Hydrodynamic Characteristics Research Articles

Numerical study on hydrodynamic characteristics, wave forces and dynamic responses of offshore jacket platform under tsunami-like solitary waves

Numerical study on hydrodynamic characteristics, wave forces and dynamic responses of offshore jacket platform under tsunami-like solitary waves

Modelling of hydrodynamic characteristics in anaerobic baffled reactors: A systematic review

Modelling of hydrodynamic characteristics in anaerobic baffled reactors: A systematic review

Urban waterlogging simulation of derived short-duration double-peak rainstorm pattern

ABSTRACT It is actually difficult to quantify the characteristics of short-duration double-peak rainstorm (SDDPR), so the current study on the urban waterlogging simulation of its rainstorm pattern is rare. In this study, a new derivation methodology of SDDPR considering rainfall statistics correlations is proposed. With the non-source inundation method with the geographic information system (GIS)-based storm water management model (SWMM), urban waterlogging is simulated to present the hydrological and hydrodynamic characteristics. The results show that the proposed new derivation methodology of SDDPR reflects the actual rainstorm well, and the simulated urban waterlogging situation of the derived rainstorm confirms the different characteristics of surface ponding at junctions, flow in conduits, and outflows in outlets: with the increase of conditional probability and recurrence period (RP), the situation with average ponding hour-duration and earlier ponding time has increased, which represents more retention water can be produced quickly. With the change of RP from 1 to 10 years, the rate of overloaded conduit numbers with its full-flow time being beyond 0.5 h to total conduit numbers has added from 48 to 78%, waterlogging area of the study area has increased from 105,400 to 2,080,000 m2, ponding depth attains to 50 cm gradually, and the southeast in the study area is prone to be waterlogged.

Influence of Gravel Coverage on Hydraulic Characteristics and Sediment Transport Capacity of Runoff on Steep Slopes

Gravel coverage on slopes influences overland flow and soil erosion. However, the effect of different gravel sizes on the soil erosion process remains underexplored. In this study, a runoff scour test was performed to examine the effects of gravel coverage on the hydrodynamic characteristics of slope runoff and sediment transport capacity (Tc). The slope gradient varied from 18% to 84%, the unit flow discharge ranged from 0.27 × 10−3 to 1.11 × 10−3 m2 s−1, and gravel coverage was adjusted from 0% to 90%. The results reveal that water depth, shear stress, and stream power increased with gravel coverage. However, once coverage exceeded 20%, flow velocity and unit stream power decreased and stabilized. As gravel coverage increased, the hydraulic regimes transitioned from laminar to turbulent flow and shifted from supercritical to subcritical. Consequently, Tc first increased and then decreased with the increase in gravel coverage, reaching a peak at 20% coverage (1.66 kg m−1 s−1). Moreover, the degree of coverage indirectly influenced Tc through grain shear stress. The new equations, based on the Box–Lucas function, incorporated slope, grain shear stress, and flow velocity, thereby effectively simulating Tc for runoff on gravel-covered slopes (R2 = 0.94, NSE = 0.94). These findings provide a basis for modeling soil erosion on gravel-covered slopes.

Offshore Submerged Aquaculture Flow-Net Interaction Simulation: A Numerical Approach for the Hydrodynamic Characteristics of Nets Produced from Different Materials

The mechanical and hydrodynamic characteristics of single-piece nets are key to the design and optimization of offshore aquaculture net cages. A numerical approach for offshore submerged aquaculture net materials based on the Morison equations and finite element is proposed, simulating the hydrodynamic characteristics of single-piece nets under varying parameters such as wire diameter, mesh size, and flow velocity, and simulating the impact of marine organism attachment on nets by modifying the drag coefficient. The simulation results of nets made from materials such as Copper–Zinc Alloy (Cu-Zn), Zinc–Aluminum Alloy (Zn-Al), Semi-Rigid Polyethylene Terephthalate (PET), and Ultra-High Molecular Weight Polyethylene (UHMWPE) are compared, which provides a theoretical basis for optimizing design parameters and selecting materials for nets based on force conditions and hydrodynamic characteristics. The simulation results indicate that the current force on the net is positively correlated with flow velocity; the maximum displacement of the net is also positively correlated with the flow rate. Compared to other materials, the Cu-Zn net is subjected to the greatest water flow force, while the UHMWPE net experiences the greatest displacement; the larger the diameter of the netting twine, the greater the current force on the net; the mesh size is inversely related to the current force on the net. With increasing drag coefficient, both the maximum displacement of the net and the current force experiences increase, and UHMWPE material nets are more sensitive to increases in the drag coefficient, which indicates a greater impact from the attachment of marine organisms. The density and elastic modulus of the netting material affect the rate of increase in force on the net. The research results can provide a basis for further research on material selection and design of deep-sea aquaculture nets.

