Hydrodynamic Tests Research Articles

Marine algae biomass energy source is increasing getting approval from policy maker and community. Beside production of seaweed for biomass energy, seaweed plantation has benefit for food, cosmetic, gelatin and pharmaceutical products. Large production of biomass will require deployment of very large multibody floating structure offshore. To ensure that the system is reliable, design needs to be built, a mooring

Marine algae biomass energy source is increasing getting approval from policy maker and community. Beside production of seaweed for biomass energy, seaweed plantation has benefit for food, cosmetic, gelatin and pharmaceutical products. Large production of biomass will require deployment of very large multibody floating structure offshore. To ensure that the system is reliable, design needs to be built, a mooring component for the mooring system, need to be properly sized to provide reliable strength for position keeping. This paper present, result of hydrodynamic test carried in UTM lab to determine coefficient required for the design and simulation of mooring system for very large floating structure for offshore aquaculture structure for ocean plantation, the paper also present safety and efficiency of the mooring system. Hydrodynamic test is traditionally used to secure coefficient require for design for environment for ship structure and offshore platform hydrodynamic interaction. The case of seaweed biomass is unique because the seaweed interacts directly and moves with the environment. The obtained the coefficient is used to model the static moorings system that assess the tension, tilt, safe mass and motion of the mooring components. Interpolated time dependent currents from the towing tank are used to estimate dynamic response of the mooring as well as the draft of the mooring components, the overall analysis is use to select required mooring components of the system. The outcome of the test presented in this paper will help for future development of offshore aquaculture system and multibody system deployment and analysis

Hydrogel Coating Optimization to Augment Engineered Soft Tissue Mechanics in Tissue-Engineered Blood Vessels.

Tissue engineering has the advantage of replicating soft tissue mechanics to better simulate and integrate into native soft tissue. However, soft tissue engineering has been fraught with issues of insufficient tissue strength to withstand physiological mechanical requirements. This factor is due to the lack of strength inherent in cell-only constructs and in the biomaterials used for soft tissue engineering and limited extracellular matrix (ECM) production possible in cell culture. To address this issue, we explored the use of an ECM-based hydrogel coating to serve as an adhesive tool, as demonstrated in vascular tissue engineering. The efficacy of cells to supplement mechanical strength in the coating was explored. Specifically, selected coatings were applied to an engineered artery tunica adventitia to accurately test their properties in a natural tissue support structure. Multiple iterations of three primary hydrogels with and without cells were tested: fibrin, collagen, and gelatin hydrogels with and without fibroblasts. The effectiveness of a natural crosslinker to further stabilize and strengthen the hydrogels was investigated, namely genipin extracted from the gardenia fruit. We found that gelatin crosslinked with genipin alone exhibited the highest tensile strength; however, fibrin gel supported cell viability the most. Overall, fibrin gel coating without genipin was deemed optimal for its balance in increasing mechanical strength while still supporting cell viability and was used in the final mechanical and hydrodynamic testing assessments. Engineered vessels coated in fibrin hydrogel with cells resulted in the highest tensile strength of all hydrogel-coated groups after 14 d in culture, demonstrating a tensile strength of 11.9 ± 2.91 kPa, compared to 5.67 ± 1.37 kPa for the next highest collagen hydrogel group. The effect of the fibrin hydrogel coating on burst pressure was tested on our strongest vessels composed of human aortic smooth muscle cells. A significant increase from our previously reported burst pressure of 51.3 ± 2.19 mmHg to 229 ± 23.8 mmHg was observed; however, more work is needed to render these vessels compliant with mechanical and biological criteria for blood vessel substitutes.

Development of a new low-volume oxygenator and creation of a hydrodynamic test bench for ex vivo lung perfusion in small animals

Small animal models are widely used in basic research. However, experimental hydrodynamic test benches, which include extracorporeal circuits, often have limitations associated with the size and filling volume of equipment. Thus, we aimed at developing and validating a miniature oxygenator as well as a low-volume hydrodynamic system for ex vivo perfusion of small animal lungs. A series of low-volume membrane oxygenators (n = 10) with 90–100 aligned microporous polypropylene hollow fibers, placed inside a sheath that is sealed at both ends to isolate the perfusing solution, was designed and manufactured. This design makes gas to flow through the hollow fibers and perfusate to circulate around the fibers. A low-volume hydrodynamic test bench was designed and assembled for isolated ex vivo lung perfusion and for evaluation of the performance characteristics of the oxygenators: gas and perfusate flow, perfusion pressure and temperature at 5–70 ml/min flow range.

