全球工业高速发展，各国对能源的需求量也越来越大，常规化石能源如煤炭、石油、天然气等可开采量越来越少。因此，各国尝试拓展能源开发利用范围，其中以深海矿产资源、天然气水合物等为代表的深海资源和以页岩油气、致密油等为代表的非常规油气资源颇受关注。深海矿石的集矿机与管道结合的水力提升开采方法、深海天然气水合物的固态开采方法、非常规油气的水力压裂开采方法都具有相似的物理过程即固体颗粒输送过程。这是一个典型的固液两相流动问题，此过程特征是含粗颗粒、颗粒浓度高且颗粒粒径组成跨度大，流动过程非常复杂，目前还没有成熟的理论去定量描述此问题。数值模拟方法是研究此问题的重要手段。但是，常规欧拉-拉格朗日方法处理粗颗粒问题时会出现颗粒相分数过大、固液相插值方法不适用等问题。因此，有必要提出一种可动态模拟含粗颗粒稠密固液两相流动的数值模拟方法，并基于此方法研究管道和裂缝中含粗颗粒稠密固液两相流的特性，为实际开采系统的安全和优化设计提供参考。

本文以深海资源和非常规油气资源开采为工程背景，通过数值模拟、室内实验和理论分析相结合的方法研究管道和裂缝含粗颗粒的稠密固液两相流的特性。主要包括数值模拟方法研究、管道系统内两相流动特性研究和裂缝网络内两相流动特性研究三方面的内容。

首先，针对常规欧拉-拉格朗日方法处理粗颗粒问题不适用的情形提出了修正模型。提出了含相分数和动量交换源项的连续相伪单相流N-S方程求解的PISO算法，给出了粗颗粒相分数场计算的虚拟质量分布函数方法，同时提出了基于颗粒尺寸的固液相权函数插值方法，并引入了质心坐标方法追踪颗粒位置。将各修正模型在开源软件OpenFOAM中进行算法植入，开发得到求解器CoarseDPMFoam。通过标准气固流化床实验以及基于自主研制实验设备开展的液固颗粒分离实验验证了数值模拟方法的适用性。

随后，对管道系统中含粗颗粒稠密固液两相流力学特性进行了研究。针对如何高效采集海床面颗粒问题，提出水力采集方法即管道抽吸方式实现颗粒收集。基于量纲分析获得了水力采集过程的几何相似律，提出了表征水力采集临界抽吸过程的无量纲数，并给出水力采集临界抽吸流量的预测方法。在竖直管道水力提升中，采用本文提出的数值模拟方法对竖直管道内颗粒稳定输送过程进行模拟。研究了各输送参数对管道内局部变量的影响规律，总结了管道内瞬时、时均流场的分布特征，基于数值模拟结果为实际施工合适的参数取值提供了建议。同时分析了粗颗粒水力提升性能，给出了水力提升临界速度、局部体积分数等的预测关系式，提出了水力提升能量损失的计算方法。

最后，对裂缝网络中含粗颗粒稠密固液两相流力学特性进行了研究。首先基于自建室内实验装置研究砂比、裂缝夹角和颗粒种类对颗粒在裂缝网络中运动的影响，发现在裂缝高度变化处颗粒堆积发生突变，有砂堵隐患。陶粒和自悬浮支撑剂铺置效果优于石英砂颗粒。随后基于室内实验设计数值模拟工况，分析输送无量纲参数对颗粒铺置高度和分支裂缝中颗粒进入量的影响规律。发现输送雷诺数是颗粒铺置高度的主控无量纲数。分支裂缝相对宽度对分支裂缝中颗粒进入量影响最大。获得了颗粒进入分支裂缝的临界判别准则。

