Search Results (26)

Optimizing hydrodynamic performance and dissolved oxygen (DO) distribution is essential for improving water quality management in industrial recirculating aquaculture systems. This study combines experimental measurements and data analysis to evaluate the effects of the inlet pipe flow rate (Q), deployment distance ratio (d/r), deployment angle (θ), inlet pipe structure on hydrodynamics and the dissolved oxygen distribution across various tank layers. The flow field distribution in the tanks was measured using Acoustic Doppler Velocimetry (ADV), and the hydrodynamic characteristics, including average velocity (v_avg) and the velocity uniformity coefficient (DU₅₀), were quantitatively analyzed. The dissolved oxygen content at different tank layers was recorded using an Aquameter GPS portable multi-parameter water quality analyzer. The findings indicate that average velocity (v_avg) and the velocity uniformity coefficient (DU₅₀) are key determinants of the hydrodynamic characteristic of circular aquaculture tanks. Optimal hydrodynamic performance occurs for the vertical single-pipe porous configuration at Q = 9 L/s, d/r = 1/4, and θ = 45°,the average velocity reached 0.0669 m/s, and the uniformity coefficients attained a maximum value of 40.4282. In a vertical single-pipe porous structure, the tank exhibits higher dissolved oxygen levels compared to a horizontal single-pipe single-hole structure. Under identical water inflow rates and deployment distance ratios, dissolved oxygen levels in the surface layer of the circular aquaculture tank are significantly greater than that in the bottom layer. The results of this study provide valuable insights for optimizing the engineering design of industrial circular aquaculture tanks and addressing the dissolved oxygen distribution across different water layers. Full article

This study addresses the water basin effect in the underwater sand layer of steel pipe pile cofferdams by integrating the concept from building foundation pits to cofferdam foundation pit analysis. A theoretical derivation is presented for the deformation evolution of steel pipe piles and bottom seals within the cofferdam pit. The cofferdam construction dewatering process is divided into four stages: riverbed excavation for bottom sealing, dewatering to the second support, dewatering to the third support, and dewatering to final bottom sealing. The steel pipe piles are modeled as single-span or multi-span cantilever continuous beam structures. Using the superposition principle, deformation evolution equations for these statically indeterminate structures across the four stages are derived. The bottom seal is simplified to a single-span end-fixed beam, and its deflection curve equation under uniform load and end-fixed additional load is obtained via the same principle. A case study based on the 6# pier steel pipe pile cofferdam of Xi’an Metro Line 10 Jingwei Bridge rail-road project employs FLAC3D for hydrological–mechanical coupling analysis of the entire dewatering process to validate the water basin effect. Results reveal a unique water basin effect in cofferdam foundation pits. Consistent horizontal deformation patterns of steel pipe piles occur across all working conditions, with maximum horizontal displacement (20.72 mm) observed at 14 m below the pile top during main pier construction completion. Close agreements are found among theoretical, numerical, and monitored deformation results for both steel pipe piles and bottom seals. Proper utilization of the formed water basin effect can effectively enhance cofferdam stability. These findings offer insights for similar engineering applications. Full article

Field measurements with the Plaxis^3D 24.1 software were performed on the 17# shaft of the Shanghai Zhuyuan Bailonggang sewage connecting the pipe project to analyze the ground deformation patterns during VSM (vertical shaft sinking machine) construction in soft soil areas. The results indicate that both the shaft sinking process and construction pauses at the pit bottom significantly exacerbate soil deformation. Compared with horizontal displacement, the measured settlement is more sensitive to excavation depth. The calculations revealed that significant pit bottom heave occurs when the excavation depth reaches 40% to 70% of the maximum excavation depth (H_m). Moreover, the heave pattern transitions from a single-peak “convex” shape to a double-peak “concave” shape during the sinking process. On the basis of the deformation of the soil outside the shaft after the completion of sinking, the vertical deformation zones are classified into a groove-shaped settlement zone, heave influence zone, and heave zone. Similarly, the horizontal deformation zones are categorized as an arch-shaped deformation zone, transition deformation zone, and cantilever bending zone. For regions where the sinking depth reaches 40% to 90% of H_m, the excavation disturbance should be further minimized, and overexcavation must be strictly avoided. In areas where the horizontal distance (L) from the shaft is less than 0.3 times H_m, environmental monitoring points should be appropriately densified to optimize the fine control of deformation in the surrounding region. Full article

