Simulations of lateral mixing in cross-channel flow

Cross flow phenomena between connected sub-channels are studied by means of numerical simulations based on lattice-Boltzmann discretization. The cross (that is lateral) transfer is largely due to macroscopic instabilities developing at two shear layers. The characteristic size and advection velocity of the instabilities favorably compare with experimental results from the literature on a geometrically similar system. The strength of the cross flow strongly depends on the Reynolds number, with cross flow developing only for Reynolds numbers (based on macroscopic flow quantities) larger than 1360. Mass transfer between the sub-channels has been assessed by adding a passive scalar to the flow and solving its transport equation. As a result of the intimate connection of cross flow and lateral mass transfer, also the mass transfer coefficient is a pronounced function of Re.     

Nonlinear aircraft sensor fault reconstruction in the presence of disturbances validated by real flight data

This paper proposes an approach for Inertial Measurement Unit sensor fault reconstruction by exploiting a ground speed-based kinematic model of the aircraft flying in a rotating earth reference system. Two strategies for the validation of sensor fault reconstruction are presented: closed-loop validation and open-loop validation. Both strategies use the same kinematic model and a newly-developed Adaptive Two-Stage Extended Kalman Filter to estimate the states and faults of the aircraft. Simulation results demonstrate the effectiveness of the proposed approach compared to an approach using an airspeed-based kinematic model. Furthermore, the major contribution is that the proposed approach is validated using real flight test data including the presence of external disturbances such as turbulence. Three flight scenarios are selected to test the performance of the proposed approach. It is shown that the proposed approach is robust to model uncertainties, unmodeled dynamics and disturbances such as time-varying wind and turbulence. Therefore, the proposed approach can be incorporated into aircraft Fault Detection and Isolation systems to enhance the performance of the aircraft.     

基于线结构光传感器的公路平整度测量系统

研制了基于线结构光传感器的公路平整度测量系统,用于测量铺设完成但未凝固之前的水泥路面平整度。该系统利用四套线结构光传感器来测量路面特定点的三维数据,通过激光测距仪获得距离信息,提出了一种测量系统运动颠簸误差修正方法,设计并研制了颠簸误差传感器。设计了一种新型全局平面靶标,可一步同时完成多个传感器摄像机内、外部参数和光平面位置参数的快速标定与坐标系统一。对系统进行了标定实验、精度验证实验及实际测量实验,实验结果证明该系统测量精度可达到0.2mm以上。     

附加湍流器强化陶瓷膜微滤过程的研究

通过在管式陶瓷膜内设置不同结构形式的湍流器，试验和比较了不同主体流速和膜滤压差等工艺条件下的膜滤速率及能耗，分析了湍流器所产生的强化膜滤过程的效果以及试验条件下的一般规律。     

新型钢筋阻锈剂的合成及其阻锈性能的研究

合成了一种舍有氨基和菝基的有机阻锈刑，并用硬化砂浆法研究了该阻锈剂在砂浆中含有氯离子的条件下对钢筋锈蚀的抑制作用，同时与常用的亚硝酸盐的阻锈效果进行了比较。结果表明，该新型阻锈剂能够有效地阻止钢筋表面钝化膜的破坏，比亚硝酸盐具有更好的阻锈效果。     

Two-Dimensional Simulation Model of Sediment Removal and Flow in Rectangular Sedimentation Basin

A steady, two-dimensional numerical model was created to study the hydrodynamics of a rectangular sedimentation basin under turbulent conditions. The strip integral method was used to formulate the flow equations, using a forward marching scheme for solving the governing partial differential equations of continuity, momentum, advection–diffusion, turbulent kinetic energy, and its dissipation. In this way the flow equations were converted to a set of ordinary differential equations (ODEs) in terms of the key physical parameters. These parameters, along with a set of shape functions, describe flow variables including the velocity, the concentration of suspended sediments, and both the kinetic energy and its dissipation rate. Four Gaussian distributions were investigated, one corresponding to each flow parameter. In order to calculate the turbulent shear stresses, a two-equation turbulence model (i.e., k-ε model) was used. A fourth order Runge–Kutta method numerically integrates the set of ODEs. Simulation results were compared with experimental data, and close agreement (generally within 5–10%) was observed.     

Channel Shape and Turbulence Issues in Flood Flow Hydraulics

This paper reports the results of some further reflections by the writer on the nature of the flow physics in flooded channels where the floodplain flow overtops that in the main channel. A lot of the early conclusions drawn on this issue come from results of the Flood Channel Facility (FCF) program carried in the United Kingdom in the 1990s, but also from numerical work such as that of the writer. This paper takes this work further and reports that the FCF geometry may have led to conclusions that are dependent on a channel layout that is not fully representative of nature. It indicates that the flow structure evolves as a function of the channel width-to-depth ratio, and requires different turbulence model approaches to be computed accurately as this happens. In particular the standard k–ε is shown to become less adequate. It is also shown that the bank slope is influential in determining the flow structure, and that the flatter the slope the more likely it is to present increasing difficulties for modeling.     

沟槽面在湍流减阻中的应用

对近些年来的沟槽面湍流减阻技术的工业应用方向 ,沟槽的几何形状和尺度、流场压力梯度、沟槽面放置方式对于沟槽减阻效能的影响 ,沟槽面对于湍流边界层流动特性的影响 ,沟槽面的湍流减阻机理几方面研究进展进行了综述。从湍流拟序结构理论出发提出 :具有减阻效应的沟槽面不但能通过控制低速制条带间距来降低湍流“猝发”频率 ,而且在“猝发”后的高速“下扫”过程中因其几何结构使藏在槽内的安静流体避免或部分避免因高速“下扫”而“诱导”出较大速度剪切层 ,从而实现减阻。同时指出需要利用先进的实验技术如PIV等图像处理手段并结合直接数值模拟对湍流边界层的瞬时流场进行研究 ,以其找出湍流边界层的流动结构及其运动规律。     

Dissipation of Turbulent Kinetic Energy near a Bubble Plume

Profiles of the rate of dissipation of turbulent kinetic energy were inferred from temperature microstructure measurements near a bubble plume at the center of a tank with diameter of 13.7 m and maximum depth of 8.3 m. Six sets of between 18 and 51 profiles were collected at airflow rates of 0.1–0.6 L/s, measured at atmospheric pressure, and ensemble-averaged dissipation profiles were calculated. The dissipation in all cases was between 10?8 and 10?6?m2/s3 in most of the profile, but it increased sharply near the water surface. Energy considerations are used to discuss the experimental results in terms of previous numerical models of bubble plume turbulence. Two previous numerical studies show that the turbulence dissipates between 15 and 30% of the available power. In the experiments, the fraction is less than 1% because some of the energy of the plume is used to generate waves on the water surface and the profiles used to compute the volume-averaged dissipation were relatively far from the bubble plume.