In this laboratory study, propagation behaviour, particle deposition patterns, and suspension characteristics of non-cohesive particle-driven gravity currents formed under constant-volume release conditions were investigated. The experimental gravity currents were created in a two-dimensional lock exchange type tank using two different particles (silicon carbide and glass beads) with four different median diameters. Video imaging and image processing techniques were utilized to monitor the current propagation, laser diffraction size analysis and dry weighing techniques were utilized to examine the size and mass characteristics of the deposits and suspensions, and acoustic Doppler velocimetry was utilized for flow velocity measurements for turbulence analysis. Our observations showed that the experimental gravity currents experienced two different propagation phases based upon the particle settling regimes. The first propagation phase was named as the propagation with the turbulence-dominated settling (TDS) and the later propagation phase was named as the propagation with gravity-dominated settling (GDS). It is found that a critical turbulent Reynolds number value (estimated to be O(1)) delineates the settling regimes, hence determines the transition between the propagation phases. With increasing particle settling velocity, the observed propagation phases in our experimental currents showed increasing deviations from the slumping, inertia-buoyancy, and viscous–buoyancy propagation phases that have been reported for homogeneous constant-volume gravity currents with no or negligible settling in the literature. Propagation observations showed that the initial median particle diameters of the currents have negligible effect on the current propagation characteristics during the TDS phase, but become important during the GDS phase. The currents with smaller initial median particle diameters propagated faster and a longer distance in the GDS phase than their counterparts with larger median particle diameters. The deposited particle characteristics indicated that particles of different sizes settle at similar speeds during the TDS phase due to turbulent mixing and the settling speed becomes dependent on the particle size during the GDS phase. As a result, size sorting of the deposited particles became more pronounced during the GDS phase. At the earlier stages of propagation, the vertical profiles of suspended particle concentrations in the current head showed some extent of vertical uniformity due to turbulent mixing around the half height of the current head. On the other hand, at the later stages of propagation, suspended particle concentration profiles exhibited an exponential profile. Deposited and suspended particle characteristics showed that horizontal particle sorting, that is size grading of particles in the flow direction, was more pronounced than the vertical particle sorting, that is size grading of particles at different elevations within the current head.

在此实验室研究中，研究了在恒定体积释放条件下形成的非粘性颗粒驱动重力流的传播行为，颗粒沉积模式和悬浮特性。实验重力流是在二维锁定交换式储罐中使用两个不同的中值直径不同的颗粒（碳化硅和玻璃珠）制成的。利用视频成像和图像处理技术监测电流传播，利用激光衍射尺寸分析和干称重技术检查沉积物和悬浮液的尺寸和质量特征，并利用声学多普勒测速仪进行流速测量以进行湍流分析。我们的观察结果表明，实验重力流基于粒子沉降机制经历了两个不同的传播阶段。第一个传播阶段被称为湍流主导沉降（TDS）传播，第二个传播阶段被称为重力主导沉降（GDS）传播。发现临界湍流雷诺数值（估计为O（1））描述了沉降状态，因此确定了传播阶段之间的过渡。随着粒子沉降速度的增加，在我们的实验电流中观察到的传播阶段显示出与坍落度，惯性浮力，文献中已经报道了均质恒体积重力流的粘性和浮力传播阶段，在文献中没有沉降或沉降可以忽略不计。传播观察表明，电流的初始中值粒径在TDS阶段对电流传播特性的影响可忽略不计，而在GDS阶段则变得重要。初始中值粒径较小的电流在GDS相中的传播要快于中值粒径较大的电流。沉积的颗粒特性表明，由于湍流混合，不同尺寸的颗粒在TDS阶段以相似的速度沉降，沉降速度取决于GDS阶段的颗粒大小。结果是，在GDS阶段，沉积颗粒的尺寸分类变得更加明显。在传播的早期阶段，由于当前水头一半高度附近的湍流混合，当前水头中悬浮粒子浓度的垂直分布显示出一定程度的垂直均匀性。另一方面，在传播的后期，悬浮颗粒的浓度分布呈现出指数分布。沉积和悬浮颗粒特征表明，水平颗粒分选，即沿流动方向的颗粒尺寸分级，比垂直颗粒分选，即在当前水头内不同高度的颗粒尺寸分级，更为明显。由于当前水头一半高度附近的湍流混合，当前水头中悬浮颗粒物浓度的垂直分布显示出一定程度的垂直均匀性。另一方面，在传播的后期，悬浮颗粒的浓度分布呈现出指数分布。沉积和悬浮颗粒特征表明，水平颗粒分选，即沿流动方向的颗粒尺寸分级，比垂直颗粒分选，即在当前水头内不同高度的颗粒尺寸分级，更为明显。由于当前水头一半高度附近的湍流混合，当前水头中悬浮颗粒物浓度的垂直分布显示出一定程度的垂直均匀性。另一方面，在传播的后期，悬浮颗粒的浓度分布呈现出指数分布。沉积和悬浮颗粒特征表明，水平颗粒分选，即沿流动方向的颗粒尺寸分级，比垂直颗粒分选，即在当前水头内不同高度的颗粒尺寸分级，更为明显。悬浮颗粒浓度曲线显示出指数曲线。沉积和悬浮颗粒特征表明，水平颗粒分选，即沿流动方向的颗粒尺寸分级，比垂直颗粒分选，即在当前水头内不同高度的颗粒尺寸分级，更为明显。悬浮颗粒浓度曲线显示出指数曲线。沉积和悬浮颗粒的特征表明，水平颗粒分选（即沿流动方向的颗粒尺寸分级）比垂直颗粒分选（即在当前压头内不同高度的颗粒尺寸分级）更为明显。