The outlet flow rates and changes in behaviors of five outlet ports where water and air–water (two-phase) mixtures pass horizontally in a manifold pipe system were investigated experimentally. The effects of different air-flow rates, vacuumed from the atmosphere with a Venturi device in the system, on the outlet flow rates and diameters of the manifold port outlets were compared by measuring the outlet jet lengths. The system performance provided homogeneity of manifold port outlet flows and was tested. As a result, it was observed that homogeneous jet lengths were obtained in both single and two-phase low main manifold flows and equal outlet port diameters. When the main manifold flow rate V is 1.5–2 m/s, the system is stable and produces high jet lengths. The manifold pipe systems used in the experimental setup provide suitable working conditions for d/D = 0.433. The system does not show a smooth flow pattern with Venturi devices for d/D < 0.433. The low flow rates in this study’s tests are key. They are vital for designing micro irrigation systems. This depends on the critical d/D ratio of the system. Full article

In recent years, the pipe shed advanced support method has emerged as a new technique for excavating tunnels in weak surrounding rock. However, the necessity to maintain a certain inclination angle when constructing large pipe sheds unavoidably increases the excavation and lining quantities. Consequently, as the length of the pipe shed increases, construction errors also grow, resulting in larger excavations and backfilling works, thereby making it difficult to control the quality of pipe shed installations and limiting the development of the pipe shed method. Faced with the challenges presented by tunnel support construction as part of subway tunnel construction, this paper is based on the Songhuai Youyuan Station tunnel project involving Zhengzhou Metro Line 9. Field experiments were conducted, using high-torque horizontal drilling machines and pipe shed guiding technology to successfully complete the installation of a 208 m long pipe shed in a single operation (the longest in the world). Through case analysis and technological innovation, a feasible and effective drilling technology scheme was proposed. Compared with traditional methods, the key technology for installing super-long pipe sheds in a single operation reduced the construction time by 35% and construction costs by 25%, providing valuable insights for similar projects. Full article

Considering the current limitations and restricted scope of existing experiments, as well as the absence of corresponding numerical simulation verifications and comparisons, and the lack of actual case studies of variable mass flow calculation and comparison, this study focuses on high production oilfields in the Mideast and South China Sea. The objective is to investigate single-phase and multiphase variable mass flow through numerical and experimental simulations. The study develops linear regression equations to establish the relationship between the mixture pressure drop caused by side flow and the velocities of the main flow, as well as the ratio between side and main flow velocities. Actual calculations using these equations are provided. The comprehensive analysis reveals that, for a fixed total flow rate, an increase in the side versus main injection velocity ratio leads to an increase in pressure loss before and after the injection hole. In single-phase flow, the friction factor for side hole flow is generally higher than that for only axial main flow, with the same total flow rate. In multiphase flow, when the gas-liquid ratio (GLR) is relatively large, the side flow has minimal impact on pressure drop, while at lower GLR values, the side flow significantly increases the pressure drops. When predicting the pressure drop for single-phase variable mass flow in horizontal wellbores, it is appropriate to consider only the mixture pressure drop caused by the closest hole to the calculation section, assuming the injection hole flow rates are approximately equal. In terms of predicting the productivity of single-phase variable mass flow, it is crucial to consider the mixture pressure drop. Neglecting the mixture pressure drop can lead to relatively larger productivity prediction results, with potential production rate errors exceeding 50%. The accuracy of the prediction is influenced by the ratio of mixture pressure drop to production pressure differential, and the pressure along the external zone of the screen pipe is higher when considering the mixture pressure drop compared to when it is neglected. Additionally, the flow rate along the external zone of the screen pipe becomes more non-uniform when the mixture pressure drop is considered. Furthermore, the findings from the single-phase and multiphase flow experiments suggest that significant deviations in production rates may occur in scenarios with low gas-liquid ratio (GLR), highlighting the need for further investigation in this area. Full article

