Two-dimensional Numerical Model Research Articles

Mechanism of wave-induced flow in reshaping breakwaters

The aim of this work was to investigate the reshaping mechanisms of a reshaping berm breakwater (BB) by assessing the results of a two-dimensional numerical model in OpenFoam. The flow inside and outside the breakwater was numerically simulated. The initial and reshaped form of the breakwater was modelled using the Darcy–Forchheimer equation and k–ϵ closure model. The numerical model was calibrated with and validated against experimental data of wave-induced pressure and water-level fluctuations inside and outside the breakwater. Both the initial and reshaped BB were evaluated for calibration and validation processes. The results show that the minimum run-down level on the breakwater slope is a critical area for armour instability due to outward driving forces caused by the critically synchronised outward flow and excess pressure gradient. Moreover, parallel downward flow occurs during a wave run-down, which can push the displaced armour down the slope. After reshaping, the breakwater profile has a milder slope than the initial profile, and the outward forces due to the excess pressure gradient are reduced to less than one-half of their initial amount, a result of the change in breaker type. Accordingly, the reshaped profile is modified to harmonise with the new flow field conditions.

Numerical modelling of enhancement of the capacity of buried metal culverts by using geogrids

This paper presents a two-dimensional numerical modelling analysis of a flexible buried corrugated metal arch culvert in Enkoping, Sweden. The numerical results of this study are validated against field measurements of the culvert crown deformation, thrust, and bending moments recorded during backfilling. To model the backfill soil, the hardening soil with small strains (HSs) material model is used because of its efficiency in simulating the soil-structure interaction. Furthermore, in a numerical investigation of the stress distribution at the culvert invert, it is found that weakness of the foundation soil has an insignificant impact, due to stress dissipation resulting from arching actions. The numerical modelling analysis also investigates the use of geogrid layers with dead end bolts in the soil cover above the culvert crown during the application of static surface loads, as an innovative technique to improve the load capacity of the soil-culvert system. The results show a reduction in culvert crown deformation and internal forces when geogrid layers are used. This indicates the efficiency of geogrid layers in improving the load capacity of existing buried culverts or overcoming deficiencies in culvert serviceability by reducing the impact of applied loads.

Analysis of hydrodynamics and thermal dispersion by numerical modelling in Sele Strait, West Papua

Indonesian standard for wastewater quality regulates 40°C for the maximum outfall temperature. Meanwhile, the seawater temperature below 30°C is utilized for the cooling facility which the intake area is close to the outfall source. This research examine the hydrodynamics and thermal dispersion condition in PT Kilang Pertamina Internasional Kasim process plant in Sele Strait, West Papua. This study uses a two-dimensional numerical model Mike21 for a one-year simulation. Considering the limited field data, the ERA5 reanalysis satellite was utilized for the model input boundary. It also finds the discharge from the river with a temperature assumption of 26.5°C also in the boundary. The model validated with tidal field data with an R-squared number is 0.86. The hydrodynamics model shows the current speed in the intake area varied between 0-0.5 m/s. Two-scenario thermal simulation model (outfall condition 37°C & 40°C) shows that the frequency of 27°C water temperature is 81.5% and 85.8% respectively. Both scenarios give less than 10% for the temperature above 30°C. It concludes that the intake and outfall design planned is proper in the Kasim process plant.

Mathematical Modeling and Simulation of a Compound Parabolic Concentrators Collector with an Absorber Tube

CPC solar collectors are a combination of new technologies that make it possible to generate heat from radiant solar energy by transferring heat between the absorber and the fluid. This study was performed based on heat transfer equations by proposing a mathematical model, as reported in the literature. A compound parabolic concentrators solar collector (CPC) numerical model was simulated and coded in Aspen HYSYS and MATLAB software and validated by comparing its results with other researchers and experimental results. The simulated mathematical model includes a two-dimensional numerical model to describe the thermal and dynamic behavior of the fluid inside the CPC solar collector absorber tube. Numerical simulations of the fluid flow equations inside the CPC solar collector absorber tube, along with the energy equation for the absorber tube wall, coating, insulation and reflector, and solar collector heat analysis, were performed repeatedly in MATLAB and Aspen HYSYS software. This method is the most appropriate and reliable method for solving equations for numerical convergence. The experimental results of the parabolic concentrated solar collector (CPC) were used to evaluate and validate the numerical model. A solar compound parabolic concentrators collector (CPC) with short reflectors was used. This collector includes a cylindrical absorber with a real density ratio of 1.8, a reception angle of 22 degrees and a length of 2.81 m, a width of 0.32 m, and an opening of 0.1764 m. Analysis and uncertainty of the proposed model were performed with the measured sample. In the thermal efficiency analysis, the average deviation of the model from the experimental results of other researchers was equal to 7%, for increasing the temperature by 9 °C. According to these results, a good correlation between numerical results and experimental results for this proposed model has been obtained.

