scholarly journals Theoretical description of drawing body shape in an inclined seam with longwall top coal caving mining

2019 ◽  
Vol 7 (1) ◽  
pp. 182-195 ◽  
Author(s):  
Jiachen Wang ◽  
Weijie Wei ◽  
Jinwang Zhang
Keyword(s):  
Numerical Simulations ◽  
Body Shape ◽  
Theoretical Calculations ◽  
Theoretical Equation ◽  
Angle Variation ◽  
Shape Difference ◽  
Development Area ◽  
Dip Angle ◽  
Longwall Top Coal Caving ◽  
Two Sides

AbstractUnderstanding the characteristics of drawing body shape is essential for optimization of drawing parameters in longwall top coal caving mining. In this study, both physical experiments and theoretical analysis are employed to investigate these characteristics and derive a theoretical equation for the drawing body shape along the working face in an inclined seam. By analyzing the initial positions of drawn marked particles, the characteristics of the drawing body shape for different seam dip angles are obtained. It is shown that the drawing body of the top coal exhibits a shape-difference and volume-symmetry characteristic, on taking a vertical line through the center of support opening as the axis of symmetry, the shapes of the drawing body on the two sides of this axis are clearly different, but their volumes are equal. By establishing theoretical models of the drawing body in the initial drawing stage and the normal drawing stage, a theoretical equation for the drawing body in an inclined seam is proposed, which can accurately describe the characteristics of the drawing body shape. The shape characteristics and volume symmetry of the drawing body are further analyzed by comparing the results of theoretical calculations and numerical simulations. It is shown that one side of the drawing body is divided into two parts by an inflection point, with the lower part being a variation development area. This variation development area increases gradually with increasing seam dip angle, resulting in an asymmetry of the drawing body shape. However, the volume symmetry coefficient fluctuates around 1 for all values of the seam dip angle variation, and the volumes of the drawing body on the two sides are more or less equal as the variation development volume is more or less equal to the cut volume. Both theoretical calculations and numerical simulations confirm that the drawing body of the top coal exhibits the shape-difference and volume-symmetry characteristic.

Separation and imaging of seismic diffractions using migrated dip-angle gathers

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. S131-S143 ◽  
Author(s):  
Alexander Klokov ◽  
Sergey Fomel
Keyword(s):  
Radon Transform ◽  
Real Data ◽  
Separation Procedure ◽  
Shape Difference ◽  
Depth Migration ◽  
Time Migration ◽  
Reflection Angle ◽  
Radon Space ◽  
Dip Angle ◽  
Analytical Expressions

Common-reflection angle migration can produce migrated gathers either in the scattering-angle domain or in the dip-angle domain. The latter reveals a clear distinction between reflection and diffraction events. We derived analytical expressions for events in the dip-angle domain and found that the shape difference can be used for reflection/diffraction separation. We defined reflection and diffraction models in the Radon space. The Radon transform allowed us to isolate diffractions from reflections and noise. The separation procedure can be performed after either time migration or depth migration. Synthetic and real data examples confirmed the validity of this technique.

Theoretical Analysis of a Reactive Reinforcement Method for Cylindrical Explosion-Containment Vessels

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Sui Yaguang ◽  
Zhang Dezhi ◽  
Tang Shiying ◽  
Li Jie ◽  
Lin Qizhao
Keyword(s):  
Shock Wave ◽  
Theoretical Analysis ◽  
Plastic Strain ◽  
Numerical Simulations ◽  
Circumferential Strain ◽  
Theoretical Calculations ◽  
Practical Application ◽  
Related Research ◽  
Explosion Loading ◽  
Approximate Expressions

A method for cylindrical explosion-containment vessels was presented, which used symmetrical implosion loading cooperating with the vessels to control the out-explosion loading, increasing the anti-explosion ability of explosion-containment vessels. In this study, theoretical analysis was developed first and response of cylindrical vessels loaded with implosion and out-explosion was discussed. Approximate expressions for final circumferential strain were obtained. Comparison between the theoretical calculations and the numerical simulations showed that the proposed method could effectively reduce the plastic strain of cylindrical explosion-containment vessels. The theoretical analysis introduced in this study can provide reference for related research. In addition, problems such as spall and defense of shock wave need to be solved before the presented method could be carried out in practical application.

