Browsing by Author "Savill, Mark"

Now showing 1 - 17 of 17
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    ADOPT: An augmented set-based design framework with optimisation
    (Cambridge University Press, 2019-03-07) Georgiades, Alexandros; Sharma, Sanjiv; Kipouros, Timoleon; Savill, Mark
    During the early stages of any system design, a thorough exploration of the design space can prove to be challenging and computationally expensive. The challenges are further exacerbated when dealing with complex systems, such as an aircraft, due to the high dimensionality of their design space. Arising from the Toyota Product Development System, Set-Based Design allows parallel evaluation of multiple alternative configurations in the early design stages. At the same time, optimisation methods can be employed at later stages to fine-tune the engineering characteristics of design variants. Presented in this paper, is the Augmented set-based Design and OPTimisation (ADOPT) Framework that introduces a novel methodology for integrating the two areas. This allows for a thorough design space exploration while ensuring the optimality of the selected designs. The framework has been developed using a process-independent and tool-agnostic approach so that it can be applied to the design process of varying kinds of systems. To demonstrate the implementation and potential benefits, the framework has been applied to the design of a generic aircraft fuel system. The results from the case study and the framework itself are discussed, with a number of areas for further development and future work being identified and presented.
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    Computational design optimization for S-ducts
    (MDPI, 2018-10-12) D’Ambros, Alessio; Kipouros, Timoleon; Zachos, Pavlos; Savill, Mark; Benini, Ernesto
    In this work, we investigate the computational design of a typical S-Duct that is found in the literature. We model the design problem as a shape optimization study. The design parameters describe the 3D geometrical changes to the shape of the S-Duct and we assess the improvements to the aerodynamic behavior by considering two objective functions: the pressure losses and the swirl. The geometry management is controlled with the Free-Form Deformation (FFD) technique, the analysis of the flow is performed using steady-state computational fluid dynamics (CFD), and the exploration of the design space is achieved using the heuristic optimization algorithm Tabu Search (MOTS). The results reveal potential improvements by 14% with respect to the pressure losses and by 71% with respect to the swirl of the flow. These findings exceed by a large margin the optimality level that was achieved by other approaches in the literature. Further investigation of a range of optimum geometries is performed and reported with a detailed discussion.
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    Dynamic distortion simulations for curved aeronautical intakes
    (Royal Aeronautical Society (RAeS), 2015-07) Chiereghin, Nicola; MacManus, David G.; Savill, Mark; Dupuis, Romain
    This research focuses on the numerical simulation of the dynamic distortion in highly convoluted aeronautic intakes and extends the current knowledge with a systematic study of the influence of duct diameter, Mach number and offset. A comparison against experimental data revealed the capability of Delayed Detached Eddy Simulation to reproduce the trends of variation of distortion descriptors and pressure recovery although the absolute values are not yet captured. Analysis of the temporal distribution of the flow parameters identified the relevant fluctuating components both for total pressure distortion and swirl. A Proper Orthogonal Decomposition of the flow highlighted important differences of the major flow structures for different duct curvatures and a strong dependence of the distortion parameters also on the finer flow structures.
