An Improved Coupling of Numerical and Physical Models for Simulating Wave Propagation

An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model （FEM） based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used for the physical wave generation. An innovative scheme combining fourth-order Lagrange interpolation and Runge-Kutta scheme is described for solving the coupling equation. A Transfer function modulation method is presented to minimize the errors induced from the hydrodynamic invalidity of the coupling model and/or the mechanical capability of the wavemaker in area where nonlinearities or dispersion predominate. The overall performance and applicability of the coupling model has been experimentally validated by accounting for both regular and irregular waves and varying bathymetry. Experimental results show that the proposed numerical scheme and transfer function modulation method are efficient for the data transfer from the numerical model to the physical model up to a deterministic level.

2D Coupled 3D:A New Numerical Model for Dual - Structured - Aquifer System

This paper points out that a successful numerical simulation is to construct a correct conceptional model which is very dose to the natural condition. A new model, two dimensional coupled three dimensional model (2D -3D ) is presented in the Present paper,which is the most suitable one for the dual - structured - aquifer system. An example of Wenyinghu area is shown.By using the 2D-3D model, a satisfied result of the simulated area is achieved.

3D numerical simulation of boreholes for gas drainage based on the pore–fracture dual media

A gas migration controlling equation was formulated based on the characteristics of the dual pore–fracture media of coal mass and in consideration of the matrix exchange between pores and fractures.A model of permeability dynamic evolution was established by analyzing the variation in effective stress during gas drainage and the action mechanism of the effect of coal matrix desorption on porosity and fracture in the coal body.A coupling model can then be obtained to characterize gas compressibility and coal deformability under the gas–solid coupling of loading coal.In addition,a 3D model of boreholes was established and solved for gas drainage based on the relevant physical parameters of real mines.The comparison and analysis results for the law of gas migration and the evolution of coal body permeability around the boreholes before and after gas extraction between the dual media and the single-seepage field models can provide a theoretical basis for further research on the action mechanism of gas drainage.

Study on the temperature characteristic and high temperature risk of asphalt layer of Beijing-Xinjiang ExpresswayWutong Daquan to Yiwu Section

High temperature rutting is a typical highway damage in Xinjiang, China, and its trigger process usually has a close relationship with characteristics of road temperature distribution. A numerical model of earth-atmosphere coupling heat transfer on a typical section of the Beijing-Xinjiang Expressway(G7) from Wutong Daquan to Yiwu was established in this work. Spatiotemporal characteristics of pavement structure layer temperature distribution, frequency and duration times of road surface high temperature from May 1 to September 30 are statistically studied. The effects of wind speed, weather and air temperature on asphalt layer and pavement temperature are analyzed. The results show that:(1) Spatial and temporal temperature distribution characteristics of pavement structural layers are greatly affected by the coupled earth-atmosphere heat transfer process. Surface temperature increases along the airflow direction and daily temperature variation of the pavement structure layer decreases with an increase of depth.(2) G7 expressway will face the challenge of high rutting damage. The proportion of temperature higher than 50 ℃ for pavement surface and asphalt upper layer both exceeds 50%and high temperature of road lasts for more than six hours in numerous days.(3) High temperatures of asphalt pavement are usually associated with low ambient wind speeds, while the wind flow has little cooling effect when the road surface temperature is relative high. Weather conditions have a significant impact on temperature of the road surface. The probability of high temperature in sunny days is obviously higher than other weather conditions.(4) Pavement temperature rises as air temperature rises. When air temperature is higher than 30 °C, the proportion of pavement daily maximum temperature over softening point reaches up to 78%.

Coupled 3D discrete-continuum numerical modeling of pile penetration in sand

A coupled discrete-continuum simulation incorporating a 3D aspect and non-circular particles was performed to analyze soil-pile interactions during pile penetration in sand.A self-developed non-circular particle numerical simulation program was used which considered sand near the pile as interacted particles using a discrete element method;the sand away from the pile was simulated as a continuous medium exhibiting linear elastic behaviors.The domain analyzed was divided into two zones.Contact forces at the interface between the two zones were obtained from a discrete zone and applied to the continuum boundaries as nodal forces,while the interface velocities were obtained from the continuum zone and applied to the discrete boundaries.We show that the coupled discrete-continuum simulation can give a microscopic description of the pile penetration process without losing the discrete nature of the zone concerned,and may significantly improve computational efficiency.

Fracture propagation,proppant transport and parameter optimization of multi-well pad fracturing treatment

This paper establishes a 3D multi-well pad fracturing numerical model coupled with fracture propagation and proppant migration based on the displacement discontinuity method and Eulerian-Eulerian frameworks,and the fracture propagation and proppant distribution during multi-well fracturing are investigated by taking the actual multi-well pad parameters as an example.Fracture initiation and propagation during multi-well pad fracturing are jointly affected by a variety of stress interference mechanisms such as inter-cluster,inter-stage,and inter-well,and the fracture extension is unbalanced among clusters,asymmetric on both wings,and dipping at heels.Due to the significant influence of fracture morphology and width on the migration capacity of proppant in the fracture,proppant is mainly placed in the area near the wellbore with large fracture width,while a high-concentration sandwash may easily occur in the area with narrow fracture width as a result of quick bridging.On the whole,the proppant placement range is limited.Increasing the well-spacing can reduce the stress interference of adjacent wells and promote the uniform distribution of fractures and proppant on both wings.The maximum stimulated reservoir volume or multi-fracture uniform propagation can be achieved by optimizing the well spacing.Although reducing the perforation-cluster spacing also can improve the stimulated reservoir area,a too low cluster spacing is not conducive to effectively increasing the propped fracture area.Since increasing the stage time lag is beneficial to reduce inter-stage stress interference,zipper fracturing produces more uniform fracture propagation and proppant distribution.