Effect of the Fish-Bone Dam Angle on the Flow Mechanisms of a Fish-Bone Type Dividing Dike

2020 ◽  
Vol 54 (3) ◽  
pp. 58-67
Author(s):  
Jia Ni ◽  
Linwei Wang ◽  
Xixian Chen ◽  
Luan Luan Xue ◽  
Isam Shahrour
Keyword(s):  
Water Level ◽  
Longitudinal Velocity ◽  
Flow Characteristics ◽  
Fish Bone ◽  
Flume Experiments ◽  
Lateral Velocity ◽  
Engineering Structures ◽  
Flow Mechanisms ◽  
River Training ◽  
Large Velocity Gradient

AbstractFish-bone type dividing dikes are river engineering structures used for river training and to protect a mid-channel bar from scour. The flow characteristics around fish-bone type dividing dikes are very complicated, especially near its fish-bone dam. To understand the flow and scour processes associated with fish-bone dams, this paper conducts a numerical simulation of flow characteristics for different fish-bone dam angles. Based on the Yudaizhou fish-bone type dividing dike of the Dongliu Waterway, a 3-D numerical model is established via Flow-3D to simulate the flow characteristics around a fish-bone type dividing dike, which is verified by flume experiments. Based on the results, the effects of different fish-bone dam angles on water level and velocity distribution are investigated. With increasing fish-bone dam angle, the longitudinal and lateral gradients of the water level gradually decreased, and the variation degree of the longitudinal velocity also decreased; however, the variation degree of the lateral velocity increased. Vortex areas formed around the fish-bone dam and the downstream zone of the dike. A large velocity gradient was found around the dike, and the downstream vortex area decreased with increasing fish-bone dam angle.

scholarly journals Study on the 3D Hydrodynamic Characteristics and Velocity Uniformity of a Gravity Flow Circular Flume

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 927
Author(s):  
Yi Zhang ◽  
Longxi Han ◽  
Lina Chen ◽  
Chenfang Wang ◽  
Bo Chen ◽  
...  
Keyword(s):  
Flow Field ◽  
Environmental Science ◽  
Structural Characteristics ◽  
Longitudinal Velocity ◽  
Flow Characteristics ◽  
Science Research ◽  
Hydrodynamic Characteristics ◽  
Straight Channel ◽  
Uniformity Coefficient ◽  
Annular Flume

Flumes have been widely used in water conservancy science and environmental science research. It is of great significance to obtain the hydrodynamic characteristics and flow field uniformity in the flume. In this study, a new type of annular flume was taken as an example. The 3D flow field was simulated by using a commercial computational fluid dynamics (CFD) code, and was also measured by acoustic doppler velocimeter (ADV) to verify the simulation results. The average relative error range was between 8.37% and 9.95%, the simulated results basically reflected the actual situation of the flow field. On this basis, the structural characteristics of flow field were analyzed. A new calculation method of flow velocity uniformity was presented according to the flow characteristics of natural open channels. The velocity uniformity in the straight channel was calculated and analyzed based on this method, and the influence of speed on the velocity uniformity was further discussed. The length of uniform section was negatively correlated with the rotational speed (average velocity), which was between 39 cm and 101 cm in the straight, and the uniformity coefficient was less than 10%. Finally, the water flow characteristics in the straight channel without wheel were compared with the natural open channel flow. The longitudinal velocity was well fitted with the Prandtl logarithmic distribution formula (R2 > 0.977), and the application feasibility of the flume was analyzed. This study can provide technical support for the development and application of annular flume.