Compared with high-pressure water and reagent washing decontamination, foam decontamination has a promising application due to its ability to significantly reduce the volume of radioactive waste liquids and effectively decontaminate the inner surface of the pipes, the interior of the large cavities, and the vertical walls. However, the foam is less stable, leading to a low decontamination rate. Currently, three main types of stabilizers with different stabilizing mechanisms, namely nanoparticles, polymers, and cosurfactants, are used to improve foam stability and thus increase the decontamination rate. Nanosilica (NS), xanthan gum (XG), and n-tetradecanol (TD) were used as typical representatives of nanoparticles, polymers, and cosurfactants, respectively, to improve the stability of the foam detergent with pH < 2 and chelating agents. The differences in the effects of these three types of stabilizers on foam properties were investigated. Although NS, XG, and TD all increase the half-life of the foam from 7.2 min to about 40 min, the concentration of TD is much lower than that of NS and XG in the foaming solution, and TD foaming solution has the highest foaming ratio. Moreover, TD can markedly lower the surface tension, resulting in a significant reduction of the wetting contact angle on the surfaces of glass, ceramic tile, stainless steel, and paint, while NS and XG cannot signally change the surface tension and have no obvious effect on the wetting contact angle. At low shear rates, TD can increase the apparent viscosity of foam by two orders of magnitude, and the wall-hanging time of the foam on the vertical wall is more than 30 min. In contrast, NS and XG cause a limited increase in the apparent viscosity of the foam, and the wall-hanging times are both less than 5 min. In addition, TD foaming solution has excellent storage stability, and the storage time has no obvious effect on the performance of the foam. And after only three days of storage, NS undergoes severe agglomeration and precipitation in the foaming solution, resulting in a complete loss of the stabilizing effect. After 90 days of storage, the half-life of XG foam decreases by 26%. For simulated radioactive uranium contamination on both horizontal and vertical surfaces, TD can significantly improve the decontamination rate, especially for vertical surfaces, where TD can increase the single decontamination rate by more than 50%. Full article

This paper focuses on the hydrodynamic interaction between the large floating body and a small transfer platform in a jettyless floating transfer system. A high-order boundary-element method combined with a direct time-domain-solution method to calculate and analyze the hydrodynamic response of the small platform while berthed with the fixed large floating body and freely floating large body under wave action was applied and compared with the hydrodynamic response of a single small transfer platform. It was found that when the large floating body and the small transfer platform were both located on the leeward side, they had little mutual influence, and the hydrodynamic response agreed well with that of the single small transfer platform and the single large floating body. While the small platform was located on the leeward side of the large floating body, it significantly affected the hydrodynamic response of the platform, resulting in a significant reduction in horizontal motion and pitch motion, meaning that the shielding effect was significant. Within a certain range of wave periods, the heave-motion amplitudes can be significantly reduced, but beyond that range, they increase. Therefore, it is important to carefully consider the relative motions of LNG transport ships and small platforms when connecting them via aerial jumper pipes in jettyless floating transfer systems. Full article

This experimental study investigates the effect of changes in the arrangement of horizontal pipelines on changes in the velocity pattern in three dimensions and the scouring process around these submarine pipelines. Experiments have been carried out in four cases: single pipe, two pipes with a distance of 0.5 D, two pipes with a distance of D, and three pipes with a distance of 0.5 D (D is the diameter of the pipes). The velocity upstream, downstream, and on the pipes have been measured by the Acoustic Doppler Velocimeter (ADV). The results show that a single pipe’s scouring depth in the first case is more significant than in the other cases. In the second case, the presence of the second pipe at a distance of 0.5 D from the first pipe significantly reduced the scour depth (28.6%) compared to the single pipe condition by changing the velocity pattern around the pipelines. By increasing the number of pipes to 3 with a distance of 0.5 D, this reduction in scouring depth has reached 47.6% compared to the single pipe condition. However, in the case of two pipes with a distance of D, the reduction of scouring depth was 21.4% compared to the case of a single pipe, and compared to the case of two pipes with a distance of 0.5 D, it increased by 10%. Full article

