Delft University of Technology

About: Delft University of Technology is a education organization based out in Delft, Zuid-Holland, Netherlands. It is known for research contribution in the topics: Computer science & Catalysis. The organization has 37681 authors who have published 94404 publications receiving 2741710 citations. The organization is also known as: TU-Delft & Technische Hogeschool Delft.

Inertial and Interfacial Effects on Pressure Drop of Taylor Flow in Capillaries

Abstract: In a capillary, the two-phase pressure drop in Taylor slug flow was measured. A carefully designed inlet section for the capillary allowed the independent variation of gas bubble and liquid slug length. Gas and liquid superficial velocities were varied from 0.04 m/s to 0.3 m/s. If the slug length was smaller than 10 times the capillary diameter, the length-averaged friction factor for the liquid slug increased drastically from the single phase value (f = 16/Re) due to differences in curvature at the front and the back of the bubble. The use of different liquids allowed the independent variation of Re and Ca. The flow of elongated bubbles in capillaries was simulated using the CFD code FIDAP. It was found both numerically and experimentally that for Re ≫ 1, the extra pressure terms may be taken account using (Ca/Re) as a parameter. The numerical results agreed with the experimental data, provided that Marangoni effects of impurities are taken into account. The results allow the determination of slug length from pressure drop measurements in closed equipment where the slug length cannot otherwise be measured easily, such as monoliths and microreactors. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Topological Confinement in Bilayer Graphene

Abstract: We study a new type of one-dimensional chiral states that can be created in bilayer graphene (BLG) by electrostatic lateral confinement. These states appear on the domain walls separating insulating regions experiencing the opposite gating polarity. While the states are similar to conventional solitonic zero modes, their properties are defined by the unusual chiral BLG quasiparticles, from which they derive. The number of zero mode branches is fixed by the topological vacuum charge of the insulating BLG state. We discuss how these chiral states can manifest experimentally and emphasize their relevance for valleytronics.

Experimental and numerical analysis of micromechanisms of fracture of cement-based composites

Abstract: In this paper experimental evidence of fracture toughening of concrete and mortar through a mechanism called crack face bridging is presented. The classical explanation for softening of concrete, viz. the formation of a zone of discontinuous microcracking ahead of a continuous macrocrack seems only partially true. Instead, crack face bridging in the wake of the macrocrack tip seems a physically sounder explanation. The crack face bridges are flexural ligaments between ovelapping crack tips. The failure of the flexural ligaments occurs in a stable and controlled manner because the two overlapping crack tips shield each other. The cohesive stress over the macrocrack is directly related to the size of the crack face bridges, which depends on the heterogeneity of the material. The typical failure mechanism can be simulated using a simple numerical lattice model. First the grain structure of the material is generated either by manual methods or by adopting a random generator. Secondly a tringular lattice of brittle breaking beam elements is projected on the grain structure. Aggregate, matrix and bond properties are assigned to the lattice elements at the respective locations, and a simple algorithm allows for crack growth simulation. The main conclusion is that the crack patterns and the associated load-deformation response are largely governed by the properties of the constituents. The bond between aggregates and matrix is the weakest link in the system, and variation of this parameter leads to profoundly different crack patterns.