Preliminary analysis of the hanging wall effect and velocity pulse of the 5.12 Wenchuan earthquake

A preliminary study of the PGA attenuation, hanging wall effect and velocity pulse characteristics from the 2008 Wenchuan earthquake ofMS -8.0 is described in this paper. The study was carried out through analyses in the time and frequency domains of main earthquake records. In the PGA attenuation study, records from 316 stations less than 1000 km from the surface rupture of the fault were used as a database and attenuation relationships were developed and compared with some existing relationships that are widely used in China's Mainland, Chinese Taiwan and the US. At the same time, records from 28 stations less than 100 km from the fault were used to study the hanging wall effect and velocity pulse characteristics of this earthquake based on the distribution of PGA, PGV, spectral acceleration, and the velocity pulse peak, and the results are compared with the 1999 Chi-Chi earthquake. In addition, the large PGAs of the UD components observed in this event are also discussed in this paper. From the results of the preliminary study, some conclusions are developed and suggestions for further research are proposed.

Side Wall Effects on the Hydrodynamics of a Floating Body by ImageGreen Function Based on TEBEM

A novel numerical model based on the image Green function and first-order Taylor expansion boundary element method(TEBEM), which can improve the accuracy of the hydrodynamic simulation for the non-smooth body, was developed to calculate the side wall effects on first-order motion responses and second-order drift loads upon offshore structures in the wave tank. This model was confirmed by comparing it to the results from experiments on hydrodynamic coefficients, namely the first-order motion response and second-order drift load upon a hemisphere, prolate spheroid, and box-shaped barge in the wave tank. Then,the hydrodynamics of the KVLCC2 model were also calculated in two wave tanks with different widths. It was concluded that this model can predict the hydrodynamics for offshore structures effectively, and the side wall has a significant impact on the firstorder quantities and second-order drift loads, which satisfied the resonant rule.

Wall Effect of Underwater Explosion Load Based on Wave Motion Theories

Owing to the existence of the flow field boundary, the shock wave load near the boundary is different from the freefield shock wave load. In the present paper, the hull plate load subjected to underwater shock wave is investigated based onwave motion theories; in addition, the experimental study of the hull plate load is carried out. According to the theoreticalanalysis of the hull plate pressure, we find that the hull plate pressure oscillates repeatedly and decays rapidly with timepassing, the maximum hull plate pressure is 2/（1＋n） times the maximum free field pressure, where n is the ratio ofimpedance, and the impulse is much smaller than the free field impulse. Compared with the experimental study, thetheoretical results agree well with the experimental data.

Effects of hanging wall and footwall on demand of structural input energy during the 2008 Wenchuan earthquake

Systematic differences in the duration and frequency content of ground motions from the hanging wall and footwall during the 2008 Wenchuan earthquake are investigated,focusing on the influence of these differences on structural input energy based on the elastic and inelastic energy responses of structures.A comparison of the input energy spectra between the hanging wall and the footwall reveal that the structural input energy on the hanging wall is not amplified due to the short duration and low peak ground velocity to acceleration ratio（V/A）.However,the larger demand of structural input energy on the footwall in the range of medium and long periods is observed and the demand increases up to 50% relative to the average level of structural input energy for rupture distances larger than 30 km.The importance of considering the footwall effect on structural input energy when comparing ground motions in the range of medium and long periods is recognized.

Flow behavior in microchannel made of different materials with wall slip velocity and electro-viscous effects

In a microfluidic system, flow slip velocity on a solid wall can be the same order of magnitude as the average velocity in a microchannel. The flow-electricity interaction in a complex microfluidic system subjected to joint action of wall slip and electro-viscous effect is an important topic. This paper presents an analytic solution of pressuredriven liquid flow velocity and flow-induced electric field in a two-dimensional microchannel made of different materials with wall slip and electro-viscous effects. The Poisson- Boltzmann equation and the Navier-Stokes equation are solved for the analytic solutions. The analytic solutions agree well with the numerical solutions. It was found that the wall slip amplifies the fow-induced electric field and enhances the electro-viscous effect on flow. Thus the electro-viscous effect can be significant in a relatively wide microchannel with relatively large kh, the ratio of channel width to thickness of electric double layer, in comparison with the channel without wall slip.