This paper presents an experimental investigation of condensation heat transfer by gradient heatmetry. The experiments were carried out during the condensation of saturated steam at atmospheric pressure on the cooled surface of a horizontal pipe. The distributions of the local heat flux, surface temperature, and heat transfer coefficient along the circumference of the horizontal pipe were experimentally determined. The surface average condensation heat flux on the horizontal pipe was about 141.06 kW/m${}^2$. The proposed method allows us to determine the area of condensate accumulation on the pipe (in the range of azimuth angle $\phi$ = 150…180${}^{\circ }$) in which the heat flux decreases by 34% of the average value. The heat flux per unit area relative uncertainty was about 5.2%. The surface-averaged heat transfer coefficient during condensation on the horizontal pipe was about 5.5 kW/(m${}^2\times$K), and relative uncertainty was about 9.4%. Full article

During drilling in deep shale gas reservoirs, drilling fluid losses, hole wall collapses, and additional problems occur frequently due to the development of natural fractures in the shale formation, resulting in a high number of engineering accidents such as drilling fluid leaks, sticking, mud packings, and buried drilling tools. Moreover, the horizontal section of horizontal well is long (about 1500 m), and the problems of friction, rock carrying, and reservoir pollution are extremely prominent. The performance of drilling fluids directly affects drilling efficiency, the rate of engineering accidents, and the reservoir protection effect. In order to overcome the problems of high filtration in deep shale formations, collapse of borehole walls, sticking of pipes, mud inclusions, etc., optimization studies of water-based drilling fluid systems have been conducted with the primary purpose of controlling the rheology and water loss of drilling fluid. The experimental evaluation of the adsorption characteristics of “KCl + polyamine” anti-collapse inhibitor on the surface of clay particles and its influence on the morphology of bentonite was carried out, and the mechanism of inhibiting clay mineral hydration expansion was discussed. The idea of controlling the rheology and water loss of drilling fluid with high temperature resistant modified starch and strengthening the inhibition performance of drilling fluid with “KCl + polyamine” was put forward, and a high temperature-resistant modified starch polyamine anti-sloughing drilling fluid system with stable performance and strong plugging and strong inhibition was optimized. The temperature resistance of the optimized water-based drilling fluid system can reach 180 °C. Applied to on-site drilling of deep shale gas horizontal wells, it effectively reduces the rate of complex accidents such as sticking, mud bagging, and reaming that occur when resistance is encountered during shale formation drilling. The time for a single well to trip when encountering resistance decreases from 2–3 d in the early stages to 3–10 h. The re-use rate of the second spudded slurry is 100 percent, significantly reducing the rate of complex drilling accidents and saving drilling costs. It firmly supports the optimal and rapid construction of deep shale gas horizontal wells. Full article

This study develops a geometry adaptive, physical field predictor for the combined forced and natural convection flow of a nanofluid in horizontal single or double-inner cylinder annular pipes with various inner cylinder sizes and placements based on deep learning. The predictor is built with a convolutional-deconvolutional structure, where the input is the annulus cross-section geometry and the output is the temperature and the Nusselt number for the nanofluid-filled annulus. Profiting from the proven ability of dealing with pixel-like data, the convolutional neural network (CNN)-based predictor enables an accurate end-to-end mapping from the geometry input and the desired nanofluid physical field. Taking the computational fluid dynamics (CFD) calculation as the basis of our approach, the obtained results show that the average accuracy of the predicted temperature field and the coefficient of determination R² are more than 99.9% and 0.998 accurate for single-inner cylinder nanofluid-filled annulus; while for the more complex case of double-inner cylinder, the results are still very close, higher than 99.8% and 0.99, respectively. Furthermore, the predictor takes only 0.038 s for each nanofluid field prediction, four orders of magnitude faster than the numerical simulation. The high accuracy and the fast speed estimation of the proposed predictor show the great potential of this approach to perform efficient inner cylinder configuration design and optimization for nanofluid-filled annulus. Full article

