Pressure Zone Research Articles

Ultra-sensitive strain sensor based on Sagnac interferometer with different length panda fiber

A high-sensitivity harmonic Vernier effect (HVE) strain sensor is fabricated by cascading Sagnac interferometer (SI) and Fabry-Perot interferometer (FPI). SI is fabricated by the panda fiber (PF). PF is a typical polarization maintaining fiber (PMF) that has two pressure zones, making it particularly sensitive to strain. SI1, SI2, and SI3 are constructed using PF with lengths of 20 cm, 50 cm, and 80 cm, respectively. They have interference spectra similar to sine waves in the wavelength range of 1250 nm to 1650 nm. Research has found that the sensitivity of SI is directly proportional to the effective PF length under strain action. In addition, if the strain acts on the entire length of the PF, the strain sensitivities of SI1, SI2, and SI3 are 30.4 pm/με, 28.4 pm/με, and 30.1 pm/με, respectively, which are relatively close. Then, FPI is fabricated by splicing single mode fiber (SMF) and quartz capillary, and it is an “SMF-Capillary-SMF” sandwich structure, and the free spectral range (FSR) of FPI is approximately half of that of SI2. FPI and SI2 are cascaded to produce a first-order HVE sensor, further amplifying the strain sensitivity of SI2. The intersection point of the internal envelope based on the HVE sensor spectrum can provide accurate spectral wavelength position and drift, and the strain sensitivity of the HVE sensor reaches 293.0 pm/με, improving the strain sensitivity of SI2 by 10.3 times. The detection limit of the HVE sensor is 0.5 µε as the strain varies from 0 to 700 µε. This HVE strain sensor is relatively easy to manufacture, low-cost, linear and reliable, and can achieve high sensitivity strain measurement. It has certain application value in the field of strain measurement.

Polynomial Excitation Current Compensation Control for Dead Zone and Hysteresis of Three-way Proportional Pressure Reducing Valve

Polynomial Excitation Current Compensation Control for Dead Zone and Hysteresis of Three-way Proportional Pressure Reducing Valve

Hydrodynamic performance analysis of swimming processes in self-propelled manta rays

To fill the research gap regarding the whole process (steady-state and nonsteady-state phases) of median and/or paired fin (MPF) mode swimming in underwater organisms, a two-degree-of-freedom self-propelled coupling method of motion and hydrodynamics based on user-defined functions of Fluent software was established, and numerical simulations were carried out for the startup, acceleration, and steady-state phases of manta rays. The interaction mechanism among the hydrodynamic characteristics, vortex evolution, and pressure distribution was investigated in the mentioned phases. We concluded that the negative pressure zone generated by the leading edge vortex and the shear layer contributes to thrust generation and changes in swimming velocity dominate the hydrodynamic characteristics by affecting the evolution of the shear layer and the leading edge vortex, with a 17.54% increase in forward average velocity in the fourth cycle compared to the third cycle and a consequent 9.5% increase in average thrust. In the end, the relationship between the formation of trailing edge vortex rings and changes in thrust was revealed. The vortex ring contributes to the increase in thrust, but the formation of the vortex ring comes at the cost of the loss of the leading edge vortex negative pressure zone, which greatly affects thrust, decreasing to 38.3% of its peak. The swimming mechanism revealed in this study provides a reference for the study of MPF-driven biodynamics and a new simulation strategy for the prediction of bionic navigator motions.