A new attenuation model of near-fault ground motions with consideration of the hanging wall effect in the Wenchuan earthquake

The hanging wall effect is an important factor that impacts the characteristics of strong ground motions in near-fault areas. Based on a residual analysis of ground motion parameters characterizing the hanging wall effect and in recognition of the nature of the effect, many models have been developed. In this study, after a comprehensive analysis of two existing models, a new model is proposed and used to model the hanging wall effect in horizontal peak ground acceleration （PGAH） and spectral acceleration （SAH） at a period of 0.1s in the Wenchuan earthquake. Finally, comparisons between the modeling results of the hanging wall effect in the Wenchuan earthquake and the results predicted by using Abrahamson and Silva＇s NGA model （AS NGA） indicate that the AS NGA model predicts a much higher hanging wall effect than the model developed in this paper. Furthermore, the AS NGA model predicts a large hanging wall effect even at great distances, while the proposed model more accurately captures the trend of the effect.

Structural effect of a soft-hard backfill wall in a gob-side roadway

The stability of a backfill wall is critical to implement gob-side entry driving technology in which a small coal pillar is substituted by a waste backfill wall. Based on features of surrounding rock structures in the backfill wall, we propose a mechanical model on the structural effect of a soft-hard backfill wall using theory analysis, physical experiments and a numerical simulation. The results show thatChe deformation of the structure of the soft-hard backfill wall is coordinated with the roof and floor. The soft structure on the top of the backfill wall can absorb the energy in the roof by its large deformation and adapt to the given deformation caused by the rotation and subsidence of a key rock block. The hard structure at the bottom of the backfill wall can absorb the strong supporting resistance from the top surrounding rock. The soft structure on the top protecting the hard bottom structure by its large deformation contributes to the stability of the entire backfill wall. An application indicated that the stress in the backfill wall effec- tively decreased and its deformation was significantly reduced after the top coal remained. This ensured the stability of the backfill wall.

Influence of Wall Effect on Comprehensive Controllability for Ducted Fan Aircraft

A novel coaxial ducted fan structure aircraft is proposed to enable the aircraft near vertical walls at high altitudes.The state space equation of the system can be obtained by correlation deduction and identification of the whole prototype model.Based on the duct test bench experiment and computational fluid dynamics(CFD)simulation analysis,the expressions between the different distances dWE from the rotor center of the prototype to the wall and the thrust,reaction torque,and tilting moment of the system under hovering conditions are obtained.The influence of the wall effect of the prototype is incorporated into the system model to analyze the relationship between distance dWE and the comprehensive controllability of the system.The results show that the system comprehensive controllability vector of other channels changes little with the decrease of the distance dWE,and only the controllability vector of the rolling channel increases significantly.At the same time,the tilting moment also increases significantly,which strengthens the tendency of the prototype to tilt towards the wall.

Geometric effects resulting from the asymmetry of dipping fault:Hanging wall/ footwall effects

Root-mean-square distance Drms with characteristic of weighted-average is introduced in this article firstly. Drms can be used to capture the general proximity of a site to a dipping fault plane comparing with the rupture distance Drup and the seismogenic distance Dseis. Then, using Drup, Dseis and Drms, the hanging wall/footwall effects on the peak ground acceleration (PGA) during the 1999 Chi-Chi earthquake are evaluated by regression analysis. The logarithm residual shows that the PGA on hanging wall is much greater than that on footwall at the same Drup or Dseis when the Drup or Dseis is used as site-to-source distance measure. In contrast, there is no significant difference between the PGA on hanging wall and that on footwall at the same Drms when Drms is used. This result confirms that the hanging wall/footwall effect is mainly a geometric effect caused by the asymmetry of dipping fault. Therefore, the hanging wall/footwall effect on the near-fault ground motions can be ignored in the future attenuation analysis if the root-mean-square distance Drms is used as the site-to-source distance measure.

Horizontal gas mixing in rectangular fluidized bed:A novel method for gas dispersion coefficients in various conditions and distributor designs

In a rectangular fluidized bed combustor, the tracer gas is injected continuously into the bed from a point source at the center of the distributor plate. In this study, a general governing equation is formulated for tracer gas dispersion in the bed. An analytical solution is derived to estimate the dispersion coefficients, Dxand Dy, in a horizontal plane. The concentration profiles at different sampling heights with various gas velocities are plotted.Subsequently, to estimate the dispersion coefficients, surface fitting of the obtained analytical solution to the experimental data is performed. The dispersion coefficients obtained from this model are compared with those of a conventional model. Additionally, the effect of walls, bed height and gas injection rate on the dispersion coefficients in a horizontal plane is investigated, and the effect of distributor design on the dispersion coefficients in a horizontal plane is investigated with different tracer positions. It is found that Dxand Dyare nearly equivalent at a lower tracer gas ratio of the injected gas to the total gas flow rate. It is also demonstrated that the effect of bed height on Dxis minor. This model is also able to estimate the dispersion coefficients in the case of a multihorizontal nozzle distributor.

