Three-dimensional Numerical Analysis Research Articles

Three-dimensional steady state numerical analysis of inclined two phase closed thermosyphon for solar applications

A three-dimensional steady state CFD model was developed in ANSYS-Fluent CFD solver to analyze heat transfer capability as well as the wall temperature distribution along the lateral walls of thermosyphon. The physical properties of the fluid and other formulations were taken from the literature to perform the analysis. The CFD simulation predicted the temperature and pressure profile of liquid vapor mixture as well as the distribution of temperature over an entire wall of the thermosyphon for various operating conditions like heat transfer rates and inclination angles. The model was also validated with available experimental results.The CFD simulation helped to visualize the steady state wall temperatures over the entire wall of the two-phase closed thermosyphon (TPCT) the first time which is very difficult to find out by experiments. The influence of inclination angle on the wall temperatures distribution of the lateral surface of the thermosyphon was also analyzed. An optimum inclination angle for heat flux and filling ratio was determined by comparing thermal resistances values.

Three-dimensional and anisotropic numerical analysis of a PEM fuel cell

In this study, the effects of cell temperature and relative humidity on charge transport parameters are numerically analyzed. In order to perform this analysis, three-dimensional and anisotropic numerical models are developed. The numerical models are integrated into the experimental values for anisotropic electrical conductivities, as depending on cell temperature and relative humidity, that were obtained from our previous study. The achieved results indicate that the values of current densities in the in-plane direction increase with increasing cell temperature and relative humidity, while the current densities reach a maximum in the rib regions for both the numerical model at the through-plane direction. The behaviors of electrolyte potentials are similar with changes in the cell temperature and relative humidity. In addition, the cathode electrical potentials in both the in-plane direction and through-plane direction do not change to a considerable amount with increasing cell temperature and relative humidity.

Modeling Test and Numerical Simulation of Vertical Bearing Performance for Rigid-Flexible Composite Pouch Piles with Expanded Bottom (RFCPPEB)

Rigid-flexible composite pouch piles with expanded bottom (RFCPPEB) are generally considered as new symmetrical piles in practical engineering, but their bearing characteristics and design method are still not completely understood. The objective of this study is to investigate the vertical bearing performance and the optimal design scheme of RFCPPEB. Hence, laboratory modeling tests for this symmetric structure and an ABAQUS three-dimensional (3D) numerical simulation analysis were used to study the vertical bearing characteristics on bottom-expanded piles and rigid-flexible composite piles with expanded bottom. The vertical bearing capacity, shaft resistance, pile tip resistance distribution rule, and load sharing ratio of RFCPPEB were analyzed and verified using different bottom expansion dimensions and cemented soil thicknesses. The results revealed that the optimal bottom expansion ratio of rigid bottom-expanded piles was 1.8 when the ratio of pile body to bottom-expanded pile head was 9:1. When the bottom expansion ratio (D/d) was increased, the bearing capacity of bottom-expanded piles was significantly increased at D/d = 1.4 and D/d = 1.8 compared to that of D/d = 1.0, reaching 1.67 and 2.29 times, respectively, while for D/d = 1.6 and D/d = 2.0, the ultimate bearing capacity remained unchanged. Besides, shaft resistance played an important role in the bearing process of the rigid bottom-expanded piles and RFCPPEB. When the shaft resistance was increased, the ultimate bearing capacity of the pile foundation was significantly improved. The shaft resistance of RFCPPEB was increased with increasing cemented soil thickness. The increases in the shaft resistance and thickness of the cemented soil showed a nonlinear growth, and the maximum shaft resistance was approximately 75 cm from the pile top. When the diameter of the expanded head was 1.8 times the diameter of the pipe pile and slightly larger than the thickness of the cemented soil (0.5 times the diameter of the pipe pile), the optimal amount of concrete 425.5 kN/m3 required for per unit volume around piles was obtained, with the RFCPPEB ultimate bearing capacity of 7.5 kN. For RFCPPEB, the soil pressure at the pile tip was directly proportional to the pile top load under small load and was decreased in the form of a half quadric curve under large load. It reached the most reasonable position where the slope of the quadric curve was the largest when the thickness of the cemented soil was larger than 0.5 times the diameter of the pipe pile.

