Impact Of Water Flow Research Articles

Numerical research on the influence of sail leading edge shapes on the hydrodynamic noise of a submarine

As a protruding part of submarine surfaces, sails will produce large hydrodynamic noise under the impact of water flow. To reduce the noise generated by the sail, the effects of different sail leading edges on the submarine flow field and hydrodynamic noise are investigated. Combining the WMLES S-Omega turbulence model and the Ffowcs Williams-Hawkings equation, the flow field and hydrodynamic noise of submarines are numerically simulated. The simulation results are compared with the experimental data. Good comparative results reveal the accuracy and performance of the employed numerical method. Subsequently, the computational fluid dynamics (CFD) code Fluent is used to simulate the variations in the flow field and hydrodynamic noise with different sails. The results show that the hydrodynamic noise of submarines can be effectively suppressed by changing the leading edge of the sail, and the sound pressure level can be dropped by 4.69 dB.

A comparative study on the construction methods of animal models of aortic arch dissection

Objective: To compare the effectiveness and safety of different methods to construct animal models of aortic arch dissection (AAD), and explore safe and effective methods for constructing AAD animal models. Methods: Twenty-four healthy mongrel dogs were divided into 4 groups by random number table (n=6). Group A: Venous incision needle high pressure water flow impact method; Group B: Venous incision needle non-high pressure water flow impact method; Group C: Transarterial sheath non-high pressure water flow impact method; Group D: Two-way balloon expansion combined with elastase perfusion method. Imaging examinations were performed immediately and 7 days after operation, aortic tissue biopsy and pathological staining were performed 15 days after operation to observe the formation of AAD. The operation time, aortic blood flow block time, model construction success rate, dissection tear length, postoperative survival rate and survival time of four groups of experimental dogs were collected to compare the effectiveness and safety of different construction methods. Results: There were no significant difference of the gender, age and weight between four groups of experimental dogs (all P>0.05). The operation time of four groups of experimental dogs were (111.6±8.0), (168.0±17.4), (164.4±13.9), (202.8±21.5)min, and the difference was statistically significant (F=39.973, P<0.001). The operation time of group A was significantly lower than group B, C and D (all P<0.001). The aortic blood flow block time of four groups of experimental dogs were (5.2±1.8), (19.6±3.8), (20.6±3.9), and (18.6±3.0) min, and the difference was statistically significant (all P<0.001). The aortic blood flow block time of group A was significantly lower than group B, C and D (F=27.598, P<0.001). The four groups of experimental dogs had 5, 5, 4, and 1 model were successfully constructed, respectively, and the difference was statistically significant (P=0.008). The successful rate of model construction in group A was significantly higher than that in group D (P=0.040). The dissection tear length of four groups were (14.4±3.0), (11.3±4.2), (7.0±2.3), (4.7±0.6) cm,and the difference was statistically significant (F=8.103, P=0.003). The dissection tear length of group A was significantly longer than group C, D (all P<0.05). The postoperative survival time were 15.0(10.0, 15.0), 5.0(3.0, 10.0), 3.5(1.5, 4.8), 10.0(2.8, 15.0) days, and the difference was statistically significant (χ2=7.825,P=0.036). The postoperative survival time of group A was significantly higher than group B, C (all P<0.05). There was no significant difference in the survival rate of the four groups (P=1.000). The pathological staining results showed that the elastic fiber at the tearing point of AAD was destroyed, and the elastic fiber on the outer wall of the false cavity was over-stretched, which was consistent with the pathological changes of aortic dissection. Conclusion: Transvenous incision needle high-pressure water flow impact modeling method is easy to operate. The aortic blood flow block time is short, the dissection tear length is wide, and the postoperative survival time is long, can be used as the preferred method of animal AAD model construction.

