Flow Regimes and Formation Mechanisms of Coarse Particle Solid-Liquid Two-Phase Flow in Vertical Pipe

随着&ldquo;双碳&rdquo;战略的深入推进，储量丰富的深海矿产资源展现出重要战略价值，将在未来新能源产业发展中发挥关键作用。在众多深海采矿技术中，垂直管水力提升因具有效率高、环境扰动相对可控等优势，被视为最具商业化潜力的深海采矿技术。然而，当垂直管道输送大粒径、高浓度且非球形矿石颗粒时，极易出现如栓塞流甚至管道堵塞等现象，严重影响矿石颗粒的安全输送。此外，非球形颗粒在流体中呈现更为复杂的运动特性，包括翻滚、旋转及碰撞等行为，其流动特征与流态演变规律目前仍缺乏系统性研究。为此，本文首先探讨了球形粗颗粒在垂直管道中的流态演化规律，进而发展了适用于非球形颗粒的计算流体力学-离散元方法（Computational Fluid Dynamics - Discrete Element Method，CFD-DEM），并结合室内实验，系统研究了垂直管道中非球形颗粒的流态演变规律及其形成机制。 首先，针对深海采矿垂直管道内颗粒粒径大、浓度高及非球形等特点，本文发展了适用于非球形颗粒的固液两相流数值计算方法。该方法采用超二次曲面函数对非球形颗粒进行建模，仅需少量形状参数即可高效描述多种非球形几何形态。为了提升非球形颗粒间的碰撞判定效率，引入了基于最大外接球和定向包围体的快速预判策略，并结合牛顿迭代算法实现高效的碰撞检测。在颗粒-流体耦合方面，该方法充分考虑了非球形颗粒的几何各向异性及其空间取向效应，完善了流体曳力计算模型，考虑了流体升力和俯仰力矩，同时提出了颗粒体积标记点方法，可精确计算颗粒相和流体相的体积分数。此外，还通过流化床、垂直管道输送及自由沉降等典型工况对该方法进行了全面验证。 随后，本文结合小型水力提升实验与新提出的粗颗粒图像识别与处理算法，系统研究了单一粒径球形颗粒群在堵塞后再启动过程中的流动特性。根据输送特征与颗粒体积分数的分析，该过程可划分为局部脉动、栓塞流、疏密流和均匀输送四个典型阶段，并结合可视化观测和定量分析，探究了其流态演变规律。针对双粒径组合及球与非球混合输送，研究发现大粒径比颗粒群更易在短暂混合后产生分离，而球与非球形颗粒混合时更易形成局部堵塞。基于实验现象，本文进一步结合数值模拟手段，系统研究了双粒径颗粒群在垂直管道中的分离与混合行为，揭示了不同粒径颗粒群分离与混合行为的主导机制。随后，分别比较了粗颗粒与细颗粒在流固相互作用力、碰撞力等方面的差异，进一步阐明了其各向异性、空间分布特征及碰撞频率变化的根本原因。此外，结合深海采矿垂直管水力提升的特点，还探讨了脉动流条件下水力提升的流态演变特征，并分析了颗粒粒径与入口浓度对流态演变过程的影响规律。 最后，针对深海矿石颗粒多呈类椭球的特点，本文基于所提出的非球形颗粒 CFD-DEM 耦合方法，系统研究了单一、双分散及多分散非球形颗粒群的水力提升特性与流态演变机制。对于单一非球形颗粒群，通过相似分析明确了影响水力提升过程的关键控制参数（包括颗粒相对直径、长短轴比、雷诺数、入口颗粒体积分数、弗劳德数等），并在此基础上系统研究了非球形颗粒的基本运动特征以及流态演变机制。研究发现，当椭球颗粒长短轴比从1（球形）逐渐增大时，颗粒与流体及周围颗粒的相互作用显著增强，促使颗粒向管道中心聚集并形成典型的环核流态。深入分析表明，流体作用于非球形颗粒的升力和俯仰力矩是驱动该流态形成的关键因素。随后，通过分析关键控制参数对水力提升特性的影响，并基于数值模拟结果的拟合分析，建立了非球形颗粒群速度、局部浓度及管道压力损失的预测关系式。针对双分散与多分散非球形颗粒群，研究发现形状差异导致的定向排列效应与复杂流固耦合作用，使得混合体系中颗粒团聚与分离行为更为复杂，而通过优化椭球颗粒的长短轴比或输入比例，可有效抑制颗粒团聚现象，提升输送过程的均匀性与稳定性。最后，基于自主研制的大型颗粒循环水力提升实验平台，开展了完全非规则颗粒的输送实验，实验表明适度的颗粒粒径差异与非球形颗粒的合理配比组合，能够有效提升水力提升过程的稳定性，并显著降低局部堵塞风险。 本文的研究揭示了深海矿石颗粒水力提升过程中关键流态的演变规律及其形成机制，为深海矿产资源规模化商业化开采提供了重要的理论指导与技术支撑，有望进一步助力深海采矿垂直管道输送系统的设计优化与实际工程应用。</p