Ductile behavior and heat transfer efficiency in polymer extrusion by self-controlled “flipping melt-pancakes” with multi-fields synergy

A new design approach of “Flipping Melt-Pancakes” structure was proposed to improve the ductile behavior and heat transfer capacity for polymer melt extrusion. Three-dimensional numerical analysis of novel proposed structures was implemented compared with Maddock element and conventional screw that are commonly used in industry. Results indicated that flow patterns of polymer fluid affected by the screw configurations, inducing different ductile deformation, i.e., shear deformation occurred in Maddock channel and torsional deformation yielded in the “Flipping Melt-Pancakes” structure. Deformation flow patterns can contribute to radial mass transfer, achieving effective exchange of local heat and making temperature distribution more uniform. Besides, the change of velocity direction brought by the circumferential movement facilitated the synergy between velocity and temperature gradient and, improved heat transfer. The novel proposed structure based on the polymeric multi-fields synergy principle- “Flipping Melt-Pancakes” structure- has good heat transfer properties, low pressure loss and good synergy effect, reflecting that the field synergy principle can be applied to optimize the screw structures in polymer processing. It provides a new theoretical perspective to solve the increasingly severe challenges due to the insufficient control of mass transfer and heat management in plasticization process of extrusion or injection.

Control method of natural circulation flow by helium gas injection

There is a possibility that the mixture gas of air and helium diffuse into the reactor core at the depressurization accident of a HTGR. In order to investigate a method to control natural circulation flow of air and helium, we have conducted an experiment using an apparatus that simulates the flow path configuration of the HTGR. The experimental apparatus consists of two vertical channels with rectangular cross-sections, a connecting channel at the top of the channels, and a storage vessel at the bottom of the channels. The temperature of the heated and cooled walls and the temperature of the mixture gas in the vertical slots were measured. The concentration of air was also measured by ultrasonic concentration meter. From the results obtained in this experiment, it was confirmed that the natural circulation flow stopped for a while after helium gas injection. We will also describe the results obtained in the three-dimensional numerical analysis.

A multi-model approach for wooden furniture failure under mechanical load

Furniture failure generally appears at junctions between wooden parts. Failure prediction is a challenging problem considering the various technologies used for the assembly, the geometric dimensions of the wooden assembled parts and of the assembly components as well as the material properties of the wooden parts. Being able to provide a procedure for failure analysis is of great interest to the furniture industry. This paper proposes a multi-model approach in 3 steps: (i) a simplified global modeling of the whole structure (high loft bed) taking into account the specific geometry of each wooden part (beams or plates), (ii) a three-dimensional local numerical analysis of a through-bolt junction subjected to the mean critical load identified during a series of experimental compression tests to determine the local stresses in such a corner-type junction, and (iii) the application of an ad hoc failure criterion adapted to the anisotropic behavior of wood for failure prediction in through-bolt junctions.

Comprehension of shock wave modulation phenomena due to electromagnetic energy by using three-dimensional numerical simulation

Recently, the development of the supersonic transportation system is desired. For the development, the reduction of the wave drag and sonic boom is crucial problem. For the solution of the problem, the shock wave modulation technique by using the electro-magnetic power is one of the promising methods. This technique makes use of the baroclinic effect. For the application of this method to the other method of vortex generation method in the supersonic flow field, such as the scram jet engine inlet, the comprehension of the baroclinic effect is inevitable. In this study, for the comprehension of the baroclinic effect due to the electro-magnetic power, the three-dimensional numerical analysis code to simulate the interaction between the shock wave and the temperature modulated field was developed. The results were verified by comparing with the experimental visualization data.

液々界面を横切って上昇する気泡運動の三次元数値解析

Ternary fluid flows that single bubbles rise across the interface separating two immiscible liquids (liquid-liquid layer) are investigated through three-dimensional numerical analysis based on the moment-of-fluid (MOF) method. In this study, the effect of the viscosity of both liquids on the bubble rise motion and the behavior of the liquid-liquid interface is discussed. From numerical results, it is clearly shown that the viscosity of the liquids has a significant effect on the motion of a single bubble rising through the liquid-liquid layer. When a bubble rises in the lower layer with the low-viscosity, the bubble rise motion shows dynamic behavior, and the behavior of the liquid-liquid interface is complicated. Also, after passing the liquid-liquid interface, the bubble largely trails the lower layer with the low-viscosity fluid. On the other hand, the dynamic behavior of a bubble cannot be seen when a bubble rises through the liquid-liquid interface between high-viscosity fluids. The MOF method allows us to reproduce the dynamic motion of a single bubble rising across a liquid-liquid layer with a ternary fluid interface.

