Water Head Research Articles

A comprehensive experimental investigation on discharge formulae of free flow over fully contracted rectangular sharp-crested weirs

In this study, laboratory experiments were conducted to investigate the discharge characteristics of free flow over rectangular sharp-crested weirs under the situation of large discharges and high water heads. By adding the weir plates with contraction ratios which were not considered in the literature, a new division for the rectangular sharp-crested weirs was proposed. The performances of the available discharge coefficient equations from the literature were evaluated and improved. It was found that the water head has significant effect on the accuracy of the proposed discharge coefficient equations. The discharge coefficient is suitable to be described by the Reynolds number at low heads and the contraction ratio at high heads, this is determined by the flow characteristics of the rectangular sharp-crested weir. The work presented in this paper would be useful to enrich and develop the research on the flow discharge of rectangular sharp-crested weirs.

Comprehensive computational analysis of the impact of regular head waves on ship bare hull performance

This paper focuses on investigating the impact of waves on ship hydrodynamic performance, enhancing our understanding of seakeeping characteristics and contributing to advanced ship and propeller design. It examines the resistance, motions, and nominal wake of the KVLCC2 bare hull, which is free to surge, heave, and pitch, in both calm water and regular head waves using a RANS approach. The research reveals a substantial dependency of the wake on grid resolution, particularly in calm water and shorter waves, while motions and resistance display a weaker dependency. The computed nominal wake is compared against towing tank SPIV measurements. Utilizing Fourier analyses and reconstructed time series, the study examines correlations among various factors influencing the bare hull’s performance in waves. The axial velocity component of the wake in waves demonstrates significant time variations, mainly driven by higher harmonic amplitudes. This dynamic wake is influenced by instantaneous propeller disk velocities due to hull motions, orbital wave velocities, boundary layer contraction/expansion, bilge vortex and shaft vortex dynamics. The wake distribution at the propeller plane not only differs significantly from the calm water wake in longer waves but also exhibits notably larger time-averaged values (up to 21%).

A numerical test of soil layering effects on theoretical and practical Beerkan infiltration runs

AbstractWith reference to a more compacted and less conductive upper soil layer overlying a less compacted and more conductive subsoil, a simple three‐dimensional (3D) infiltration run is expected to yield more representative results of the upper layer than the subsoil. However, there is the need to quantitatively establish what is meant by more representativeness. At this aim, numerically simulated infiltration was investigated for a theoretically unconfined process under a null ponded head of water (d0H0 setup, with d = depth of ring insertion and H = ponded depth of water) and a practical Beerkan run (d1H1 setup, d = H = 1 cm). The considered layered soils differed by both the layering degree (from weak to strong; subsoil more conductive than the upper soil layer by 2.3–32.4 times, depending on the layering degree) and the thickness of the upper soil layer (0.5–3 cm). It was confirmed that water infiltration should be expected to be more representative of the upper soil layer when this layer is the less permeable since, for a 2‐h experiment, the instantaneous infiltration rates for the layered soil were 1.0–2.1 times greater than those of the homogeneous low‐permeable soil and 1.3–20.7 smaller than those of the homogeneous coarser soil that constituted the subsoil. Similarity with the homogeneous fine soil increased as expected as the upper layer became thicker. For a weak layering condition, the layered soil yielded an intermediate infiltration as compared with that of the two homogeneous soils forming the layered system. For a strong layering degree, the layered soil was more similar to the homogeneous fine soil than to the homogeneous coarse soil. Using the practical setup instead of the theoretical one should have a small to moderate effect on the instantaneous infiltration rates since all the calculated percentage differences between the d1H1 and d0H0 setups fell into the relatively narrow range of −18.8% to +17.4%. A sequential analysis procedure appeared usable to detect layering conditions but with some modifications as compared with the originally proposed procedure. The practical setup enhanced the possibility to recognize the time at which the characteristics of the subsoil start to influence the infiltration process. In conclusion, this investigation contributed to better interpret both the theoretical and the practically established 3D infiltration process in a soil composed of a less conductive upper soil layer overlying a more conductive subsoil and it also demonstrated that modifying the recently proposed sequential analysis procedure only using infiltration data could be advisable to determine the time when layering starts to influence the process.

