DYNAMICAL EVOLUTION OF ROTATING ACCRETION USING DIFFERENT BOUNDARY CONDITIONS: STATE AFTER STABLE ACCRETION DISK CREATED

2007 ◽  
Vol 16 (10) ◽  
pp. 1541-1553
Author(s):  
ORHAN DÖNMEZ
Keyword(s):  
Boundary Condition ◽  
Black Hole ◽  
Shock Waves ◽  
Boundary Conditions ◽  
Accretion Disk ◽  
Binary Systems ◽  
Schwarzschild Black Hole ◽  
Different Boundary Conditions ◽  
Outflow Boundary ◽  
Armed Spiral

The 2D time-dependent solution of the thin and stable accretion disk with two-armed spiral shock waves in a closed binary system have been presented on the equatorial plane around the Schwarzschild black hole in Donmez (2004).2 The subject of this paper is to study the influence of two different boundary conditions, far away from a black hole called the outer boundary, on an accretion disk around the black hole during the time evolution. We have started with a stable accretion disk after the point where two-armed spiral shock waves were created (Donmez, 2004).2 The initial data which is also called the freezing boundary is used as a first boundary condition. As a second one, we use the outflow boundary condition. In both cases, the accretion disk is created and gases on the disk made closed trajectories. As a stable tori close to the black hole is created by using the first boundary, freezing condition, which has a ~10M radius where M is the mass of black hole, and the other boundary, outflow, creates stable two-armed spiral shock waves. The last stable circular orbit around the Schwarzschild black hole for this type of accretion disk is located around 11M in the case of the freezing boundary condition. The results of these simulations show that the tori and spiral shock waves are created in each case using freezing and the outflow boundary, respectively, and it also suggests that spiral waves are a robust feature of accretion disks in binary systems, and that these spiral shocks can indeed transfer the gravitational energy to the radiation energy observed by different X-ray satellites.

THE EFFECTS OF DIFFERENT PERTURBATIONS ON THE DYNAMICS OF THE ACCRETION DISK AROUND THE BLACK HOLE

2007 ◽  
Vol 22 (10) ◽  
pp. 1875-1898 ◽  
Author(s):  
ORHAN DÖNMEZ
Keyword(s):  
Shock Wave ◽  
Black Hole ◽  
Shock Waves ◽  
Accretion Disk ◽  
Periodic Oscillation ◽  
Single Star ◽  
Special Cases ◽  
Galactic Black Hole ◽  
General Relativistic ◽  
Armed Spiral

We investigate the special cases of the formation of shocks in the accretion disks around the nonrotating (Schwarzschild) black holes in cases where one or few stars perturb the disk. We model the structure of disk with a 2D fully general relativistic hydrodynamic code and investigate a variety of cases in which the stars interacting with the disk are captured at various locations. We have found the following results: (1) if the stars perturb the disk at nonsymmetric locations, a moving one-armed spiral shock wave is produced and it destroys the disk eventually; (2) if the disk is perturbed by a single star located close to the black hole, a standing shock wave is produced while the disk becomes an accretion tori; (3) if the disk is perturbed by stars at symmetric locations, moving two-armed spiral shock waves are produced while the disk reaches a steady state; (4) continuous injection of matter into the stable disk produces a standing shock wave behind the black hole. Our outcomes reinforce the view that different perturbations on the stable accretion disk carry out different types of shock waves which produce Quasi-Periodic Oscillation (QPO) phenomena in galactic black hole candidates and it is observed as a X-ray.

Strength of Surface Micromachined Diaphragms

1998 ◽  
Vol 518 ◽  
Author(s):  
Xing Yang ◽  
Frances M. Siu ◽  
Yu-Chong Tai
Keyword(s):  
Boundary Condition ◽  
Silicon Nitride ◽  
Boundary Conditions ◽  
Fabrication Process ◽  
Surface Micromachining ◽  
Fabrication Technique ◽  
Different Boundary Conditions ◽  
The Common

AbstractThis paper presents the study of the strength of surface micromachined diaphragms. It is found that the diaphragm strength strongly depends on the diaphragm boundary conditions. A new fabrication technique which does not change the mask and fabrication process is proposed to improve the common step-up boundary condition. Test diaphragms with diameters from 200 µm to 800 µm and three different boundary conditions have been fabricated using silicon nitride/PSG and silicon nitride/polysilicon surface micromachining processes. Experimentally, it is found that the strength of the diaphragms is significantly improved with the new boundary conditions. The application of this technique to other surface micromachined structures is also described.