Chemical Characteristics of Discharges from Two Derelict Coal Mine Sites in Enugu Nigeria: Implication for Pollution and Acid Mine Drainage

In this study, the chemical composition of water and soils contiguous to two abandoned coal mines in southeastern Nigeria, was assessed to evaluate the impact of water flow from the mines ponds on the geoenvironment and potential for acid mine drainage (AMD). Parameters including the pH, anions and cations, and the heavy metals were measured. These were used to evaluate contamination/pollution using hybrid factors including Pollution Load Index, factors, enrichment factors, pollution load index and index of geoaccumulation. The pH range of 3.4 to 5.9 classified the water as weakly to strongly acidic, typical of AMD. The SO42– ion, which indicates pollution by mine waters, showed moderate to high concentrations. Iron, zinc lead and copper were the most abundant heavy metals. Pollution Load Index values were greater than unity which show progressive deterioration in water and sediment quality. The Enrichment Factor values of up to 1 indicated enrichment through lithogenic and anthropogenic sources. The mine dumps serve as pools that can release toxic heavy metals into the water bodies by various processes of remobilization. Based on the lithology, mineralogy, chemical concentrations and environmental factors, the study has shown that there exists a potential for the generation of AMD. The heavy metals enriched mine flow, especially iron, empty into the nearby water bodies which serve as sources of municipal water supply. Consumption of untreated water over a prolonged period from these water sources may be detrimental to health. Remedial measure and continuous monitoring are recommended for good environmental stewardship.

A Facile Method for Preparing a Superhydrophobic Block with Rapid Reparability

Superhydrophobic surfaces are fragile and are prone to failure in harsh outdoor environments. The preparation of robust superhydrophobic surfaces with stable performance and excellent properties can extend their application. In this paper, we report a simple and cost-effective method to prepare a superhydrophobic block using superhydrophobic zinc oxide powder and die pressing. The prepared sample has a contact angle of 163° and a sliding angle of 7°. Tests show that the superhydrophobic block can resist the impact of water flow, maintain its superhydrophobicity after friction or knife scraping, and quickly repair the destroyed surface by sandpaper abrasion. The sample exhibited excellent self-cleaning effect, robust mechanical property, and rapid repairability. This preparation method is also environmental-friendly and easy to operate. It will have a wide application prospect in many important fields.

Piezo-potential facilitated photocatalytic activation of persulfate over α-Fe2O3 and mechanism insight

Superoxide radical (O2−) is the main active species to generate sulfate radicals during the persulfate (PS) activation assisted by photocatalysis. As a widely-used photocatalyst, α-Fe2O3 usually exhibits negligible activity for O2− generation attributed to the low conduction band (CB) and photogenerated carrier mobility. In this work, we try to overcome the drawbacks by means of negative piezo-potential generated from strained ZnO nanorod. ZnO nanorod array is prepared by a hydrothermal method, and α-Fe2O3 is attached on it through a sol-gel process. The as-prepared showed obviously enhanced visible-light activity for PS activation under the impact of water flow, and the PS activation efficiency could reach 70% in 1 h. The activity is rarely decreased in 5 cycles and no Fe ions detected in the solution, indicating the nanocomposite possesses high stability. The enhanced activity is largely related to the additional negative piezo-potential generated in the top of ZnO nanorod. The resulted negative electric field could evaluate the CB of α-Fe2O3, thereby improving photogenerated charge reduction activity. Moreover, the field facilitates the opposite transports of photoelectrons and holes, due which the separation rate is enhanced. Consequently, the generation of O2− radicals which act as the dominant species in PS activation is promoted.

Stability Monitoring and Analysis of High and Steep Slope of a Hydropower Station

Slope deformation and failure are major challenges for hydropower station engineering. Taking the left bank slope at the exit of the flood discharge tunnel of the Wudongde Hydropower Station in China as an example, the deformation mechanism of the high-steep rock slope was studied. The height of the slope is about 200 m, which is affected by slope excavation, rainfall, and atomized rain. The results of multipoint displacement meters, surface deformation monitoring, and anchoring stress meters showed that the deformation and deformation rate of the slope have increased dramatically. Through the comprehensive analysis of the slope, it is found that the overall lithology of the slope is poor, the excavation disturbance causes the redistribution of the stress in the slope, and the excavation surface is relatively steep, which provides space for the deformation of the slope rock mass. Unloading relaxation leads to a large number of new fissures in the slope rock mass. These new fissures and fault fracture zones provide convenient conditions for rainfall and atomized rain infiltration. The rainwater infiltrated along the slope surface, formed the seepage field in the slope body, and weakened the rock-soil mass parameters. Meanwhile, saturated runoff is formed on the slope, causing large deformation of the slope rock mass. However, the migration of water in the slope has a time effect, and its influence on the stability of the slope also has a time effect. It is difficult for traditional monitoring methods to monitor the resulting changes in internal sliding force of the slope. Therefore, a remote monitoring and early warning system for landslide anchor cable force was introduced to monitor the slope stability changes caused by the impact of water flow and rainfall infiltration, which provided a reasonable and scientific reference for subsequent slope construction.