ADVANTAGES AND DISADVANTAGES OF HEART VALVE PROSTHESES WITH FLEXIBLE SUPPORTING FRAME COMPARED WITH THE CLASSIC STENTED PROSTHESES: EVALUATION OF THE HYDRODYNAMIC INDICATORS OF THE “UNILINE” AND “TIARA” BIOPROSTHESES

HighlightsThe «TiAra» bioprosthetic heart valves have better hemodynamic characteristics, such as higher effective orifice area and a lower mean pressure gradient.The «UniLine» bioprosthetic heart valve demonstrated better closing dynamic, expressed in a smaller regurgitation volume. Aim. To assess hydrodynamic characteristics of the «TiAra» bioprosthetic heart valve with flexible supporting frame compared with the classic stented «UniLine» bioprosthetic aortic valve.Methods. Using the Vivitro Pulse Duplicator (Vivitro Labs, Canada), we simulated the function of the heart via generating pulsatile flow to analyze bioprosthetic heart valves. To comprehensively assess the bioprosthesis function, three valves of each standard size (21, 23, 25 mm) were submitted to hydrodynamic testing, thus making a sample of nine bioprostheses of each model. The article provides the analysis of the effective orifice area, mean pressure gradient, regurgitation volume, and assessment of the statistical sensitivity of the parameters between groups at p = 0.05.Results. The assessment revealed that the «TiAra» bioprosthesis has bigger effective orifice area (p = 0.006) and lower mean pressure gradient (p = 0.02): 1.6–2.2 cm2 and 3.6–6.3 mmHg versus 1.08–1.73 cm2 and 4.8–12.1 mmHg, respectively. The regurgitation volume, however, was lower in the «UniLine» bioprostheses 0.8–4.1 mL/cycle versus 6.2–9.0 mL/cycle (p = 0.0004).Conclusion. Despite the fact that both studied models showed good hydrodynamic performance, the prosthesis with the flexible supporting frame («TiAra») showed better results regarding its effectiveness in vitro via presenting with bigger effective orifice area and lower mean pressure gradient. At the same time, the «UniLine» stented bioprosthesis had lower regurgitation volume, i.e. better closing dynamics.

Hydrodynamic Tests of Innovative Tourist Submarine

This paper deals with the resistance, towing, seakeeping, and open water propeller tests of an innovative tourist submarine model. Tests were performed in a 276 m long towing tank. As the submarine model is a complex structure composed of various parts attached to the pressure hull, the largest possible model, in the scale of 1:5.0, was produced, considering the towing tank depth and the capabilities of the measurement equipment. Resistance tests were performed in deep water and on the surface in calm water. The tested speed range in both cases was up to 5.5 knots. To ensure the avoidance of free surface effects, resistance tests in deep water were performed for different draughts and then extrapolated to infinite water depth. Smaller effective powers were found for the surface condition. The results are compared to an independently performed computational fluid dynamics (CFD) analysis using OpenFOAM. A fair agreement between the experimentally and numerically predicted effective power is found, while the reasons for the differences found are explained. The free submarine model was towed with a rope performed for the speed range 1.7 kn–3.5 kn, and the towing force in the rope was measured. Seakeeping tests in irregular beam waves at zero speed were performed to check the flooding risk on open hatches. Open water tests of the main thrusters for propelling the submarine were conducted, indicating that both power demand and propeller thrust are slightly larger compared to the initial estimates.

