### Browsing by Author "Skote, Martin"

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Item Open Access CFD simulation of dense gas dispersion in neutral atmospheric boundary layer with OpenFOAM(Springer, 2019-08-02) Tran, Vu; Ng, E. Y. K; Skote, MartinShow more In this study, Monin–Obukhov similarity theory is used to specify the profiles of velocity, turbulent kinetic energy (k), and eddy dissipation rate (ϵ) in atmospheric boundary layer (ABL) flow. The OpenFOAM standard solver buoyantSimpleFoam is modified to simulate neutrally stratified ABL. The solver is able to obtain equilibrium ABL. For gas dispersion simulation, buoyantNonReactingFoam is developed to take into account fluid properties change due to temperature, buoyancy effect, and variable turbulent Schmidt number. The solver is validated for dense gas dispersion in wind tunnel test and field test of liquefied natural gas vapour dispersion in neutrally stratified ABL.Show more Item Open Access Characterising mesoscale variability in low-level jet simulations for CBLAST-LOW 2001 campaign(Springer, 2020-04-30) Tay, Ken; Koh, Tieh-Yong; Skote, MartinShow more A low-level jet (LLJ) event observed during a frontal passage in the 2001 Coupled Boundary Layers and Air–Sea Transfer Experiment in Low Winds campaign was simulated using the Weather Research and Forecasting model (WRF). The sensi-tivity of the modeled LLJ characteristics, such as formation time, height and the strength of the LLJ core, to the choice of initial and boundary conditions, planetary boundary layer (PBL) schemes and vertical resolution was evaluated with a suite of diagnostic tools. The model simulations were compared against available soundings from the campaign observations as well as with surface observations from the Automated Surface Observing Systems. The simulation initialized with ERA-interim reanalysis and using the Mellor–Yamada–Nakanishi–Niino PBL scheme gave the best mix of diagnostic scores for surface temperature and wind speed predictions. The choice of boundary conditions introduced a stronger variability in the LLJ characteristics than the changes in PBL schemes or vertical resolution. The variability emerged primarily due to the timing of the frontal passage in the boundary condition datasets.Show more Item Open Access Characterizing mesoscale variability in low-level jet simulations for CBLAST-LOW 2001 campaign(Springer, 2020-04-30) Tay, Ken; Koh, Tieh-Yong; Skote, MartinShow more A low-level jet (LLJ) event observed during a frontal passage in the 2001 Coupled Boundary Layers and Air–Sea Transfer Experiment in Low Winds campaign was simulated using the Weather Research and Forecasting model (WRF). The sensitivity of the modeled LLJ characteristics, such as formation time, height and the strength of the LLJ core, to the choice of initial and boundary conditions, planetary boundary layer (PBL) schemes and vertical resolution was evaluated with a suite of diagnostic tools. The model simulations were compared against available soundings from the campaign observations as well as with surface observations from the Automated Surface Observing Systems. The simulation initialized with ERA-interim reanalysis and using the Mellor–Yamada–Nakanishi–Niino PBL scheme gave the best mix of diagnostic scores for surface temperature and wind speed predictions. The choice of boundary conditions introduced a stronger variability in the LLJ characteristics than the changes in PBL schemes or vertical resolution. The variability emerged primarily due to the timing of the frontal passage in the boundary condition datasets.Show more Item Open Access Conceptual design of a new experimental setup to simulate aircraft tyre spin-up dynamics(Emerald, 2023-06-02) Mahjouri, Saeed; Shabani, Rasoul; Skote, MartinShow more The first touchdown moment of aircraft tyres on a runway is the critical phase where maximum of the vertical and horizontal ground loads is produced. Some valuable drop tests have been performed at Langley research centre to simulate the touchdown and the spin-up dynamics. However, a long impact basin and a huge power source to accelerate and decelerate the landing gear mechanism have been used. Based on a centrifugal mechanism, the purpose of this paper is to propose the conceptual design of a new experimental setup to simulate the spin-up