Influence Analysis of Runner Inlet Diameter of Hydraulic Turbine in Turbine Mode with Ultra-Low Specific Speed

The hydraulic turbine in turbine mode (HTTM) with an ultra-low specific speed (HTTM-ULSS) has the advantages of a simplified structure, high efficiency, and good stability and has great application value in the industry. However, the influence of the runner inlet diameter (D1) on the performance of HTTM-ULSS has not yet been fully studied. Therefore, the three-dimensional models of Francis runners were established in the ultra-low specific speed range by examining D1 = 0.49 m, 0.5 m, and 0.51 m, and the two-stage hydraulic turbine models were constructed with flow passage components. Then, internal flow and energy characteristics were calculated using Fluent 16.0 software. Further, the influence of D1 on HTTM performance was studied by comparing numerical simulation results. The results show that the water head of the HTTM-ULSS can reach 540.87 m when D1 = 0.51 m, showing its powerful ability to recover the pressure energy in high-pressure water. Moreover, the head and efficiency are closely related to D1; when D1 increases, the circulation at the runner inlet increases, resulting in an enhancement in the ability to recover the water head and decreases in efficiency and in the operating range of the high-efficiency zone; with D1 increasing, the flow pattern inside the runner becomes better, but the high-pressure area of the blade increases. When selecting the D1, attention should not only be paid to the ability to recover the water head but also to the pressure of the runner blades and the internal water flow pattern.

Advanced monitoring and numerical modelling of the stability, safety and reliability indicators of the earthen dam of Songloulou (Cameroon).

For the determination of global stability after long term advanced monitoring, artificial intelligence have been used for the data analysis of water level and displacements of Songloulou earth dam at Cameroon. Measurements of safety and reliability indicators follow changes set by piezometric and pendulums measurements. The results obtained from the artificial intelligence on the base of many years recording data have confirmed the relevance and robustness of this model. The ANFIS model combining the concept of neural network and fuzzy logic was used to simulate the behaviour of piezometers and pendulums in the dam. This model has provided satisfactory results, given in the large amount of data to be processed. The water level evolution is modelled using the ANFIS function integrated in the MATLAB software and the result is compared to that obtained by the HST method. Afterwards, the state of stress on the structure and stability of the slope at shear have been assessed based on the hydro mechanical behaviour using the GEOSTUDIO Finite Element computation software. The input parameters are: the head of water recorded in the piezometers and geotechnical parameters of the dam. The modelling results in terms of displacement are accurately consistent with the displacement measurements. The horizontal displacement of pendulums obtained by GEOSTUDIO is 80 mm and those measured directly of the pendulums have 70 mm of average value. The safety factor for slope stability according to 530 m water level is 1.5.

Investigation of labyrinth weirs discharge coefficient with the same length

One of the approaches to reduce flood depth in dams and rivers is the application labyrinth weirs instead of simple linear weirs. Labyrinth weirs have a longer length than linear weirs; therefore, the flood will pass through it with a lower depth. In this study, two types of triangular and semicircular labyrinth weirs were experimentally investigated. Experiments were performed in a flume with a width of 0.8 m and a flow discharge of up to 70 L/s. Eight weir models with a thickness of 4 mm were made, of which four models are triangular weirs and four models are semicircular weirs. Weirs were used in two types, one-cycle and two-cycle. The height of the weirs is 15 cm and the ratio of the weir length to the flume width (L/W) is equal to 1.57. The results showed that the increase in the total water head ratio (HT/P) decreases the discharge coefficient in all models, which is due to the increase in the Nappe interference and the local submergence. Also, increasing the number of cycles in labyrinth weirs has reduced its efficiency. The reason for this decrease is the impact of the issuing jets at the junction of the cycles and the flow disturbance over the weir. The comparison between triangular and circular weirs showed the better efficiency of triangular weirs. In addition, the results showed that the placement of the top of the cycle towards the upstream will cause a better performance in the weir. It seems that the low angle of the weir wall in the downstream with the channel wall causes the Nappe flow to collide with the channel wall and consequent local submergence will ultimately reduce the discharge coefficient.

Wetting front migration model of ion-adsorption rare earth during the multi-hole unsaturated liquid injection

In the process of ion-adsorption rare earth ore leaching, the migration characteristics of the wetting front in multi-hole injection holes and the influence of wetting front intersection effect on the migration distance of wetting fronts are still unclear. Besides, wetting front migration distance and leaching time are usually required to optimize the leaching process. In this study, wetting front migration tests of ion-adsorption rare earth ores during the multi-hole fluid injection (the spacing between injection holes was 10 cm, 12 cm and 14 cm) and single-hole fluid injection were completed under the constant water head height. At the pre-intersection stage, the wetting front migration laws of ion-adsorption rare earth ores during the multi-hole fluid injection and single-hole fluid injection were identical. At the post-intersection stage, the intersection accelerated the wetting front migration. By using the Darcy's law, the intersection effect of wetting fronts during the multi-hole liquid injection was transformed into the water head height directly above the intersection. Finally, based on the Green-Ampt model, a wetting front migration model of ion-adsorption rare earth ores during the multi-hole unsaturated liquid injection was established. Error analysis results showed that the proposed model can accurately simulate the infiltration process under experimental conditions. The research results enrich the infiltration law and theory of ion-adsorption rare earth ores during the multi-hole liquid injection, and this study provides a scientific basis for optimizing the liquid injection well pattern parameters of ion-adsorption rare earth in situ leaching in the future.