Understanding the Lateral Dimension of Traffic: Measuring and Modeling Lane Discipline

2021 ◽  
pp. 036119812110318
Author(s):  
Rafael Delpiano
Keyword(s):  
New Technologies ◽  
Autonomous Vehicle ◽  
Longitudinal Velocity ◽  
Lateral Position ◽  
Multiple Cameras ◽  
Lateral Velocity ◽  
Lane Changing ◽  
Lateral Dimension ◽  
Vehicle Position ◽  
Longitudinal Position

There is growing interest in understanding the lateral dimension of traffic. This trend has been motivated by the detection of phenomena unexplained by traditional models and the emergence of new technologies. Previous attempts to address this dimension have focused on lane-changing and non-lane-based traffic. The literature on vehicles keeping their lanes has generally been limited to simple statistics on vehicle position while models assume vehicles stay perfectly centered. Previously the author developed a two-dimensional traffic model aiming to capture such behavior qualitatively. Still pending is a deeper, more accurate comprehension and modeling of the relationships between variables in both axes. The present paper is based on the Next Generation SIMulation (NGSIM) datasets. It was found that lateral position is highly dependent on the longitudinal position, a phenomenon consistent with data capture from multiple cameras. A methodology is proposed to alleviate this problem. It was also discovered that the standard deviation of lateral velocity grows with longitudinal velocity and that the average lateral position varies with longitudinal velocity by up to 8 cm, possibly reflecting greater caution in overtaking. Random walk models were proposed and calibrated to reproduce some of the characteristics measured. It was determined that drivers’ response is much more sensitive to the lateral velocity than to position. These results provide a basis for further advances in understanding the lateral dimension. It is hoped that such comprehension will facilitate the design of autonomous vehicle algorithms that are friendlier to both passengers and the occupants of surrounding vehicles.

scholarly journals Numerical Investigation on the Flow Characteristics in a 17 × 17 Full-Scale Fuel Assembly

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 397 ◽  
Author(s):  
Zihao Tian ◽  
Lixin Yang ◽  
Shuang Han ◽  
Xiaofei Yuan ◽  
Hongyan Lu ◽  
...  
Keyword(s):  
Fuel Assembly ◽  
Flow Characteristics ◽  
Full Scale ◽  
Pressurized Water Reactor ◽  
Lateral Velocity ◽  
Pressurized Water ◽  
Spacer Grids ◽  
Rod Bundle ◽  
Real Size ◽  
Cfd Method

In a previous study, several computational fluid dynamics (CFD) simulations of fuel assembly thermal-hydraulic problems were presented that contained fewer fuel rods, such as 3 × 3 and 5 × 5, due to limited computer capacity. However, a typical AFA-3G fuel assembly consists of 17 × 17 rods. The pressure drop levels and flow details in the whole fuel assembly, and even in the pressurized water reactor (PWR), are not available. Hence, an appropriate CFD method for a full-scale 17 × 17 fuel assembly was the focus of this study. The spacer grids with mixing vanes, springs, and dimples were considered. The polyhedral and extruded mesh was generated using Star-CCM+ software and the total mesh number was about 200 million. The axial and lateral velocity distribution in the sub-channels was investigated. The pressure distribution downstream of different spacer grids were also obtained. As a result, an appropriate method for full-scale rod bundle simulations was obtained. The CFD analysis of thermal-hydraulic problems in a reactor coolant system can be widely conducted by using real-size fuel assembly models.

scholarly journals Vehicle Velocity Estimation Fusion with Kinematic Integral and Empirical Correction on Multi-Timescales

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1242
Author(s):  
Jiangyi Lv ◽  
Hongwen He ◽  
Wei Liu ◽  
Yong Chen ◽  
Fengchun Sun
Keyword(s):  
Autonomous Vehicles ◽  
Estimation Error ◽  
Longitudinal Velocity ◽  
Estimation Method ◽  
Velocity Estimation ◽  
Model Parameters ◽  
Lateral Velocity ◽  
Empirical Correction ◽  
Vehicle Velocity ◽  
Wide Range