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    Embedded large eddy simulation of transitional flow over NACA0012 aerofoil
    (Sage, 2020-07-06) Lin, Yujing; Wang, Jian; Savill, Mark
    An accurate computation of near-field unsteady turbulent flow around aerofoil is of outstanding importance for aerofoil trailing edge noise source prediction, which is a representative of main contributor to airframe noise and fan noise in modern commercial aircraft. In this study, an embedded large eddy simulation (ELES) is fully implemented in a separation-induced transitional flow over NACA0012 aerofoil at a moderate Reynolds number. It aims to evaluate the performance of the ELES method in aerodynamics simulation for wall-bounded aerospace flow in terms of accuracy, computational cost and complexity of implementation. Some good practice is presented including the special treatments at RANS-LES interface to provide more realistic turbulence generation in LES inflow. A comprehensive validation of the ELES results is performed by comparing with the experimental data and the wall-resolved large eddy simulation results. It is concluded that the ELES method could provide sufficient accuracy in the transitional flow simulations around aerofoil. It is proved to be a promising alternative to the pure LES for industrial flow applications involving wall boundary layer due to its significant computational efficiency
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    Impact of fluid substitution on the performance of an axial compressor blade cascade working with supercritical carbon dioxide
    (ASME, 2019-12-11) Tello, Carlos; Muñoz, Alejandro; Sánchez, David; Kipouros, Timoleon; Savill, Mark
    Recent research on turbomachinery design and analysis for supercritical Carbon Dioxide (sCO2) power cycles has relied on Computational Fluid Dynamics. This has produced a large number of works whose approach is mostly case-specific, rather than of general application to sCO2 turbomachinery design. As opposed to such approach, this work explores the aerodynamic performance of compressor blade cascades operating on air and supercritical CO2 with the main objective to evaluate the usual aerodynamic parameters of the cascade for variable boundary conditions and geometries, enabling 'full' or 'partial' similarity. The results present both the global performance of the cascades and certain features of the local flow (trailing edge and wake). The discussion also highlights the mechanical limitations of the analysis (forces exerted on the blades), which is the main restriction to applying similarity laws to extrapolate the experi- ence gained through decades of work on air turbomachinery to the new working fluid. This approach is a step towards the understanding and appropriate formulation of a multi-objective optimisation problem for the design of such turbomachinery components where sCO2 is used as the operating fluid. With this objective, the paper aims to identify and analyse what would be expected if a common description of such computational design problems similar to those where air is the working fluid were used.
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    The importance of coupling aerodynamic and cost analysis in aircraft design
    (Springer, 2022-08-03) Di Pasquale, Davide; Savill, Mark
    Companies 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.
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    Influence of bluff-body and swirl on mixing and intermittency of jets
    (2010-09-30T00:00:00Z) Ranga Dinesh, K. K. J.; Jenkins, Karl W.; Savill, Mark; Kirkpatrick, M. P.
    In this paper we present the modelled results of turbulence, scalar mixing and intermittency for three different basic fluid dynamical problems using large eddy simulation (LES). The modelled problems are a turbulent round jet, a bluff body stabilised jet, and a bluff body stabilised swirl jet in a co-flow environment. Both instantaneous and time averaged results along with the probability density functions (pdf) and intermittency of velocity and passive scalar are presented. Simulations well captured the flow features of jet, bluff body stabilised jet and bluff body stabilised swirl jet. The instantaneous and time averaged data show the differences in turbulence and mixing and also an improvement of mixing in the presence of a bluff body and swirl. The addition of bluff body and swirl affect the structure of pdfs for both velocity and passive scalar at different axial and radial locations. The radial variation of intermittency at locations close to the centreline indicates turbulent to non- turbulent phenomena respect to bluff body and swirl at both upstream and downstream recirculation regions.
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    Loading and planform shape influence on the wing structural layout through topology optimization
    (AIAA, 2018-07-31) Crescenti, Fabio; Kipouros, Timoleon; Savill, Mark
    Topology optimization is a technique used to identify the optimal layout of a structure for a given objective and assigned boundary conditions. The progress it has experienced over the last three decades made it ready for industrial applications. In this paper topology optimization is employed to investigate the influence of sweep angle, aspect ratio and loading condition on the wing internal structure. The planform of the Common Research Model wing is used as a baseline. The geometry is modified parametrically to alter sweep angle and aspect ratio. Regarding the baseline planform, the optimization is performed considering the aerodynamic loading induced by the pull-up manoeuvre. Results are provided for AR=7 and AR=1, as well as sweep angle of 20 and 30 degrees. The results of topology optimization for all cases are compared. Common patterns are identified and exported to provide guidelines for the preliminary design of the wing primary structure.