CARD33: Analyzing Off-Design Point Operation for LVADs Using Flexible Rotor Blades

Introduction: The use of left ventricular assist devices (LVADs) has exhibited clinical success in both destination and bridge-to-transplant therapy for patients suffering from end stage heart failure (HF). However, the operating speeds of the LVAD are often tuned to accommodate patient variability which might lead to operating the LVAD at off design points. This could cause a potential loss in efficiency and an increased risk of thrombosis/hemolysis. The flexible rotor blades will deform in response to the complex inflow conditions, and with an appropriate geometry and flexibility generate a flatter performance curve. This would not only improve the preload sensitivity of the LVAD but also offer a wider range of operation with optimal efficiencies. In this study, we investigate the hydraulic performance of varied impeller geometries for a centrifugal LVAD with flexible rotor blades at pediatric and adult pressure/flow conditions. Methods: The flexible rotor blades are manufactured by casting polyurethane resin (Easton, PA) of shore hardness 60A in a four-piece mold. These mold pieces were 3D printed using a J850 Pro (Stratasys Ltd, MN, USA). The inlet angle of the blades was set at 20o and the outlet angle was varied from 10o to 70o. The blade thickness was 1.2 mm and the blade height was 7 mm. These flexible rotor blades were evaluated on a hydrodynamic test setup with 40%wt glycerin solution as the working fluid. This setup consisted of a motor to drive the rotor, a flow probe, pressure transducers upstream and downstream of the rotor and a pinch valve to vary the downstream resistance. The mounted rotor is driven at 3000 RPM, and the flow produced by the rotor is measured as the pinch valve incrementally increases downstream resistance. The hydrodynamic results were then scaled to achieve pediatric and adult pressure/flow conditions of 70mmHg-2L/min and 90mmHg-5L/min respectively. To analyze the off-design point operation, the gradient of the pressure/flow curve at two operating conditions was calculated using the equation in Figure 1. Results: For a flexible rotor blade with an outlet angle of 30o, the operating speed for pediatric and adult pressure/flow conditions was found to be 2550 RPM and 3230 RPM respectively. The gradient at the pediatric and adult operating conditions was – 6.14 mmHg/ (L/min)-1 and – 11.12 mmHg/ (L/min)-1. Results for the remaining flexible rotor blades is currently being generated and will be presented at the conference. Conclusion: We successfully analyzed the hydraulic performance of a centrifugal LVAD with flexible rotor blades. The flexible rotor blades proposed in this study will be a positive step towards improving the off-design point operation of LVADs and thereby, reducing the blood damage associated with it.Figure 1. Equation used to calculate the gradient of the pressure/flow curve at two operating conditionsFigure 2. Hydrodynamic Test Setup SchematicFigure 3. Hydrodynamic Performance Results for Flexible Rotor Blade with 30o Outlet Angle

Experimental Study on Hydrodynamic Aspects of Turbine which Convert Hydrokinetic and Potential Coastal Wave Energy

Currently, the exploration of ocean renewable energy sources was mostly carried out to obtain optimal results and low cost. The waves that arrive on the beach consist of both potential energy where the water surface moves up and down and hydrokinetic energy where the volume of water comes and goes into the beach sand. They had the potential to be converted to electricity. This paper explained the study of the hydrodynamic aspects of turbines that convert hydrokinetic and potential coastal wave energy. The vertical axis darrieus turbine was modified to catch both energies. It could convert energies from hydrokinetics and the potential of waves simultaneously, whereas a vertical axis turbine with 6 horizontal blades and 3 vertical blades in a shaft. Testing was done at the testing Tank, Hydrodynamic Technology Research Center, National Research and Innovation Agency. The hydrodynamic tests were with 3 turbine variations, wave variations, and current velocity. The test results, vertical axis turbines with horizontal blades could receive wave energy, due to the orbital motion of water particles and vertical blades were very effective in receiving current energy so that turbines with 2 types of vertical and horizontal blades could convert wave and current energy.