Dynamic Response and Damage Assessment of Partially Confined Metallic Cylinders Under Transverse Blast Loading

An analysis of the dynamic response and damage assessment of partially confined metallic cylinders under transverse air-blast loading is presented in this paper. The examination of the blast shock wave load distribution and the consequences of standoff distances on the plastic deformation of cylinders was conducted with meticulous attention in the experimental testing. The charges of TNT were determined to have masses of 16.3 kg and 29.5 kg, while the distances at which they were placed from the target varied between 1.5 m and 4.25 m. Three unique deformation modes were found to exist in the unilaterally supported cylinder, all of which were directly connected to the distribution of the blast load. In order to obtain an improved understanding of the dynamic behaviors exhibited in cylinders, a finite element simulation model was utilized and subsequently validated using an examination of the experimental results. The assessment of shock wave damage was conducted by utilizing the residual deformation of the metallic cylinder as an equivalent characterization under lateral blast shock wave loading. The duration of the positive pressure zone of the shock wave was determined to be between one-fourth and ten times the vibration period of a unilaterally supported cylinder, indicating that the P-I (overpressure-impulse) criterion could be utilized for damage evaluation. The incorporation of the P-I criterion was subsequently employed to evaluate the detrimental consequences, taking into consideration the radial distribution of residual deformation identified in metal cylindrical shell constructions subjected to lateral blast shock wave loading. This research contributed to a better comprehension of the dynamic behavior of partially confined metallic cylinders subjected to lateral blast loading and highlights the significance of the P-I criterion for evaluating and mitigating the damage effects in such scenarios.

ANALYSIS OF ACCIDENTS DURING DRILLING WITH FLOATING DEVICES IN THE CASPIAN SEA

At drilling of chinks on areas Gunashli, May 28, Bahar, Neft Dashları, Bulla with density of a chisel solution above (1.9-2,0)·104 N/m3 on depth 2000÷4500 m with balance in system the chink-layer is observed decrease in density of a chisel solution to 1,25÷1,30 g/sm3 with the subsequent open gas fountains. The gas getting in chink by diffusion basically comes to light at washing after lifting and descent of the boring tool. In trenches there are elements of the aerated solution, which density a little above before the circulating. Diffusion is the phenomenon caused by movement of molecules. A principal cause of diffusion of gas is presence of a gradient of concentration. Receipt of gas with diffusion from a layer in a chink will take place until gas molecules goes from a zone with high concentration in zones with low concentration, i.e. in chink. Getting to a chisel solution, diffusion gas, go up together with solutions and passing from zones of high pressures in zones low, extends, therefore its density decreases, that, in turn, conducts to decrease in hydrostatic pressure in a face of a chink and to serious complications. The article examines and analyzes the main causes of complications and accidents that arise during the construction, operation and repair of oil and gas wells, and leading to gas and oil shows, open fountains and fires in the fields of Azerbaijan. The ways in which complications arise during the extraction of hydrocarbons are briefly discussed. The conditions and nature of the occurrence of complications leading to accidents, gas manifestations, open fountains and fires are analyzed. Based on an analysis of the complications that arise during the construction, operation and repair of oil and gas wells, technologies and technical means are presented that make it possible to improve the quality of repair work carried out on oil and gas wells during their construction and operation. Equipment and tools for emergency response are considered. Technologies are proposed for eliminating accidents associated with the breakage and fall of downhole tool equipment onto the bottom, with cleaning the bottom of foreign objects, and with the elimination of stuck pipes. Modern technologies for eliminating gas shows and open fountains complicated by a fire at the mouth of a gushing well are proposed. In a chink it is required to make washing of a chisel solution for prevention of complications with closed preventer with dispersing of a boring column. Keywords: well, manifestation, gas, diffusion, pressure, washing solution.

Volcanic Unrest After the 2021 Eruption of La Palma

AbstractLa Palma, Canary Islands, had its largest historical eruption in 2021. From January 2022 to May 2023 there were >2,100 seismic events, primarily at depths ≤20 km, prompting us to update the deformation and modeling study, using interferometric synthetic aperture radar observations and a last generation interpretation tool. We detect the evolution of the remaining magmatic body in the SW portion of the island, with arrival of new magma moving into the oceanic crust out to sea, and a pressurized zone in the central‐eastern area, at regions of structural weakness. The current source characteristics have some similarities to the early stage dynamics prior to the 2021 eruption. Operational and multidisciplinary studies must continue to monitor either their stabilization or growth and destabilization. The ability to identify magma ascent using only deformation data over short time periods allows us to characterize unrest patterns and provide new insights into volcanic processes.

