Research on the Characteristics of Turnout Flow Based on the Eccentricity Index of Maximum Flow Velocity

On the one hand, the characteristics of the turnout flow in the river are related to the stability of the turnout flow, and on the other hand, it is related to the safety of the flowing buildings near the bend turnout river. To observe the characteristics of the flow field in the chaotic river, the open channel surface layer digital particle image velocity (DPIV) system is used to measure the data in the physical model of the curved turnout river, and the maximum flow eccentricity (MFE) of the channel section is established. The flow pattern of the turnout flow is analyzed. The results show that the MFE index can effectively evaluate the flow pattern of the turnout flow. The MFE of the upper stream section of the curved river changes with the sudden change position of the flow between twice to 3.5 times the water surface width from the center point, and moves upstream with the increase of the flow rate, and moves downstream with the increase of the water level. This characteristic has guiding significance for the adjustment of the flow pattern of the front pool of the building.

Analysis of Risks Associated With Water Pipes in Rapid Flow Waterways Through Waterway Modeling Experiments

In this study, waterway modeling experiments were conducted by incorporating the information obtained by analyzing accident sites to prevent frequent accidents of firefighters that occur during water rescue operations conducted near water pipes in rapid flow waterways. Based on the conducted experiments, it was observed that the flow velocity increased with decreasing distance from the water pipe. Furthermore, the maximum flow velocity was found to be 3.99 times higher at the posterior end than at the anterior end of the water pipe, and the flow velocity was found to be higher at the lower side than at the upper side of the water pipe’s anterior end. The maximum flow velocity was measured to be 1.65 m/s at a distance of 10 cm from the entrance to the pipe, 2.63 m/s at a distance of 5 cm from the entrance to the pipe, 7.12 m/s within the pipe, and 5.33 m/s at a distance of 5 cm from the pipe’s exit. The average flow velocity was measured to be 0.94 m/s at a distance of 10 cm from the entrance to the pipe, 5.53 m/s within the pipe, and 4.64 m/s at a distance of 5 cm from the pipe’s exit. Furthermore, in this study, relevant standard operating procedures and regulations were taken into consideration. Based on the results obtained from this study, recommendations and guidelines were then accordingly devised for preventing accidents of firefighters that occur during water rescue operations.

Spatio-Temporal Variations in Phytoplankton Communities in Sediment and Surface Water as Reservoir Drawdown—A Case Study of Pengxi River in Three Gorges Reservoir, China

The resting stages of phytoplankton are usually regarded as the seed bank and source of harmful algal blooms because of the recruitment of phytoplankton from sediment to the water column under suitable environmental conditions. Information about resting stages of phytoplankton is abundant in shallow lakes and littoral sea; yet, studies on river–reservoir systems are rare. The river–reservoir continuum shows a unique structuring of longitudinal gradients of hydrological and hydrodynamic conditions. We hypothesized that the seed bank and algal blooms in reservoirs are influenced by the hydrodynamic conditions of each reservoir. We used Illumina Miseq sequencing to examine the spatio-temporal variation in the phytoplankton community in the sediment as reservoir drawdown and in surface water during algal blooms in Pengxi River, a tributary of China’s Three Gorges Reservoir. The results show that the cyanobacteria community in sediment is significantly influenced by temperature, total carbon, maximum flow velocity, and total phosphorous, the eukaryotic phytoplankton community in sediment is significantly influenced by total phosphorous, temperature, total carbon, maximum flow velocity, and total nitrogen. Additionally, the dominant species in sediment is significantly different from that in surface water during algal blooms. Our results suggest that the dominant species in surface water during algal blooms is more influenced by the environmental factors and hydrodynamic conditions in the water column than the seeds in the sediment. These findings are fundamental for further research on the influence of hydrodynamic conditions on algal blooms in artificially regulated river-reservoir systems.

The mechanical origin of snow avalanche dynamics and flow regime transitions

Snow avalanches cause fatalities and economic damage. Key to their mitigation is the understanding of snow avalanche dynamics. This study investigates the dynamic behavior of snow avalanches, using the material point method (MPM) and an elastoplastic constitutive law for porous cohesive materials. By virtue of the hybrid Eulerian–Lagrangian nature of the MPM, we can handle processes involving large deformations, collisions and fractures. Meanwhile, the elastoplastic model enables us to capture the mixed-mode failure of snow, including tensile, shear and compressive failure. Using the proposed numerical approach, distinct behaviors of snow avalanches, from fluid-like to solid-like, are examined with varied snow mechanical properties. In particular, four flow regimes reported from real observations are identified, namely, cold dense, warm shear, warm plug and sliding slab regimes. Moreover, notable surges and roll waves are observed peculiarly for flows in transition from cold dense to warm shear regimes. Each of the flow regimes shows unique flow characteristics in terms of the evolution of the avalanche front, the free-surface shape, and the vertical velocity profile. We further explore the influence of slope geometry on the behavior of snow avalanches, including the effect of slope angle and path length on the maximum flow velocity, the runout angle and the deposit height. Unified trends are obtained between the normalized maximum flow velocity and the scaled runout angle as well as the scaled deposit height, reflecting analogous rules with different geometry conditions of the slope. It is found that the maximum flow velocity is mainly controlled by the friction between the bed and the flow, the geometry of the slope, and the snow properties. We reveal the crucial effect of both flow and deposition behaviors on the runout angle. Furthermore, our MPM modeling is calibrated and tested with simulations of real snow avalanches. The evolution of the avalanche front position and velocity from the MPM modeling shows reasonable agreement with the measurement data from the literature. The MPM approach serves as a novel and promising tool to offer systematic and quantitative analysis for mitigation of gravitational hazards like snow avalanches.

