A combined approach for the simulation of reactive, neutral, partially or fully ionized plasma flows is presented. This is realized in a code framework named “PICLas” for the approximate solution of the Boltzmann equation by particle based methods. PICLas combines the particle-in-cell method for the collisionless Vlasov–Maxwell system and the direct simulation Monte Carlo method for neutral reactive flows. Basic physical and mathematical modeling of both methods is addressed, and some application examples are presented in order to demonstrate the capabilities and the broad applicability of the solution strategy.
The utilisation of the Very Low Earth Orbit (VLEO) region offers significant application specific, technological, operational, and cost benefits. However, attaining sustained and economically viable VLEO flight is challenging, primarily due to the significant, barely predictable and dynamically changing drag caused by the residual atmosphere, which leads to a rapid deterioration of any spacecraft's orbit unless mitigated by a combination of active and passive techniques. This article addresses one passive method by optimising satellite shapes in order to achieve a minimisation of the atmospheric drag force and thus extension of operational lifetime. Contrary to previous investigations in the field, a constant internal volume is maintained to account for the placement of satellite instruments and payload inside the structure. Moreover, the satellite geometry is not varied heuristically but optimised via a numerical 2D profile optimisation specifically developed for this purpose. From the resulting optimal satellite profiles, 3D satellite bodies are derived, which are then verified via the Direct Simulation Monte Carlo method within the open-source particle code PICLas. In addition, rather unconventional designs, i.e. ring geometries, which are based on the assumption of fully specular particle reflections, are proposed and assessed. The optimised satellite geometries offer pure passive lifetime extensions of up to 46 % compared to a GOCE like reference body, while the above-mentioned ring geometries achieve passive lifetime extensions of more than 3000 %. Finally, the article presents design recommendations for VLEO satellites in dependence of different surface properties.
Curtailment of distributed generation and demand side management may be a feasible alternative to network expansions in future medium voltage networks. Hence both must be considered in network planning today to develop cost efficient networks. Different control strategies are possible and each will result in a distinct optimal network structure. Network and energy costs will also differ. So far network operators and regulators do not know what control strategy should be striven for. Furthermore no planning algorithm exists that allows considering different control strategies. In this paper, a new algorithm is presented in this paper to solve the planning and control problem in an integrated manner. The distribution system operator of the city of Aachen (STAWAG) has decided to use this algorithm to evaluate different control strategies and derive an optimal long term network structure. The results of this study are also elaborated in the following.
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