Assessment of oil vertical diffusion in waters following an oil spill incident in an urban inland waterway.

Accidental oil spills can have a serious impact on water bodies. While most current studies have focused on waves, few have examined water flows, which represent the most common hydrodynamic environment in urban inland waterways. In this study, 12 hydrodynamic conditions were constructed, and the oil vertical diffusion characteristics under hydrodynamic conditions were investigated by measuring oil concentration and oil droplet size distribution at different depths. The main findings include: (1) Oil concentration decays exponentially along the vertical direction, the related parameters follow power and quadratic functions in relation to mean flow velocity, respectively; (2) Oil droplet size distribution was influenced by hydrodynamic characteristics, mean flow velocity was significantly positively correlated with its distribution range; (3) Oil droplet size distribution patterns at different depths were similar, in line with the characteristics of Rosin-Rammler distribution. Based on experimental data, a set of models was constructed to describe and predict the vertical distribution of oil concentration and oil droplet size distribution under hydrodynamic conditions. This study not only reveals the characteristics of oil vertical diffusion under hydrodynamic conditions, but also provides a quantitative framework for understanding the relevant features, which is helpful for the response to the oil spill accident in urban inland waterways.

Steady and dynamic load measurements over a generic submarine hull form with various appendage configurations

Experimental studies for the steady and dynamic loads over a generic submarine hull form ( SUBOFF) with various appendage configurations in submerged motion was investigated through scaled model tests in the High Speed Towing Tank facility at Naval Science & Technological Laboratory, India. Steady load measurements were performed for a range of angles of incidence in angle of attack (± 35°) and drift (0° to 35°) including control surface deflections (± 20°). Measurements for dynamic loads were performed in both vertical and horizontal plane of motion for oscillating frequencies ranging from 0.21 to 0.55 Hz. The studies were carried out for four different configurations of SUBOFF comprising of bare hull, bare hull with sail, bare hull with control fins and fully appended hull. The aim of the present study for the load measurements is to gather steady and dynamic force/moment data, estimate hydrodynamic coefficients, validate and extend such data over a wide range of operation scenarios experienced by a submarine including high angle of incidence. The particulars of the SUBOFF model, experimental facility and measurement technique, test results for load measurements and estimated hydrodynamic coefficients are highlighted in the paper. The measurements data generated from the above studies will greatly complement the current research on hydrodynamic load characteristics for submerged bodies both computationally and experimentally.

Hydrodynamic Characteristics Study of Bionic Dolphin Tail Fin Based on Bidirectional Fluid-Structure Interaction Simulation.

Using bidirectional fluid-structure interaction technology, the dorsal-ventral motion of the dolphin tail fin was simulated, and the feasibility of the numerical simulation method was validated through underwater motion experiments. This study investigated the effects of structural parameters and motion modes of bionic dolphin tail fins on their propulsion performance. The results show that flexible tail fins can enhance propulsion performance. Compared to equal-thickness flexible tail fins, variable-thickness flexible tail fins that conform to the structural characteristics of real dolphin tail fins exhibit better propulsion performance. Asymmetric motion modes have a certain thrust-enhancing effect, but altering the frequency ratio F and amplitude ratio H of heaving motion leads to an increase in pitching moment, reducing swimming stability. Additionally, the greater the difference in frequency and amplitude between the up-and-down motions, the larger the pitching moment. The study results provide references for the optimized design and motion control of bionic tail fins.