Effect of uneven inflow on hydrodynamic performance of bulb turbine

Abstract Bulb turbine unit is characterized by its low head, large discharge, and short flow passage. The guiding wall separating the power house section from the flood discharge section may cause uneven inflow before its neighbor units when the power house section is located off the river’s mainstream. In this study, selecting a bulb turbine hydropower station in China as the subject, we establish a three-dimensional CFD model that contains the full flow passage of the turbine unit and partial upstream reservoir, to analyze the effects of uneven inflow on the hydrodynamic performance of the bulb turbine. The results show that under this power station layout, flow separation occurs on the left side of the guiding wall, resulting in a low pressure zone and causing the flow in a three-dimensional vortical pattern. The low pressure and flow energy loss lead to the reduction of the neighbor units’ head, causing the discharge decreasing, and the output cannot reach the expectations. This situation can be improved by shortening the guiding wall, indicating that the unit’s performance is strongly related to the hydraulic structure arrangement. The results can provide some references for the design and operation of the related project.

Experimental study on the load bearing behavior of shored mechanically stabilized earth wall

Shored mechanically stabilized earth (SMSE) walls have been increasingly applied in the projects of widening existing roads or new construction of roads on slopes because of their good carbon emission reduction and mechanical performance. In this paper, a scaled-down model test of SMSE wall with shoring wall batter of 1H:2V was conducted to study the load-bearing behavior of SMSE wall under this terrain condition, and the results including wall deformations, earth pressures, reinforcement strains, and potential failure surface were analyzed. The results show that although the backfill near the shoring wall was not directly compressed by the load, it still slipped along the backfill-shoring wall interface. The loading created a tensile pressure zone in the upper part of the backfill-shoring wall interface, which may lead to tensile cracking. The uppermost layer of geogrid was more prone to sliding, while the tensile deformation was smaller, and its strain value was overall smaller than the strain value of the geogrid below it. As the load increases, the potential failure surface changed from a Rankine failure surface to a bilinear potential failure surface. The potential failure surface did not pass through the heel of the SMSE wall under large loads.

Numerical simulation of flow over short crested weirs - case study: Quarter-circular crested weir

In this study, the flow characteristics over a quarter-circular crested spillway (QCCS) were investigated using computational fluid dynamics (CFD) simulations. The simulations included an in-depth analysis of parameters such as flow velocity, pressure distribution, and streamline patterns. The RNG turbulence model was used to simulate the flow field and hydraulic characteristics. In particular, the simulations were performed at the design discharge. The numerical results were carefully compared with laboratory observations, showing that there is good agreement between the simulated results and the observed data. The results of the numerical simulation showed that the streamlines are completely in line with the curvature of the crest and that there is no separation zone (separation of the streamlines from the surface of the crest). furthermore, there is no negative pressure zone along the crest, which means that the risk of cavitation is eliminated. The highest value of velocity and the lowest pressure of flow occur at the outlet end of the crest.

Untangling the environmental and tectonic drivers of the Noto earthquake swarm in Japan.

The underlying mechanism of the ongoing seismic swarm in the Noto Peninsula, Japan, which generates earthquakes at 10 times the average regional rate, remains elusive. We capture the evolution of the subsurface stress state by monitoring changes in seismic wave velocities over an 11-year period. A sustained long-term increase in seismic velocity that is seasonally modulated drops before the earthquake swarm. We use a three-dimensional hydromechanical model to quantify environmentally driven variations in excess pore pressure, revealing its crucial role in governing the seasonal modulation with a stress sensitivity of 6 × 10-9 per pascal. The decrease in seismic velocity aligns with vertical surface uplift, suggesting potential fluid migration from a high-pore pressure zone at depth. Stress changes induced by abnormally intense snow falls contribute to initiating the swarm through subsequent perturbations to crustal pore pressure.

