| 1. |
- Binios, A., et al.
(author)
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Moon compact satellite for hazard assessment (MOOCHA) - Proposing an international Earth-Moon small satellite constellation
- 2019
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In: Proceedings of the International Astronautical Congress, IAC. - : International Astronautical Federation, IAF.
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Conference paper (peer-reviewed)abstract
- The recent developments in space exploration have reinstated the Moon as a primary target for near future space missions. The principal reasons include the Moon being the closest test bed and analogue for planetary space missions and the prospect of scientific lunar bases and orbital stations within the next decade. Previous space missions have vastly improved our understanding on hazards of human spaceflights but not fully regarding the threats affecting a prospective lunar base or orbital station. The micrometeorite hazard has been partially addressed as an issue which can potentially impact both astronauts' health and safety as well as create issues for lunar bases and orbital stations, such as degradation or permanent damage of equipment and facilities. The current understanding is based partly on dust and micrometeoroid flux measurements and impact flash observations. However, observations with improved spatial and temporal resolution are imperative for advancing existing hazard models. In this paper, a mission concept of a constellation of nanosatellites is proposed that can both observe larger parts of cis-lunar and trans-lunar space while providing higher temporal resolution. Nanosatellite missions are a cost-effective solution providing data for significant improvement of our current understanding of lunar micrometeoroid flux models, and thus directly the scale of hazards caused by micrometeoroid impacts to future lunar missions. Additionally, such a distributed constellation mission will offer countless opportunities for academia, students and young scientists worldwide. The mission concept (Moon Compact Satellite for Hazard Assessment - MOOCHA) is a result of the Nordic-European Astrobiology Campus Summer School 2018 themed “Microsatellites in Planetary and Atmospheric Research” and was further developed during the 2019 follow-up summer school “Design of Small Satellite Missions for Planetary Studies”, both taking place in Tartu, Estonia and co-organized by the Stockholm University Astrobiology Centre, the University of Tartu, the European Astrobiology Campus and the Nordic Network of Astrobiology and supported by European Union's European Regional Development Fund and Estonia.
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| 2. |
- Vuorinen, V., et al.
(author)
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On the implementation of low-dissipative Runge-Kutta projection methods for time dependent flows using OpenFOAM (R)
- 2014
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In: Computers & Fluids. - : Elsevier BV. - 0045-7930. ; 93, s. 153-163
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Journal article (peer-reviewed)abstract
- Open source computational fluid dynamics (CFD) codes provide suitable environments for implementation, testing and rapid dissemination of algorithms typically used for large-eddy simulations (LES) and direct numerical simulations (DNS). In particular, it is important to test low-dissipative algorithms in unstructured codes of industrial relevance. In the present paper, the implementation of incompressible, explicit Runge-Kutta (RK) based projection methods into the OpenFOAM (R) library is discussed. We search for low-dissipative alternatives to the second order time integration methods which are commonly used together with the standard pressure correction approach PISO (Pressure Implicit with Splitting of Operators) in many commercial and open source codes including OpenFOAM (R). The practical implementation of the projection methods in OpenFOAM (R) is provided together with theory. The method is tested with the classical fourth order RK-method and the accelerated third order RK-method. Four numerical experiments are carried out in order to cross-validate the solvers and in order to investigate the drawbacks/ benefits of the solution approaches. The test problems are: (1) 2d lid driven cavity flow at Re = 2500, (2) DNS of 3d turbulent channel flow at Re-tau = 180, (3) LES of a 3d mixing layer, and (4) the 2d inviscid Taylor-Green vortex. The RK-methods are benchmarked against the standard OpenFOAM (R) LES/DNS solver based on the PISO pressure correction method. The results indicate that the RK projection methods provide low-dissipative alternatives to the PISO method. The turbulent test cases show also that the RK-methods have a good computational efficiency. (C) 2014 Elsevier Ltd. All rights reserved.
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| 3. |
- Kangasniemi, Oskari, et al.
(author)
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Volatility of a Ship’s Emissions in the Baltic Sea Using Modelling and Measurements in Real-World Conditions
- 2023
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In: Atmosphere. - 2073-4433. ; 14:7
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Journal article (peer-reviewed)abstract
- Shipping emissions are a major source of particulate matter in the atmosphere. The volatility of gaseous and particulate phase ship emissions are poorly known despite their potentially significant effect on the evolution of the emissions and their secondary organic aerosol (SOA) formation potential. An approach combining a genetic optimisation algorithm with volatility modelling was used on volatility measurement data to study the volatility distribution of a ship engine’s emissions in real-world conditions. The fuels used were marine gas oil (MGO) and methanol. The engine was operated with 50% and 70% loads with and without active NOx after-treatment with selective catalytic reduction (SCR). The volatility distributions were extended to higher volatilities by combining the speciation information of the gas phase volatile organic compounds with particle phase volatility distributions and organic carbon measurements. These measurements also provided the emission factors of the gas and particle phase emissions. The results for the particle phase volatility matched well with the existing results placing most of the volatile organic mass in the intermediate volatile organic compounds (IVOC). The IVOCs also dominated the speciated gas phase. Partitioning of the emissions in the gas and particle phases was affected significantly by the total organic mass concentration, underlining the importance of the effect of the dilution on the phase of the emissions.
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