Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

National Institute of Standards and Technology における超伝導研究及び生活

To investigate the initial chemical events associated with high-temperature gas-phase oxidation of hydrocarbons, we have expanded the ReaxFF reactive force field training set to include additional transition states and chemical reactivity of systems relevant to these reactions and optimized the force field parameters against a quantum mechanics (QM)-based training set. To validate the ReaxFF potential obtained after parameter optimization, we performed a range of NVT−MD simulations on various hydrocarbon/O2 systems. From simulations on methane/O2, o-xylene/O2, propene/O2, and benzene/O2 mixtures, we found that ReaxFF obtains the correct reactivity trend (propene > o-xylene > methane > benzene), following the trend in the C−H bond strength in these hydrocarbons. We also tracked in detail the reactions during a complete oxidation of isolated methane, propene, and o-xylene to a CO/CO2/H2O mixture and found that the pathways predicted by ReaxFF are in agreement with chemical intuition and our QM results. We o...

ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation

https://www3.nd.edu/~powers/ame.60636/maas1992.pdf

Simplifying chemical kinetics: Intrinsic low-dimensional manifolds in composition space

Turbulent stratified combustion is often found in practical combustion devices, however, for large eddy simulations (LES) of it is still a challenge. In the present work, LES of the Darmstadt turbulent stratified flame (TSF) cases are conducted. In total, one isothermal flow case A-i2 and four reacting cases with different combinations of stratification and shear, i.e., A-r, C-r, E-r, G-r cases, are simulated. The employed sub-grid scale (SGS) combustion model is the REDIM-PFDF model, in which the chemical kinetics is reduced into a two-dimensional chemistry look-up table by the reaction-diffusion manifolds (REDIM) method, which performs a model reduction based on the coupling of the chemical kinetics with molecular transport. The fluctuation of scalars within the LES filter volume is modeled by the presumed filtered density function (PFDF). The overall good agreement of the statistics of velocity, temperature and species with the experimental data demonstrates the capability of the REDIM-PFDF model for TSF. Additionally, the probability distributions of the alignment angle, α, between the reaction layer and mixing layer, are analyzed in detail. It is shown that the probability distributions of the alignment angel vary with the axial distance from the jet nozzle. It also reveals that, with a stronger turbulence, the stratification effect can be weakened and the probability difference for finding ‘back-supported’ and ‘front-supported’ flame modes tends to decrease.

Large Eddy Simulations of the Darmstadt Turbulent Stratified Flames with REDIM Reduced Kinetics

2D-Simulation of Ignition Induced by Electrical Discharges

Mathematical modeling of the coupling of chemical kinetics with laminar and turbulent transport processes

This work focuses on the prediction of phase transformations and shape deviations for drilling of demonstrator workpieces. In a first step, a 2D chip formation simulation was developed with all physical effects. Based on this simulation a simplified workpiece geometry with only one drilling hole was 3D modeled and tested for its predictive capability of phase transformations and shape deviations. Therefore, the feed rate, the rotation of the drilling tool and the material removal were considered for the process kinematics. Using these results the modeling approach was optimized and transferred into a simulation model with a demonstrator workpiece to minimize shape deviations and control phase transformations using different compensation strategies. The simulations were validated by experiments.

Experimental and Simulative Modeling of Drilling Processes for the Compensation of Thermal Effects

In the current paper the so-called REaction-DIffusion Manifold (REDIM) method of model reduction is discussed within the framework of standard singular perturbation theory. According to the REDIM a reduced model for the system describing a reacting flow (accounting for chemical reaction, advection and molecular diffusion) is represented by a low-dimensional manifold, which is embedded in the system state space and approximates the evolution of the system solution profiles in space and in time. This pure geometric construction is reviewed by using Singular Perturbed System (SPS) theory as the only possibility to formalize, to justify and to verify the suggested methodology. The REDIM is studied as a correction by the diffusion of the slow invariant manifold defined for a pure homogeneous system. A main result of the study is an estimation of this correction to the slow invariant manifold. A benchmark model of Mechaelis-Menten is extended to the system with the standard diffusion described by the Laplacian and used as an illustration and for validation of analytic results.

Ulrich Maas

Papers

Large Eddy Simulations of the Darmstadt Turbulent Stratified Flames with REDIM Reduced Kinetics

2D-Simulation of Ignition Induced by Electrical Discharges

Mathematical modeling of the coupling of chemical kinetics with laminar and turbulent transport processes

Experimental and Simulative Modeling of Drilling Processes for the Compensation of Thermal Effects

Singularly perturbed profiles