Deformation mechanism of gob‐side entry at top coal caving mining face: A numerical study

AbstractTo investigate the significant deformation of the surrounding rock within the dynamic pressure zone of the gateroad, this study utilized the tailgate of the 1506 longwall face in Anyang Coal Mine as the engineering context. A combined approach of field measurement and numerical analysis was employed to explore the deformation and failure mechanisms of the surrounding rock under dynamic pressure. The findings indicate that before the exploitation of the 1506 longwall face, there was a notable reduction in stress across the floor and immediate roof, with minimal stress concentration observed in the coal pillar and the entity rib side. The plastic zone surrounding the tailgate was limited, suggesting a high degree of stability in the entry's surrounding rock. However, during the extraction of the 1506 longwall face, the tailgate, extending 60 m ahead of the working face, was subjected to dynamic pressure, leading to a marked increase in stress within the floor, coal pillar, and immediate roof. Stress concentration was more pronounced on the entity rib side than on the pillar rib side. This resulted in significant fissuring and severe deformation of the entry's surrounding rock. The primary failure mechanism involved damage to both the roof and floor corners, with the severity of damage escalating alongside the stress in the surrounding rock. This culminated in the failure of roof corner bolts and anchor cables, thereby compromising the stability of the entry within the dynamic pressure zone.

Research on the drag reduction of high-speed train based on bottom two-multistage wing deflector

To address the challenge of reducing aerodynamic drag while further enhancing the speed of high-speed trains, this research employs the concept of flow control for the bottom parts and draws inspiration from the front wings of Formula 1 (F1) race cars. Three kinds of two-multistage wing deflectors are designed and systematically analyzed by unsteady Reynolds-averaged Navier–Stokes (URANS) turbulent model. The most suitable design is determined by the single bogie model with a simplified train body. Using the improved delayed detached eddy simulation method, the aerodynamic drag of 1:8 three-car train models with or without two-multistage wing deflector is studied at different operational speeds. The results present the total drag reduction is higher at higher speeds. The reductions of 4.26%, 3.92%, 3.63%, and 3.49% are obtained at the operating speeds of 400, 350, 300, and 200 km/h, respectively. The two-multistage wing deflector desirably improves the flow structure at the bottom of the train, which leads to the reduction of aerodynamic drag and a corresponding reduction in the positive pressure zones within the bogie area. Furthermore, the deflector restricts shedding vortices, effectively narrowing the interference range of airflow under the train, which will provide a potential drag reduction method for the next generation high-speed train.

Prospectivity of Pliocene-Miocene deposits of the Khasilat field of the Absheron oil and gas bearing region according to surface and well seismic data

Prospectivity of Pliocene-Miocene deposits of the Khasilat field of the Absheron oil and gas bearing region according to surface and well seismic data

Dynamic modelling of supplemental cooling systems with vapor compression refrigeration units in civil aircrafts

Newly developed airliners have adopted supplemental cooling systems (SCS) to provide for non-cabin cooling requirements. In the present study, dynamic component models for compressor and phase change heat exchangers were developed with dynamic decoupling and explicit solution methods, and pressure zone separation and solution methods are developed based to obtain dynamic pressures as key values. A dynamic VCRU subsystem model is established, and the result under single-unit startup condition shows pressure deviations less than 0.16 %, with a simulation time ratio of 5.65 %, exhibiting good overall performance at both precision and speed. A dynamic SCS system model is developed, and the simulation of a 9000 s flight took 1973.3 s to complete. Result in the cruise phase shows the condensation and evaporation temperatures are in the ranges of 28.39–31.33 °C and −17.93 to −10.71 °C, respectively, meeting their respective designed ranges of 30 ± 5 °C and −15 ± 5 °C. These results reflects good consistency of the model with actual system characteristics. Control optimization is conducted based on the developed model to eliminate temperature fluctuation. The optimization reduced the maximum temperature deviation from 0.4004 K to 0.0019 K after system starting process, proving the feasibility of control method optimization based on the developed dynamic simulation model.