Numerical Simulation Study on Hydrodynamic Characteristics of Offshore Floating Photovoltaics

With the development of renewable energy and the utilization of marine resources, large-scale offshore floating photovoltaics have gradually attracted widespread attention. In order to develop offshore floating photovoltaics and promote sustainable development, it has become necessary to explore the hydrodynamic characteristics of floating photovoltaic units and floating arrays. In this work, based on the viscous flow theory, the Computational Fluid Dynamics (CFD) and the discrete element method (DEM) methods are used to analyze the hydrodynamics of the floating body unit of offshore floating photovoltaics. The influencing factors include mooring length, mooring radius, and floating unit length. In addition, the hydrodynamic performance of the floating body unit and the floating body array under different wave heights and periods is also discussed to explore the influence of environmental loads on the floating body unit and the floating body array. The results indicate that the mooring tension exhibits an opposite trend with the surge and heave motions when the mooring line length and radius are varied. The motion is found to be more pronounced when the floating body unit length is 0.4 times the wavelength. The heave motion of the floating body unit exhibits a strong linear relationship with wave height, increasing by 0.01 m for every 0.015 m increase in wave height. The motion of the floating body units on both sides connected to the mooring lines decreases as the array length increases.

Reconstruction of Water Entry Cavity by OECT through combining Field Transformation and Group-based Sparse Representation

Abstract Due to the fact that a water entry cavity directly affects the hydrodynamic characteristics of underwater vehicles, its monitoring is crucial for controlling the motion stability of the vehicles. However, there is limited research on the visualization and measurement of cavities during vehicle motion. Based on Open-Electrical Capacitance Tomography (OECT), this article presents an image reconstruction method to measure the water entry cavity by combining field transformation and group-based sparse representation (FT-GSR). To address the openness of the cavity measurement domain, a field transformation method is proposed that unifies open- and closed-domain image reconstruction while reducing the dimensionality of the unknowns to be resolved and the computational complexity of the forward problem. To achieve high-resolution reconstruction, a group-based sparse representation method is proposed that utilizes global sparsity and neighborhood self-similarity in the reconstructed image, which shows good performance in simulation. Finally, water entry experiments were conducted to validate the performacne of the proposed method. Images captured by a high-speed camera were used as references to assess the accuracy of the calculated equivalent cavity diameter. The experimental results indicate that the proposed method can outperform typical reconstruction methods while maintaining computational cost. Based on the aforementioned performance, the proposed method is anticipated to be integrated into system-on-chip technology to enable real-time, high-precision monitoring of the water entry cavity.

Realization of Intermolecular Interactions as a Basis for Controlling Pervaporation Properties of Membranes Made of Aromatic Polyamide-Imides.

New aromatic co-polyamide-imides (coPAIs) containing both carboxyl and hydroxyl groups in the repeating units were synthesized for the first time. Transport, thermal and morphological properties of dense nonporous membranes from PAIs obtained using the diacid chloride of 2-(4-carboxyphenyl)-1,3-dioxoisoindoline-5-carboxylic acid and diamines 5,5'-methylene-bis (2-aminophenol)) and 3,5-Diaminobenzoic acid, taken in molar ratios of 7:3, 1:1, and 3:7, have been studied. High levels of membrane permeability accompanied by high selectivity for mixtures of liquids with significantly different polarities were determined by realization of intra- and intermolecular interactions in polymer, which was proved by thermal analyses and hydrodynamic characteristics of coPAIs. This effect is discussed in the context of the effectiveness of intermolecular interactions between polymer chains containing carboxyl and hydroxyl functional groups.