dynamics. Design/methodology/approach A schematic view of the proposed mechanism is presented, and its components are introduced. Operating condition of the system and the test procedure are discussed in detail. Finally, tyre spin-up dynamics of Boeing 747 is considered as a case study, and operating condition of the system and the related test parameters are extracted. Findings It is shown that the aircraft tyre spin-up dynamics can be simulated in a limited laboratory space with low energy consumption. The proposed setup enables the approach velocity, sink rate and vertical ground load to be adjusted by low power actuators. Hence, the proposed mechanism can be used to simulate the tyre spin-up dynamics of different types of aircraft. Research limitations/implications It is important to note that more details of the setup, including the braking and actuating mechanisms together with their control procedures, should be clarified in practice. In addition, the curved path introduced as the runway will cause errors in the results. Hence, a compromise should be made between the tyre pressure, path curvature, the induced error and the cost of the experimental setup. Practical implications The proposed experimental setup could be constructed in a limited space and at a relatively low cost. Low power actuators are used in the proposed system. Hence, in addition to the performance tests, fatigue tests of the landing gear mechanism will also be possible. Originality/value Based on a centrifugal mechanism, the conceptual design of a new experimental setup is presented for simulating the tyre spin-up dynamics of aircraft. Considering that the drag load developed during tyre spin-up following initial touchdown is an important factor governing the design of the landing gear mechanism and aircraft structure, the authors hope this paper encourages engineers to continuously make efforts to increase the transparency of the touchdown process, enabling optimisation of landing gear design.Show more Item Open Access CWENO finite-volume interface capturing schemes for multicomponent flows using unstructured meshes(Springer, 2021-11-09) Tsoutsanis, Panagiotis; Adebayo, Ebenezer Mayowa; Carriba Merino, Adrian; Perez Arjona, Agustin; Skote, MartinShow more In this paper we extend the application of unstructured high-order finite-volume central-weighted essentially non-oscillatory (CWENO) schemes to multicomponent flows using the interface capturing paradigm. The developed method achieves high-order accurate solution in smooth regions, while providing oscillation free solutions at discontinuous regions. The schemes are inherently compact in the sense that the central stencils employed are as compact as possible, and that the directional stencils are reduced in size, therefore simplifying their implementation. Several parameters that influence the performance of the schemes are investigated, such as reconstruction variables and their reconstruction order. The performance of the schemes is assessed under a series of stringent test problems consisting of various combinations of gases and liquids, and compared against analytical solutions, computational and experimental results available in the literature. The results obtained demonstrate the robustness of the new schemes for several applications, as well as their limitations within the present interface-capturing implementation.Show more Item Open Access Data for paper "A Modular Multifidelity Approach for Multiphysics Oleo-Pneumatic Shock Absorber Simulations"(Cranfield University, 2024-02-21 18:42) Sheikh Al Shabab, Ahmed; Silva, Paulo; Grenko, Bojan; Tsoutsanis, Panagiotis; Skote, MartinShow more Dataset for the underlying data discussed in the paper titled "A Modular Multifidelity Approach for Multiphysics Oleo-Pneumatic Shock Absorber Simulations"Show more Item Open Access Data for Paper "Numerical Investigation of Oleo-Pneumatic Shock Absorber: A Multi-Fidelity Approach"(Cranfield University, 2023-08-25 14:35) Sheikh Al Shabab, Ahmed; Grenko, Bojan; Vitlaris, Dimitrios; Tsoutsanis, Panagiotis; Antoniadis, Antonios; Skote, MartinShow more Raw data of simulations used in the ECCOMAS 2022 paper titled: Numerical Investigation of Oleo-Pneumatic Shock Absorber: A Multi-Fidelity ApproachShow more Item Open Access Data for Paper "Numerical Investigation of Orifice Nearfield