Experimental study on the dynamic responses of the end‐anchored floating bridge subjected to joint actions of earthquakes and water waves

AbstractThis study experimentally investigates a dynamic behavior of an end‐anchored floating bridge under the joint actions of earthquakes and water waves. A truncated model with a geometrical scale of 1:100 was utilized for the hydrodynamic test, and an actuator was used to generate the earthquake input. A series of trials were conducted for the floating bridge model under the combined action of two different sea states and three earthquake inputs with increasing intensity based on the concept of the incremental dynamic analysis method. For comparison, the dynamic responses of the floating bridge model under earthquake action in still water and pure wave action were also conducted. Based on the test data, the dynamic responses, particularly focused on the sway, heave, roll, and pitch motions of the pontoons, of the test model were experimentally analyzed. The experimental results showed that earthquake excitation along the longitudinal axis of the bridge girder would induce noticeable oscillation of the bridge pontoons in still water. The magnitude of the coupled effects of earthquakes and water waves is dependent on the intensity of the earthquake inputs and the sea state.

Experimental Investigation of the Hydrodynamic Characteristics of Longline Aquaculture Facilities under Current and Wave Conditions

In this study, a longline aquaculture facility with lantern nets off the coast of northern China was modelled to conduct hydrodynamic tests starting from the culture unit to the entire facility under various current and wave conditions. The experimental results indicated that the drag coefficients of the lantern net model with weights of 0.5, 0.75, and 1.0 kg were 0.75, 0.83, and 0.91, respectively, in the Reynolds number range of 1 × 104–1 × 106. The current-driven upstream mooring line was more dominant than the wave-driven tension, and a simplified model of the longline facility accurately predicted the mooring line tension under the current conditions. The scope of the mooring line (defined as the length of the mooring line related to the water depth) played an important role in eliminating an order of magnitude difference in mooring tension under the wave conditions. The amplitudes of the vertical movement of the longline facility were smaller than the wave height when L/Lm was less than 1.5. Therefore, detailed information is needed to better understand the hydrodynamic characteristics and motion response of longline aquaculture facilities for the safe operation of longline structures in offshore environments, in order to process high-quality oyster products.

Directly irradiated fluidized bed autothermal reactor (DIFBAR): Hydrodynamics, thermal behaviour and preliminary reactive tests

The advancements of the Concentrating Solar Thermal (CST) technologies in the heat and power sector are pushing researchers to find new ways to exploit solar energy. Solar-driven thermochemical processes can open new scenarios and set a milestone towards a greener industry. This paper presents the development of a Directly Irradiated Fluidized Bed Autothermal Reactor (DIFBAR), that exploits fluidization technology and the principle of an autothermal reactor to carry out solar chemical processes with high efficiency. The viability of recovering the sensible energy of the solid products to preheat the reactants is studied in an experimental prototype that couples a cavity receiver/reactor and a countercurrent double-pipe heat exchanger. The prototype is operated as a circulating fluidized bed: the inner tube of the heat exchanger is a fluidized bed riser, the receiver works as a gas–solid separator, the outer tube (annulus) of the heat exchanger is an overflow standpipe and a buffer tank (reservoir) connects the annulus to the riser, closing the loop. The reservoir can also be operated as a fluidized bed reactor like in a dual-fluidized bed system. The first experimental results are reported using a Geldart B sand as bed inventory. A hydrodynamic study has been carried out to verify proper control of the system. Solid circulation rates have been determined and match the design target of 1.4 g/s. Pressure measurements have been used to control bed levels and the flow of the sand through the standpipe. The effects of gas velocities and outlet pressure drops are reported. Internal gas flow patterns have been determined by a gas tracing technique. Undesired gas by-passing streams are very small and can be zeroed by regulating the operating conditions. High temperature experiments have been conducted with a high-flux solar simulator under inert and reactive conditions, to prove the operating principle of the reactor. Steady state temperature profiles have been analyzed to assess the performance of the heat exchanger: the heat transfer coefficient ranges between 340 and 490 W/(m2 K). The operability of a solar-driven chemical process has been proved by calcining a batch of magnesium carbonate (MgCO3) particles, added to the inventory.