Numerical Model of the Double-Pipe System with Protective Layer

Nowadays, higher performance is being sought in newly built power plants. The efficiency of power plants is mainly achieved by maximizing the steam parameters. Consequently, ever more expensive high-alloy steels are being used. For this reason, design concepts, in which high efficiency with lower investment costs are becoming increasingly popular. Such an innovation is the double-pipe system with a protective coating, which provides thermal insulation for the primary pipe in which the supercritical steam flows. This pipe is also cooled by an external flow by the steam with lower parameters. The article presents the developed two-dimensional numerical model. The use of the Galerkin method enables the complete transient analysis of a double-pipe system to be carried out, considering temperature-dependent material properties. The numerical model was compared with the computational fluid dynamics model. The temperature gradient in the inner pipe wall with and without coating was determined. In addition, the response of the wall temperature to a change in steam temperature was investigated. As observed, the protective layer can improve boiler performance characteristics when applied to thick-walled boiler components. It can also enable the use of less demanding steel.

A peridynamic study on the effects of surface topography on rolling contact fatigue

A peridynamic(PD) fatigue simulation model is developed to study the effect of surface topography on rolling contact fatigue(RCF). Based on the PD fatigue damage-cumulative model proposed and verified in a previous study, a two-dimensional PD numerical model of the contact area of the rolling bearing is established, and the crack evolution and fatigue life of the model including surface topography with different dents and roughness are analyzed. The results show that cracks initiate from the shoulders of the dent, and then form spalling at the trailing edge, which is consistent with the experimental observations. Simulation of the model with sinusoidal and random rough profiles shows that there is competition between surface and subsurface crack nucleation. The larger the roughness amplitude or wavelength, the more prone to surface nucleation. Finally, the effects of roughness amplitude and wavelength on surface-originated pitting, subsurface-originated spalling and fatigue life are analyzed.

Enhanced heat transfer in a phase change energy storage with helical tubes

Solar collectors integrated with phase change materials (PCM) store heat energy for later use. However, the settling of PCM prolongs the melting duration in a vertical cylindrical container. Hence, selective methods are required to alleviate such solid PCM settling issues. A helical heat transfer tube (HTT) can improve melting by increasing the contact surface. The present research studies the charging and discharging of PCM using three helical coil HTT configurations: fully expanded, semi-compressed, and fully compressed. The fluid flow rate and inlet temperatures are 20 LPH and 80 °C, respectively. The simulation involves two-dimensional numerical modeling using Ansys Fluent software and the finite volume method with the enthalpy-porosity technique. The fully compressed HTT melt settled PCM inside the vertical cylindrical container faster. The experimental results show that using a fully compressed HTT reduced the melting time by 50 % compared with a fully expanded HTT of 160 min due to the effective melting of settled PCM. Its peak heat stored, energy efficiency, Nusselt, Stefan, and Rayleigh numbers are 356 kJ, 34.8 %, 75.34, 0.47, 2.8036 × 107, respectively. The compressed HTT is a practical design suggested for solar collectors and low-temperature heat recovery systems, which demand a fast heat storage rate.

Study of lateral assembly of magnetic particles in magnetorheological fluids under magnetic fields

This study uses a numerical simulation method to investigate the lateral assembly mechanism exhibited by equal-radius circular magnetic particles in magnetorheological fluids (MRFs). We used a direct numerical simulation method based on the finite element and arbitrary Lagrangian–Eulerian methods to establish a two-dimensional numerical model on particle–particle, particle–magnetic field, and particle–flow field interactions. The critical lines of gravitational and repulsive forces between magnetic particles and magnetic particle chains in a uniform magnetic field were investigated. The lateral assembly areas were found through these critical lines. Experiments confirmed that the sizes of the lateral assembly areas of the magnetic particle chains positively correlated with the lengths of the magnetic particle chains. In addition, the coarsening mechanism of magnetic particle chains was investigated by lateral assembly areas. Hence, this work offers insights toward understanding the mechanisms of microstructure formation in MRFs under magnetic fields.