Investigation on Velocity Distribution in the Subchannels of Pin Bundle With Wrapping Wire: Evaluation of Reynolds Number Dependence in 3-Pin Bundle

A sodium-cooled fast reactor is designed to attain a high burn-up core in commercialized fast reactor cycle systems. In high burn-up fuel subassemblies, the deformation of fuel pin due to the swelling and thermal bowing may decrease local flow velocity in the subassembly and influence the heat removal capability. Therefore, it is important to obtain the flow velocity distribution in a wire wrapped pin bundle. In this study, the detailed flow velocity distribution in the subchannel has been obtained by PIV (Particle Image Velocimetry) measurement using a wire-wrapped 3-pin bundle water model. The test section consisted of an irregular hexagonal acrylic duct tube and fluorinated resin pins which had nearly the same refractive index with that of water and a high light transmission rate. This enables to visualize the inner subchannel through the outer pins. Flow velocity conditions in the pin bundle were set from 0.036 m/s (Re = 270) to 1.6m/s (Re = 13,500). From the PIV results, it was confirmed that the normalized flow velocity near the wrapping wire in low Re number condition was decreased relatively compared to that in high Re number condition. In the region away from the wrapping wire, the maximum flow velocity was increased by decreasing the Re number. In particular, the maximum flow velocity was more than twice the cross section average velocity in the laminar flow (Re = 270). Moreover, the PIV measurements by using the 3-pin bundle geometry without the wrapping wire were conducted. From the results, the effect of the wrapping wire on the flow field in the subchannel was understood. There experimental results useful not only for understanding of pin bundle thermal hydraulics but also code validation.

Application of Color Doppler Ultrasound in the Treatment of Vascular Diseases Around the Cardia

Objective: This paper uses color Doppler ultrasound technology to study the hemodynamic characteristics of portal hypertension and splenectomy plus pericardial vascular disruption, to understand the pathogenesis of portal hypertension, and to understand the spleen. The effects of resection and pericardial vascular dissection on portal vein and hepatic artery hemodynamics were analyzed. Methods: Nine male in our hospital’s hepatobiliary surgery from January 2017 to December 2018 were selected. The preoperative upper gastrointestinal barium meal or gastroscopy confirmed that all patients had moderate to severe esophageal and gastric fundus. The surgical method was splenectomy and pericardial vascular disconnection. Color Doppler ultrasound was performed on portal vein and hepatic arterial hemodynamics to observe the presence or absence of portal vein thrombosis. Result: Preoperative hemodynamic status of the case group: the diameter of the hepatic artery was (0.34±0.01) cm, the value is 0.34 cm; the maximum flow velocity of the hepatic artery was (64.6±5.0) cm/s, the value of 64.7 cm/s; The postoperative hemodynamic status of the case group: the diameter of the hepatic artery was (0.41±0.02) cm, the value of 0.41 cm; the maximum flow velocity of the hepatic artery was (88.5±6.1) cm/s, the value of 89.6 cm/s. Conclusion: Color Doppler ultrasound has obvious application value in the treatment of pericardial vascular diseases. 1 splenectomy and pericardial vascular disconnection can increase the flow of hepatic artery, and reduce the total blood flow into the liver after surgery. The proportion of hepatic arterial blood flow increased, and the oxygen supply to increase.