Flow Development in Oleo-Pneumatic Shock Absorbers"(Cranfield University, 2022-02-18 09:57) Sheikh Al Shabab, Ahmed; Skote, Martin; Tsoutsanis, Panagiotis; Antoniadis, Antonios; Vitlaris, Dimitrios; Grenko, BojanShow more Data for the journal paper titled: Numerical Investigation of Orifice Nearfield Flow Development in Oleo-Pneumatic Shock AbsorbersShow more Item Open Access Data for Paper "Unsteady Multiphase Simulation of Oleo-Pneumatic Shock Absorber Flow"(Cranfield University, 2024-02-21 18:05) Sheikh Al Shabab, Ahmed; Grenko, Bojan; Silva, Paulo; Antoniadis, Antonios; Tsoutsanis, Panagiotis; Skote, MartinShow more Dataset for the paper "Unsteady Multiphase Simulation of Oleo-Pneumatic Shock Absorber Flow"Show more Item Open Access Data Supporting "Study of Orifice Design on Oleo-Pneumatic Shock Absorber"(Cranfield University, 2024-05-02 11:15) Silva, Paulo; Tsoutsanis, Panagiotis; Skote, Martin; Sheikh Al Shabab, AhmedShow more This data contain the results of the paper.Show more Item Open Access Data supporting: High-order hybrid DG-FV framework for compressible multi-fluid problems on unstructured meshes""(Cranfield University, 2024-02-12 17:07) Maltsev, Vadim; Skote, Martin; Tsoutsanis, PanagiotisShow more This dataset contains binary output in Tecplot format for the test problems analysed in the "High-order hybrid DG-FV framework for compressible multi-fluid problems on unstructured meshes" JCP paper. Test cases included are: - Gas-water isolated material interface advection - 2D and 3D helium bubble interaction with shock wave - 2D shock driven air bubble collapse in water - 2D and 3D shock driven air bubble array collapse in water - 2D underwater explosionShow more Item Open Access Data: Modeling and performance evaluation of sustainable arresting gear energy recovery system for commercial aircraft(Cranfield University, 2023-08-07 11:48) Deja, Jakub; Skote, Martin; Dayyani, ImanShow more Datasets showing the system performance for different aircraftShow more Item Open Access Drag reduction of turbulent boundary layers by travelling and non-travelling waves of spanwise wall oscillations(MDPI, 2022-02-05) Skote, MartinShow more Turbulence control in the form of a streamwise travelling wave of transverse wall motion was studied numerically by employing direct numerical simulations (DNS). Both total and phase averaging were utilised to examine the statistical behaviour of the turbulence affected by the wall forcing, with a focus on the skin friction. Comparison with results from pure temporal and spatial wall forcing are conducted, and a compilation of data is used to explore analogies with drag-reduced channel flow.Show more Item Open Access Effects of streamlining a bluff body in the laminar vortex shedding regime(American Society of Mechanical Engineers, 2019-10-21) Dobriyal, Ritvik; Mishra, Maneesh; Bölander, Markus; Skote, MartinShow more Two-dimensional flow over bluff bodies is studied in the unsteady laminar flow regime using numerical simulations. In previous investigations, lift and drag forces have been studied over different cross section shapes like circles, squares and ellipses. We aim to extend the previous research by studying the variation of hydrodynamic forces as the shape of the body changes from a circular cylinder to a more streamlined or a bluffer body. The different body shapes are created by modifying the downstream circular arc of a circular cylinder into an ellipse, hence elongating or compressing the rear part of the body. The precise geometry of the body is quantified by defining a shape factor. Two distinct ranges of shape factors with fundamentally different behavior of lift and drag are identified. The geometry constituting the limit is where the rear part ellipse has a semi minor axis of half the radius of the original circle, independent of the Reynolds number. On the other hand, the vortex shedding frequency decreases linearly over the whole range of shape factors. Furthermore, the variation of the forces and frequency with Reynolds number, and how the relations vary with shape factor are reported.Show more Item Open Access Graphic abstract(Cranfield University, 2022-06-07 12:41) Deja, Jakub; Dayyani, Iman; Skote, MartinShow more Modelling and Performance Evaluation of Sustainable ArrestingGear Energy Recovery System for Commercial AircraftShow