Direct numerical simulations of rotating turbulent channel flow

2008 ◽  
Vol 598 ◽  
pp. 177-199 ◽  
Author(s):  
OLOF GRUNDESTAM ◽  
STEFAN WALLIN ◽  
ARNE V. JOHANSSON
Keyword(s):  
Numerical Simulations ◽  
Channel Flow ◽  
Rotation Number ◽  
Turbulent Channel Flow ◽  
Shear Velocity ◽  
Direct Numerical Simulations ◽  
A Value ◽  
Rotation Numbers ◽  
Wall Shear ◽  
Two Sides

Fully developed rotating turbulent channel flow has been studied, through direct numerical simulations, for the complete range of rotation numbers for which the flow is turbulent. The present investigation suggests that complete flow laminarization occurs at a rotation number Ro = 2Ωδ/Ub ≤ 3.0, where Ω denotes the system rotation, Ub is the mean bulk velocity and δ is the half-width of the channel. Simulations were performed for ten different rotation numbers in the range 0.98 to 2.49 and complemented with earlier simulations (done in our group) for lower values of Ro. The friction Reynolds number Reτ = uτδ/ν (where uτ is the wall-shear velocity and ν is the kinematic viscosity) was chosen as 180 for these simulations. A striking feature of rotating channel flow is the division into a turbulent (unstable) and an almost laminarized (stable) side. The relatively distinct interface between these two regions was found to be maintained by a balance where negative turbulence production plays an important role. The maximum difference in wall-shear stress between the two sides was found to occur for a rotation number of about 0.5. The bulk flow was found to monotonically increase with increasing rotation number and reach a value (for Reτ = 180) at the laminar limit (Ro = 3.0) four times that of the non-rotating case.

scholarly journals Formation of Wide Binaries by Fragmentation

2001 ◽  
Vol 200 ◽  
pp. 13-22 ◽  
Author(s):  
Peter Bodenheimer ◽  
Andreas Burkert
Keyword(s):  
Numerical Simulations ◽  
Formation Mechanism ◽  
Initial Conditions ◽  
Theoretical Calculations ◽  
Numerical Results ◽  
Statistical Properties ◽  
Core Material

Although observations strongly suggest that fragmentation during the protostar collapse is the primary formation mechanism for wide binaries, the theoretical calculations as yet do not well explain the statistical properties of such systems. The results of a number of numerical simulations are discussed, and it is pointed out that, although fragmentation is obtained in such calculations, in many cases either the initial conditions are not realistic, or the calculations are insufficiently resolved, or the calculations have not been taken far enough to account for the accretion of most of the initial core material onto the components of the forming system. Certain aspects of the numerical results are, however, consistent with the fragmentation hypothesis.

scholarly journals Large equatorial seasonal cycle during Marinoan snowball Earth

2020 ◽  
Vol 6 (23) ◽  
pp. eaay2471 ◽  
Author(s):  
Yonggang Liu ◽  
Jun Yang ◽  
Huiming Bao ◽  
Bing Shen ◽  
Yongyun Hu
Keyword(s):  
Numerical Simulations ◽  
Air Temperature ◽  
Seasonal Cycle ◽  
Theoretical Calculations ◽  
Surface Air Temperature ◽  
Snowball Earth ◽  
Earth Orbit ◽  
Seasonal Cycles ◽  
The Earth

In the equatorial regions on Earth today, the seasonal cycle of the monthly mean surface air temperature is <10°C. However, deep (>1 m) sand wedges were found near the paleoequator in the Marinoan glaciogenic deposits at ~635 million years ago, indicating a large seasonal cycle (probably >30°C). Through numerical simulations, we show that the equatorial seasonal cycle could reach >30°C at various continental locations if the oceans are completely frozen over, as would have been the case for a snowball Earth, or could reach ~20°C if the oceans are not completely frozen over, as would have been the case for a waterbelt Earth. These values are obtained at the maximum eccentricity of the Earth orbit, i.e., 0.0679, and will be approximately 10°C smaller if the present-day eccentricity is used. For these seasonal cycles, theoretical calculations show that the deep sand wedges form readily in a snowball Earth while hardly form in a waterbelt Earth.

Hydrodynamics and deposition in lacustrine shallow-water delta front: A combination of numerical simulations and modern sedimentation measurements

2020 ◽  
Vol 8 (3) ◽  
pp. SM39-SM52
Author(s):  
Yunlong Zhang ◽  
Zhidong Bao ◽  
Luxing Dou ◽  
Li Jiang ◽  
Mingyang Wei ◽  
...  
Keyword(s):  
Shear Stress ◽  
Numerical Simulations ◽  
Shallow Water ◽  
River Flow ◽  
Oil And Gas ◽  
Bed Shear Stress ◽  
Delta Front ◽  
Sedimentary Architecture ◽  
Dip Angle ◽  
Mouth Bars