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    Modelling of a three-shaft high-bypass-ratio engine performance and emission prediction using hydrogen fuel
    (BEIE&SP, 2019-05-25) Wan Yahya, M. Z.; Azami, M. H.; Savill, Mark; Li, Yi-Guang; Khan, S.A; Warimani, Mahammad Salman
    The price of oil has seen an unprecedented increase and the resulting demand for oil, especially from the transportation industries. The pollution emits from the vehicle has affected human health and environmental problems especially aviation industries because the emission covers much broader spectrums. Drop-in alternative fuels such as liquefied hydrogen fuel are believed to offer better engine performance and reduce the emission. An in-house computer tool, PYTHIA was used to model the performance of RB211 engine at a wide range of flight operations. Liquid hydrogen fuel will increase the thrust and the specific fuel consumption up to 63.9% reduction at higher speed. Liquid hydrogen fuel resulted in higher burning temperature which encourage the formation of NOx. At the sea level, it was found that EINOx was increased to about 5.5% when 20% blended ratio was used.
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    Modelling the performance and emission prediction of RB211 aero-gas turbine engine fuelled by Jatropha-based biofuel
    (IOP Publishing: Conference Series / IOP Publishing, 2019-04-30) Azami, Muhammad Hanafi; Noorazman, Zahid; Savill, Mark; Li, Yi-Guang; Hilmi, Mohd Razi
    Fossil fuel is one of the world vital energy resources. The development of transportation technologies increases the demand for petroleum derivative globally. Fossil fuel consumption produces emissions, which potentially harm the environment and human health. Many mitigations have been implemented to address the two main crises; the energy scarcity and environmental calamity. This paper will discuss on one of the potential solutions by analyzing the performance and emission prediction of aero-gas turbine engine fuelled by Jatropha-based biofuel. Performance analysis was made based on the thrust and specific fuel consumptions at different blended ratio percentages for various flight conditions. The three-shaft high-bypass-ratio engine model, which is identical to the Rolls Royce RB211-524 was used to model in an in-house Cranfield's University software, PYTHIA. PYTHIA is integrated with the TURBOMATCH performance evaluation programme by iterating the mass and energy balance for each engine component. The analysis is then continued to predict Nitrogen Oxides emission index (EINOx) at every flight conditions using an in-house Cranfield's University computer tool, HEPHAESTUS. HEPHAESTUS is an emission prediction software by using Zel'Dovich equations (for NOx) and models the emission by implementing a partially-stirred reactor (PSR) model and perfectly stirred reactor (PSRS) models at different zones in the combustor. Validation showed that HEPHAESTUS is able to capture a reasonable prediction as compared to the International Civil Aviation Organization (ICAO) databank. The performance the biofuel has shown an improvement in engine performance at higher percentage blended ratio but also increase the nitrous oxide indices emission slightly
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    Modelling the performance of aero-gas turbine engine using algae-based biofuel with emission prediction
    (IOP Publishing: Conference Series / IOP Publishing, 2019-04-30) Azami, Muhammad Hanafi; Zaki, Muhamad; Savill, Mark; Li, Yiguang
    The world oil consumption is at the peak where the fuel price is insubstantial and can increase dramatically due to economic, social, and political factors andunprecedentedstability.Since fuel resourcesare scarce, it is an urgent need to find alternative fuel. Biofuel is one of the favorable choices in the market. Algae-based biofuel is the fourth generation of biofuel where it does not compete with the food production and it has myriad of advantages.These abundant algae are easy to cultivate and researchers found that algae-based biofuel is capable of reducing engine emission. This paper modelled the RB211aero-gas turbine engine by utilizing algae-based biofuel with various blended percentageratios at different flight conditions. Cranfield’s University in-house software, PYTHIA,and HEPHAESTUSare used to model the engine performance and emission prediction respectively.PYTHIA programme uses a modified Newton-Raphson convergence technique in the zero-dimensional steady-state model for both design and off-design conditions. Meanwhile, HEPHAESTUSsoftware uses the Zeldovich equations (for NOx) and models the emission by implementing a partially-stirred reactor (PSR) model and perfectly stirred reactor (PSRS) models at different zones in the combustor.Results have shown that thrust force produced is increasing at higher blended percentage ratio of algae biofuel. Through emission analysisprediction, generally,the nitrous oxide emission formation is lower at a higher altitude during the cruising. Results also predicted that higher percentage blended ratio of algae biofuel also reduces the emission formation.