more Item Open Access High-order hybrid DG-FV framework for compressible multi-fluid problems on unstructured meshes(Elsevier, 2024-02-06) Maltsev, Vadim; Skote, Martin; Tsoutsanis, PanagiotisShow more In this work we extend the hybrid Discontinuous Galerkin/ Finite Volume framework, introduced in V. Maltsev, D. Yuan, K. W. Jenkins, M. Skote, P. Tsoutsanis, “Hybrid discontinuous Galerkin-finite volume techniques for compressible flows on unstructured meshes, Journal of Computational Physics 473 (2023)” [1], to multi-species problems involving gas-gas and gas-liquid systems. The numerical scheme achieves high order accuracy in smooth flow regions thanks to the DG discretisation, yet avoiding oscillations at material interfaces and shocks thanks to a FV type reconstruction. This strategy, as typically represented in literature, makes use of the so-called troubled cell indicators for the detection of numerical oscillations generated by an unlimited high-order scheme in presence of discontinuities, and enables a more dissipative scheme in the troubled cells only in order to suppress the spurious oscillations. As will be shown in a series of increasingly challenging test-cases, when applied to multi-species flows in the context of diffuse-interface models, the hybrid framework is able to limit the excessive material interface dissipation, characteristic of these interface-capturing methods, allowing at the same time a control over the amount of dissipation necessary to solve stiffer problems.Show more Item Open Access High-order methods for diffuse-interface models in compressible multi-medium flows: a review(AIP, 2022-02-03) Maltsev, Vadim; Skote, Martin; Tsoutsanis, PanagiotisShow more The diffuse interface models, part of the family of the front capturing methods, provide an efficient and robust framework for the simulation of multi-species flows. They allow the integration of additional physical phenomena of increasing complexity while ensuring discrete conservation of mass, momentum, and energy. The main drawback brought by the adoption of these models consists of the interface smearing, increasing with the simulation time, therefore, requiring a counteraction through the introduction of sharpening terms and a careful selection of the discretization level. In recent years, the diffuse interface models have been solved using several numerical frameworks including finite volume, discontinuous Galerkin, and hybrid lattice Boltzmann method, in conjunction with shock and contact wave capturing schemes. The present review aims to present the recent advancements of high-order accuracy schemes with the capability of solving discontinuities without the introduction of numerical instabilities and to put them in perspective for the solution of multi-species flows with the diffuse interface method.Show more Item Open Access How wavelength affects hydrodynamic performance of two accelerating mirror-symmetric undulating hydrofoils(American Institute of Physics (AIP), 2023-08-02) Lin, Zhonglu; Liang, Dongfang; Bhalla, Amneet Pal Singh; Sheikh Al-Shabab, Ahmed A.; Skote, Martin; Zheng, Wei; Zhang, YuShow more Fish schools are capable of simultaneous linear acceleration. To reveal the underlying hydrodynamic mechanism, we numerically investigate how Reynolds number Re ¼ 1000–2000, Strouhal number St ¼ 0:2–0:7, and wavelength k ¼ 0:5–2 affect the mean net thrust and net propulsive efficiency of two side-by-side hydrofoils undulating in anti-phase. In total, 550 cases are simulated using immersed boundary method. The thrust increases significantly with the wavelength and the Strouhal number, yet only slightly with the Reynolds number. We apply a symbolic regression algorithm to formulate this relationship. Furthermore, we find that mirror-symmetric schooling can achieve a net thrust more than ten times that of a single swimmer, especially at low Reynolds numbers. The highest efficiency is obtained at St ¼ 0:5 and k ¼ 1:2, where St is consistent with that observed in the linear-accelerating natural swimmers, e.g., Crevalle jack. Six distinct flow structures are identified. The highest thrust corresponds to an asymmetric flow pattern, whereas the highest efficiency occurs when the flow is symmetric with converging vortex streets.Show more Item Open Access Hybrid discontinuous Galerkin-finite volume techniques