Investigation of motion characteristics of coarse particles in hydraulic collection

The solid-fluid two-phase flow with coarse particles is an important research object in the two-phase transportation field, such as deep-sea mining. This paper adopts the resolved computational fluid dynamics-discrete element method to investigate the motion and mechanical characteristics of the coarse particles during the hydraulic collection. First, the rising process of coarse particles by combining the particle trajectory with the qualitative force analysis is analyzed during the hydraulic collection. The spiral phenomenon of the particle is found through the particle trajectory in numerical results, and the centripetal force is the reason for the spiral phenomenon of the particle. Second, the variations of the normalized fluid drag force and the rise time of particles are investigated at different fluid velocities and particle sizes. The results show that the rise of particles during hydraulic collection results from the rising and settling effects characterized by the fluid drag force and the relative gravity, respectively. Finally, appropriate particle size is recommended to save energy and improve the efficiency of hydraulic collection. In addition, the influence of the horizontal distance between coarse particles and the inlet of the suction pipe on particle rise is discussed

The impact of pulsating parameters on particle dynamics in vertical pipe during hydraulic conveying with pulsating inlet flow

This paper presents a numerical investigation of the hydraulic conveying performance of coarse particles with the inlet pulsating fluid velocity in a vertical pipe. The influence of pulsating parameters, in terms of pulsating amplitudes and frequencies, on hydraulic conveying is mainly considered. The pulsations of particle and slip velocity are as periodic and regular as the inlet pulsating velocity. The variation of the normalized force in one pulsating time cycle is also analyzed. Then the laws of particle group distribution with transient time and vertical distance are obtained: the plug phenomenon is more obvious at the larger pulsating amplitude, further leading to pipe blockage, while a larger pulsating frequency is beneficial to the weakening of the plugs. Particle relaxation time is introduced to explain the changes in particle group distribution. Additionally, the temporal variations of flow fields are also used to illustrate the propagation of kinematic waves

The impact of particle size and concentration on the characteristics of solid-fluid two-phase flow in vertical pipe under pulsating flow

Vertical pipe hydraulic conveying is currently considered the most promising method for deep-sea mining. The conveying velocity at the inlet of the vertical pipe is often close to a pulsating form due to the influence of the flexible pipe and the marine environment. This study employs a combined Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) approach to investigate the impact of various particle sizes and concentrations on the flow behavior of solid-fluid two-phase flow in a vertical pipe under pulsating flow. The study reveals that fluid velocities exhibit periodic fluctuations within the vertical pipe under pulsating inlet flow. Moreover, the periodic phenomenon of local increases in particle velocity and concentration becomes more pronounced as particle size and concentration increase. Larger particle sizes increase particle inertia, reducing the ability to follow the fluid and leading to more localized particle aggregation. Therefore, the flow pattern within the vertical pipe transitions from homogeneous flow to plug flow as particle size increases. Variations in fluid-solid interaction forces and particle collision forces are explored to explain this phenomenon. When the particle size exceeds a critical threshold, the collision force surpasses the fluid-solid interaction force, leading to the transition

垂直管中双尺寸颗粒群的混合及分离规律研究

深海能源的开发利用近年来受到各国关注，而深海矿石是深海能源的重要组成部分。本文以深海采矿的垂直管水力输送为研究背景，其管道内流的典型特征是颗粒级配宽且颗粒浓度高。宽级配特征下，管道内存在粗细颗粒混合及分离的现象，可能导致颗粒局部浓度增加，危害输送安全。因此，本文研究垂直管内双尺寸颗粒群的混合及分离机理。采用计算流体力学-离散元方法开展数值模拟，针对粗细颗粒尺寸差异大导致体积浓度计算不准确的问题，提出颗粒群体积浓度计算修正模型以及欧拉场到拉格朗日场的数据映射模型，并进行程序实现及模型验证。研究发现粗细颗粒混合及分离过程会造成颗粒群前后出现间断，并且增加颗粒群局部体积浓度及颗粒碰撞频率。本文还定义无量纲颗粒碰撞应力和流固相互作用应力，表征颗粒碰撞强度和流固相互作用强度。颗粒群混合到分离过程中颗粒碰撞应力显著增加，因此可通过颗粒碰撞应力曲线确定初始混合到完全分离的时刻。此外，流固相互作用的差异是引起粗细颗粒分离的根本原因

一种垂直管道内固液两相流动特性测量的实验装置及方法

本发明公开一种垂直管道内固液两相流动特性测量的实验装置及方法， 主要包括循环水箱、流体输送控制模块、颗粒堆积模块、温度和压力测量模块、图像采集模块。本发明可以实时测量垂直管道内固液两相流动的流量变化、温压变化、颗粒群运动形态变化， 为垂直管颗粒物料输送规律的研究提供科学依据和技术支持。本发明也为垂直管道固液两相流动研究提供新的实验系统和测试技术， 应用场景包括但不限于深海采矿、深海天然气水合物输送、食品工业、煤炭工业等