The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe

Comparisons of novel and efficient approaches for permeability prediction based on the fabric architecture

Permeability models based on the structure of the fabric are attractive for any design process to enhance the experimental permeability data. The authors have proposed two efficient numerical approaches to predict permeability based on the architecture of the fabric. The 'Stream Surface' method reduces the complexity of the flow domain by representing the 3D volumes with their 2D curvilinear mid-surfaces while retaining the 3D attributes. The second method, 'Grid Average', discretises the 3D domain into a 2D regular grid with weighted average permeabilities for the individual elements. Flow equations are solved for the reduced meshes generated from these two approaches to calculate the effective permeability. These approaches are applied firstly to a single tow model, and then to a 2×2 twill weave fabric, whereby the effects of in-plane shear and the statistical behaviour of fabrics is discussed. Comparisons with the computationally intensive CFD approach are favourable