for compressible flows on unstructured meshes(Elsevier, 2022-11-11) Maltsev, Vadim; Yuan, Dean; Jenkins, Karl W.; Skote, Martin; Tsoutsanis, PanagiotisShow more In this paper we develop a family of arbitrarily high-order non-oscillatory hybrid Discontinuous Galerkin(DG)-Finite Volume(FV) schemes for mixed-element unstructured meshes. Their key ingredient is a switch between a DG method and a FV method based on the CWENOZ scheme when invalid solutions are detected by a troubled cell indicator checking the unlimited DG solution. Therefore, the high order of accuracy offered by DG is preserved in smooth regions of the computational domain, while the robustness of FV is utilized in regions with strong gradients. The high-order CWENOZ variant used has the same spatial order of accuracy as the DG variant, while representing one of the most compact applications on unstructured meshes, therefore simplifying the implementation, reducing the computational overhead associated with large stencils of the original WENO reconstruction without sacrificing the desirable non-oscillatory properties of the schemes. We carefully investigate several parameters associated with the switching between DG and FV methods including the troubled cell indicators in a priori fashion. For the first time in the literature, we investigate the definition of the bounds for an admissible solution, the frequency by which we use the troubled cell indicators, and the evolution of the percentage of troubled cells for unsteady test problems. The 2D and 3D Euler equations are solved for well established test problems and compared with computational or experimental reference solutions. All the methods have been implemented and deployed within the UCNS3D open-source high-order unstructured Computational Fluid Dynamics (CFD) solver. The present coupling has the potential to improve the shortcomings of both FV-DG in a computational efficient manner. The improved accuracy and robustness provided is a characteristic of paramount importance for industrial-scale CFD applications, and favours the extension to other systems of governing equations.Show more Item Open Access Integral relations for the skin-friction coefficient of canonical flows(Cambridge University Press, 2022-06-20) Ricco, Pierre; Skote, MartinShow more We show that the Fukagata et al.’s (Phys. Fluids, vol. 14, no. 11, 2002, pp. 73–76) identity for free-stream boundary layers simplifies to the von Kármán momentum integral equation relating the skin-friction coefficient and the momentum thickness when the upper bound in the integrals used to obtain the identity is taken to be asymptotically large. If a finite upper bound is used, the terms of the identity depend spuriously on the bound itself. Differently from channel and pipe flows, the impact of the Reynolds stresses on the wall-shear stress cannot be quantified in the case of free-stream boundary layers because the Reynolds stresses disappear from the identity. The infinite number of alternative identities obtained by performing additional integrations on the streamwise momentum equation also all simplify to the von Kármán equation. Analogous identities are found for channel flows, where the relative influence of the physical terms on the wall-shear stress depends on the number of successive integrations, demonstrating that the laminar and turbulent contributions to the skin-friction coefficient are only distinguished in the original identity discovered by Fukagata et al. (Phys. Fluids, vol. 14, no. 11, 2002, pp. 73–76). In the limit of large number of integrations, these identities degenerate to the definition of skin-friction coefficient and a novel twofold-integration identity is found for channel and pipe flows. In addition, we decompose the skin-friction coefficient uniquely as the sum of the change of integral thicknesses with the streamwise direction, following the study of Renard & Deck (J. Fluid Mech., vol. 790, 2016, pp. 339–367). We utilize an energy thickness and an inertia thickness, which is composed of a thickness related to the mean-flow wall-normal convection and a thickness linked to the streamwise inhomogeneity of the mean streamwise velocity. The contributions of the different terms of the streamwise momentum equation to the friction drag are thus quantified by these integral thicknesses.Show more