With the exploration of tight oil and gas, shallow-water deltaic reservoirs have been attracting more and more attention. The sedimentary architecture of a shallow-water delta shows distinctive differences with that of a deep-slope delta. These differences may be associated with the mechanism and characteristics of the deposition in the area where the sediments unloaded. Based on modern sedimentary research of the Poyang Lake in China, this paper focuses on the processes of river flow entering a lake with a low dip angle. We conducted six sets of numerical simulations with different initial sedimentary flow velocities using Fluent software for analyzing the hydrodynamics and the sediment transportation in the shallow-water delta. We combined the simulation results with an analysis of the geomorphology of the Gangjiang Delta to reveal the deposition along the shoreline of the lacustrine shallow-water delta. The numerical simulation shows that the shallow-water delta is dominated by bed friction with an extensive hydrodynamical boundary layer. The bed shear stress, which varies with the changes in river flux, dominated the sediment transport and deposition at the shallow-water delta front, where the effluent flow mixes with lake water. The distributary channels show characteristics of repeatedly occurred erosion, scouring, filling, and reoccupation. We argue that the depositional characteristics are associated with the changes in bed shear stress controlled by variation of flow velocity. Mouth bars are less likely to grow to a reasonable scale because of the seasonal scouring of extreme floods. Moreover, the lake flow potentially reworks the mouth bars. Consequently, mouth bar deposits were difficult to preserve as hydrocarbon reservoirs in ancient shallow-water delta.

In-pipe crack detection for multiple diameters using TE11 mode microwaves

2020 ◽  
Vol 64 (1-4) ◽  
pp. 39-46
Author(s):  
Guanren Chen ◽  
Takuya Katagiri ◽  
Noritaka Yusa ◽  
Hidetoshi Hashizume
Keyword(s):  
Numerical Simulations ◽  
Experimental Verification ◽  
Crack Detection ◽  
Theoretical Calculations ◽  
Pipe Diameter ◽  
Mode Converters

This study evaluated the effect of pipe diameter on the applicability of a technique using TE11 mode microwaves for in-pipe crack detection. Three TE11 mode converters of different inner diameters were designed based on theoretical calculations and verified via numerical simulations. The working bandwidths of these mode converters were 7.0, 4.0, and 1.9 GHz. Experimental verification was carried out using brass pipes with the corresponding three inner diameters, and with pipe lengths up to 21–25.5 m. An axial and a circumferential slit were introduced to simulate cracks and deployed at multiple positions along the pipes under test. The results showed that both axial and circumferential slits could be detected and located for an inner pipe diameter up to 39 mm and at a distance of 15 m–24 m.

scholarly journals Large Equatorial Seasonal Cycle during Marinoan Snowball Earth

2021 ◽  
Author(s):  
Yonggang Liu
Keyword(s):  
Numerical Simulations ◽  
Air Temperature ◽  
Seasonal Cycle ◽  
Theoretical Calculations ◽  
Surface Air Temperature ◽  
Snowball Earth ◽  
Earth Orbit ◽  
Seasonal Cycles ◽  
The Earth ◽  
Very High

&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;In the equatorial regions on Earth today, the seasonal cycle of the monthly mean surface air temperature is &lt;10&amp;#176;C. However, deep (&gt;1 m) sand wedges were found near the paleoequator in the Marinoan glaciogenic deposits at ~635 million years ago, indicating a large seasonal cycle (probably &gt;30&amp;#176;C). Such observations have been used to argue that the Earth had a very high obliquity (&gt;54&amp;#176;) during that time, leading to the proposal of high-obliquity hypothesis. Although the hypothesis was criticized for not being able to find a mechanism for the Earth to return to a low-obliquity state, there was no other explanation for the observed large equatorial seasonal cycle. Through numerical simulations, we show that the equatorial seasonal cycle could reach &gt;30&amp;#176;C at various continental locations if the oceans are completely frozen over, as would have been the case for a snowball Earth, or could reach ~20&amp;#176;C if the oceans are not completely frozen over, as would have been the case for a waterbelt Earth or slushball Earth. It is pointed out that the eccentricity is important for the equatorial seasonal cycle especially when the climate is cold and dry. These large equatorial seasonal cycle above are obtained at the maximum eccentricity of the Earth orbit, i.e., 0.0679, and will be approximately 10&amp;#176;C smaller if the present-day eccentricity is used. For these seasonal cycles, theoretical calculations show that the deep sand wedges form readily in a snowball Earth while hardly form in a waterbelt Earth. Therefore, our results remove a loophole of the (hard) snowball Earth hypothesis, while make the waterbelt Earth and high-obliquity Earth hypotheses much less appealing.&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;

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