Analysis of the main factors determining the value of the specific flow rate of a water well

Purpose of research – numerical characterization of the main factors affecting the value of the specific flow rate of a water well. The relevance of the study is due to the possibility of using the obtained functional relationships to predict the value of the specific flow rate of a water well. Research methods: interpretation of gamma logging curves of water wells, correlation of its results with the core survey data, interpolation of the obtained values over the section area, processing of hydrodynamic well testing materials, comparison of its results with the data of geophysical research, establishment of statistical relationships between the parameters. The results of the study and their application. It was found that the value of the double difference parameter of natural radioactivity of water-bearing rocks statistically significantly correlated with the value of the clay content of core samples, studied in the laboratory way, as well as with the value of water permeability of rocks determined by hydrodynamic tests wells, which allows using this parameter to characterize the filtration properties of rocks aquifer by the value of their clay content. Significant statistical relationship was obtained between the specific flow rate of the water intake well and water conductivity of water-bearing rocks, the parameter of imperfection of the well by the nature of the formation opening, as well as the parameter, numerically equal to the ratio of the well filter length to the value of the double difference parameter of natural radioactivity of rocks of its installation interval. The presence of statistical uncertainty in the relationships is due to the mutual influence of the parameters. The obtained functional relations can be used in the design of wells. Conclusions. During the study the assumption was confirmed that water intake wells with the longest water intake part, equipped in the least clayey and, accordingly, more water-permeable interval of aquifer have the least value of imperfection by nature of formation opening and are able to provide the highest specific flow rate. Such wells are the most effective in operation.

First Experience of Hydrodynamic Testing of Pediatric Heart Valve Bioprostheses in the Aortic Position

First Experience of Hydrodynamic Testing of Pediatric Heart Valve Bioprostheses in the Aortic Position

Investigation of Flow and Spectral Characteristics in a Flow-Flow Hydrodynamic Generator of the Flat Type with Changes in the Degree of Flow Blockage

The paper presents the results of studying the flow past cylindrical bodies located in a flattype flow-through hydrodynamic generator. The result were obtained on the hydrodynamic test bench of the experimental base of the Scientific Center of the Mechanical Engineering Research Institute of the Russian Academy of Sciences with the degree of flow blockage by the bluff bodies St /S0 = 10– 82%, the Re numbers (0.5–5) × 105 , and the inlet pressure Рin= 0.1–0.9 MPa. It was found that at certain values of the inlet/outlet pressure ratio, which are constant for each of the degrees of flow blockage, powerful resonant-type pressure peaks arise at frequencies of 0.5–5 kHz with the amplitude more than 4–5 times higher than the maximum inlet pressure.

Experimental Study on the Dissolution Characteristics and Microstructure of Carbonate Rocks under the Action of Thermal-Hydraulic-Chemical Coupling.

Microdamage in a rock induces a change in the rock's internal structure, affecting the stability and strength of the rock mass. To determine the influence of dissolution on the pore structure of rocks, the latest continuous flow microreaction technology was used, and a rock hydrodynamic pressure dissolution test device simulating multifactor coupling conditions was independently developed. The micromorphology characteristics of carbonate rock samples before and after dissolution were explored using computed tomography (CT) scanning. To conduct the dissolution test on 64 rock samples under 16 groups of working conditions, 4 rock samples under 4 groups were scanned by CT under working conditions, twice before and after corrosion. Subsequently, the changes in the dissolution effect and pore structure before and after dissolution were quantitatively compared and analyzed. The results show that the dissolution results were directly proportional to the flow rate, temperature, dissolution time, and hydrodynamic pressure. However, the dissolution results were inversely proportional to the pH value. The characterization of the pore structure changes before and after sample erosion is challenging. After erosion, the porosity, pore volume, and aperture of rock samples increased; however, the number of pores decreased. Under acidic conditions near the surface, carbonate rock microstructure changes can directly reflect structural failure characteristics. Consequently, heterogeneity, the presence of unstable minerals, and a large initial pore size result in the formation of large pores and a new pore system. This research provides the foundation and assistance for predicting the dissolution effect and evolution law of dissolved pores in carbonate rocks under multifactor coupling, offering a crucial guide for engineering design and construction in karst areas.