Accurate and reliable vehicle velocity estimation is greatly motivated by the increasing demands of high-precision motion control for autonomous vehicles and the decreasing cost of the required multi-axis IMU sensors. A practical estimation method for the longitudinal and lateral velocities of electric vehicles is proposed. Two reliable driving empirical judgements about the velocities are extracted from the signals of the ordinary onboard vehicle sensors, which correct the integral errors of the corresponding kinematic equations on a long timescale. Meanwhile, the additive biases of the measured accelerations are estimated recursively by comparing the integral of the measured accelerations with the difference of the estimated velocities between the adjacent strong empirical correction instants, which further compensates the kinematic integral error on short timescale. The algorithm is verified by both the CarSim-Simulink co-simulation and the controller-in-the-loop test under the CarMaker-RoadBox environment. The results show that the velocities can be accurately and reliably estimated under a wide range of driving conditions without prior knowledge of the tire-model and other unavailable signals or frequently changeable model parameters. The relative estimation error of the longitudinal velocity and the absolute estimation error of the lateral velocity are kept within 2% and 0.5 km/h, respectively.

scholarly journals Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 964 ◽  
Author(s):  
Shampa ◽  
Yuji Hasegawa ◽  
Hajime Nakagawa ◽  
Hiroshi Takebayashi ◽  
Kenji Kawaike
Keyword(s):  
Shear Stress ◽  
Longitudinal Velocity ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Efficient Solutions ◽  
Staggered Grid ◽  
Bed Shear Stress ◽  
Experimental Conditions ◽  
Alluvial Rivers ◽  
Spur Dike

This paper focuses on finding efficient solutions for the design of a highly permeable pile spur (or slit type) dike field used in morphologically dynamic alluvial rivers. To test the suitability of different arrangements of this type of permeable pile spur dike field, laboratory experiments were conducted, and a three-dimensional multiphase numerical model was developed and applied, based on the experimental conditions. Three different angles to the approach flow and two types of individual pile position arrangements were tested. The results show that by using a series of slit-type spurs, the approach velocity of the flow can be considerably reduced within the spur dike zone. Using different sets of angles and installation positions, this type of permeable spur dike can be used more efficiently than traditional dikes. Notably, this type of spur dike can reduce the longitudinal velocity, turbulence intensity, and bed shear stress in the near-bank area. Additionally, the deflection of the permeable spur produces more transverse flow to the opposite bank. Arranging the piles in staggered grid positions among different spurs in a spur dike field improves functionality in terms of creating a quasi-uniform turbulence zone while simultaneously reducing the bed shear stress. Finally, the efficacy of the slit-type permeable spur dike field as a solution to the riverbank erosion problem is numerically tested in a reach of a braided river, the Brahmaputra–Jamuna River, and a comparison is made with a conventional spur dike field. The results indicate that the proposed structure ensures the smooth passing of flow compared with that for the conventional impermeable spur structure by producing a lower level of scouring (low bed shear stress) and flow intensification.

Observer-based state-feedback robust control for path following of autonomous ground vehicles

2019 ◽  
Vol 234 (2) ◽  
pp. 222-239 ◽  
Author(s):  
Pengpeng Feng ◽  
Jianwu Zhang ◽  
Weimiao Yang
Keyword(s):  
State Feedback ◽  
Longitudinal Velocity ◽  
Path Following ◽  
Linear Matrix ◽  
Ground Vehicles ◽  
Parameter Uncertainties ◽  
Lateral Velocity ◽  
External Disturbances ◽  
Static State ◽  
Autonomous Ground Vehicles

In this article, a robust [Formula: see text] observer-based static state-feedback controller is designed for the path following of autonomous ground vehicles. The Takagi–Sugeno fuzzy modeling technique is used for modeling of vehicle dynamics with varying longitudinal velocity first. Then considering the high cost of direct lateral velocity measurement, an observer is designed to estimate the value of lateral velocity. Meanwhile, a robust controller is proposed to deal with the parameter uncertainties and external disturbances simultaneously, including the variation of the tire-cornering stiffness of both front and rear tires. Afterward, the condition of designing such an observer-based controller is transformed into the feasible problem of linear matrix inequalities. Numerical simulations using a high-fidelity and full vehicle model are performed based on a Carsim–Simulink joint platform. Simulation results under different conditions and comparison with other controller show that the proposed controller is effective irrespective of the variation in the road condition, the change in the vehicle longitudinal velocity and the external disturbances.