2Pb2-6 Three-dimensional numerical analysis of ultrasonic propagation behavior in a powder layer between metals

2Pb2-6 Three-dimensional numerical analysis of ultrasonic propagation behavior in a powder layer between metals

Nitrogen reductions have decreased hypoxia in the Chesapeake Bay: Evidence from empirical and numerical modeling

Seasonal hypoxia is a characteristic feature of the Chesapeake Bay due to anthropogenic nutrient input from agriculture and urbanization throughout the watershed. Although coordinated management efforts since 1985 have reduced nutrient inputs to the Bay, oxygen concentrations at depth in the summer still frequently fail to meet water quality standards that have been set to protect critical estuarine living resources. To quantify the impact of watershed nitrogen reductions on Bay hypoxia during a recent period including both average discharge and extremely wet years (2016–2019), this study employed both statistical and three-dimensional (3-D) numerical modeling analyses. Numerical model results suggest that if the nitrogen reductions since 1985 had not occurred, annual hypoxic volumes (O2 < 3 mg L−1) would have been ~50–120% greater during the average discharge years of 2016–2017 and ~20–50% greater during the wet years of 2018–2019. The effect was even greater for O2 < 1 mg L−1, where annual volumes would have been ~80–280% greater in 2016–2017 and ~30–100% greater in 2018–2019. These results were supported by statistical analysis of empirical data, though the magnitude of improvement due to nitrogen reductions was greater in the numerical modeling results than in the statistical analysis. This discrepancy is largely accounted for by warming in the Bay that has exacerbated hypoxia and offset roughly 6–34% of the improvement from nitrogen reductions. Although these results may reassure policymakers and stakeholders that their efforts to reduce hypoxia have improved ecosystem health in the Bay, they also indicate that greater reductions are needed to counteract the ever-increasing impacts of climate change.

Optimal design of radial inflow turbine for ocean thermal energy conversion based on the installation angle of nozzle blade

Ocean Thermal Energy Conversion (OTEC), as a new type of renewable energy, has huge development potential. Turbine is the most critical component in the ocean thermal energy conversion system, which directly determines the performance and energy conversion efficiency of the system. Therefore, the optimal design of turbines is very important to improve the efficiency of ocean thermal energy conversion. Based on the full consideration of the small temperature difference application characteristics of ocean thermal energy conversion and the special thermophysical properties of organic working fluids, this paper designs an ammonia working centripetal turbine with a power of 100 kW for OTEC applications, and then analyzes the effect of different geometric parameters on turbine performance. At the same time, the key parameters of the turbine are optimized based on full three-dimensional CFD numerical simulation analysis. It's shown that the nozzle blade installation angle has a very important impact on the performance of the turbine. Through optimization, when the nozzle blade installation angle reaches 30.5°, the efficiency is 91.77%, which is 6.25% points higher than the design value. The internal flow field performance is the best without obvious shock wave and reverse vortex phenomenon, which further improves the efficiency of the turbine and improves the internal flow.

Effect of multi-zone effusion cooling on an adiabatic flat plate for gas turbine application

Abstract The present study performed a three-dimensional numerical analysis on an adiabatic flat plate with forward injection holes for multi-zone film cooling. The cooling holes were divided into three-zone, and the cold air was supplied from cylindrical holes at a velocity ratio of 0.5 and 1.5 with 30° inclination to the primary flow. The effect of multi-zone arrangement in film cooling effectiveness is studied, and a comparison between two-zone and three-zone arrangement has been made. Results show that the three-zone arrangement helps achieve better film cooling effectiveness than the two-zone arrangement due to the uniform flow of coolant at a higher velocity ratio. It also reduces the mass flow rate of secondary flow by decreasing the number of cylindrical holes in the perforated plate.

Rotordynamic characteristics prediction for scallop damper seals using computational fluid dynamics

Enhancing damping characteristic is one of the effective methods to solve the instability problem of the rotor system. The three-dimensional numerical analysis model of scallop damper seal was established, and the effects of inlet pressures, preswirl ratios, rotational speeds, interlaced angles and seal cavity depths on the rotordynamic characteristics of scallop damper seal were studied based on dynamic mesh method and multi-frequencies elliptic whirling model. Results show that the direct stiffness of the scallop damper seal increases with decreasing inlet pressure and increasing rotational speed and cavity depth. When the seal cavity is interlaced by a certain angle, which shows positive direct stiffness. The effective damping of the scallop damper seal increases with the increasing inlet pressure, the decreasing preswirl ratio and the rotational speed and cavity depth. There exists an optimal interlaced angle to maximize the effective damping and the system stability. The leakage of the scallop damper seal is significantly reduced with decreasing inlet pressure. The preswirl will reduce the leakage flowrate, and the rotational speed has a slight effect on the leakage performance. The leakage of the scallop damper seal decreases with increasing seal cavity depth.