Active galactic nuclei jets simulated with smoothed particle hydrodynamics

ABSTRACTSimulations of active galactic nuclei (AGN) jets have thus far been performed almost exclusively using grid-based codes. We present the first results from hydrodynamical tests of AGN jets, and their interaction with the intracluster medium (ICM), using smoothed particle hydrodynamics as implemented in the swift code. We launch these jets into a constant-density ICM, as well as ones with a power-law density profile. We also vary the jet power, velocity, opening angle, and numerical resolution. In all cases we find broad agreement between our jets and theoretical predictions for the lengths of the jets and the lobes they inflate, as well as the radii of the lobes. The jets first evolve ballistically, and then transition to a self-similar phase, during which the lobes expand in a self-similar fashion (keeping a constant shape). In this phase the kinetic and thermal energies in the lobes and in the shocked ICM are constant fractions of the total injected energy. In our standard simulation, two thirds of the initially injected energy is transferred to the ICM by the time the jets are turned off, mainly through a bow shock. Of that, $70{{\%}}$ is in kinetic form, indicating that the bow shock does not fully and efficiently thermalize while the jet is active. At resolutions typical of large cosmological simulations (mgas ≈ 107 M⊙), the shape of the lobes is close to self-similar predictions to an accuracy of $15{{\%}}$. This indicates that the basic physics of jet-inflated lobes can be correctly simulated even at such resolutions (≈500 particles per jet).

Three-Dimensional Numerical Simulation of Flow Structure in Annular Flume Based on CFD Study of Water

The annular flume is an ideal hydrodynamic test device for studying river sediment, and it has been widely used in recent years to study the movement patterns of sediment and other particulate matter. Annular flumes have made outstanding contributions to research in fields related to sediment transport and the diffusion and migration of pollutants. The existence of circumfluence structures in annular flumes leads to complex and variable flow structures. To obtain a more stable and controllable water flow structure, a sophisticated three-dimensional mathematical model based on the Fluent software was established to study the development law of water flow structure in the flume by changing the size of the annular flume speed ratio. The results show the following: (1) The overall trend of the simulation results basically matched with the measured results; the average relative error was 3.54% and the Nash efficiency coefficient was 0.9934, close to 1. The model calculation data were highly credible. (2) The axial flow velocity of the water tank gradually showed a “U”-shape distribution with the increase in the speed ratio. (3) When the speed ratio was R ≤ 0.17 (where the speed ratio R refers to the ratio of annular groove to shear ring speed), there was only one vortex in the tank; when the speed ratio was R > 0.17, there were multiple vortices in the tank, and the flow pattern was more complicated. (4) When the rotational speed ratio R = 0.28, the secondary flow intensity of the annular flume reached the lowest point, which was only 39.28% of the secondary flow intensity of the conventional annular flume. (5) It was determined that the annular flume water flow structure was most stable and controllable when the rotational speed ratio R = 0.24. The results of the study can provide a further theoretical basis for research on sediment dynamics and its related fields conducted by applying an annular flume.

Timing of bioprosthetic valve fracture in transcatheter valve-in-valve intervention: impact on valve durability and leaflet integrity.

Bioprosthetic valve fracture (BVF) can be used to improve transcatheter heart valve (THV) haemodynamics following a valve-in-valve (ViV) intervention. However, whether BVF should be performed before or after THV deployment and the implications on durability are unknown. Aims: We sought to assess the impact of BVF timing on long-term THV durability. The impact of BVF timing was assessed using small ACURATE neo (ACn) or 23 mm SAPIEN 3 (S3) THV deployed in 21 mm Mitroflow valves compared to no-BVF controls. Valves underwent accelerated wear testing up to 200 million (M) cycles (equivalent to 5 years). At 200M cycles, THV were evaluated by hydrodynamic testing, second-harmonic generation (SHG) microscopy, scanning electron microscopy (SEM) and histology. At 200M cycles, the regurgitant fraction (RF) and effective orifice area (EOA) for the ACn were 8.03±0.30%/1.74±0.01 cm2 (no BVF), 12.48±0.70%/1.97±0.02 cm2 (BVF before ViV) and 9.29±0.38%/2.21±0.0 cm2 (BVF after ViV), respectively. For the S3 these values were 2.63±0.51%/1.26±0.01 cm2, 2.03±0.42%/1.65±0.01 cm2, and 1.62±0.38%/2.22±0.01 cm2, respectively. Further, SHG and SEM revealed a higher degree of superficial leaflet damage when BVF was performed after ViV for the ACn and S3. However, the histological analysis revealed significantly less damage, as determined by matrix density analysis, through the entire leaflet thickness when BVF was performed after ViV with the S3 and a similar but non-significant trend with the ACn. Conclusions: BVF performed after ViV appears to offer superior long-term EOA without increased RF. Ultrastructure leaflet analysis reveals that the timing of BVF can differentially impact leaflets, with more superficial damage but greater preservation of overall leaflet structure when BVF is performed after ViV.