Verification of experimental saltwater intrusion interface in unconfined coastal aquifers using numerical and analytical solutions

Saltwater intrusion (SWI) is a widespread environmental problem that poses a threat to coastal aquifers. To address this issue, this research employs both numerical and experimental methods to study saltwater intrusion under the impact of sea level rise and varying freshwater boundary conditions in two homogeneous aquifers. The study compares transient numerical groundwater heads and salt concentrations to experimental results under receding-front and advancing front conditions. In the low permeability aquifer, the root mean square error is 0.33 cm and the R2 is greater than 0.9817. Similarly, in the high permeability aquifer, the root mean square error is 0.92 cm and the R2 is greater than 0.9335. The study also compares the results of ten experimental tests for steady-state saltwater intrusion wedge and toe length with seven different analytical solutions. The experimental results are then compared to these analytical solutions to find the most suitable equation. The Rumer and Harleman equation shows good agreement with experimental saltwater intrusion wedge, while the Anderson equation is a good fit for saltwater intrusion toe length. Overall, this research provides valuable insights into saltwater intrusion in coastal aquifers, and the findings can be used to inform policies and management strategies to mitigate the negative impacts of saltwater intrusion. The investigation shed light on how inland water head and Sea Level Rise (SLR) affect SWI behavior.

Divergent effects of food waste derived hydrochar on hydraulic properties and infiltration in a sandy soil

Hydrothermal carbonization of food waste (FW) and application of the solid product (hydrochar, HC) in agriculture, is expected to be an effective way to promote the circulation in food-energy-water nexus. However, little is known on the effects of applying FW-derived HC as a soil amendment on soil properties and functions. The current study investigated the effects of FW-derived HC on soil hydraulic properties and infiltration process. Two types of FW-derived HC were mixed into the top 0–20 cm soil layer at a rate of 1 % and 2 % (w/w) in a soil column experiment with grass growth. In-situ infiltration experiment was conducted within the soil column using a disc infiltrometer at different negative pressure (−20 cm, −6 cm, and −2 cm water head). Unsaturated hydraulic conductivity (K0) and sorptivity (S0) at each negative pressure head was estimated by fitting experimental cumulative infiltration data to a 4-terms infiltration model. Saturated hydraulic conductivity (Ks) and soil water retention curve (SWRC) were measured using undisturbed soil cores taken from the soil column. Soil pore size distribution and soil water constants were estimated from the SWRCs. The results indicate that application of FW-derived HC significantly (p < 0.05) affected soil structure by increasing meso (0.03–0.0002 mm) and macro (> 0.03 mm) pores, which can be attributed to the promoted soil aggregation. Saturated hydraulic conductivity was significantly increased and water retention characteristics were changed with significantly (p < 0.05) increased soil water holding capacity and plant available water content. Besides, FW-derived HCs were found hydrophobic and can render wettable sandy soil water repellent. The K0 and S0 were significantly (p < 0.05) decreased and cumulative infiltration was reduced when soil was wetted from an initial dry condition. Negative effect was found on grass growth with significantly (p < 0.05) decreased aboveground biomass after HCs application. Our study indicates that agriculture application of FW-derived HC as a soil amendment could effectively improve soil fertility by recycling nutrient elements and improving soil structure. However, attention should be paid to the hydrophobicity and phototoxicity of FW-derived HC to avoid the related detrimental influences on plant growth and environment.