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    Predicting and visualizing cost propagation due to engineering design changes
    (Design Society, 2017-12-31) Georgiades, Alexandros; Sharma, Sanjiv; Kipouros, Timoleon; Savill, Mark
    During product development changes in the initial design are ubiquitous. The ability to predict such changes, along with the expected costs, is a challenge on its own. This challenge increases exponentially when a single design change on one element of the system propagates to other components. As change propagates, so does the cost associated with it; where cost is more than just financial. A number of knowledge-based methods have been developed in the past that assist in the prediction of how change propagates through a system, and the impact that it can have on other components. None of the methods developed, however, considers how cost propagates due to design changes. This paper presents a novel methodology for predicting, visualizing, and assessing the propagation of change and the cost associated with it. As part of the methodology, a new method, CP2, has been developed to calculate the propagated costs. The methodology has been applied to a conceptual example of a simple system to demonstrate the procedure and the use of the methods. The visualization of the results arising from this methodology is also demonstrated as a mechanism for design decision-making.
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    Shape optimization of a curved duct with Free Form Deformations
    (AIAA, 2017-06-09) Chiereghin, Nicola; Guglielmi, Luigi; Savill, Mark; Manca, Enrico; Rigobello, Aurora; Barison, Marco; Benini, Ernesto
    The Free Form Deformation method was applied to a S-duct geometry to reduce total pressure losses and flow distortion. The deformation method was coupled with a multiobjective genetic algorithm to optimize the shape of a diffusing S-duct, which was previously investigated, both numerically and experimentally. During the optimization process, 200 deformed shapes were tested with steady-state CFD simulations and the performances were evaluated both in terms of total pressure losses and swirl angle at the outlet. It was obtained a Pareto front with a maximum total pressure losses reduction of 20% and a maximum swirl reduction of 10%. The two extreme points of the Pareto front were further investigated by transient Detached Eddy Simulations to assess also the impact of the optimization on the flow instability. Surprisingly, one of the solutions showed stable and stationary vortical structures. This is in strong contrast with the previous investigations of the flow field time history of the baseline configuration, which outlined strong oscillations of the flow field combined with a high increase of the distortion parameters in comparison with the time-averaged flow field.
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    Simulation-based optimisation of maintenance systems: Industrial case studies
    (Elsevier, 2017-06-20) Alrabghi, Abdullah; Tiwari, Ashutosh; Savill, Mark
    Investigating the optimum blend of maintenance strategies for a given manufacturing system is a continuing concern amongst maintenance academics and professionals. Recent evidence suggests that little research is conducted on the simulation optimisation of maintenance in industrial systems. This study was designed to make an important contribution to the field of simulation-based optimisation of maintenance by presenting two empirical case studies: a tyre re-treading factory and a petro-chemical plant. It is one of the first to optimise various maintenance strategies simultaneously with their parameters in industrial manufacturing systems while considering production dynamics. Stochastic Discrete Event Simulation models were developed and connected to a Multi-Objective Optimisation engine. Various maintenance strategies were investigated including Corrective Maintenance, Preventive Maintenance, Opportunistic Maintenance and Condition-Based Maintenance. The results of this research suggest that over-looking the optimisation of maintenance on the strategic level may lead to sub-optimal solutions. In addition, it appears that traditional trade-offs between maintenance cost and production throughput are not present in some maintenance systems. This is an interesting observation that requires further investigation and experimentation.