Comparison of acoustic and hydrodynamic cavitation: Material point of view

This study investigated the difference in mechanical response of the martensitic stainless steel X3CrNiMo13-4/S41500/CA6 NM QT780 between hydrodynamic and acoustic cavitation erosion. The results show that acoustic cavitation erosion generates small pits at a high temporal frequency on the material, while hydrodynamic cavitation erosion produces larger pits at a lower frequency. Acoustic cavitation erosion tests have been performed using a 20 kHz ultrasonic horn located at 500 μm in front of a specimen. This experimental setup, known as an indirect method, is inspired from the ASTM G32 standard. Hydrodynamic cavitation erosion tests were conducted with classic experimental conditions of a PREVERO device: a cavitation number of 0.87 corresponding to a flow velocity of 90 m s−1 and an upstream pressure of 40 bars. In addition, for a given exposure time, the percentage of surface covered by the pits is smaller for acoustic cavitation than for hydrodynamic cavitation. Three successive steps have been identified during the damage process: persistent slip bands (PSB) first appear on the surface, cracks initiate and propagate at the PSB locations and nonmetallic interfaces, and finally, parts of the matter are torn off. A careful time examination of the same small area of the exposed sample surface by scanning electron microscopy reveals that acoustic cavitation is faster to initiate damage than hydrodynamic cavitation.

Theoretical analysis and simulation calculation of hydrodynamic pressure pulsation effect and flow induced vibration response of radial gate structure

This work aims to explore the characteristics of stochastic fluctuant water pressure acted on the surface of large radial gate, and to investigate the flow-induced vibration response of the whole radial gate structure. The finite element calculation model structure of the radial gate is established by taking a large-scale radial gate as prototype to discuss the hydrodynamic pressure acting on the gate leaf with different opening, analyze the dynamic pressure time curves, and achieve the flow-induced vibration response by deeming hydrodynamic pressure as dynamic load. When taking 10% opening of the radial gate, the results indicate that the hydrodynamic pressure distributed on the arc surface of the radial gate changes with the flow conditions, with the maximum pressure occurred at the center of the lower edge of the gate leaf. One point in the time history curve of fluctuating water pressure can be taken as the dynamic load for the flow-induced vibration analysis. The flow-induced vibration responses at the monitoring point of the radial gate structure show periodic changes in the X, Y, and Z directions. The finite element simulation results agree well with the theoretical calculation results, so reference can be provided for the hydrodynamic pressure testing and the flow-induced vibration response calculations.

Influence of groundwater extraction on rock filtration properties in the territory of the Latitudinal Ob region

The problem of groundwater protection in areas, where oil and gas production is taking place, is especially important today. The article focuses on the impact of groundwater extraction on the state of the filtration medium in small water bodies. Studies including hydrodynamic testing (cluster pumping) were being carrying out from 9 years at the same site. As a result of three exper-iments, experimental data were obtained, and then were interpreted in the framework of the Hantush model. The parameters of the aquifer are determined: coefficient of water conductivity and pressure conductivity factor, overflow factor, overflow coefficient. The article gives an analysis of changes in reservoir parameters. As a result, it was found that the long-term operation of ground-water in small water bodies also leads to an improvement in the state of the filtration medium, as well as in large deposits of fresh groundwater. It should be emphasized that in conditions of continuous extraction of groundwater the subsoil user should pay special attention to groundwater monitoring, namely, hydrodynamic studies, the results of which determine the hydrogeological parameters of the reservoir, and their changes indicate the state of the filtration medium.