On enhanced non-linear free surface flow simulations with a hybrid LBM–VOF model

In this paper, we present extensions, extensive validations and applications of our previously published hybrid volume-of-fluid-based (VOF) model for the simulation of free-surface flow problems. For the solution of the flow field, the lattice Boltzmann method is used, where the free surface is represented by a VOF approach. The advection equation for the VOF fill level is discretized with a finite volume method, on the basis of a 3D Piecewise Linear Interface Reconstruction (PLIC) algorithm. The model is validated for several standard free surface benchmarks, such as breaking dam scenarios and a free falling jet. Finally, the hybrid algorithm is applied to the simulation of a wave breaking by overturning during shoaling, which is considered to be a demanding test case, especially for VOF solvers. In this case, the flow field is initialized early in the shoaling process with a solitary wave solution from inviscid, irrotational potential flow. The wave breaking process is then simulated with the 3D transient and turbulent LBM–VOF solver. All validation and benchmark tests confirm the accuracy of the proposed hybrid model.     

TIME'S ARROW IN PARTICLE PHYSICS

This article gives an introduction into the current understanding of time invariance and evidence of its violation in experimental particle physics. The connection between time invariance and other discrete symmetries, particularly, CP-invariance, is explained. The first experimental determination of CP-violation is explained, and recent experiments on CP-violation and on T-violation are discussed.     

Slip behaviour at cyclic pullout tests under transverse tension

In case of a reinforced concrete structure being exposed to bond stresses that transfer great forces, a relative displacement between reinforcing bar and concrete occurs. The slip is an important parameter in order to evaluate the quality of the bond concerning repeated pullout loads. A rapid slip increase is caused by bond weakening due to longitudinal cracks resulting from transverse tension. Within the bond area the slip is not uniformly distributed along the reinforcing bar. It is still unexplained how far fatigue and transverse tension affect the distribution. This paper focuses on the development of the slip curve under repeated loading and transverse tension. Results from cyclic pullout tests were applied and particularly the slip difference between the loaded and unloaded end of the pullout bar was investigated. It could be observed that both an increase in load cycles and transverse tension did not cause an appreciable change in slip difference.     

Modification of CaCO3 precipitation rates by water-soluble nacre proteins

Mineral growth in nacre and other CaCO₃-containing biominerals is controlled by biopolymers. Water-soluble proteins were extracted from nacre of the sea snail Haliotis laevigata by dissolving the mineral phase with 6% acetic acid. The influence of this protein mixture on CaCO₃ precipitation rates was investigated at different concentrations. A well-established assay for measuring the pH-value during CaCO₃ precipitation with and without protein additives was extended by calculating maximum precipitation rates from the pH-values. It could be shown that precipitation rates are greatly influenced by the mixtures of water-soluble nacre proteins. At very low protein concentrations (0.02 μg/ml) a rate enhancement in comparison to the pure supersaturated calcium carbonate solution by a factor of 1.4 was observed. At higher protein concentrations, a strong inhibitory effect occurred, with total inhibition at concentrations of 1.0 μg/ml and higher. Two unspecific proteins (bovine serum albumin and lysozyme) showed little or no modification of precipitation rates. In vivo, the function of the strong inhibition of CaCO₃ precipitation by nacre proteins at higher concentrations is presumably to prevent uncontrolled crystallization in the extrapallial fluid. The rate-enhancing capability of proteins at low concentrations may be explained by the presence of acidic and/or hydrophilic moieties.     

Properties of blocked linear systems

This paper presents a systematic study on the properties of blocked linear systems that have resulted from blocking discrete-time linear time invariant systems. The main idea is to explore the relationship between the blocked and the unblocked systems. Existing results are reviewed and a number of important new results are derived. Focus is given particularly on the zero properties of the blocked system as no such study has been found in the literature.     

Handling Climate Change – Establishing Waste CO2 Management A View from Biotechnology

The biggest material flows induced by industry are realized in energy production. Coal, oil and gas as raw material streams are moved from their deposits to their further converting. From there product streams are branched out. However, the biggest material flow of this industry is waste CO₂ mobilized by chemical conversion from fossil deposits and released into the atmosphere. A waste management is urgently needed to reduce the amount of this flow, to neutralize its effects on environment and to establish applications yielding a return. Natural backflow of CO₂ from the atmosphere to the biosphere waits for completion by industrial methods in order to shift it to a dimension equalizing the finally unavoidable amount of waste CO₂ flow into the atmosphere.     

Dynamic X-ray radiography for the determination of foamed bitumen bubble area distribution

Foam bitumen is highly efficient in wetting and coating the surface of mineral aggregate at lower temperature. In order to improve understanding and characterization of the bitumen foam, X-ray radiography was used to study the formation and decay of bitumen foam in 2D representation. Image segmentation analysis was used to determine the foam bubble size distribution. In addition, the main parameters influencing foam bitumen formation, water content, and temperature were also investigated. The results demonstrate the influence of the water content on morphology and expansion of foam bitumen bubbles. Adding more water in the foaming process leads to quick collapse of bubbles and intensifies coalescence of foam bitumen. Higher temperatures produces larger bubbles at early foaming stage compared to lower temperature. Moreover the morphology of bubble formation depends on the types of bitumen used. An exponential function has been implemented to represent the bubble area distribution.