Browsing by Author "Grenko, Bojan"

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    A modular multifidelity approach for multiphysics oleo-pneumatic shock absorber simulations
    (Springer Nature, 2024-12-03) Sheikh Al-Shabab, Ahmed A; Silva, Paulo ASF; Grenko, Bojan; Tsoutsanis, Panagiotis; Skote, Martin
    A numerical framework is developed and tested to simulate the internal dynamics of oleo-pneumatic shock absorbers. A modular approach is devised to address the multiphysics nature of the problem, starting with three dimensional scale resolving turbulence simulations and two dimensional axisymmetric multiphase URANS simulations. These simulations capture the main dominant aspects of energy dissipation through turbulence, and the multiphase mixing which can affect the working fluid properties. Internal flow simulations are run on a representative shock absorber geometry based on dimensions provided in the validation study together with sizing guidelines from the literature. A lower fidelity two-equation dynamic system solver is used to scan the design space and test the sensitivity towards various design parameters, in addition to identifying parameter combinations that would be of interest to investigate using higher fidelity methods.
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    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, Bojan
    Data for the journal paper titled: Numerical Investigation of Orifice Nearfield Flow Development in Oleo-Pneumatic Shock Absorbers
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    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, Martin
    Dataset for the paper "Unsteady Multiphase Simulation of Oleo-Pneumatic Shock Absorber Flow"
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    Data for the 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, Martin
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    Data for: Numerical Investigation of Oleo-Pneumatic Shock Absorber: A Multi-Fidelity Approach
    (Cranfield University, 2023-08-25) Sheikh Al Shabab, Ahmed; Grenko, Bojan; Vitlaris, Dimitrios; Tsoutsanis, Panagiotis; Antoniadis, Antonios; Skote, Martin
    Raw data of simulations used in the ECCOMAS 2022 paper titled: Numerical Investigation of Oleo-Pneumatic Shock Absorber: A Multi-Fidelity Approach
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    Numerical investigation of oleo-pneumatic shock absorber: a multi-fidelity approach
    (ECCOMAS, 2022-11-24) Sheikh Al Shabab, Ahmed; Grenko, Bojan; Vitlaris, Dimitrios; Tsoutsanis, Panagiotis; Antoniadis, Antonis; Skote, Martin
    A representative shock absorber geometry is developed based on the general guidelines available in the literature, and it is validated against experimental measurements from a drop test. Simulations are conducted using a multi-fidelity approach ranging from unsteady scale resolving three-dimensional simulations to dynamic system models. High fidelity simulations provide a detailed insight into the flow physics inside the shock absorber, as well as help calibrate and validate lower fidelity methods, under conditions for which no experimental measurements are available to achieve that purpose. On the other hand, lower fidelity methods are used to efficiently scan the design space and test the dependency of the shock absorber performance on the various design parameters, in addition to identifying parameter combinations that would be of interest to investigate using a high-fidelity approach.
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    Numerical investigation of oleo-pneumatic shock absorber: setup and validation
    (ECCOMAS, 2021-03-11) Sheikh Al-Shabab, Ahmed A.; Vitlaris, Dimitrios; Lin, Zhonglu; Grenko, Bojan; Tsoutsanis, Panagiotis; Antoniadis, Antonis; Skote, Martin
    The simulation of an oleo-pneumatic shock absorber is discussed focusing on the solver validation and high fidelity case setup. The multi-physics nature of the problem is tackled by conducting a range of validation cases in the base areas expected to be of relevance. A dynamic system model of the shock absorber is used to generate physically consistent boundary conditions. In addition, steady RANS simulations provide a preliminary insight into the internal flow development and to assist in the design of higher resolution grids.
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    Numerical investigation of orifice nearfield flow development in oleo-pneumatic shock absorbers
    (MDPI, 2022-01-25) Sheikh Al-Shabab, Ahmed A.; Grenko, Bojan; Vitlaris, Dimitrios; Tsoutsanis, Panagiotis; Antoniadis, Antonis F.; Skote, Martin
    The flow field development through a simplified shock absorber orifice geometry is investigated using a single phase Large Eddy Simulation. Hydraulic oil is used as the working fluid with a constant inlet velocity and an open top boundary to allow the study to focus on the free shear layer and the flow development in the vicinity of the main orifice. The flow field is validated using standard mixing layer dynamics. The impact of the orifice shape is discussed with regards to the initial free shear layer growth, boundary layer development and the potential appearance of cavitation bubbles. Observations are made regarding the presence of flow field disturbances upstream of and through the orifice, thereby, leading to a notable turbulence intensity level in those regions.
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    Unsteady multiphase simulation of oleo-pneumatic shock absorber flow
    (MDPI, 2024-03-07) Sheikh Al-Shabab, Ahmed A.; Grenko, Bojan; Silva, Paulo A. S. F.; Antoniadis, Antonis F.; Tsoutsanis, Panagiotis; Skote, Martin
    The internal flow in oleo-pneumatic shock absorbers is a complex multiphysics problem combining the interaction between highly unsteady turbulent flow and multiphase mixing, among other effects. The aim is to present a validated simulation methodology that facilitates shock absorber performance prediction by capturing the dominant internal flow physics. This is achieved by simulating a drop test of approximately 1 tonne with an initial contact vertical speed of 2.7 m/s, corresponding to a light jet. The flow field solver is ANSYS Fluent, using an unsteady two-dimensional axisymmetric multiphase setup with a time-varying inlet velocity boundary condition corresponding to the stroke rate of the shock absorber piston. The stroke rate is calculated using a two-equation dynamic system model of the shock absorber under the applied loading. The simulation is validated against experimental measurements of the total force on the shock absorber during the stroke, in addition to standard physical checks. The flow field analysis focuses on multiphase mixing and its influence on the turbulent free shear layer and recirculating flow. A mixing index approach is suggested to facilitate systematically quantifying the mixing process and identifying the distinct stages of the interaction. It is found that gas–oil interaction has a significant impact on the flow development in the shock absorber’s upper chamber, where strong mixing leads to a periodic stream of small gas bubbles being fed into the jet’s shear layer from larger bubbles in recirculation zones, most notably in the corner between the orifice plate and outer shock absorber wall.