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    Surrogate modelling for wing planform multidisciplinary optimisation using model-based engineering
    (Hindawi Publishing Corporation, 2019-05-09) Pagliuca, Giampaolo; Kipouros, Timoleon; Savill, Mark
    Optimisation is aimed at enhancing aircraft design by identifying the most promising wing planforms at the early stage while discarding the least performing ones. Multiple disciplines must be taken into account when assessing new wing planforms, and a model-based framework is proposed as a way to include mass estimation and longitudinal stability alongside aerodynamics. Optimisation is performed with a particle swarm optimiser, statistical methods are exploited for mass estimation, and the vortex lattice method (VLM) with empirical corrections for transonic flow provides aerodynamic performance. Three surrogates of the aerodynamic model are investigated. The first one is based on radial basis function (RBF) interpolation, and it relies on a precomputed database to evaluate the performance of new wing planforms. The second one is based on an artificial neural network, and it needs precomputed data for a training step. The third one is a hybrid model which switches automatically between VLM and RBF, and it does not need any precomputation. Its switching criterion is defined in an objective way to avoid any arbitrariness. The investigation is reported for a test case based on the common research model (CRM). Reference results are produced with the aerodynamic model based on VLM for two- and three-objective optimisations. Results from all surrogate models for the same benchmark optimisation are compared so that their benefits and limitations are both highlighted. A discussion on specific parameters, such as number of samples for example, is given for each surrogate. Overall, a model-based implementation with a hybrid model is proposed as a compromise between versatility and an arbitrary level of accuracy for wing early-stage design.
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    Technoeconomic distribution network planning using smart grid techniques with evolutionary self-healing network states
    (Hindawi - Wiley, 2018-10-10) Nieto-Martin, Jesus; Kipouros, Timoleon; Savill, Mark; Woodruff, Jennifer; Butans, Jevgenijs
    The transition to a secure low-carbon system is raising a set of uncertainties when planning the path to a reliable decarbonised supply. The electricity sector is committing large investments in the transmission and distribution sector upon 2050 in order to ensure grid resilience. The cost and limited flexibility of traditional approaches to 11 kV network reinforcement threaten to constrain the uptake of low-carbon technologies. This paper investigates the suitability and cost-effectiveness of smart grid techniques along with traditional reinforcements for the 11 kV electricity distribution network, in order to analyse expected investments up to 2050 under different DECC demand scenarios. The evaluation of asset planning is based on an area of study in Milton Keynes (East Midlands, United Kingdom), being composed of six 11 kV primaries. To undertake this, the analysis used a revolutionary new model tool for electricity distribution network planning, called scenario investment model (SIM). Comprehensive comparisons of short- and long-term evolutionary investment planning strategies are presented. The work helps electricity network operators to visualise and design operational planning investments providing bottom-up decision support.
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    Wall-resolved large eddy simulation for aeroengine aeroacoustic investigation
    (Cambridge University Press, 2017-06-22) Lin, Yujing; Vadlamani, Rao; Savill, Mark; Tucker, Paul
    The work presented here forms part of a larger project on Large-Eddy Simulation (LES) of aeroengine aeroacoustic interactions. In this paper, we concentrate on LES of near-field flow over an isolated NACA0012 aerofoil at zero angle-of-attack and a chord based Reynolds number of Rec = 2 × 105. A wall-resolved compressible Numerical Large Eddy Simulation (NLES) approach is employed to resolve streak-like structures in the near-wall flow regions. The calculated unsteady pressure/velocity field will be imported into an analyticallybased scheme for far-field trailing-edge noise prediction later. The boundary-layer mean and root-mean-square (rms) velocity profiles, the surface pressure fluctuation over the aerofoil, and the wake flow development are compared with experimental data and previous computational simulations in our research group. It is found that the results from the wall-resolved compressible NLES are very encouraging as they correlate well with test data. The main features of the wall-resolved compressible NLES, as well as the advantages of such compressible NLES over previous incompressible LES performed in our research group, are also discussed. This paper will be presented at the ISABE 2017 Conference, 5-8 September 2017, Manchester, UK.