A Free Surface Frequency Domain Green Function with Viscous Dissipation and Partial Reflections from Side Walls

The free-surface Green function method is widely used in solving the radiation or diffraction problems caused by a ship or ocean structure oscillating on the waves. In the context of inviscid potential flow, hydrodynamic problems such as multi-body interaction and tank side wall effect cannot be properly dealt with based on the traditional free-surface frequency domain Green function method, in which the water viscosity is omitted and the energy dissipation effect is absent. In this paper, an open-sea Green function with viscous dissipation was presented within the theory ofvisco-potential flow. Then the tank Green function with a partial reflection from the side walls in wave tanks was formulated as a formal sum of open-sea Green functions representing the infinite images between two parallel side walls of the source in the tank. The new far-field characteristics of the tank Green function is vitally important fur improving the validity of side-wall effects evaluation, which can be used in supervising the tank model tests.

Settling velocity of equiaxed dendrites in a tube

The settling velocity of equiaxed dendrites can cause macrosegregation and influence the structure of the equiaxed zone during the casting solidification process. So an understanding of the settling characteristics is needed to predict the structure and segregation in castings. The settling velocity of NH4Cl equiaxed dendrites of non-spherical geometry was studied experimentally in an NH4Cl-70wt.%H2O solution. A calculation formula was proposed to calculate the settling velocity of sediment equiaxed dendrites in a tube filled with saturated solution at a moderate Reynolds number region. The retardation effects of the wall and morphology of the equiaxed dendrite on the settling velocity were taken into account in the development of the calculation formula, and the correction function B of the drag coefficient with consideration of the retardation effects of the wall and morphology of the equiaxed dendrite on the settling velocity of the equiaxed dendrite was calibrated according to the experimental results. A comparison showed that the formula has a good accordance with the experimental results.

Numerical study on three-dimensional flow field of continuously rotating detonation in a toroidal chamber

Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.

Three-dimensional dynamics of a single bubble rising near a vertical wall:Paths and wakes

In order to clarify the migration mechanism and wake behavior of a single bubble rising near a vertical wall,three-dimensional direct numerical simulations are implemented based on the open-source soft-ware Basilisk and various types of migration paths like linear,zigzag and spiral are investigated.The volume of fluid(VOF)method is used to capture the bubble interface at a small scale,while the gas-liquid interface and high-velocity-gradient regions in the flow field are encrypted with the adaptive mesh refinement technology.The results show that the vertical wall has an obstructive effect on the diffusion of the vortex boundary layer on the surface of the bubble migrating in a straight line,and the resulting reaction force tends to push the bubbles away from the wall surface.For the zigzag or spiral movement of a bubble in the x-y plane,the perpendicular wall is an unstable factor,but on the contrary,the motion in the z-y plane is stabilized.

COALESCENCE INDUCED GRADIENT MORPHOLOGY NEAR A WALL IN PHASE SEPARATED POLYMER BLENDS DURING QUIESCENT ANNEALING

A fast coalescence mechanism is proposed to account for the wall effect on the formation of gradient morphology in phase separated polymer blends during quiescent annealing. The existence of solid wall with high polarity is believed to change the potential field around the dispersed particles near the wall. This additional potential interaction between the solid wall and the dispersed particles causes faster coalescence of the dispersed particles near the wall than in the bulk. The gradient phase morphology thus formed can be predicted by combining the wall-particle interaction and the touch-coalescence mechanism. The effect of interfacial tension on the gradient morphology is also discussed.

Settling behavior of spherical particles in eccentric annulus filled with viscous inelastic fluid

Hole cleaning is a complex process as there are many variables affecting cuttings removal(e.g.drilling fluid type,density,flow rate and rheological properties,cuttings size,drill pipe rotation speed).With the increasing number of drilling small diameter wells(e.g.coiled tubing drilling applications,ultra-deep wells drilled for exploitations of unconventional oil and gas resources),the wall resistance of the micro annulus also emerges as one of the most critical factors affecting the cuttings accumulation in wellbore.The eccentricity of drill pipes commonly observed during the drilling process of ultra-deep well and coiled tubing well makes the wall resistance effect on the cuttings transport even more prominent.Understanding the wall resistance effect on the particle settling behavior in eccentric annuli is,therefore,crucial for hydraulic design of efficient cuttings transport operations in these wells.In this study,a total of 196 sets of particle settling experiments were carried out to investigate the particle settling behavior in eccentric annuli filled with power-law fluids.The test matrix included the eccentricity ranges of 0-0.80,the dimensionless diameter ranges of 0.13-0.75 and the particle Reynolds number ranges of 0.09-32.34.A high-speed camera was used to record the particle settling process and determine the influences of the eccentricity,the dimensionless diameter,the fluid rheological properties,and the solid particle characteristics on the wall factor and the particle settling velocity.The functional relationship among the dimensionless diameter,the particle Reynolds number,and the wall factor was determined by using the method of controlling variables.An eccentric annulus wall factor model with average relative error of 5.16%was established.Moreover,by introducing Archimedes number,an explicit model of particle settling velocity in the eccentric annulus with average relative error of 10.17%was established.A sample calculation of particle settling velocity was provided to show the application of the explicit model.Results of this study can be used as a guideline by field engineers to improve hydraulic design of cuttings transport operations in concentric and eccentric annuli.

