Browsing by Author "Asproulis, Nikolaos"

Now showing 1 - 7 of 7
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    Boundary slip dependency on surface stiffness
    (American Physical Society, 2010-06-24T00:00:00Z) Asproulis, Nikolaos; Drikakis, Dimitris
    The paper investigates the effects of surface stiffness on the slip process aiming to obtain a better insight of the momentum transfer at nanoscale. The surface stiffness is modeled through the stiffness, kappa, of spring potentials, which are employed to construct the thermal walls. It is shown that variations of stiffness, kappa, influence the slip mechanism either toward slip or stick conditions. Increasing the values of kappa alters the oscillation frequency and the mean displacement of the wall particles toward higher and lower values, respectively. Our results suggest that the amount of slip produced as a function of stiffness follows a common pattern that can be modeled through a fifth-order polynomial function.
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    Development of a staged anaerobic pond for methane recovery from domestic wastewater
    (Elsevier, 2018-08-08) Cruddas, Peter; McAdam, Ewan; Asproulis, Nikolaos; Antoniadis, Antonis F.; Ansari, Irfan; Best, D.; Jefferson, Bruce; Cartmell, Elise; Collins, G.; Porca, E.; Peña-Varón, M. R.
    Since their inception in larger pond systems, the focus of anaerobic ponds has shifted from solids removal to optimising biogas production and reducing physical footprint to minimise land requirements. In this study, a horizontally baffled (HBAP) and vertically baffled (VBAP) anaerobic pond were compared. Distinct differences in the removal efficiency of COD fractions were observed, with particulate COD removal of 78% and 32%, and soluble COD removal of −26% and 19% in the HBAP and VBAP, respectively. A staged pond (SAP) was constructed through an HBAP placed upstream of a VBAP, with an additional HBAP used as a control (CAP). The SAP demonstrated superior biogas recovery potential over the control: methane production by the conclusion of the study was 6.09 and 9.04 LCH4 m−3 wastewater treated for the CAP and SAP, respectively. Methanogenic activity in the ponds was higher closer to the outlet, and hydrogenotrophic methanogenesis dominated over acetoclastic pathways.
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    Environmental impact assessment of the manufacturing of a commercial aircraft
    (Cranfield University Press, 2013-09-19) Kolios, Athanasios; Asproulis, Nikolaos; Howe, Stuart; Salonitis, Konstantinos
    This paper documents the methodology and presents the results of a comprehensive LCA study of an Airbus A320 commercial airliner to determine the relative environmental impact of its manufacturing phase. The study was conducted in accordance with ISO 14040/44 using SimaPro LCA software, the EcoInvent inventory database and Eco-Indicator 99 weighting method, which allows the analysis to be outputted in a single score representing a number of damage models including damage to human health, ecosystem quality or resource depletion. Results indicate CFRP wings to have the most significant contribution to the overall environmental impact as a proportion to mass.
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    Environmental impact assessment of the manufacturing of a commercial aircraft
    (2013-09-02T00:00:00Z) Kolios, Athanasios J.; Howe, Stuart; Asproulis, Nikolaos; Salonitis, Konstantinos; Shehab, Essam; Ball, Peter D.; Tjahjono, Benny
    This paper documents the methodology and presents the results of a comprehensive LCA study of an Airbus A320 commercial airliner to determine the relative environmental impact of its manufacturing phase. The study was conducted in accordance with ISO 14040/44 using SimaPro LCA software, the EcoInvent inventory database and Eco-Indicator 99 weighting method, which allows the analysis to be outputted in a single score representing a number of damage models including damage to human health, ecosystem quality or resource depletion. Results indicate CFRP wings to have the most significant contribution to the overall environmental impact as a proportion to mass.
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    Equilibrium molecular dynamics modeling of diffussion and adsorption of fluids in armchair single walled carbon-nanotube
    (International Astronautical Federation, 2014-12-31) Kio, Michael; Asproulis, Nikolaos; Könözsy, László Z.; Drikakis, Dimitris
    The aim of this paper is to study adsorption and diffusion of gases and liquids especially Argon and Carbon-dioxide in single walled carbonnanotube at room temeperature using equilibrium molecular dynamic simulation. The simulation domain is developed by the large atomic/molecular massively parallel simulator (LAMMPS). The domain consists of a simulation box of volume 100 x 100 x 100 A having periodic boundary conditions at the x. y and z direction.The adsorption and diffusion of different chiral- ity of carbonnanotubes are reported. The Molecular Dynamics Simulation (MD) result shows that single walled carbonnanotube have affinity to attract carbon dioxide to itself than argon, with argon acting as a catalyst for adsorption of more C02 confirming a high adsorption at higher loading. The highest adsorption and diffussion inside the Single-walled carbon-naotube (SWCNT) was determined at certain loading and temperature. The SWCNT is as-sumed to be rigid due to the fact that, flexibility is insignificant and can increase computational time. This study will bring about a better understanding of storage and filtering of gases in SWCNTs and so leading its usefullness in applications such as gasification for jet engines, Co2 removal in the international space station, desalination for water systems, air purification, longer space batteries and enhanced oil recovery.
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    Filtering carbon dioxide through carbon nanotubes
    (Elsevier Science B.V., Amsterdam., 2011-04-11T00:00:00Z) Mantzalis, Dimitrios; Asproulis, Nikolaos; Drikakis, Dimitris
    Layering phenomena of carbon dioxide transported through carbon nanotubes are investigated through molecular dynamics simulations. The layering formation is examined for carbon nanotubes spanning from (8,8) to (20,20) subjected to pressures and temperatures that range from 1 to 20 bar and 300 to 400 K, respectively. Well defined layers are developed around the internal and external surface of the nanotubes for all the examined cases. It is shown that the number of layers along with their relative strength varies as a function of the nanotube's diameter, size, carbon dioxide density and gas-structure interactions.
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    Mesoscale flow and heat transfer modelling and its application to liquid and gas flows
    (2009-11-09T00:00:00Z) Asproulis, Nikolaos; Kalweit, Marco; Shapiro, Evgeniy; Drikakis, Dimitris
    Advances in micro and nanofluidics have influenced technological developments in several areas, including materials, chemistry, electronics and bio-medicine. The phenomena observed at micro and nanoscale are characterised by their inherent multiscale nature. Accurate numerical modelling of these phenomena is the cornerstone for enhancing the applicability of micro and nanofluidics in the industrial environment. We investigated different strategies for applying macroscopic boundary conditions to microscopic simulations. Continuous rescaling of atomic velocities and velocity distribution functions, such as Maxwell-Boltzmann or Chapman-Enskog, were investigated. Simulations were performed for problems involving liquids and gases under different velocity and temperature conditions. The results revealed that the selection of the most suitable method is not a trivial issue and depends on the nature of the problem, availability of computational resource and accuracy requirement.