Solution of the conjugate heat exchange problem for conical heat exchangers

RELEVANCE The article is devoted to the development of new designs of heat exchangers and evaluating the efficiency of their operation. According to the authors, currently of particular interest are conical heat exchangers of the "pipe-in-pipe" type, so the object of research in this paper is a heat exchanger in the form of a truncated cone based on a spring-twisted channel. The introduction of the proposed heat exchange elements and apparatuses into the industry requires additional research. To assess the effectiveness of the application of the considered TA, it is proposed to evaluate its performance in comparison with conical and cylindrical TA based on a smooth-walled pipe. Due to this, two hypotheses will be tested at once: the use of a conical coil heat exchanger is more efficient than a cylindrical one, and the replacement of a smooth-walled pipe with a spring-twisted channel increases the efficiency of the heat exchanger.OBJECT. The aim of the research is to develop a method for setting and solving the conjugate heat exchange problem for a heat exchanger in the form of a truncated cone with a heat exchange element in the form of a spring-twisted channel, analyze the results obtained and evaluate the efficiency in comparison with conical and cylindrical heat exchangers based on smooth-walled heat exchange elements. METHODS. For the numerical solution of the conjugate heat transfer problem, the FEM implemented by means of Ansys was used Fluent. RESULTS. The main results consist in the fact that the authors developed a model and algorithm for calculating conical coil heat exchangers of the pipe-in-pipe type, implemented in the Ansys program, and determined the thermal and hydrodynamic parameters of coil devices. A comparison of coil heat exchangers was also made: a conical one based on a spring-twisted channel with a conical one and a cylindrical one with a smooth-walled heat exchange element. The calculation results showed that replacing a smooth-walled pipe with a spring-wound channel significantly increases the efficiency of heat exchange equipment. CONCLUSION. The significance of the obtained results lies in the possibility of using modern, more efficient and compact heat exchange equipment for technological needs and in the justification of this choice. Thus, with equal initial data, conical heat exchangers are more efficient than cylindrical ones with a heat exchange element in the form of a smooth tube, since they need a smaller heat exchange surface to achieve the necessary thermal and hydrodynamic parameters. The results of calculations prove the prospects of using a conical TA based on a spring-twisted channel and show the need for further study of the influence of the geometric characteristics of both the coil itself and the heat exchange element on the thermal and hydrodynamic characteristics of the proposed HE.

The Impact of Biochar and Olive Mill Wastewater Amendments on Soil Physical and Hydrodynamic Characteristics and Soybean Productivity in the Syrian Coast

The Impact of Biochar and Olive Mill Wastewater Amendments on Soil Physical and Hydrodynamic Characteristics and Soybean Productivity in the Syrian Coast

Hydrodynamic characteristics around offshore pipelines and oscillatory pore pressures in sand beds under combined random wave and current loads

Hydrodynamic characteristics around offshore pipelines and oscillatory pore pressures in sand beds under combined random wave and current loads

Impacts of wind forcing on microplastics kinematic in a sensitive water area.

Microplastics (MPs) have been found in different environmental department globally, and the threat to organisms posed by MPs is also widely recognized. Kinematic characteristics of low-density fiber MPs in Poyang Lake under different due-south wind were calculated by combining hydrodynamic model with particle tracking model in this study. Poyang Lake is divided into north lake and south lake for study based on its topographic and hydrodynamic characteristics, and the results are as follows: the critical wind speeds causing vertical mixing of MPs in the water column ranges from 6 to 9m·s-1 in the north lake, while it is >9m·s-1 in the south lake, and the MPs beaching rate decreases by 7.08%/(m·s-1) as the due-south wind speed increases. The MPs speed is mainly affected by surface current, while the direction of the velocity is more affected by wind. The MPs velocity in the south lake is only 27.10% of that in the north lake, and the direction is more dispersed, so the due-south wind concentrates the direction of MPs velocity more to the north in the south lake. The northern wards movement of MPs resulted in a noticeable decrease in FS in the south lake, with FS decreasing by 0.10 for every 1m·s-1 increase in wind speed, and therefore, the due-south wind reduces the ecological risk posed by MPs through reducing the range of movement and retention time. However, since the FS in the north lake has been close to the minimum value of 1, the reduction of the FS is not significant, and the wind reduces the risk mainly by shortening the retention time of the MPs. Therefore, the ecological risk caused by MPs in Poyang Lake under no or weak wind conditions should be taken into consideration.

Numerical study on aerodynamic and hydrodynamic load characteristics of a floating pneumatic wave energy converter under real sea conditions

Numerical study on aerodynamic and hydrodynamic load characteristics of a floating pneumatic wave energy converter under real sea conditions

Characterization of hydrodynamics around plates shaped like dragonfly wings as a sediment reduction measure in a sewer system.