Slope stability analysis of a landfill subjected to leachate recirculation and aeration considering bio-hydro coupled processes

During the operation of landfills, leachate recirculation and aeration are widely applied to accelerate the waste stabilization process. However, these strategies may induce high pore pressures in waste, thereby affecting the stability of the landfill slope. Therefore, a three-dimensional numerical analysis for landfill slope stability during leachate recirculation and aeration is performed in this study using strength reduction method. The bio-hydro coupled processes of waste are simulated by a previously reported landfill coupled model programmed on the open-source platform OpenFOAM and then incorporated into the slope stability analysis. The results show that both increasing the injection pressure for leachate recirculation and maximum anaerobic biodegradation rate will reduce the factor of safety (FS) of the landfill slope maximally by 0.32 and 0.62, respectively, due to increased pore pressures. The ignorance of both waste biodegradation and gas flow will overestimate the slope stability of an anaerobic bioreactor landfill by about 20–50%, especially when the landfilled waste is easily degradable. The FS value of an aerobic bioreactor landfill slope will show a significant reduction (maximally by 53% in this study) when the aeration pressure exceeds a critical value and this value is termed as the safe aeration pressure. This study then proposes a relationship between the safe aeration pressure and the location of the air injection screen (i.e., the horizontal distance between the top of the injection screen and the slope surface) to avoid landfill slope failure during aeration. The findings of this study can provide insights for engineers to have a better understanding of the slope stability of a bioreactor landfill and to design and control the leachate recirculation and aeration systems in landfills.

Effects of scour-hole dimensions and bulb positions on the lateral response of under-reamed pile in soft clay

The failures of pile foundations in water-borne structures are often attributed to the scouring phenomenon. Even though many studies are available on the countermeasures against scour around the pile, no attempt is made to increase the load-carrying capacity of pile foundation by changing the pile geometry. Therefore, in the present study, the effect of scouring on the lateral response of a single under-reamed pile in soft clay is investigated using three-dimensional numerical analysis. The variables considered in the present study are embedment ratio and bulb position of the under-reamed pile, depth, slope angle, and bottom width of the scour-hole. For a given scour-hole dimension, the lateral load-carrying capacity of the under-reamed pile increases; whereas, deflection, maximum negative shear force, and bending moment in the shaft portion reduce compared to the pile without bulb. A notable improvement in the pile response is found when the bulb is placed just below the scour-hole. The lateral load-carrying capacity of the under-reamed pile reduces with an increase in depth and bottom width of scour-hole from the pile surface and a decrease in slope angle of scour-hole. Pile responses reduce with the consideration of stress history due to excavation.

Stability of Shield-Bored Tunnel for the Challenge of Nile Crossing

Underwater tunnel structures are vital in urban areas, and their use is continuously increasing. The engineering assessments for these impressive phenomena have to be performed from both geotechnical and structural engineering perspectives. The designer should take account of the requirements of the underwater structures to adequately withstand different applied loads. The underwater tunnel might be particularly vulnerable at locations where the geological conditions are uncertain. This study will cover all aspects concerning the stability of the tunnel crossing of the River Nile. The protentional exists for the tunnel failure during construction due to insufficient cover thickness and after construction due to a combination of long-term degradation and local scour. There were no imposed constraints on the alignment and the original design with a cover between the tunnel crown and the riverbed of at least one tunnel diameter. The tunnel stability was analyzed based on the most critical underwater section with a minimum cover thickness of the Greater Cairo Metro, Line 2 as the case study. Then, three-dimensional (3D) numerical analysis based on the Finite Element (F.E.) models was employed to explore soil–tunnel interactions. Comparison between numerical models’ results indicated that the safe cover thickness was equal to the tunnel diameter. The minimum cover thickness can be used to verify the required factor of safety calculated by theoretical analysis. The safety factor of the tunnel stability should not be less than 1.5 for construction and service stages and 1.3 for the exceptional case; scour accrues.

