Hydraulic characteristics of combined weir-gate structure

1. A study of the structural characteristics of PGMs produced by rolling packs of one-sided sergewoven Kh18N10T steel gauzes has demonstrated that they are determined by the structure of the starting gauzes and the degree of pack deformation during rolling. 2. It has been established that expressions relating the coefficient of relative compression, porosity, and pore size of a PGM to one another make it possible to calculate suitable process parameters for the production of PGMs of predetermined structural characteristics. 3. The hydraulic resistance of PGMs has been determined; it is shown that the pressure loss experienced by a fluid during its filtration through a PGM is determined chiefly by the degree of deformation of the starting gauze pack.

Biochar as a soil amendment can influence the physical and solute transport properties of soils and, thus, provide a means to improve soil fertility. However, the use of different sized biochar particles down to the nano‐scale has revealed inconsistent results, with the mechanisms poorly understood owing to a lack of experimental data. This study investigated the effects and mechanisms of nano‐sized biochar particles (NBC) applied to a sandy loam soil with regard to impacts on the hydraulic characteristics and soil structure. Column experiments were carried out with NBC application rates of 0.0%, 0.3%, 0.5%, 0.7% and 1.0% (by weight). It was found that the NBC changed the distribution of the soil pore structure and affected the degrees of anisotropy, fractal dimension, soil porosity and stability of soil aggregates. NBC applications also increased the water repellency of the soil and reduced the surface energy of soil particles. Regarding soil hydraulic properties, NBC applications increased the saturated hydraulic conductivity of the soil and decreased soil water retention. Increasing the amount of NBC applied to the mixing‐layer decreased cumulative infiltration values (reduced by 3.75%–13.75%). The above results reveal how NBC affects the soil pore structure and soil hydraulic characteristics, which provides a theoretical basis for the systematic evaluation of soil improvement and environmental effects of nano‐sized biochar.

An exchangeable sodium percentage (ESP) >15 is traditionally considered to affect soil structural and hydraulic characteristics. Recent investigations show that both this critical value and the concept of critical threshold need reconsideration, because soil degradation often takes place even at lower ESP in dilute solutions, and soil behavior at increasing ESP appears to be a continuum. This study was carried out to analyze the response of two Sicilian Typic Haploxererts to ESP values up to 15, at a low cationic concentration. The investigation was carried out on aggregate stability, rating of soil shrink‐swell potential, and both saturated and unsaturated hydraulic conductivity. The specific purpose was to verify if a critical ESP threshold exists, or if the hypothesis of a continuum behavior is more appropriate. The high‐energy moisture characteristic technique was used for determining aggregate stability, and Brasher's method for the shrinkage characteristic. The constant‐head method was used for determining saturated hydraulic conductivity, and the parameter estimation method based on one‐step outflow experiments for unsaturated hydraulic conductivity. Almost linear relationships were found between the investigated soil properties and ESP, indicating no critical ESP threshold; furthermore, the results obtained indicate that an effective hazard of soil quality degradation can be forecast even in a 2 to 5 ESP range at a low cationic concentration. This is a basic indication for irrigation management aimed to combat and prevent degradation of soil quality.

Disc pump is widely used in difficult-pump-medium transportation such as petroleum and chemical industry. Discontinuous blade impellers play an important role in the passability and energy efficiency of disk pump. The research of design and internal flow mechanism are particularly important. Based on the structural characteristics and the internal flow mechanism of the original model, the improved design of the blade structure is carried out. Through the experimental verification and the numerical analysis of multiple working conditions, the influence law of the new composite blade on the hydraulic characteristics and internal flow mechanism of the disc pump is obtained. The results show that the error of energy efficiency characteristics of simulation and experiment under different flow conditions is within 5%, and the accuracy of simulation results meets the requirements; The hydraulic characteristics of the improved model are about 5.8% higher than that of the original model. The driving force of the new composite blade is more sufficient and the flow field is improved more obviously; The low pressure is located in the center of the impeller and gradually increases to the outlet of the impeller. There is obvious energy and mass conversion between the bladed region and bladeless region. The research results can provide a reference for the structural design of disc pump composite blade and the analysis of internal flow mechanism.