A GPU-based 2D shallow water quality model

Abstract In this study, a 2D shallow water flow solver integrated with a water quality model is presented. The interaction between the main water quality constituents included is based on the Water Quality Analysis Simulation Program. Efficiency is achieved by computing with a combination of a Central Processing Unit (CPU) and a Graphics Processing Unit (GPU) device. This technique is intended to provide robust and accurate simulations with high computation speedups with respect to a single-core CPU in real events. The proposed numerical model is evaluated in cases that include the transport and reaction of water quality components over irregular bed topography and dry–wet fronts, verifying that the numerical solution in these situations conserves the required properties (C-property and positivity). The model can operate in any steady or unsteady form allowing an efficient assessment of the environmental impact of water flows. The field data from an unsteady river reach test case are used to show that the model is capable of predicting the measured temporal distribution of dissolved oxygen and water temperature, proving the robustness and computational efficiency of the model, even in the presence of noisy signals such as wind speed.

WO3-Based Slippery Liquid-Infused Porous Surfaces with Long-Term Stability.

Slippery liquid-infused porous surfaces (SLIPS) inspired by Nepenthes pitcher plants exhibit excellent hydrophobicity, antifouling and anti-icing properties, and long-term durability under pressure and temperature. SLIPS have potential applications including in biomedical devices, self-cleaning structures, and water-resistant coatings. A big challenge posed by SLIPS is the durability of the lubricant in the porous layer. Herein, uniform tungsten oxide nanofiber networks were synthesized on the surface of stainless steel through a simple one-step hydrothermal method. WO3 nanofiber networks on stainless steels were chemically modified, filled with a lubricant, and prepared as SLIPS with excellent liquid repellency and good anti-biofouling properties. The relationship of the nanostructures and the slippery properties of the obtained WO3-based SLIPS have been investigated in detail in this work. The liquid retention and long-term stability of the SLIPS were characterized using high shear force and water flow impact. We found that the long-term durability of the SLIPS is strongly related to the diameters and the Brunauer-Emmett-Teller surface areas of the WO3 nanostructures. The durability of the SLIPS is better when the diameter of the WO3 nanostructures is smaller. The WO3-based SLIPS prepared in this work exhibit outstanding slippery property, anti-biofouling, and long-term stability under extreme conditions such as high shear rate and water washing and thus may have potential application for surface modification of medical devices in the future.

Application of Diversion Construction Technology in Hydraulic Engineering Construction

Since the reform and opening up, China’s various construction undertakings have developed rapidly, especially the water conservancy engineering undertaking. As a basic industry for national economic development, it has achieved leapfrog development. Water conservancy projects play an important role in the development of China’s industry, agriculture and people’s daily life, it can promote the development of production and life, and improve people’s quality of life. Diversion construction technology is a widely used and important construction technology in basic water conservancy projects. It can reduce the impact of water flow during the construction process by using related technical measures, while ensuring the quality of water conservancy projects and improving the construction efficiency of the entire project. And other aspects have played an important role that cannot be replaced. This paper started with a brief description of diversion construction technology, and then studied the application of diversion construction technology in water conservancy projects.