Research on Multi-Physical Field Characteristics of Deep Coal Seam Mining Based on the Rock-Coal-Rock Model

In order to disclose the multi-physical field characteristics of the deep coal seam mining process and their dynamic evolution legislation, based on the “rock-coal-rock” model, during the mining process, the stress field, displacement field, energy field, and plastic zone evolution process are all simulated using FLAC3D6.0. The findings show that stress in the original rock is redistributed as a result of coal seam mining, creating a pressure relief zone in the middle of the goaf and advanced support pressure in the front part of the working face. The roof falls following the termination of coal seam mining. The collapsed blocks fill the middle of the goaf, playing a supporting role. The floor bulges as a new supporting pressure zone forms and builds up high elasticity. The stress reduction zone shifts from a rectangular to an inner circular distribution and an outer square as the working face’s mining distance increases and the range of the fracture field expands accordingly. In addition, a complete model was constructed to verify the correctness of the “rock-coal-rock” model. The stress, displacement, and energy curves of the overlying strata at a distance of 12 m from the bottom of the coal seam in the middle of the goaf obtained by the two methods were basically consistent. Ultimately, the findings of the numerical simulation were compared with the advanced support pressure data that were acquired on-site and they were good. This work can provide a reference for the safe mining of deep coal seams.

Использование численного моделирования при анализе аэроупругого взаимодействия подвижного состава с тоннельными сооружениями

Purpose of the work: study of the formation of a complex air structure under conditions of rolling stock movement along extended underground structures using numerical modeling methods. Methods: an analysis of the influence of aerodynamic factors on rolling stock, passengers and railway infrastructure was carried out based on the finite element and volume method. The reasons for the occurrence of a compacted air zone, which appears in front of the head car of the train and exerts significant resistance to the movement of the train using the “Frozen Rotor” method, have been investigated. The indicators of energy efficiency and safety of the process of freight and passenger transportation are analyzed, taking into account the processes of aerodynamic interaction of moving rolling stock and artificial tunnel-type structures. Results: using numerical modeling and the use of the “Frozen Rotor” method, it was possible to obtain a qualitative picture of the distribution of transverse vortex air flows resulting from the occurrence of viscous friction. Regularities were discovered in the changes in the dynamics of pressure and speed of air masses on the surface of the head fairing when a train enters a tunnel. The fact of the negative impact of zones of high and low pressure, as well as their sharp drop, on the locomotive crew and passengers has been established. Practical significance: the possibility of conducting research in the field of aerodynamics of railway transport using modern numerical modeling methods is shown. This topic is very relevant in the field of designing high-speed rolling stock.

Evolution mechanism and parametric investigation of relative negative pressure zone in spiral groove gas face seal for aero-engine at high rotational speed

As an advanced sealing technology, spiral groove gas face seal has excellent sealing performance. However, it is rarely used in aero-engine. Previous investigation proposed that the relative negative pressure zone (RNPZ) in the spiral groove gas face seal can regulate the sealing performance. In this paper, further numerical simulation work is carried out. By quantifying the obstruction effect, viscous pumping effect and shear effect, the evolution mechanism of RNPZ under different film thicknesses and groove depths is revealed. Then, the parametric analysis of spiral groove configuration and groove number is carried out. Through the sub-regional quantitative analysis of the groove, the influence mechanism of structural configuration on RNPZ is revealed. Finally, combined with the hydrodynamic performance analysis, the spiral groove seal structure under optimal conditions is obtained. It is found that under the condition of high speed and low inlet pressure of aero-engine, RNPZ is suppressed by adjusting the structure of the spiral groove to enhance the shear effect, the pumping effect at the top of the groove and reduce the pumping effect at the bottom of the groove. When the number of grooves is 20 and the groove depth is 3 μm, the stiffness-leakage ratio of structure B and C can be increased by 10.15 % and 12.68 %, and the sealing performance is the strongest. This work can provide a theoretical and data basis for the subsequent optimization design of aero-engine gas face seals.

Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature.