Three-Dimensional Numerical Simulation and Analysis of Geomechanical Controls of Hydraulic Fracturing in Heterogeneous Formations

Three-Dimensional Numerical Simulation and Analysis of Geomechanical Controls of Hydraulic Fracturing in Heterogeneous Formations

Material distortion in laser-based additive manufacturing of fuel cell component: Three-dimensional numerical analysis

Laser powder bed fusion (LPBF), an important additive manufacturing (AM) technique, has received a great deal of research attention and industrial application. The capability to fabricate complicated shapes and structures enables this technique to be applied for the manufacturing of rapid prototypes and complex parts. In operation, the constant melting and cooling of metal powders in a layer-by-layer fashion leads to large gradients and a rapid evolution of temperature, which may cause considerable residual stress and deformation. Polymer electrolyte membrane (PEM) fuel cells are a major type of fuel cells that operate under low temperature with high efficiency. PEM fuel cell components must be free of major distortion to avoid leakage of the reactant gases, intrusion of contaminants, and a large interfacial resistance. In this study, a three-dimensional (3D) numerical study is conducted to investigate the residual stress and deformation in a fuel cell inlet/outlet fitting directly built on the bipolar plate by LPBF. Both Inconel 718 (IN718) and stainless steel 316 L (SS316L) are used as the building materials. The distortion prifle predictions are compered with literature data. Additionally, the validated tool is employed to investigate several major parameters in LPBF fabrication to assess their impacts on distortion, including laser power, laser speed, and layer thickness. In our case, the laser power and speed have a significant impact on the distortion of the inlet/outlet fitting. SS316L shows a much less distortion (about 40 µm) than that of IN71 (about 90 µm) for the maximum distortion and a nearly 30% smaller average distortion at all measuring locations. The middle height of the fitting is subject to the largest distortion. A strain parameter ε* is discussed to facilitate the analysis of the simulation results.

Slope stability analysis and protection of deep accumulation excavation foundation pit in the Sichuan Bank of the Kahalo Jinsha River Bridge

The Kahalo Jinsha River Super Large Bridge of the Sichuan Riverside Expressway spans the deep canyon of the Jinsha River and is situated in a high-intensity, complex, and dangerous mountainous area. Long-term deformation and stability of the gravity anchor slope are the main controlling factors affecting bridge safety. The maximum slope height formed by the excavation of the gravity anchor foundation pit on the Sichuan Bank of the Kahalo Jinsha River Bridge is 110m, and the anchorage area is located on the Q3h thick accumulation with a thickness of more than 170 m. First, the important soil mechanical parameters, such as shear strength, deformation modulus and bearing capacity eigenvalues of rock and soil were obtained by conducting field shear tests, deformation tests, and load tests. On this basis, the pseudo-static method was used to simulate the seismic conditions, and a three-dimensional numerical analysis and calculations of the potential instability range of the high slope of the gravity anchor foundation pit excavation were conducted. The results reveal that the slope of the super-deep foundation pit with a huge thick mixed accumulation layer will deform and become unstable under the influence of an earthquake, with a maximum deformation of about 20 m in the slope body. A two-level earthquake prevention and disaster-reduction target for the bridge foundation pit and slope engineering protection is proposed based on the two-level seismic fortification requirements of super-long-span suspension bridges. An active reinforcement scheme of excavation pre-reinforcement, step-by-step excavation, and zoning protection is designed and proposed based on this target and the deformation and stability analysis results of the field test and three-dimensional numerical calculation.

Three-dimensional numerical analysis of tubular adhesive joints under torsional loads

Bonding method using adhesives has gained a lot of presence in the design of mechanical structures in several industries, especially in the aeronautics and automobile industry. Bonded joints are widely used to join tubular components, in vehicle frames like aeroplanes and automobiles. For the design process of these joints, analytical or numerical predictive techniques can be used. This work performs a numerical study in order to evaluate the torsional performance of aluminium tubular adhesive joints (AW6082-T651), considering the variation of the main geometric parameters, such as overlap length (L O) and tubes’ thickness. In order to predict the strength, the Finite Element Method (FEM) was used with Cohesive Zone Models (CZM), whose analysis based itself on the internal stresses of the adhesive, namely the analysis of shear stress (τxy) and joint strength, measured by the maximum torsional moment (M m). Previously, validation with experimental data was carried out. The technique was positively validated, and a significant geometry on M m was found, except for L O.