Ultrafast laser hybrid fabrication of hierarchical 3D structures of nanorods on microcones for superhydrophobic surfaces with excellent Cassie state stability and mechanical durability

Superhydrophobic surfaces have been attracting considerable attention due to potential applications in self-cleaning, anti-icing, water/oil separation, drag reduction, water collection, etc. However, to date, except for a few textile surfaces and coating products, only a limited number of superhydrophobic applications have been commercialized. The main reasons for the limited number of applications are attributed to the poor Cassie state stability and inadequate mechanical durability of superhydrophobic surfaces. Although numerous efforts have been invested to improve the Cassie state stability or mechanical durability of such surfaces, the surfaces with both acceptable Cassie state stability and mechanical durability have been rarely reported. In the present study, a 3D hierarchical structure composed of nanorods on periodically structured microcones was fabricated on a copper surface by an ultrafast laser–chemical hybrid method. The effect of microcone heights of the proposed structures on the Cassie state stability and mechanical durability was investigated. It is demonstrated that Cassie state stability of the manufactured surfaces could be improved efficiently by increasing the microcone height. However, when the height of the microcone gets to a certain magnitude (e.g., 50 μm in present study), a further increase of microcone height has a little influence on the stability of the Cassie state. The mechanical durability study shows that the superhydrophobic surface with the optimal microcone height could withstand 500 tape peeling cycles in a tape peeling test, 4 abrasion cycles in a linear abrasion test, and 35 min of water flow impact, before the contact angle decreases to 150° and the sliding angles increase to 10°, indicating good mechanical durability. Our proposed structures with both great Cassie state stability and mechanical durability could be promising candidates for many potential applications such as for solar cells, infrared sensors, and some space-related equipment, among others.

Radial propagation of yield-power-law grouts into water-saturated homogeneous fractures

This study presents analytical solutions for single-phase radial flow of yield-power-law fluids between homogeneous fractures (smooth parallel plates), which covers the special cases of yield-power-law fluids, i.e., Herschel-Bulkley, Bingham and power-law fluids, as well as Newtonian fluids. The analytical solution for radial flow of Herschel-Bulkley fluids is given for the first time. A formula for the plug flow region created by the yield stress is deduced, showing that this is constant and independent of the radius for radial flow of yield-stress fluids, which is also verified by numerical simulations. For modeling of the rock grouting process where the yield-power-law grouts are injected into water-saturated fractures, we also established a general mathematical model for the two-phase (one yield-power-law grout and one Newtonian fluid) radial flow in homogeneous fractures using the Reynolds equation based on the derived analytical solutions for single-phase radial flow of yield-power-law grouts. By solving the two-phase radial flow problem, the evolution of pressure distribution and grout propagation length is illustrated. The results generally show the high sensitivity of the rheological parameters and the potentially important impact of water flow and time-dependent rheological properties on the radial propagation of yield power-law grouts.

Assessing the role of thermal erosion in channel deformation processes in rivers of permafrost zone

The study is focused on the deformations caused by the impact of water flow in a river channel composed of melt-able permafrost rocks. It is based on the results of laboratory and mathematical simulation. The results of numerical calculations are compared with data of laboratory and field observations. The study shows that a comprehensive and adequate model of river channel deformations should take into account not only ablation, but also other factors, including heat transfer in the soil, sediment transport, and bank slope collapses. Numerical experiments with an improved mathematical model, applied to long time intervals, have shown that the differences between the averaged deformations, calculated by a model of ablation alone, i.e., ignoring bank slope collapses and sediment transport, and a comprehensive model can be considerable. Experiments in a hydraulic flume were good enough to reproduce the effect of delayed collapse, consisting in nonsimultaneous impacts of channel-forming rock melting and a freshet.

Research on Correction Methods of Errors in Multi-beam Sounding Resulted from Water Flow

The multi-beam sounding system combines multi-beam bathymetry and integrated navigation technology, which can obtain underwater topography data quickly and accurately, it has become the most important way of marine investigation. Therefore, it is urgent for improving the accuracy of sounding system in the detection industry. During the study of multi-beam error processing, the installation error coefficient of transducer installation will be corrected, but all the time, the transducer mounting bracket is regarded would be corrected. However, the transducer mounting bracket has been regarded as a rigid body in the correction for a long time. In this paper, the transducer bracket is regarded as a non-rigid body, and the reversible elastic deformation of transducer bracket occurs due to the impact of water flow. With the change of ship speed and water flow velocity, the degree of elastic deformation is also time-varying. The elastic deformation of bracket leads to the deflection of transducer shafting, which can not be corrected when correcting the installation deviation, so that leading to the influence of this error in final sounding results. This paper aims at the fact of deformation of multi-beam bracket caused by the water flow velocity, ship speed etc., leading to the deflection of transducer relative to the deviation of inertial navigation system shafting and resulting in attitude deviation which affect accuracy of result is researched.