scholarly journals The weak cosmic censorship conjecture may be violated

2020 ◽  
Author(s):  
Wen-Xiang Chen
Keyword(s):  
Black Hole ◽  
Wave Function ◽  
Boundary Conditions ◽  
Cosmic Censorship ◽  
Traditional Theory ◽  
Schwarzschild Black Hole ◽  
Entropy Reduction ◽  
Set Up ◽  
Coupled Wave ◽  
Cosmic Censorship Conjecture

According to traditional theory, the Schwarzschild black hole does not produce superradiation. If the boundary conditions are set up in advance, this possibility will be combined with the boson-coupled wave function in the Schwarzschild black hole, where the incident boson will have a mirrored mass, so even the Schwarzschild black hole can generate superradiation phenomena.Recently, an article of mine obtained interesting results about the Schwarzschild black hole can generate superradiation phenomena. The result contains some conclusions that violate the "no-hair theorem". We know that the phenomenon of black hole superradiation is a process of entropy reduction I found that the weak cosmic censorship conjecture may be violated.

scholarly journals Effects of Boundary Condition Models on the Seismic Responses of a Container Crane

2019 ◽  
Vol 9 (2) ◽  
pp. 241 ◽  
Author(s):  
Jungwon Huh ◽  
Van Nguyen ◽  
Quang Tran ◽  
Jin-Hee Ahn ◽  
Choonghyun Kang
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Time History ◽  
Dynamic Responses ◽  
Seismic Excitation ◽  
Different Boundary Conditions ◽  
Container Crane ◽  
Condition Model ◽  
Boundary Condition Model ◽  
Significant Difference

In recent years, several large earthquakes have caused the collapse of container cranes, which have resulted in halting of freighting, and significantly affected the economy. Some reports are concerned the uplift and derailment events of crane legs, and the collapse of the crane itself. In this study, the effects of different boundary conditions used in the numerical method are investigated for a container crane under seismic excitation. Three different boundary conditions are considered in terms of the connection of the crane’s legs (wheels) and the ground (rails), namely pin support (PIN), gap element (GAP), and Friction contact (FC) elements, by using the SAP2000 program for a typical container crane. Then, time history dynamic analyses are conducted using nine recorded ground motions. Dynamic behaviors of the container crane are studied in terms of the total base shear, portal drift, and relative displacement of legs, by investigating the three types of base boundary conditions. The results of the study show that when the intensity of earthquakes is large enough to create uplift and derailment events, the selection of the boundary condition model considerably affects the dynamic responses of the container crane. In addition, when uplift and derailment of the crane occur, the FC support condition is the most compatible with the real behavior of the crane. On the other hand, under low seismic excitation, there is no significant difference of the crane behavior according to the choice of boundary condition model.

Evaluation of Buckling Performance of Fibre Metal Rectangular Plates: Experimental and Numerical Investigation

2014 ◽  
Vol 575 ◽  
pp. 185-190
Author(s):  
M. Vasumathi ◽  
Murali Vela
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Buckling Load ◽  
Thin Layers ◽  
Maximum Deviation ◽  
Critical Buckling Load ◽  
Buckling Strength ◽  
Different Boundary Conditions ◽  
Simply Supported ◽  
Fibre Metal

Carbon reinforced aluminium laminate (CARAL) is a fibre metal laminate which consists of layers of carbon fibre and thin layers of aluminium. Buckling strength of CARAL under various support conditions is studied in this paper. Since CARAL is composed of fibre and metal, the pattern of failure of the laminate under compressive loads is truly imperative. The compressive buckling strength depends on geometrical parameters like length and width of the specimen and the sequence in which the layers are stacked. It also depends on the boundary condition. In this study, the critical buckling load is determined by varying the parameters such as aspect ratio (length/width), stacking sequence and boundary condition. Two different boundary conditions are considered, simply supported and fixed support condition. Numerical simulation analysis shows a maximum deviation of 16.72% from experimental results. The different failure modes executed by the laminate under compressive loading are also determined. The critical buckling load of CARAL constrained on all sides is evaluated numerically for different boundary conditions. Buckling load, in this case, takes maximum value when CARAL is clamped on all sides whereas it takes minimum value when the plate is simply supported on three sides keeping the fourth side fixed.