Motion through spherical droplet with non-homogenous porous layer in spherical container

The problem of the creeping flow through a spherical droplet with a non-homogenous porous layer in a spherical container has been studied analytically.Darcy’s model for the flow inside the porous annular region and the Stokes equation for the flow inside the spherical cavity and container are used to analyze the flow.The drag force is exerted on the porous spherical particles enclosing a cavity,and the hydrodynamic permeability of the spherical droplet with a non-homogeneous porous layer is calculated.Emphasis is placed on the spatially varying permeability of a porous medium,which is not covered in all the previous works related to spherical containers.The variation of hydrodynamic permeability and the wall effect with respect to various flow parameters are presented and discussed graphically.The streamlines are presented to discuss the kinematics of the flow.Some previous results for hydrodynamic permeability and drag forces have been verified as special limiting cases.

Simulation of Near-Fault Strong Ground Motion in the Beijing Region

On the basis of previous study of the 1679 Sanhe-Pinggu(M8.0) earthquake,the biggest event in history ever recorded in Beijing and its adjacent area,we made a 3-D strong ground motion simulation utilizing the staggered-grid finite differences method to study the distributions of peak ground velocity with different earthquake source models in the Beijing region.In the paper,earthquake source models and a transmission medium velocity model are established and the corresponding parameters are given in accordance to the results from a related previous study.Then,using a three-dimensional finite difference computing program of near-fault strong ground motion developed by Graves,the peak ground velocity caused by a destructive earthquake in the Beijing area is simulated.In our computation model,the earthquake source is 3km in depth,and a total number of 21,679 observation points on the ground surface are figured out.The transmission medium velocity model is composed of four stratums which are the Quaternary deposit,the upper crust,the upper part of the middle crust and the lower part of the middle crust.With the minimum grid spacing of 0.15km,a total of 2.28×106 grids are generated.Using a time step of 0.02 seconds we calculated the peak ground velocity for a duration of 8 seconds.After the analysis of the simulation results,we observed some basic characteristics of near-fault strong ground motion such as the concentration effect of near-fault peak ground velocity,rupture directivity effect,hanging wall effect,and basin effect.The results from our simulation and analysis suggest that the source and transmitting medium parameters in our model are suitable and the finite difference method is applicable to estimate the distribution of strong ground motion in the study region.

Analytical Study of the Electroosmotic Flow of Two Immiscible Power-Law Fluids in a Microchannel

The multilayer microchannel flow is a promising tool in microchannel-based systems such as hybrid microfluidics. To assist in the efficient design of two-liquid pumping system, a two-fluid electroosmotic flow of immiscible power-law fluids through a microtube is studied with consideration of zeta potential difference near the two-liquid interface. The modified Cauchy momentum equation in cylindrical coordinate governing the two-liquid velocity distributions is solved where both peripheral and inner liquids are represented by power-law model. The two-fluid velocity distribution under the combined interaction of power-law rheological effect and circular wall effect is evaluated at different viscosities and different electroosmotic characters of inner and peripheral power-law fluids. The velocity of inner flow is a function of the viscosities, electric properties and electroosmotic characters of two power-law fluids, while the peripheral flow is majorly influenced by the viscosity, electric property and electroosmotic characters of peripheral fluid. Irrespective of the configuration manner of power-law fluids, the shear thinning fluid is more sensitive to the change of other parameters.

Preliminary Study on the Correlation between Intensity Isoseismals and the Seismic Source Process of the Wenchuan Earthquake in Sichuan,China

The M_S8.0 Wenchuan earthquake in Sichuan caused heavy casualties and serious economic loss because of damage to engineering structures in high earthquake intensity regions. Earthquake intensity, especially in the near source region, as a macroscopic description of distribution of strong ground motions certain correlations with the earthquake source process, such as rupture directivity and the hanging-wall effect of the near-fault ground motions of this earthquake. In this article some qualitative analyses are carried out. The conclusion of this study may be useful for emergence response and rescue after earthquakes, when the strong ground motion recordings and the intensity distribution are not available immediately.