MODELLING THE HEAVE OSCILLATIONS OF VERTICAL CYLINDERS WITH DAMPING PLATES

The laminar flow around heaving axisymmetric and three-dimensional cylinders with damping plates is numerically studied for various Keulegan-Carpenter numbers. The Navier-Stokes equations are solved using OpenFOAM, which is applied to the flow on a moving mesh. For processing of results the semi-empirical Morison equation is used. Calculations are conducted for one cylinder, one cylinder with one disk, one cylinder with two disks, and one cylinder with one pentagonal plate. The calculated values are compared against experimental data.

Phase Diagram and Order Reconstruction Modeling for Nematics in Asymmetric π-Cells

Intense electric fields applied to an asymmetric π-cell containing a nematic liquid crystal subjected to strong mechanical stresses induce distortions that are relaxed through a fast-switching mechanism: the order reconstruction transition. Topologically different nematic textures are connected by such a mechanism that is spatially driven by the intensity of the applied electric fields and by the anchoring angles of the nematic molecules on the confining plates of the cell. Using the finite element method, we implemented the moving mesh partial differential equation numerical technique, and we simulated the nematic evolution inside the cell in the context of the Landau–de Gennes order tensor theory. The order dynamics have been well captured, putting in evidence the possible existence of a metastable biaxial state, and a phase diagram of the nematic texture has been built, therefore confirming the appropriateness of the used technique for the study of this type of problem.

How well is angular momentum accretion modelled in semi-analytic galaxy formation models?

Gas cooling and accretion in haloes delivers mass and angular momentum on to galaxies. In this work, we investigate the accuracy of the modelling of this important process in several different semi-analytic (SA) galaxy formation models (galform , l-galaxies and morgana ) through comparisons with a hydrodynamical simulation performed with the moving-mesh code arepo . Both SA models and the simulation were run without any feedback or metal enrichment, in order to focus on the cooling and accretion process. All of the SA models considered here assume that gas cools from a spherical halo. We found that the assumption that the gas conserves its angular momentum when moving from the virial radius, rvir, to the central region of the halo, r ∼ 0.1rvir, is approximately consistent with the results from our simulation. We also found that, compared to the simulation, the morgana model tends to overestimate the mean specific angular momentum of cooled-down gas, the l-galaxies model also tends to overestimate this in low-redshift massive haloes, while the two older galform models tend to underestimate the angular momentum. In general, the predictions of the new galform cooling model developed by Hou et al. agree agree the best with the simulation.