Evaluation of dynamic impact of flow with bridge pier using smoothed particle hydrodynamics method

This paper presents a numerical model for the hydrodynamic impact of water flow with a bridge pier placed on a group of piles using the smoothed particle hydrodynamics (SPH) method. A new boundary processing technique using a combination of ghost particles and dynamic boundary particles is implemented in the SPH simulations of this study. The numerical probes are uniformly distributed over the vertical surface of the structure in order to obtain detailed measurements of the flow pressure on the structure over time. Using the SPH simulations, the velocity field of the unstable flow surrounding the piles and the equivalent hydrodynamic force acting on the pile cap are determined. The vulnerable impact locations on the structure surface are also predicted from the time-pressure histories. Additionally, the predicted hydrodynamic pressure values are compared with those proposed by AASHTO (2012) for bridge design considerations.

Evaluation of dynamic impact of flow with bridge pier using smoothed particle hydrodynamics method

This paper presents a numerical model for the hydrodynamic impact of water flow with a bridge pier placed on a group of piles using the smoothed particle hydrodynamics (SPH) method. A new boundary processing technique using a combination of ghost particles and dynamic boundary particles is implemented in the SPH simulations of this study. The numerical probes are uniformly distributed over the vertical surface of the structure in order to obtain detailed measurements of the flow pressure on the structure over time. Using the SPH simulations, the velocity field of the unstable flow surrounding the piles and the equivalent hydrodynamic force acting on the pile cap are determined. The vulnerable impact locations on the structure surface are also predicted from the time-pressure histories. Additionally, the predicted hydrodynamic pressure values are compared with those proposed by AASHTO (2012) for bridge design considerations.

Durable superhydrophobic surface prepared by designing “micro-eggshell” and “web-like” structures

A durable superhydrophobic PVDF/FAC-SiO 2 /CNF coating with stable superhydrophobicity was prepared by designing “egg-shell” and “web-like” structures. Combined with the eggshell and web-like structure, the stable air cushion trapped on the PVDF/FAC-SiO 2 /CNF SHC surface can provide excellent hydrophobic stability, even for slurry, hot water or 98% H 2 SO 4 . • A novel superhydrophobic coating was successfully prepared by designing ‘micro-eggshell’ and ‘web-like’ structures. • The locked gas of “egg-shell” and “web-like” can enhance the hydrophobic stability of the coating surface. • The PVDF/FAC-SiO 2 /CNF coating can withstand hot water immersion or 98% H 2 SO 4 dumped. • The prepared coating possesses high charge transfer resistance (1.44 × 10 10 Ω cm 2 ) after 30 d immersion. Superhydrophobic surfaces (SHSs) have drawn a lot of interest in both academic and industry by its special wettability, but most artificial SHSs suffer from their poor hydrophobic and mechanical durability. Here, a durable PVDF/FAC-SiO 2 /CNF superhydrophobic coating (SHC) was successfully fabricated by designing “egg-shell” and “web-like” structures. We have in situ loaded nano-SiO 2 particles on the azodicarbonamide (AC) surface to provide a layer of barrier, which can prompt the formation of a special egg-shell structure after AC thermal decomposition. Moreover, CNF divided the pore structure to smaller spaces by forming web-like structure in the coating surface. Cooperation of the egg-shell and web-like structures, the PVDF/FAC-SiO 2 /CNF SHC surface can lock the gas stably and block the diffusion of corrosive media into the coating. Therefore, the prepared PVDF/FAC-SiO 2 /CNF coating can withstand 250 kPa water flow impact and possesses high charge transfer resistance (1.44 × 10 10 Ω cm 2 ) after 30 d immersion in 3.5 wt% NaCl solution. Furthermore, the prepared coating also exhibited outstanding mechanical and hydrophobic stability, which can maintain its superhydrophobicity even after 1000 abrasion cycles, hot water immersion, or dealing with 98% H 2 SO 4 . This fabrication process is scalable and provides a new avenue for the fabrication of robust superhydrophobic coatings.