An Experimental Investigation of Gas-Liquid Heat Transfer in Rectangular Micro-Channels

2013 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises ◽  
Piyawat Kuaseng ◽  
Chompunut Nuibutr ◽  
Wattana Chanphan
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Camera System ◽  
Micro Channels ◽  
Flow Mechanisms

The investigations of heat transfer and fluid flow characteristics of non-boiling air-water flow in micro-channels are experimentally studied. The gas-liquid mixture from y-shape mixer is forced to flow in the 21 parallel rectangular microchannels with 40 mm long in the flow direction. Each channel has a width and a depth of 0.45 and 0.41 mm, respectively. Flow visualization is feasible by incorporating the stereozoom microscope into the camera system and different flow patterns are recorded. The experiments are performed under low superficial velocities. Two-phase heat transfer gives better results when compared with the single-phase flow. It is found from the experiment that heat transfer enhancement up to 53% is obtained over the single-phase flow. Also, the change in the configuration of the inlet plenum can result in the different two-phase flow mechanisms.

Experimental Study on the Flow Characteristics of Fish-Bone Type Dividing Dike

2013 ◽  
Vol 353-356 ◽  
pp. 2620-2624
Author(s):  
Li Chen ◽  
Ping Yi Wang ◽  
Tao Yu ◽  
Fan Zhang ◽  
Liang Li
Keyword(s):  
Experimental Study ◽  
Velocity Distribution ◽  
Flow Regime ◽  
Model Experiment ◽  
Water Surface ◽  
Flow Characteristics ◽  
Fish Bone ◽  
Spacing Length

The flow characteristics of fish-bone type dividing dike is very complicated. By model experiment, this paper deeply research in water surface line, velocity distribution and the flow regime of fish-bone type dividing dike. It can Provided the certain basis for the design of fish-bone type dividing dike, such as a fishbone in dam engineering stab dam ridge direction, length, and layout spacing, length.

Helium Turboexpander for Cryogenic Refrigeration and Liquefaction Cycles: Transient Analysis of Rotor–Stator Interaction

2016 ◽  
Author(s):  
Ashish Alex Sam ◽  
Parthasarathi Ghosh
Keyword(s):  
Turbulent Flows ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Space Length ◽  
Turbine Wheel ◽  
Mechanical Constraints ◽  
Computational Fluid Dynamics Analysis ◽  
Flow Mechanisms ◽  
Rotor Stator Interaction

Computational fluid dynamics analysis of the complex flows in a cryogenic turboexpander is essential for any improvement in its performance. This includes a detailed analysis of the unsteady turbulent flows imparted mainly by the rotor stator interactions. The flow unsteadiness due to rotor stator interaction is caused by the relative motion between the stationary and rotating component, interaction of the turbine wheel blades with the wakes and vortices generated by the upstream blades and at trailing edges. In order to minimize the loss generation due to this unsteadiness, the vaneless space length at the nozzle-turbine wheel interface and the length of the straightening portion at the turbine wheel-diffuser interface should be optimised considering the mechanical constraints. In this paper three dimensional unsteady viscous flow analysis of a helium cryogenic turboexpander was carried out using Ansys CFX to investigate the origin and flow mechanisms that cause these unsteady phenomena. The analysis has been done for three different lengths of straightening duct at the turbine wheel diffuser interface. The performance parameters from the computational results were compared and analysed to understand the flow characteristics in each case.

Study on the Resistance of Structural Optimization of Pipeline Elbow in Civil Engineering

2012 ◽  
Vol 568 ◽  
pp. 119-124
Author(s):  
Hong Mei Sun ◽  
Zhi Long Zan
Keyword(s):  
Structural Optimization ◽  
Civil Engineering ◽  
Structural Parameters ◽  
Flow Characteristics ◽  
Engineering Structures ◽  
Pipe System ◽  
Pipe Elbow ◽  
Civil Engineering Structures

In the pipe system of infusion, elbow is widely applied in Civil Engineering Structures based on structure materials.This paper studies a new infusion of the pipe elbow. Calculated and analyzed resistance of different structural parameters deflector is on the effect of flow characteristics.

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