Revealing the infiltration process and retention mechanisms of surface applied free DNA tracer through soil under flood irrigation

It has been recently demonstrated that free DNA tracers have the potential in tracing water flow and contaminant transport through the vadose zone. However, whether the free DNA tracer can be used in flood irrigation area to track water flow and solute/contaminant transport is still unclear. To reveal the infiltration process and retention mechanisms of surface applied free DNA tracer through soil under flood irrigation, we tested the fate and transport behavior of surface applied free DNA tracers through packed saturated sandy soil columns with a 10 cm water head mimicking flood irrigation. From the experimental breakthrough curves and by fitting a two-site kinetic sorption model (R2 = 0.83–0.91 and NSE = 0.79–0.89), adsorption/desorption rates could be obtained and tracer retention profiles could be simulated. Together these results revealed that 1) the adsorption of free DNA was dominantly to clay particles in the soil, which took up 1.96 % by volume, but took up >97.5 % by surface area and densely cover the surface of sand particles; and 2) at a pore water pH of 8.0, excluding the 4.9 % passing through and 3.1 % degradation amount, the main retention mechanisms in the experimental soil were ligand exchange (42.0 %), Van der Waals interactions (mainly hydrogen bonds), electrostatic forces and straining (together 44.7 %), and cation bridge (5.3 %). To our knowledge, this study is the first to quantify the contribution of each of the main retention mechanisms of free synthetic DNA tracers passing through soil. Our findings could facilitate the application of free DNA tracer to trace vadose zone water flow and solute/contaminant transport under flood irrigation and other infiltration conditions.

Optimization and decision making of guide vane closing law for pumped storage hydropower system to improve adaptability under complex conditions

The pumped storage hydropower system (PSHS) is considered a high-quality peaking and frequency regulation energy source due to its operational flexibility and fast response. However, its frequent regulation leads to complex operating conditions with potential harm to the stability of the system. This paper focuses on analyzing and improving the adaptability of guide vane closing law under complex conditions. This is obtained by proposing a refined numerical model of PSHS considering non-linear factors and analyzing the effects of the guide vane closing law and initial operating conditions on the load rejection. The results revealed that a suitable two-stage guide vane closing law effectively reduces the risk of load rejection. In addition, when the initial load of two units is different, it is beneficial to improve the load rejection characteristics when the unit with the smaller load rejects the load first. Finally, three groups of parameters for the optimal guide vane closing law (the Pareto solution sets) are obtained by multi-objective sparrow search algorithm (MOSSA) under the rated, maximum water head, and maximum rotational speed conditions. The obtained Pareto solution and the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) are used for scoring the solutions and obtain an optimal suitable for complex operating conditions. The water head and rotational speed are reduced by an average of 7.76 % and 3.74 % for the different operating conditions compared to the model validation results, respectively. These results provide a theoretical basis for the selection of the optimal guide vane closing laws and improve the safety during load rejection under complex practical operating conditions.

Permeability Tests and Numerical Simulation of Argillaceous Dolomite in the Jurong Pumped-Storage Power Station, China

Due to its poor hydro-physical properties and other characteristics, argillaceous dolomite is susceptible to seepage failure under high water pressure, affecting the seepage stability of a rock mass. To ensure the safety of the project, when the argillaceous dolomite is present, it is necessary to study the conditions pertaining to its seepage failure. Taking the argillaceous dolomite of Jurong Pumped Storage Power Station as the research object, the spatial distribution, occurrence, scale, degree of weathering, and mechanical and hydrogeological characteristics of the argillaceous dolomite were studied. Through on-site water pressure tests and laboratory variable head tests, the permeability characteristics of argillaceous dolomite were analyzed, and the hydraulic conductivity of the argillaceous dolomite in the upper reservoir and underground powerhouse areas was quantified. The argillaceous dolomite specimens were collected, and seepage failure tests were conducted to determine the critical water pressure for its seepage failure. Based on the results of the laboratory tests, a numerical model of groundwater flow was established. By changing the water level of the upper reservoir and the measures of the anti-seepage and drainage, the seepage stability of the argillaceous dolomite was discussed. The actual water pressure of argillaceous dolomite in the underground powerhouse area was identified during the operation of the Jurong pumped-storage power station. The calculations show that when fully enclosed anti-seepage and drainage measures are taken for the underground powerhouse, the maximum head of water is 98 m, which is lower than the critical water pressure of seepage failure for the argillaceous dolomite. Therefore, no seepage failure will occur. The results provide a scientific basis for the anti-seepage and drainage design of the underground powerhouse area.