Sediment control is a major concern in sewer management. Early studies focused on the parameters affecting the efficiency of existing dredging facilities, and novel long-term sediment reduction measures have not been developed. Superior sediment reduction performance has been demonstrated for plates folded at 25° placed in a pipe. In this study, flushing experiments are carried out to validate the efficacy of using hydrodynamic characteristics to analyze sediment reduction performance. A detached-eddy simulation is performed to characterize the hydrodynamics around various plates shaped like dragonfly wings placed in pipes to enhance sediment reduction performance. Experimental results indicate that the maximum sediment reduction efficiency occurs in the middle section of the plates for both coarse and fine sediment beds, where the flushing thickness is extended by 1.3 cm and 3.2 cm, respectively. However, the sediment reduction efficiency is maximized for mixed sediment beds downstream, where the flushing thickness is extended by 2.4 cm. The results of numerical simulations indicate that compared with conventional sediment reduction measures, the plates produce less detrimental effects on the streamwise velocities near the pipe bottom at the plate front and increase the time-averaged vertical and transverse velocities as well as the overall turbulent kinetic energy. Therefore, the use of plates shaped like dragonfly wings is an effective sediment reduction measure.

The influence of parameters on the hydrodynamic characteristics of oscillating water column devices: A numerical study

The influence of parameters on the hydrodynamic characteristics of OWC (oscillating water column) devices exhibits a coupling phenomenon, which is frequently neglected. To elucidate the comprehensive influence and its mechanism of structure parameters on the hydrodynamic characteristics of offshore OWC devices, a structure with a bottom plate was selected in this study. Through numerical simulation, the hydrodynamic characteristics of the chamber with variations in PTO (power take off) coefficient α, chamber length Bs, internal depth Jn, and under water length of front wall Je with different wave conditions are investigated. The following conclusions are primarily drawn: The research method of using the relative wavelength L/Bs as a non-dimensional parameter and solely varying the wavelength L has its drawbacks. In cases that L/Bs is held constant, the efficiency of chambers differing only in Bs can vary by more than 70%. The influence of each parameter on the effectiveness is interrelated. Chambers with a lower α exhibit a more pronounced impact of Bs. The efficiency of device with a smaller relative wavelength L/Bs is more significantly affected by the Jn. The mechanism by which the parameters affect efficiency is primarily since chambers with shorter Bs or greater Jn exhibit smaller deformations during internal liquid surface oscillation, resembling a more uniform oscillating water column. This allows more energy to be utilized for pushing air in and out of the chamber above, thereby enhancing the energy conversion capability. The results of this research can provide valuable insights for the design of OWC devices.

Structural and hydrodynamic characteristics of hollow cylinder during high-speed water entry

Structural and hydrodynamic characteristics of hollow cylinder during high-speed water entry

Response of Soil Detachment Capacity to Hydrodynamic Characteristics Under Different Slope Gradients

The mechanism of soil detachment on steep slopes is obviously different from that on gentle slopes. However, the slope effect of soil detachment remains unclear. The objective of this study was to quantify the slope effect of soil detachment capacity at the varying hydrodynamic characteristics. In this study, the soil detachment capacity (Dc) on clay loam and hydrodynamic characteristics were measured by conducting the runoff scouring experiments at 10 slope gradients (1.7–57.7%) and 5 unit flow discharges (0.022–0.089 m2·min−1). The results showed that the relationships between Dc and hydrodynamic parameters were affected by slope gradient. Based on the optimal functional relationship, the hydrodynamic characteristics (flow velocity, flow shear stress, stream power, unit stream power, and unit energy) calculated by maximum and minimum Dc in this study changed by 19.91–95138.10%, and the Dc calculated by the maximum and minimum hydrodynamic characteristics could differ by up to nine orders of magnitude. Overall, the power function of hydrodynamic parameters was superior to the linear function in different slope gradients. The stream power was the best predictor for Dc compared with other hydrodynamic parameters. For all combinations of slope gradients, the adjusted coefficient of determination (Adj. R2) of the power relationship between Dc and stream power was 9.41–27.40% higher than it was between Dc and other hydrodynamic parameters. The coefficient and index of power function for different hydrodynamic parameters showed a trend change with increasing slope gradient, indicating that there was a slope effect on Dc. Further analysis found that Dc could be well predicted using a power combination equation of slope gradient, flow velocity, and flow depth (Adj. R2 = 0.96). This study helps to better understand the mechanism of soil detachment and emphasizes that the slope effect should be considered when establishing a soil detachment equation.