The structural and hydraulic characteristics (maximum, average, and hydraulic pore diameters, permeability, and sinuosity of the pore channels) have been studied in materials made of discrete VT6 alloy fibers obtained by rapid solidification of a melt. The materials have structural parameters that are similar to those in materials made from smooth cylindrical fibers or powders and are superior in regard to permeability.

By changing the wire diameter from 30 to 90 Μm, the number of wires in a strand from 1 to 40, and the porosity from 0.35 to 0.77, it is possible to obtain PGMs from bound lastingweave gauzes covering wide ranges of structural and hydraulic characteristics. The coefficient of variation of the mean pore size of PGMs ranges from 0.02 to 0.17, and that of the maximum pore size from 0.043 to 0.18, in the porosity range 0.35–0.77 for materials from 1-, 3-, and 6-wire strand gauzes of wire diameters 50 and 70 ym. The coefficient of variation of the coefficient of permeability of PGMs changes from 0.02 to 0.11 in the porosity range 0.40–0.77.

Hydraulic design of granular and geocomposite drainage layers in pavements based on demand-capacity modeling

It is one of the effective methods to increase the reliability of flood discharge buildings with high water head and reduce the project cost to transform the diversion tunnel of temporary buildings into permanent spillway by using the horizontal swirl flood discharge system. Based on Gongboxia hydropower station and combined with prototype monitoring, this paper studies and analyzes the key points of shape layout, structural characteristics and operation effect of horizontal swirl flood discharge system, the results show that the horizontal swirl flood discharge system has strong adaptability to topographic and geological conditions, good energy dissipation effect and hydraulic characteristics, stable inlet and outlet flow pattern, stable cyclone cavity, no obvious signs of adverse negative pressure and cavitation erosion, no adverse structural vibration and dynamic response, and safe operation of the spillway tunnel.

A composite hydraulic structure is used to solve the problems of sediment and floating materials, respectively. A pier (obstacle) is used at the downstream of the composite hydraulic structure to increase water depth, decrease flow velocity, and dissipate the flow energy. The paper deals with the effect of single pier and double piers on the hydraulic characteristics of the composite structure. Circular and square shapes are adopted in the study with different spacing measured from the downstream of the composite structure. The experiments reveal how the level of the hydraulic characteristics is changed due to the existence of the pier/piers as compared to without the existence of the pier/piers. The statistical data which is collected from the experiments shows the alteration in the average downstream water depth, discharge coefficient, Reynolds number, upstream Froude number and downstream Froude number regardless of pier shape and spacing. The alteration happens owing to a change in the separation zone of water flow along the pier circumference. Nonlinear water surface profile is appeared when the pier is located at the downstream, while linear water surface profile is appeared clearly when the downstream without pier. Also the interference between overflow velocity and underflow velocity will be reflected in the hydraulic characteristics.

Variability in soil characteristics in the field–bund transition area increases water loss potential in paddy fields

Aims Our main purposes were to determine the effects of Vigna radiata, a nitrogen fixing plant, on growth, water balance and gas exchange of the intercropping Juglans regia seedlings and to investigate the hydraulic mechanism involved in photosynthesis and growth. Methods We measured growth, hydraulic characteristics, and rate of gas exchange in J. regia seedlings, and analyzed the effects of the intercropping nitrogen fixing V. radiata on xylem anatomic structure, water balance and photosynthetic characteristics of J. regia seedlings under conditions of nitrogen deprivation and enrichment. Important findings Under conditions of nitrogen deficiency, the nitrogen fixing V. radiata facilitated the growth of the intercropping J. regia seedlings by improving xylem development, water transport and hydraulic characteristics in high transpiration demand. However, with nitrogen addition, the occurrence of V. radiata inhibited the growth of J. regia seedlings, likely by competing for water and other elements.