Field Experiments on 3D Groundwater Flow Patterns in the Deep Excavation of Gravel-Confined Aquifers in Ancient Riverbed Areas

In ancient riverbed areas, the hydro-geological conditions are extremely complex because of the cutting of ancient river channels during the sedimentary process. How to lower groundwater level in water-riched gravel-confined aquifer during deep excavation is vital for underground engineering. Groundwater flow patterns had to be understood during foundation pit dewatering. This paper presents a field case study conducted at the deep foundation pit of the Qianjiang Century City station on Hangzhou Metro Line 6, which is notable for its 52 m deep unclosed waterproof curtain. A total of 34 pumping wells were installed within the pit. During the tests, one well was subjected to a pumping well, while the others served as observation wells. The research included two sets of multi-depth pumping tests, which differed in terms of their filter lengths, aimed at investigating the flow pattern around pump wells and the roots of diaphragm walls. The study found that the use of longer filters, higher pump rates, and filters placed nearer to aquifer roofs enhances dewatering efficiency and minimizes impact on the surrounding geological environment. This paper introduces a novel concept known as the diaphragm wall–pumping well effect, which regulates the water head outside the pit and the subsidence, thereby optimizing the drawdown of the deep foundation pit with an unclosed waterproof curtain. The findings were applied in the foundation pit dewatering of Qianjiang Century City station, and the drawdown in and outside the pit was effectively controlled.

Optimization of geometric parameters of hydraulic turbine runner in turbine mode based on ISMA and BPNN

AbstractThe hydraulic turbine in turbine mode (TMHT) has significant advantages in residual energy recovery, but rapid optimization of its runner parameters has always been a challenge. To address this issue, the optimization algorithm ISMA‐BPNN is proposed based on the improved slime mold algorithm (ISMA) and back propagation neural network (BPNN). First, an efficiency characteristic neural network (ECNN) and a water head characteristic neural network (HCNN), which take the geometric parameters of the runner as input, and the efficiency and water head as outputs, respectively, are constructed by combining the orthogonal test‐based sample data, computational fluid dynamics (CFD), and BPNN. Then, the slime mold algorithm is improved and the optimal runner geometric parameters are obtained based on the ISMA, ECNN, and HCNN, to achieve rapid optimization of the TMHT runner. Finally, the CFD‐based numerical calculation accuracy is verified through real machine tests, and the feasibility of the ISMA‐BPNN‐based rapid optimization strategy for TMHT performance is further verified through CFD numerical simulation.

Statistical Modeling of Water Shortage in Water Distribution Systems in Guangzhou

In this study, data on water shortage events were collected from customer service systems. An analysis was conducted to establish the relationship between customers’ complaints and the water pressure flow conditions. A mathematical model was developed to estimate the probability of water shortage events based on water head. The Sigmoid function is commonly used as an activation function in neural networks. The function of the model is the same as the Sigmoid function, and its critical parameters correspond to the service head requirements of water facilities. By considering the interaction between human emotions and artificial systems, this study provides novel insights into improving the operational control and construction of water distribution systems.

Discharge estimation using brink depth over a trapezoidal-shaped weir

A weir is an accurate hydraulic structure for estimating water discharge in open channels and rivers. It can be constructed with a standard shape with vertical upstream and downstream faces or it can be modified by inclining one or both weir faces to enhance its hydraulic characteristics. In this study, the feasibility of using the brink depth over a trapezoidal-shaped weir (yb) for discharge estimation was experimentally investigated for free flow conditions. The experimental work involved the use of three lengths of the weir crest, L (10, 20, and 30) cm, and four different slopes (37°, 54°, 75°, and 90°) for both upstream and downstream faces, each with different water discharge. In addition, the effect of channel bed slopes on the water head over the weir (h) and the brink depth (yb) was investigated. The results indicated that the (yb) can be used for discharge estimation with good accuracy for a trapezoidal-shaped weir instead of water head over the weir (h), which is usually used in estimating water over the weir, as (yb) does not affect by the channel bed slope and insignificantly affected by changing the upstream and/or downstream face angle, contrary to the (h). Hence, an empirical equation for estimating water discharge based on (yb) with different upstream and downstream slopes was developed and examined using some available previous studies data. The mean absolute percentage error (MAPE) between (yc/L) with (yb/L) and between the measured and estimated discharge is 4.73% and 7.02%, respectively.

