Magnetohydrodynamic Winds Driven by Line Force from the Standard Thin Disk around Supermassive Black Holes: II. A Possible Model for Ultra-fast Outflows in Radio-loud AGNs

In radio-loud active galactic nuclei (AGNs), ultra-fast outflows (UFOs) were detected at the inclination angle of ∼10°–70° away from jets. Except for the inclination angle of UFOs, the UFOs in radio-loud AGNs have similar properties to that in radio-quiet AGNs. The UFOs with such low inclination cannot be explained in the line-force mechanism. The magnetic-driving mechanism is suggested to explain the UFOs based on a self-similar solution with radiative transfer calculations. However, the energetics of self-similar solution need to be further confirmed based on numerical simulations. To understand the formation and acceleration of UFOs in radio-loud AGNs, this paper presents a model of the disk winds driven by both line force and magnetic field and implements numerical simulations. Initially, a magnetic field is set to 10 times stronger than the gas pressures at the disk surface. Simulation results imply that the disk winds driven by both line force and magnetic field could describe the properties of UFOs in radio-loud AGNs. Pure magnetohydrodynamics (MHDs) simulation is also implemented. When the initial conditions are the same, the hybrid models of magnetic fields and line force are more helpful to form UFOs than the pure MHD models. It is worth studying the case of a stronger magnetic field to confirm this result.

Numerical Reproduction of the DeRisk Physical Model Tests on a Bottom-Fixed Foundation Exposed to Uni- and Multi-Directional Storm Sea States

In this work, we compare the wave and loads statistics for two different sea states with a TP = 15.0[s] on a h = 33.0[m] depth, one with a 10-year return period (HS = 7.5[m]) and one with a 100-year (HS = 9.5[m]). For each sea state, a unidirectional and a multi-directional wave realization was measured experimentally and then reproduced numerically via a fully-nonlinear potential solver. The computed wave kinematics were used to calculate loads on a stiff cylinder with a diameter of D = 7.0[m], and compared with experiments. To perform a quantitative analysis, we extracted 30-minute maxima of the free surface elevation and in-line force, and fitted a Gumbel distribution via a Bayesian methodology. The analysis of the experiments showed that the extreme forcing on a stiff cylinder was larger in the 2D sea state than in the 3D sea state. As for the crest statistics, the 2D were higher than the 3D for the milder storm, while they were quite similar for the stronger storm, likely a consequence of the increased wave breaking, limiting the maximum achievable wave crests. The reproduction of the sea states and associated loads via a fully-nonlinear potential solver was overall able to predict the main trends. However, the 3D wave crests were overestimated for the milder sea state, probably due to a too soft breaking filter. The 2D forces for the larger sea state were on the other hand underestimated, likely due to the lack of a slamming load model. The analysis of the average wave shape leading to the extreme load events showed that in the experiments the extreme events are dominated by physics linked with the particle velocity, and hence in phase with the wave elevation signal, as drag loads, slamming loads and velocity-dependent free-surface intersection loads. On the other hand, in the simulations they are more inertia dominated, hence in phase with the kinematic acceleration signal.

Experimental and Numerical Investigation of Cutting Characteristics of PA6/PE Nylon Film Subjected to Wedge Indentation Process

In this research work, we aim to evaluate the cutting resistance and deformation of a laminated nylon film subjected to a 42o wedged indentation. One of the problems occurred in the wedge indentation process is the unstable separation and quality of the sheared profile of the worksheet. In order to reveal the effect of cutting parameters on the cutting features, the indentation experiment of 0.16 mm thickness of Polyamide-6/ Polyethylene nylon film (PA6/PE) was conducted; the cutting line force was gotten using a recording unit; the bent-up angle and sheared profile of the worksheet were observed using a high-speed camera. From the experiment results, it was found that the cutting direction was an important factor affected to the bent-up angle and cutting load response of the nylon film. Also, the effect of cutting direction (PA6-PE and PE-PA6) of the nylon film was numerically investigated.

Exact Solutions for Interaction of Parallel Screw Dislocations with a Wedge Crack in One-Dimensional Hexagonal Quasicrystal with Piezoelectric Effects

The purpose of this paper is to consider the interaction between many parallel dislocations and a wedge-shaped crack and their collective response to the external applied generalized stress in one-dimensional hexagonal piezoelectric quasicrystal, employing the complex variable function theory and the conformal transformation method; the problem for the crack is reduced to the solution of singular integral equations, which can be further reduced to solving Riemann–Hilbert boundary value problems. The analytical solutions of the generalized stress field are obtained. The dislocations are subjected to the phonon field line force, phason field line force, and line charge at the core. The positions of the dislocations are arbitrary, but the dislocation distribution is additive. The dislocation is not only subjected to the external stress and the internal stress generated by the crack, but also to the force exerted on it by other dislocations. The closed-form solutions are obtained for field intensity factors and the image force on a screw dislocation in the presence of a wedge-shaped crack and a collection of other dislocations. Numerical examples are provided to show the effects of wedge angle, dislocation position, dislocation distribution containing symmetric configurations and dislocation quantities on the field intensity factors, energy release rate, and image force acting on the dislocation. The principal new physical results obtained here are (1) the phonon stress, phason stress, and electric displacement singularity occur at the crack tip and dislocations cores, (2) the increasing number of dislocations always accelerates the crack propagation, (3) the effect of wedge angle on crack propagation is related to the distribution of dislocations, and (4) the results of the image force on the dislocation indicate that the dislocations can either be attracted or rejected and reach stable positions eventually.

Coupled flow and deformation fields due to a line load on a poroelastic half space: effect of surface stress and surface bending

In the past decade, many experiments have indicated that the surfaces of soft elastic solids can resist deformation by surface stresses. A common soft elastic solid is a hydrogel which consists of a polymer network swollen in water. Although experiments suggest that solvent flow in gels can be affected by surface stress, there is no theoretical analysis on this subject. Here we study the solvent flow near a line load acting on a linear poroelastic half space. The surface of this half space resists deformation by a constant, isotropic surface stress. It can also resist deformation by surface bending. The time-dependent displacement, stress and flow fields are determined using transform methods. Our solution indicates that the stress field underneath the line load is completely regularized by surface bending—it is bounded and continuous. For small surface bending stiffness, the line force is balanced by surface stresses; these forces form what is commonly known as ‘Neumann's triangle’. We show that surface stress reduces local pore pressure and inhibits solvent flow. We use our line load solution to simulate the relaxation of the peak which is formed by applying and then removing a line force on the poroelastic half space.

Sensitivity Analysis of Different Parameters of Taut Mooring System of a Truss Spar

The taut mooring system is widely used for some advantages, such as smaller mooring radius, lighter total weight and better anti-corrosion performance. In this paper, the taut mooring system of a Truss Spar platform which was taken as the research object was investigated under the condition of 2000 m water depth in South China Sea. Firstly, the main body of the platform was analyzed in frequency domain based on the 3-d potential theory, and then the nonlinear solutions of platform displacement and mooring line force were obtained by using coupling analysis method in time domain, which determined the preliminary design parameters of mooring system. The sensitivity of the taut system is studied by changing several design parameters such as the top angle of mooring line, cable hole position and method of mooring disposal. In summary, the variation of the motion and dynamic response of the platform and mooring system has been explored and summarized by studying the design process and influential parameter of dynamic characteristics of mooring system and optimizing ideas of relevant parameters, which can further provide technical support and engineering reference for the design and application of the taut mooring system of deepwater Truss Spar platforms.