Transparent and robust SiO2/PDMS composite coatings with self-cleaning

ABSTRACTIn recent years, people have paid increasing attention to improving the durability of highly transparent superhydrophobic surfaces. In this work, we first synthesized a superhydrophobic silica powder by using a one-step sol–gel method and then compounded it with Polydimethylsiloxane. After spin-coating on the glass surface, a transparent superhydrophobic glass with a high water contact angle (158°) was acquired. In the visible region (400–800 nm), the transmittance of the coated glass substrate was higher than 80%. Moreover, the obtained coating can maintain stable superhydrophobicity after undergoing treatment from −15 to 450°C and under extreme environmental conditions, such as strong acidity and alkalinity. In addition, the coating can maintain excellent superhydrophobicity even after exposure to a large amount of water flow impact.

A Cross-current Masonry Technology for River Pole and Rock Dam in Distribution Network Maintenance and Construction

Some areas of the distribution network involve the installation of line poles through seasonal ditches or channels. In the design of rock dam construction, the traditional method has great resistance to water, which reduces the service life of rock dam itself after the formation of severe scouring. In this paper, the masonry technology of rock dam is analyzed, and a kind of cross-current dam masonry technology is designed to reduce the impact of water flow, which solves the problem of rock dam damaged by the impact of water flow and extends the practical service life of rock dam greatly.

Fast Defect Detection on Primary Pump Pipe for RSG-GAS Reactor Using Acoustics Emission Techniques

RSG-GAS reactor is one of the research reactors owned by National Nuclear Energy Agency of Indonesia (BATAN) which has been operated since 1987 and utilized its neutrons for radioisotope production and other research activities, and heat caused by nuclear fission reactions is discharged into the environment. To remove the heat is required coolant pumps taking heat from the reactor core to the environment. The RSG-GAS coolant pump consists of a primary coolant and secondary coolant with a heat transfer capacity of 33,000 kW and 5,500 kW respectively. The primary coolant pump takes heat directly from the core and the heat is then transported to the secondary coolant pump system as it passes through the heat exchanger. It then discharges the environment by the cooling system secondary on the cooling tower by blowing using a blower that works counter flow to the direction of the coolant flow. The drainage from the reactor core into the environment requires pipeline from the component system to other components at the pump. Since RSG-GAS reactor has reached 30 years, the RSG-GAS reactor coolant system has aging experienced and decrease of its performance. The occurrence of sound and vibration in the cooling primary pipe indicated a defect location or cavitation due to hard impact of water flow and exposure of gamma radiation on the pipe wall continuously during reactor operation. To ensure the occurrence of defect location, it is necessary to conduct research and testing on the material structure of the cooling pump pipe. Testing and research on the structure of the cooling pipe material can not be done by disassembling the pipes because it is installed firmly and is at risk of high exposure gamma radiation. It is, therefore, nondestructive test method (NDT), one of them using acoustic emission method, should be applied. The experiments to detect the location defect on pipe of primary cooling pump of RSG-GAS reactor have been conducted. The results on this research showed primary cooling pump pipe degradation and low cavitation existence.

Analysis of Hydrodynamic Performance of L-Type Podded Propulsion with Oblique Flow Angle

In this study, the Reynolds-averaged Navier–Stokes (RANS) method and a model experimental test in a towing tank are used to investigate the unsteady hydrodynamic performance of L-type podded propulsion under different oblique flow angles and advance coefficients. The results show that the load of the operative propeller increases with oblique flow angle and the bracket adds resistance to the pod due to the impact of water flow, leading to a reduced propeller thrust coefficient with increased oblique flow angle. Under a high advance coefficient, the speed of increase of the pressure effect is higher than that of the viscosity effect, and the propeller efficiency increases with the oblique flow angle. The nonuniformity of the inflow results in varying degrees of asymmetry in the horizontal and vertical distributions of the propeller blade pressure. Under high oblique flow angle, relatively strong interference effects are seen between venting vortexes and the cabin after blades, leading to a disorderly venting vortex system after the blade. The numerical simulation results are in good agreement with the experimental values. The study findings provide a foundation for further research on L-type podded propulsors.