Solar PV-hydropower enhanced Picogrid as sustainable energy model for hilly remote areas: analytics and prospects thereof

This paper presents a techno-economic analysis of ‘Picogrid’ in hilly remote areas of North-East India, where availability of conventional grid power is either none or limited. A Picogrid is a small microgrid (typically a few tens of kW) containing renewable energy sources like solar, wind, small hydro etc. with battery based energy storage of limited capacity. A hybrid solar PV-Hydro based Picogrid of 7.2 kW capacity in a remote hilly area is analyzed, where the solar irradiance varies between 3.5 and 6.2 kWh/Day/m2, a water fall head lies between 1 and 30 m and water flow rate varies from 100 to 50,000 L/h. The study reveals that, the annual total energy generation varies between 1200 and 5000 kWh/kW/Year. Whereas the annual average daily yield and Capacity Utilization Factors for such system are 9 kWh/kWp/Day and 40%, respectively at highest possible water head and flow rate as mentioned above. The optimized Picogrid system is shown to have a levelised cost of electricity of 1.4 INR (0.017 USD) and 1.8 INR (0.022 USD) per kWh for 100% and 30% equity investment, respectively. The energy produced by these methods can be provided in rural areas thereby making electricity and revenue producing probabilities concurrently.

The Safe Load-Bearing Capacity of Railway Tunnel Linings under High-Pressure and Water-Rich Conditions

High water pressure has been identified as the direct cause of water seepage problems in tunnels. Consequently, it is imperative to ascertain the safety load-bearing limits of tunnel linings in high-pressure, water-rich strata. In this study, FLAC3D (V5.0) numerical simulation software was employed to establish seepage models of tunnels under high-pressure, water-rich conditions, taking an actual engineering project as a reference. The hydrostatic pressure on tunnel linings under various conditions, including different permeability coefficients of the surrounding rock, grouting rings, levels of the water table, and coordinates of lining positions, was computed. By extracting the results of these simulations, correlations between lining water pressure and various parameters were analyzed, and preliminary hydrostatic pressure calculation formulas were deduced. Through regression analysis using SPSS (19.0) software, a general calculation formula for lining water pressure was derived. Given similar surrounding rock conditions, it was revealed that railway tunnel lining types adhere to a universal standard. The calculation formula for lining water pressure, when integrated with lithostatic pressure in the seepage model, facilitates the computation of the maximum pressure head that the tunnel lining can withstand under different conditions. A tabulation summarizing safe water head heights under various conditions is also presented, which enables rapid consultation of the safe load-bearing range of tunnel lining under corresponding conditions. This study provides a new calculation method for the lining water pressure of a water-rich railway tunnel, filling the literature gap. The safe tunnel head query table provides a new research approach for the design of water-rich tunnels. The research method in this article is rare in the literature, and the research approach has obvious innovations. The findings of this study have the potential to provide a theoretical foundation and data reference for the structural design of tunnel linings and the remediation of related issues.

SARS-CoV-2 fusion peptide sculpting of a membrane with insertion of charged and polar groups

The fusion peptide of SARS-CoV-2 spike is essential for infection. How this charged and hydrophobic domain occupies and affects membranes needs clarification. Its depth in zwitterionic, bilayered micelles at pH 5 (resembling late endosomes) was measured by paramagnetic NMR relaxation enhancements used to bias molecular dynamics simulations. Asp830 inserted deeply, along with Lys825 or Lys835. Protonation of Asp830 appeared to enhance agreement of simulated and NMR-measured depths. While the fusion peptide occupied a leaflet of the DMPC bilayer, the opposite leaflet invaginated with influx of water and choline head groups in around Asp830 and bilayer-inserted polar side chains. NMR-detected hydrogen exchange found corroborating hydration of the backbone of Thr827-Phe833 inserted deeply in bicelles. Pinching of the membrane at the inserted charge and the intramembrane hydration of polar groups agree with theory. Formation of corridors of hydrated, inward-turned head groups was accompanied by flip-flop of head groups. Potential roles of the defects are discussed.

Numerical Prediction of Erosion of Francis Turbine in Sediment-Laden Flow under Different Heads

Hydropower stations are an important source of clean energy, usually operating in sandy water flow, and the turbine wheels may suffer severe wear and tear. In addition, during the operation of the unit, it is necessary to operate at different water heads according to the actual situation, which will result in varying degrees of wear and tear. In this paper, the Lagrange method is used to study the wear characteristics of a Francis turbine under different water heads. The research object is the water turbine in Wanjiazhai Hydropower Station. Research has shown that wear on the walls of the turbine volute, guide vanes, and runner is inevitable, and the clearance walls are also vulnerable to wear. The difference in the water head mainly affects the movement trajectory and impact speed of particles. The higher the water head, the more severe the wear on the wall surface of the flow passage components. Both the crown and lower ring of the runner are worn. The impact of particles causes wear at this location, and the greater the relative velocity relative to the runner, the more severe the wall wear. This indicates that reasonable head operating conditions can effectively reduce wall wear, which provides guidance for the operation of hydraulic turbines.