During the starting up of the pump mode in pump turbines, the axial hydraulic force acting on the runner would develop with the guide vane opening. It causes deformation and stress on the support bracket, main shaft and runner, which influence the operation security. In this case, the axial hydraulic force of the pump turbine is studied during the starting up of pump mode. Its influences on the support bracket and main shaft are investigated in detail. Based on the prediction results of axial hydraulic force, the starting-up process can be divided into “unsteady region” and “Q flat region” with obviously different features. The mechanism is also discussed by analyzing pressure distributions and streamlines. The deformation of the support bracket and main shaft are found to have a relationship with the resultant force on the crown and band. A deflection is found on the deformation of the runner with the nodal diameter as the midline in the later stages of the starting-up process. The reason is discussed according to pressure distributions. The stress concentration of the support bracket is found on the connection between thrust seating and support plates. The stress of the runner is mainly on the connection between the crown and the blade’s leading-edge. This work will provide more useful information and strong references for similar cases. It will also help in the design of pump turbine units with more stabilized systems for reducing over-loaded hydraulic force, and in the solving of problems related to structural characteristics.

In view of the problem of poor coupling adaptability and easy rib spalling of coal wall in large mining height comprehensive mining, based on the effective inhibition effect of face guard mechanism on coal wall spalling, the structural characteristics and bearing capacity of different structural forms of the face guard mechanism are compared and analyzed. According to the surrounding rock adaptability of the face guard mechanism, established a numerical analysis model for rigid-flexible coupling of the face guard mechanism under different spalling forms. In order to accurately simulate the stress state of the protective mechanism, a variable stiffness spring damping system is used to replace the hydraulic cylinder. The load-bearing performance and response characteristics of the face guard mechanism under rib spalling coupling conditions were analyzed by applying uniform normal load and impact load to the face guard. The findings indicated that, the integral-type face guard mechanism has a better effect on suppressing rib spalling. When the face guard mechanism bears the static load of the coal wall, the entire response process of the face guard jack can be divided into three stages: initial support, increasing resistance bearing, constant resistance bearing; both the impact load position and the coupling state of the rib spalling will affect the characteristics of force transmission at the face guard mechanism’s hinge point, the hinge point between the extensible canopy and the primary face guard is most sensitive to biased load. The research results can provide reference for optimizing the face guard mechanism of large mining height hydraulic support and improving the reliability of coal wall support.

Head loss coefficient of a manhole is dependent on various hydraulic and structural characteristics. This study analyses the effect on manhole head loss coefficients using numerical VOF model due to three factors: manhole structural mold shapes, small changes in inlet orientations and changes in the manhole to inlet pipe ratios. Head loss coefficients showed a strong dependence on the available surcharge. Presence of sump created the maximum head loss while benching provided the best efficiency. Within small deviation of inlet pipe orientations, two different hydraulic regimes were observed indicating effects on both head loss coefficients and threshold surcharge heights. Change of manhole to inlet pipe diameter ratios (Φm/Φp) showed three head loss characteristics. Head loss in small manholes (Φm/Φp<3) did not change with surcharge. Medium manholes (3 < Φm/Φp< 4.0) showed high head losses up to a specific surcharge. Big manholes (Φm/Φp>4.5) showed a high head loss at all the surcharges.

This paper proposes an expected position‐attitude adjustment control method of coal mine roadway support robot (CMRSR) based on a real‐time position‐attitude detection system. Taking advantage of lateral adjustment mechanism and control method, the CMRSR has flexible maneuverability and high dynamic expected position‐attitude adjustment performance. It can guarantee stability and safety of the relative position‐attitude in time‐varying roadway environment in underground coal mines. First, the structural characteristics, hydraulic system characteristics, and kinematic characteristics of the CMRSR are considered, and the spatial mathematical relationship model on position‐attitude parameters and sensor data information, roadway environment dimensions, and CMRSR structural dimensions are established. In addition, the real‐time position‐attitude of the CMRSR with respect to the roadway is recognized by the position‐attitude detection system. Then, according to real‐time roadway environment and relative position‐attitude, the expected position‐attitude parameters are set, and the adjustment parameters and types of each lateral hydraulic cylinder are selected based on different deviated position‐attitude conditions. A position‐attitude adjustment controller is designed based on the sliding mode variable structure control algorithm to achieve precise position‐attitude adjustment of the CMRSR. In addition, the position‐attitude detection system is used to provide feedback control to maintain the relative position‐attitude of the CMRSR. Finally, the practical performance illustrates high effectiveness and feasibility of the proposed control method. The average error of distance can be controlled within ±30 mm, the average error of angle can be controlled within ±0.5°, and the adjustment time can be controlled within 20 s.