A Numerical Method for Turbulent Flows in Highly Staggered and Low Solidity Supersonic Turbine Cascades

2011 ◽  
Author(s):  
Shigeki Senoo ◽  
Kazuya Sakakibara ◽  
Takeshi Kudo ◽  
Naoaki Shibashita
Keyword(s):  
Shock Waves ◽  
Boundary Conditions ◽  
Numerical Method ◽  
Turbulent Flows ◽  
Computational Grids ◽  
Separation Flow ◽  
Turbulent Model ◽  
Transonic Compressor ◽  
Turbine Cascades ◽  
Outflow Boundary

Two main problems are associated with conventional numerical methods for simulating turbulent flows in high-reaction-type supersonic turbine cascades near the tip of the last stage blade in a steam turbine: the large skewness of computational grids and treatments of boundary conditions when the shock waves hit boundaries. This paper presents a numerical method to deal with these issues. A grid generation technique which uses five-block structured grids has been developed. The orthogonality of the grid is good even for highly staggered and low solidity cascades. In addition, the grids are completely continuous at the boundary between the blocks and at the periodic boundaries. Both the gradient of the grid lines and the change rate of the grid widths connected smoothly. As a result, shock waves can be captured accurately and stably. The inflow and outflow boundary conditions based on the two-dimensional characteristic theory have been applied and diminished the spurious reflections and fluctuations of shock waves at both the inlet and outlet boundaries. Therefore the non-physical reflection does not affect the flow in the cascades. A low Reynolds number k-ε turbulent model has been proposed. Distance from a wall is not used as the characteristic length of turbulent flows so that the turbulent model can be applied to a wake and a separation flow. The validity of the numerical method was verified by comparisons of the pressure distributions on the blade, the loss coefficients, and flow angles with linear cascade experiments of transonic compressor cascades.

scholarly journals Neumann and Robin type boundary conditions in Fractional Orlicz-Sobolev spaces

2020 ◽  
Author(s):  
Sabri Bahrouni ◽  
Ariel Salort
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Sobolev Spaces ◽  
Weak Solutions ◽  
Nonlocal Problem ◽  
Nonlocal Problems ◽  
Different Boundary Conditions ◽  
Nonstandard Growth ◽  
Type Boundary ◽  
Type Boundary Condition

In the first part of this article we deal with the existence of at least three non-trivial weak solutions of a nonlocal problem with nonstandard growth involving a nonlocal Robin type boundary condition. The second part of the article is devoted to study eigenvalues and minimizers of  several nonlocal problems for the fractional $g-$Laplacian $(-\Delta_g)^s$ with different boundary conditions, namely, Dirichlet, Neumann and Robin.

scholarly journals The Schwarzschild black hole in f(R) can exist superradiation phenomenon

2021 ◽  
Author(s):  
Wen-Xiang Chen
Keyword(s):  
Black Hole ◽  
Boundary Conditions ◽  
Event Horizon ◽  
Potential Barrier ◽  
Coordinate Transformation ◽  
Black Hole Thermodynamics ◽  
Incident Particle ◽  
Schwarzschild Black Hole ◽  
Relationship Of ◽  
The Relationship

For the relationship of the limit $y$ of the incident particle under the superradiance of the preset boundary (${\mu} = {y}{\omega}$),we find the relationship between black hole thermodynamics and superradiation, and use boundary conditions to establish the relationship between y and R. One of the modes under f(R) gravity,there is a possible solution.When r tends to infinity, as a coordinate transformation, y tends to 0. At that time, there is a potential barrier near the event horizon, that is, the Schwarzschild black hole under f(R) gravitation has superradiation at that time.

scholarly journals Annihilation-to-nothing: a quantum gravitational boundary condition for the Schwarzschild black hole

2020 ◽  
Vol 2020 (11) ◽  
pp. 002-002
Author(s):  
Mariam Bouhmadi-López ◽  
Suddhasattwa Brahma ◽  
Che-Yu Chen ◽  
Pisin Chen ◽  
Dong-han Yeom
Keyword(s):  
Boundary Condition ◽  
Black Hole ◽  
Schwarzschild Black Hole
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