Search

This paper introduces mdFoam+, which is an MPI parallelised molecular dynamics (MD) solver implemented entirely within the OpenFOAM software framework. It is open-source and released under the same GNU General Public License (GPL) as OpenFOAM. The source code is released as a publicly open software repository that includes detailed documentation and tutorial cases. Since mdFoam+ is designed entirely within the OpenFOAM C++ object-oriented framework, it inherits a number of key features. The code is designed for extensibility and flexibility, so it is aimed first and foremost as an MD research tool, in which new models and test cases can be developed and tested rapidly. Implementing mdFoam+ in OpenFOAM also enables easier development of hybrid methods that couple MD with continuum-based solvers. Setting up MD cases follows the standard OpenFOAM format, as mdFoam+ also relies upon the OpenFOAM dictionary-based directory structure. This ensures that useful pre- and post-processing capabilities provided by OpenFOAM remain available even though the fully Lagrangian nature of an MD simulation is not typical of most OpenFOAM applications. Results show that mdFoam+ compares well to another well-known MD code (e.g. LAMMPS) in terms of benchmark problems, although it also has additional functionality that does not exist in other open-source MD codes.

The Venus Emission Mapper (VEM) instrument suite consists of two channels – VEM-M and VEM-H. VEM-M is a multispectral infrared imager with strong heritage from the MERTIS instrument on BepiColombo, while VEM-H is high-resolution, nadir-pointing, infrared spectrometer with strong heritage from SOIR on VenusExpress. VEM-M can provide global compositional data on rock types, weathering, and crustal evolution by mapping the Venus surface in five atmospheric windows. We use additional filters for the removal of clouds, water, and stray light. VEM-M leverages the approach pioneered by VIRTIS on Venus Express that used narrow-band atmospheric windows, but with an order of magnitude higher sensitivity and fuller spectral and spatial coverage. VEM-H will be dedicated to extremely high-resolution atmospheric measurements. The main objective of the VEM-H channel is to detect and quantify SO2, H2O and HDO in the lower atmosphere, to enable characterisation of volcanic plumes released from the surface of Venus. VEM-H is observing through the 1μm, 1.7μm, and 2-2.3μm atmospheric windows, where viewing the lower atmosphere is possible. VEM-H complements VEM-M by providing information one Venus' surface and near-surface activity. VEM follows a highly integrate payload concept. Both instrument channels will use a common MERTIS derived instrument controller and power supply unit and will be integrated in a common housing. Due to the different optical requirements the instrument channels use separate apertures and optics that allow maximizing the performance while giving only a marginal mass penalty. In the combination of both channels VEM will provide unprecedented insights into the current state and the evolution of Venus. VEM will perform a comprehensive search for volcanic activity by targeting atmospheric signatures, thermal signatures and compositional signatures. It will provide a map of the surface composition that will help us to understand the geology of Venus. This mapping will also enable a more informed landing site selection for future missions to Venus.

Non-equilibrium molecular dynamics simulations are performed to investigate water transport through (7,7) CNTs and to examine how changing the CNT length affects the flow dynamics. We show that fluid flow rates are well in advance of continuum expectations and that this flow enhancement increases with increasing CNT length. This enhancement is related to the internal fluid structure. Water molecules form a tightly packed cylindrical shell inside (7,7) CNTs, with densities nearly 3.5 times that of the water reservoir.