With the rapid development of global industry, the demand for energy in various countries is also increasing. The amount of conventional fossil energy such as coal, oil, and natural gas that can be exploited is decreasing. Therefore, many countries are trying to expand the scope of energy, among which the deep-sea resources such as deep-sea mineral resources and natural gas hydrates and the unconventional resources such as shale oil and gas have attracted much attention. The hydraulic lifting method for deep-sea mineral resources, the solid production method for natural gas hydrate, and the hydraulic fracturing method for unconventional oil and gas have similar physical processes, which is solid particles transportation. This is a typical solid-liquid two-phase flow, which is characterized by coarse particles, high particle concentration and large particle size distribution. There is no mature theory to describe this process quantitatively. Numerical simulation is an important research method. However, the conventional numerical simulation method is inappropriate due to large particle volume fraction and inapplicability of the interpolation method with coarse particles. It is necessary to propose a numerical simulation method which can dynamically simulate the dense solid-liquid two-phase flow with coarse particles. Then, the characteristics of the dense solid-liquid two-phase flow with coarse particles in pipelines and fractures can be studied based on this method, which can provide reference for optimization design.

Concerning the exploitation of the deep-sea resources and unconventional oil and gas resources, this paper focus on the characteristics of dense solid-liquid two-phase flow with coarse particles in pipelines and cross fractures by using a combination of numerical simulation, laboratory experiment and theoretical analysis. It mainly includes three parts: the study of numerical simulation methods, the study of two-phase flow characteristics in pipeline system, and the study of two-phase flow characteristics in cross fractures.

First of all, some modified models are proposed for the situation where the conventional Eulerian-Lagrangian method is not applicable to deal with coarse particles. The PISO algorithm for solving the N-S equation of the pseudo single-phase flow with phase fraction and momentum exchange source term is proposed. A virtual mass distribution function method is proposed for calculating the coarse particle volume fraction. In addition, a weighted function method relating the particle size is given for the interpolation between the eulerian and lagrangian field. The barycentric coordinate method is introduced to track the particle. All the modified models are algorithmically implanted in the open source software OpenFOAM. The model solving program is coded to develop the solver CoarseDPMFoam. Subsequently, the applicability of the numerical simulation method is verified by gas-solid fluidized bed experiment and liquid-solid particle segregation experiments, which are carried out based on self-developed apparatus.

Secondly, the characteristics of dense solid-liquid two-phase flow with coarse particles in pipeline system are studied. A hydraulic collecting method is proposed concerning the problem of how to efficiently collect particles on the sea floor. The geometric similarity is obtained between actual exploitation process and model test based on the dimensional analysis. The dimensionless number that characterizes the critical suction process is proposed. A formula for predicting the critical suction velocity is presented. Then, the stable transportation of coarse particles in a vertical pipe is simulated by using the CoarseDPMFoam solver. The influences of transport properties on the motion of particles are studied. The distribution characteristics of the instantaneous and time-averaged flow field in the vertical pipe are summarized. Some suggestions are provided for actual construction based on the numerical simulation results. What's more, the hydraulic lifting performance of coarse particles is analyzed, and fitting formulas for the critical hydraulic lifting velocity and the local particle volume fraction are given. The calculation method of the energy loss of hydraulic lifting is also proposed.

Lastly, the characteristics of dense solid-liquid two-phase flow with coarse particles in cross fractures are investigated. The particle transportation process in the laboratory-scale cross fractures is studied based on laboratory experiments and numerical simulation method. Firstly, the influence of sand ratio, bypass angle and particle types on the transportation of particles is studied. It is found that a sudden change in the particle bed height occurred at the position where the fracture height changes, which may cause sand plugging. The ceramsite and self-suspending proppant have better performance than the quartz sand. Then, the influence of dimensionless parameters on the particle bed height and the amount of particles entering the secondary fracture are analyzed based on numerical simulation. The Reynolds number is the main controlling dimensionless number of the particle bed height, and the relative width of the secondary fracture has the greatest influence on the amount of particles entering the secondary fracture. The critical criterion for particles entering the secondary fracture is obtained.