In this study, the dynamic response of a multiconnected floating solar panel system with a vertical pontoon were studied under various scenarios. First, a floating solar panel pontoon is modeled by combining nine single-unit vertical cylinders (arranged in parallel, horizontally and vertically, 3 m apart from each other). Each cylinder will be considered a rigid body, and they are connected to each other with a frame, so that they can oscillate together. Each floating solar panel pontoon was connected to a steel pipe, and a hinged connector was attached to the connecting point of each steel pipe, while it was fixed at each pontoon. In this study, as a floating solar panel system, a 10 × 10 system was adopted at a water depth of 50 m. Furthermore, a catenary mooring system with steel wire rope was installed to enhance its station-keeping capability. As an environmental load, wave excitation force, under normal operating and extreme conditions, was considered. To confirm the dynamic behavior of the system, a connector boundary condition sensitivity test was conducted under a 0° heading (west to east). It has been proven that an unexpected dynamic response along the sway, roll, and yaw directions is observed in the hinged connector case, due to the second generated moment caused by the movement of the facilities. Furthermore, judging from extreme simulation results, the larger the external environmental loading, the greater the dynamic response of the system, due to amplified wave excitation forces. Finally, under the multiple mooring line failure scenario, the dynamic response of the system is significantly amplified, due to the loss of mooring tension, except for the roll response. Full article

Geothermal heat exchangers (GHEs) represent a buried pipe system, which can be utilised to harness renewable thermal energy stored in the ground to improve the efficiency of heating and cooling systems. Two basic arrangements of GHEs have been widely used: vertical and horizontal. Vertical GHEs generally have a better performance in comparison with the horizontal arrangement, and these systems are particularly suitable for confined spaces. Nevertheless, the main technical challenge associated with GHEs, for either the vertical or the horizontal arrangement, is the performance deterioration associated with an increase in the operation times during summer or winter seasons. In this paper, a combined horizontal-vertical GHE arrangement is proposed to address the current challenges. The combined GHE arrangement can be operated in five different modes, corresponding to different thermal loading conditions. These five operation modes of the combined GHE are analysed based on the transient finite difference models previously developed for the horizontal and vertical arrangements. The simulation results reveal that for the single operation mode (horizontal or vertical only), the vertical GHE performs better than the horizontal GHE due to relatively stable ground temperature deep down. While, for the combined operation mode, the series operations (horizontal to vertical or vertical to horizontal) of the GHE are superior to the split mode. It is found that the effect of the fluid mass flow rate ratio is trivial on the heat dissipation of the split mode GHE. The highest heat transfer rate in the split flow operational mode is rendered by the ratio of the mass flow rate of 40% horizontal and 60% vertical. In addition, the climate condition has more effect on GHE’s performance and the increase of the fluid flow rate it can enhance the amount of energy released by the GHE. Full article

The aim of this paper is to research the parameters that optimize the thermal performances of a horizontal single-duct Earth to Air Heat eXchanger (EAHX). In this analysis, the EAHX is intended to be installed in the city of Naples (Italy). The study is conducted by varying the most crucial parameters influencing the heat exchange between the air flowing in the duct and the ground. The effect of the geometrical characteristics of the duct (pipe length, diameter, burial depth), and the thermal and flow parameter of humid air (inlet temperature and velocity) has been studied in order to optimize the operation of this geothermal system. The results reveal that the thermal performance increases with length until the saturation distance is reached. Moreover, if the pipe is designed with smaller diameters and slower air flows, if other conditions remain equal, the outlet temperatures come closer to the ground temperature. The combination that optimizes the performance of the system, carried out by forcing the EAHX with the design conditions for cooling and heating, is: D = 0.1 m s⁻¹; v = 1.5 m s⁻¹; L = 50 m. This solution could also be extended to horizontal multi-tube EAHX systems. Full article