the risk of overlooking important interactions between the two. A design system that performs engineering and financial analysis simultaneously may, therefore, improve upon the efficiency and effectiveness of the traditional methods, as the existing practice of designing aircraft from a technical perspective without simultaneously considering the impact on overall program value is not optimal in a business sense. A coupled performance/financial framework enables an integrated approach to technical design and programmatic decisions. This work thus seeks to couple aero performance and financial design. Specifically, a multi-objective trade study is conducted to see the impact on the direct operating cost (DOC) and manufacturing cost of parametrically varying aircraft wing thickness to chord ratio along the wing span. While the present process is only partially automated, the purpose is to establish a useful foundation for further developments and to gain insight into the interactions between technical and program design.Item Open Access The influence of high-speed SPIV data processing parameters on aircraft wing vortex wake assessment(ICAS, 2018-12-31) Garry, Kevin; Di Pasquale, Davide; Prince, Simon A.; Lawson, Nicholas J.SPIV is a powerful tool to assess aircraft wing vortex wakes. Current optical systems enable velocity vector measurements at sample rates of 10Hz. This facilitates detailed assessment of flows containing multiple, potentially unsteady, vortices. SPIV data from the wake of a high-lift wing is used to investigate data sampling strategies on the magnitude of vortex trajectory and strength.Item Open Access The influence of high-speed SPIV data processing parameters on aircraft wing vortex wake assessment(ICAS, 2018-09-14) Garry, Kevin; Di Pasquale, Davide; Prince, Simon A.; Lawson, Nicholas J.This paper uses Stereoscopic Particle Image Velocimetry (SPIV) data from the near wake of a detailed sub-scale ½ model of a representative transport aircraft wing with leading and trailing edge high lift systems and outboard aileron representation, to analyse the influence of data sampling period and frequency on the magnitude and position of the vortices resolved within the wake. The paper also evaluates the extent of vortex ‘wander’ at various stages of development within the near wake and offers guidance for optimum time-averaging strategy when investigating complex longitudinal vortex interaction studies in similar flow fields.Item Open Access Integrated system to perform surrogate based aerodynamic optimisation for high-lift airfoil(EngOpt, 2016-06-23) Di Pasquale, Davide; Zhu, F.; Cross, M.; Savill, Mark A.; Kipouros, TimoleonThis 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 theItem Open Access Optimisation of aero-manufacturing characteristics of aircraft ribs(Cambridge University Press, 2022-02-08) Kim, T.; Kipouros, Timoleon; Brintrup, A.; Farnfield, J.; Di Pasquale, DavideThe main purpose of this study was to combine the currently separate objectives of aerodynamic performance and manufacturing efficiency, then find an optimal point of operation for both objectives. An additional goal of the study was to explore the effects of changes in design features, the position of the spars, and analyse how the changes influenced the optimal operating conditions. A machine-learning approach was taken to combine and model the gathered aero-manufacturing data, and a multi-objective optimisation approach utilising genetic algorithms was implemented to find the trade-off relationship between optimal target objectives (mission performance and manufacturability). The main achievements and findings of the study were: The study was a success in building a machine-learning model for the combined aero-manufacturing data utilising software library XGBoost; multi-objective optimisation, which did not include spar positions as a variable found the trade-off region between high manufacturability and high mission performance, with choices that offered reasonably high values of both; there was no clearly identified correlation between a small change in spar position and the target objectives; multi-objective optimisation with spar positions resulted in a trade-off relationship between target objectives, which was different from the trade-off relationship found in optimisation without spar positions; multi-objective optimisation with spar positions also offered more flexibility in the choice of manufacturing processes available for a given design; and the range of bump amplitudes for solutions found by multi-objective-optimisation with spar positions was lower and more focused than those found by optimisation without spar positions.Item Open Access Passive transonic shock control on bump flow for wing buffet suppression(MDPI, 2023-06-20) Di Pasquale, Davide; Prince, SimonSince modern transport aircraft cruise at transonic speeds, shock buffet alleviation is one indispensable challenge that civil transport research needs to be addressed. Indeed, in the transonic flow regime shock-induced separation and transonic buffet compromise the flight envelope of an aircraft, and therefore its operational safety and structural integrity. One possible solution is to control and delay the boundary layer separation. The aim of this work was to study whether sub-boundary layer scale period roughness, which locally increases the boundary layer displacement thickness, can act as a virtual shock bump, with aim of bifurcating the foot of the shock wave to reduce the shock’s adverse effect on the boundary layer in the same way as solid shock bumps are known to act. This passive approach can then enhance the buffet margin, consequently extending the safe flight envelope. An experimental investigation was performed, applying this passive technique on a wind tunnel wall bump model which simulated the flow over the upper surface of an aerofoil. The results, in terms of surface pressure distribution and corresponding shadowgraph flow visualisation, showed that such periodic roughness can, indeed, bifurcate the shock wave and delay shock-induced separations, depending on the orientation of the roughness and its periodicity. A virtual shock bump effect can be produced using the displacement effect of periodic sub-boundary layer scale roughness.Item Open Access Progress towards a rapid method for conceptual aerodynamic design for transonic cruise(AIAA, 2020-01-05) Prince, Simon A.; Di Pasquale, Davide; Garry, Kevin P.Results are presented from a study aimed at demonstrating the accuracy and efficiency of a lower order aerodynamic prediction method for transonic cruise flows around aircraft configurations, including conventional swept wing-body and also blended wing-body designs. The Viscous Full Potential (VFP) method, coupling the solution of the full potential equations with the integral boundary layer equations can yield data of almost equivalent accuracy as Navier-Stokes based CFD methods but at 0.5% - 2% of the physical time. In addition it is shown, using both the VFP approach and Delayed Detached Eddy Simulation (DDES) that the flow physics of the stall mechanism associated with blended wing-body configurations is far more complex than that experienced on more conventional swept-tapered wings. The mechanism appears to involve an initial tip stall but also involves highly 3D vortical flows inboard on the upper surface of the wing which significantly distorts the transonic shock wave.Item Open Access A rapid aerodynamic prediction method for unconventional transonic aircraft configurations(ICAS, 2018-12-31) Prince, Simon A.; Di Pasquale, Davide; Garry, Kevin; Nuzzo, CristinaThis 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.Item Open Access Validating surrogate models and incorporating uncertainty quantification in multi-element airfoil design optimisation(International Council of the Aeronautical Sciences, 2021-09-10) Di Pasquale, Davide; Bolart, CarlesThis 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.