The mechanical origin of snow avalanche dynamics and flow regime transitions

Snow avalanches cause fatalities and economic damages. Key to their mitigation entails the understanding of snow avalanche dynamics. This study investigates the dynamic behaviors of snow avalanches, using the Material Point Method (MPM) and an elastoplastic constitutive law for porous cohesive materials. By virtue of the hybrid Eulerian-Lagrangian nature of MPM, we can handle processes involving large deformations, collisions and fractures. Meanwhile, the elastoplastic model enables us to capture the mixed-mode failure of snow, including tensile, shear and compressive failure. Using the proposed numerical approach, distinct behaviors of snow avalanches, from fluid-like to solid-like, are examined with varied snow mechanical properties. In particular, four flow regimes reported from real observations are identified, namely, cold dense, warm shear, warm plug and sliding slab regimes. Moreover, notable surges and roll-waves are observed peculiarly for flows in transition from cold dense to warm shear regimes. Each of the flow regimes shows unique flow characteristics in terms of the evolution of the avalanche front, the free surface shape, and the vertical velocity profile. We further explore the influence of slope geometry on the behaviors of snow avalanches, including the effect of slope angle and path length on the maximum flow velocity, the $\\alpha$ angle and the deposit height. Unified trends are obtained between the normalized maximum flow velocity and the scaled $\\alpha$ angle as well as the scaled deposit height, reflecting analogous rules with different geometry conditions of the slope. It is found the maximum flow velocity is mainly controlled by the friction between the bed and the flow, the geometry of the slope, and the snow properties. In addition to the flow behavior before reaching the deposition zone, which has long been regarded as the key factor governing the $\\alpha$ angle, we reveal the crucial effect of the stopping behavior in the deposition zone. Furthermore, our MPM model is benchmarked with simulations of real snow avalanches. The evolution of the avalanche front position and velocity from the MPM modeling shows reasonable agreement with the measurement data from literature. The MPM approach serves as a novel and promising tool to offer systematic and quantitative analysis for mitigation of gravitational hazards like snow avalanches.

Development of Improved Drainage System for Storm Water flow at Isale koko Ilorin, Kwara State, Nigeria

Among areas prone to flood disaster yearly in Ilorin is Isale koko. The study involved the reconnaissance survey to ascertain the current capacity of the existing drainage in the flood disaster prone area of Isale Koko, Ilorin, Kwara State, Nigeria. The dimension of the drainage network of the area was taken at eight (8) various points and the average area of the drainage was obtained to be 0.44m². The already existing drainage in the area was divided into 3 sections for easy computations of flow value, length, depth and width. The rainfall intensity for the study area was found to be 98.49mm/hr. The rational method and Manning’s equation were used for the surface runoff and the proposed drainage respectively. The peak flow of the area and maximum flow velocity in the drains were determined to be 48.46mᶟ/s and 2.21mᶟ/s respectively. The best hydraulic section method was employed to obtain new drainage dimensions for both rectangular and trapezoidal channels. The new designed rectangular channel had dimensions of 1.16m × 0.812m while the trapezoidal channel had dimensions of 1.43m×0.72m×0.87m. The area of both channels was obtained to be 0.67m². A comparative analysis was carried against the average area of the pre-existing drainage that showed a 53.3% increase in drainage area; proving that the current drainage infrastructure of the area is grossly inadequate. Sequel to the analysis, the trapezoidal shaped drainage was recommended for the study area. Keywords—Drainage, Flood, Infrastructure, Runoff, Storm water

Sensitivity and identifiability of rheological parameters in debris flow modeling

Over the past decades, several numerical models have been developed to understand, simulate and predict debris flow events. Typically, these models simplify the complex interactions between water and solids using a single-phase approach and different rheological models to represent flow resistance. In this study, we perform a sensitivity analysis on the parameters of a debris flow numerical model (FLO-2D) for a suite of relevant variables (i.e., maximum flood area, maximum flow velocity, maximum flow velocity, deposit volume). Our aims are to (i) examine the degree of model overparameterization, and (ii) assess the effectiveness of observational constraints to improve parameter identifiability. We use the Distributed Evaluation of Local Sensitivity Analysis (DELSA) method, which is a hybrid local-global technique. Specifically, we analyze two creeks in northern Chile that were affected by debris flows on March 25, 2015. Our results show that SD and β1 – a parameter related to viscosity – provide the largest sensitivities. Further, our results demonstrate that equifinality is present in FLO-2D, and that final deposited volume and maximum flood area contain considerable information to identify model parameters.

Numerical Simulation of a Debris Flow on the Basis of a Two-Dimensional Continuum Body Model

A two-dimensional debris and mud flow model that considers both laminar and turbulence flow was developed. Subsequently, the model was applied to a debris flow that occurred in Asaminami, Hiroshima, Japan in August 2014. The applicability of the model and the debris flow characteristics are discussed. The calculated horizontal distribution of sediment deposited in the Asaminami residential area was in good agreement with the horizontal distribution of the deposited large rocks and driftwood. This result indicates that the fine material in the downstream area was transported by water flow resulting from heavy rain that occurred after the debris flow. The scale of the initial debris flow was small; however, it increased with time, because eroded bed material and water were entrained to it. Therefore, it is important to reproduce the development process of debris flows to predict the amount of sediment produced, the deepest flow depth, the maximum flow velocity, and the inundation area. The averaged velocity of the simulated debris flow was about 9 m/s, and the velocity at the entrance to the residential area was about 8 m/s. This kind of information can be used to design sediment deposition dams. The travel time of the simulated debris flow from the upstream end of the main channel to the entrance of the residential area was 96 s. This kind of information can be used for making evacuation plans. Valley bed steps can suppress the deepest flow depth which is very important for the design of check dams; therefore, the high-resolution elevation data and fine numerical grids that reproduce step shapes are required to accurately calculate the deepest flow depth and maximum flow velocity.