Local grid refinement for free-surface flow simulations

The principal goal of the current study is to explore and investigate the potential of local grid refinement for increasing the numerical efficiency of free-surface flow simulations in a practical context. In this thesis we propose a method for local grid refinement in the free-surface flow model ComFLOW, which is based on a finite-volume discretization of the (in)compressible Navier-Stokes equations. This numerical model finds its principal application area in the fields of marine, offshore and coastal engineering, with typical scenarios including the calculation of (wave) impact forces on ships or offshore structures and the simulation of violent physics such as liquid sloshing. In this study we aimed at the design of a compact and robust local refinement method that is applicable in a wide range of applications and does not conflict with existing and upcoming functionality. A locally refined Volume-of-Fluid method was presented for the advection of the free surface and special attention was paid to the discretization in the vicinity of cut-cell geometry. The ultimate goal of local grid refinement is to allow for more efficient grid design and reduced computational times, while maintaining a similar level of accuracy. The performance and applicability of the proposed method was assessed by means of several academic numerical test cases, such as flow around a cylinder, as well as various practical applications that locally demand high grid resolution, such as wave impact on a semi-submersible

Maggot Secretions Skew Monocyte-Macrophage Differentiation Away from a Pro-Inflammatory to a Pro-Angiogenic Type

Background: Maggots of the blowfly Lucilia sericata are used for the treatment of chronic wounds. Earlier we reported maggot secretions to inhibit pro-inflammatory responses of human monocytes. The aim of this study was to investigate the effect of maggot secretions on the differentiation of monocytes into pro-inflammatory (MØ-1) and anti-inflammatory/proangiogenic macrophages (MØ-2) as these cells play a central role in wound healing. Methodology/Principal Findings: Freshly isolated monocytes were incubated with secretions and GM-CSF or M-CSF for 6 days and then stimulated with LPS or LTA for 18 h. The expression of cell surface molecules and the levels of cytokines, chemokines and growth factors in supernatants were measured. Our results showed secretions to affect monocytemacrophage differentiation leading to MØ-1 with a partial MØ-2-like morphology but lacking CD163, which is characteristic for MØ-2. In response to LPS or LTA, secretions-differentiated MØ-1 produced less pro-inflammatory cytokines (TNF-a, IL-12p40 and MIF) than control cells. Similar results were observed for MØ-2 when stimulated with low concentrations of LPS. Furthermore, secretions dose-dependently led to MØ-1 and MØ-2 characterized by an altered chemokine production. Secretions led to MØ-2, but not MØ-1, producing enhanced levels of the growth factors bFGF and VEGF, as compared to control cells. The expression of cell-surface receptors involved in LPS/LTA was enhanced by secretions, that of CD86 and HLA-DR down-regulated, while receptors involved in phagocytosis remained largely unaffected

Numerical simulation of turbulent free-surface flow in offshore applications

To study extreme hydrodynamic wave impact in offshore and coastal engi- neering, the VOF-based CFD simulation tool ComFLOW is being developed. In this paper we will present its turbulence modeling. In particular, a blend of a QR-model and a regularization model has been designed. The QR-model belongs to a class of modern eddy- viscosity models, where the amount of turbulent eddy viscosity is kept minimal. Also, to enhance efficieny, local grid refinement has been added. For validation, experiments have been carried out at MARIN