In order to research the residual mechanical properties of concrete shield tunnel segments after exposure to high temperatures, two types of concrete segments were designed: a self-compacting concrete segment and a mixed fiber (steel fiber and polypropylene fiber) self-compacting concrete segment. The mechanical properties of seven blocks of concrete segments (five segments after high-temperature exposure and two segments at room temperature) were tested to analyze the influence of different loading sizes and fibers on the development of cracks after high temperature, failure mode, crack width, deformation, and so on in the concrete segments. The results showed that the damage model of the segment after exposure to high temperature and the segment at room temperature were crushed in the pressurized zone, but the high temperature had little effect on the concrete in the pressurized area. The size of the preload at high temperatures had little effect on the remaining load capacity, and the effect on the number of cracks was mainly concentrated on the internal arc surface of the segment. After high-temperature exposure, the number of cracks on the sides and inner arc surface of the segment increased, and the development of cracks was concentrated as several major cracks at high temperatures. When fibers were incorporated, the cracks in the segment became obvious, where the cracks at the loading point became denser and the interval distance became smaller.

MASS TRANSFER IN THE BIOREACTOR DURING GAS DISPERSION FROM THE STIRRER VORTEX CAVITY

Gas-liquid bioreactors in which the introduction of the gas substrate in the culture liquid is carried out from the vortex cavity formed by the rotation of the stirrer. In order to simplify the design and intensify mass transfer a new method of dispersing the gas substrate from the vortex cavity is proposed and studied. It consists in maintaining local zones with reduced pressure in the liquid behind the rotating paddles and creating the necessary conditions for the introduction of the gas substrate. On the basis of numerical simulation the pressure is calculated and the zones of low pressure in liquid behind the stirrer paddles are determined. The value of differential pressure necessary for gas dispersion has been estimated. The angular velocity of liquid rotation depending on the number of partitions on the apparatus wall and the number of mixer revolutions is presented. The gas content in the liquid during the implementation of the investigated method has been determined. The average surface diameter of gas bubbles and interfacial surface of gas-liquid medium were calculated from experimental data. The power spent on stirring in the apparatus has been established and the power criterion with regard to gas content has been determined. Mass transfer at intensive gas dispersion from gas vortex cavity into liquid has been investigated. Criterion dependence for calculation of mass transfer coefficient is presented, taking into account energy dissipation spent on mixing and interfacial surface. The fields of application of bioreactor with new method of gas dispersion are shown.

Decomposing significant factors of Coulomb stress and its components in injection-induced seismicity

Injection-induced seismicity has been a focus of industry for decades as it poses great challenges to the associated risk mitigation and hazard assessment. The response surface methodology is integrated into the geo-mechanical model to analyze the effects of multiple factors on induced seismicity during the post shut-in period. We investigate the roles of poroelastic stress and pore pressure diffusion and examine the differences in the controlling mechanism between fault damage zones and the fault core. A sensitivity analysis is conducted to rank the selected factors, followed by a Box‒Behnken design to form response surfaces and formulate prediction models for the Coulomb stress and its components. Reservoir properties significantly affect the potentials of induced seismicity in the fault by changing pore pressure diffusion, which can be influenced by other factors to varying degrees. Coulomb stress is greater in pressurized damage zones than in fault cores, and the seismicity rate exhibits a consistent variation. Poroelastic stress plays a similar role to pore pressure diffusion in the stability of the fault within the pressurized damage zones. However, pore pressure diffusion dominates in the fault core due to the low rigidity, which limits the accumulation of elastic energy caused by poroelastic coupling. The slip along the fault core is a critical issue to consider. The potential for induced seismicity is reduced in the right damage zones as the pore pressure diffusion is blocked by the low-permeability fault core. However, poroelastic stressing still occurs, and in deep basements, the poroelastic effect is dominant even without a direct increase in pore pressure. The findings in this study reveal the fundamental mechanisms behind injection-induced seismicity and provide guidance for optimizing injection schemes in specific situations.