Mechanism study on the synergistic coupling of the double-dish solar latent heat storage system to enhance heat transfer

With the rapid advance of the global economy, latent heat storage (LHS) is critical to solar thermal utilization. In this study, a double-dish solar Stirling LHS power generation system was designed. The heat transfer performance of the thermal storage system was improved by using the gradient tree-shaped fins and adding graphene nanoparticles to paraffin. Two-dimensional numerical models of three thermal storage systems were developed to study the effects of natural convection and graphene nanoparticle concentration on the melting characteristics of paraffin. From the perspective of field synergy, the coupling effect of fin structure and graphene nanoparticle concentration on the heat transfer process was analyzed. The results show that natural convection exerts an important role in the heat transfer characteristics of paraffin melting. Compared with the six-longitudinal and snowflake fin structures, the gradient tree-shaped fin structure shows a 52.13% and 27.73% reduction in the complete melting time and a 52.16% and 9.53% increase in thermal storage efficiency. Little variation is observed in the liquid phase rate and the average temperature of the composite phase change materials (PCMs) with different concentrations of graphene nanoparticles. The total thermal storage capacity of composite PCMs is higher than that of pure paraffin. The synergistic coupling of gradient tree-shaped fin arrangement and graphene nanoparticles added in paraffin can enhance heat transfer.

Volumic Eddy-Current Losses in Conductive Massive Parts with Experimental Validations

In this paper, the analytical determination of volumic eddy-current losses in rectangular-shaped conductive massive parts is presented with experimental validations. Eddy currents, as well as the resulting volumic losses, are generated by a sinusoidal spatially uniform applied magnetic field. A U-shaped electromagnetic device with a flat mobile armature (or adjustable air gap) is used to measure the eddy-current losses. The experimental device, its instrumentation, and the conductive massive parts are presented in detail in the paper. Thereafter, the magnetic field distribution applied on the conductive massive parts, which is the mean input data for the eddy-current loss model, is studied. A two-dimensional (2D) numerical model, under the FEMM software, for the magnetic field calculation was also developed. A comparative analysis between the experimental measurements and the numerical results allowed the distribution of the applied magnetic field to be accurately validated. In the final phase, the objective was to estimate the volumic eddy-current losses in rectangular-shaped aluminium conductive massive parts generated by the variation of this applied magnetic field. An analytical model, based on the Maxwell–Fourier method, for the accurate prediction of eddy-current losses has also been developed. An electromagnet with and without the conductive massive parts is characterized in terms of power consumption. By using the power conservation method (i.e., Boucherot’s theorem), the eddy-current losses could be quantified experimentally. The influence of segmentation is also studied. The analytical results are compared to the experimental test results.

Numerical Analysis on Spanwise Correlation of Vortex-Induced Force of Split Double-Box Beam

The vortex-induced force of bridges is not synchronized along the span direction. The spatial correlation of vortex-induced force becomes obvious when the span of the bridge structure gradually increases, and the mass gradually decreases. Therefore, it is important to study the spanwise correlation of vortex-induced forces of long-span bridges to ensure the accuracy of the prediction of vortex-induced vibration response of bridges. The study established and improved the theory and experimental research methods for vortex-induced vibration analysis of large-span bridges by discussing the spanwise correlation during vortex-induced vibration of the split double-box beam. Taking Xihoumen Bridge as the object, two-dimensional (2D) and three-dimensional (3D) numerical models of the scaled-down sections were designed and established based on the ANSYS Fluent platform and the RANS SST turbulence model. Based on the Newmark-β algorithm, a User Defined Function (UDF) was written for vortex vibration calculation, the three-dimensional bypass of the split double-box beam in static conditions and vortex-induced vibration of the split double-box beam of which were calculated, and the spanwise correlations of the aerodynamic coefficients, the surface pressure coefficients, and the wake wind velocity of the main girder section were analyzed for the static and vibration states of the bridge. The results show that the self-excited force of the split double-box beam in vortex-induced vibration improved its spanwise correlation. Compared with those in a static state, the spanwise correlation of the lift coefficient and torque coefficient increased by 55% and 87%, respectively, and the resistance coefficient increased by more than 10 times. The correlation of the pressure coefficients increased by 153%. The correlation of wake wind velocity increased by 37% in the along-wind direction and that in the across-wind and vertical-wind direction increased by more than 10 times. The accuracy of the numerical simulation results was verified by comparing the pressure distribution and pressure spanwise correlation of the main beam with field-measured data.

Dynamic Evolution Modeling of a Lake-Terminating Glacier in the Western Himalayas Using a Two-Dimensional Higher-Order Flowline Model

To better understand the future evolution of Jiemayangzong Glacier (JMYZG), the headstream of the Yarlung Zangbo River, we simulated its future ice thickness evolution using a two-dimensional higher-order numerical flowline model. Due to the sparsity of in situ observational data, we used a combination of field observations and inversion models of velocity and ice thickness to initialize the model parameters. We validated the parametrizations of the calving scheme by comparing the modeled and observed glacier terminus retreats. To estimate the response of JMYZG to climate change, the ice flow model was forced with different climate scenarios. We found that the JMYZG will retreat under different climate scenarios. By 2100, the volume loss of JMYZG will be approximately 34%, 67% and 81% under SSP1-2.6, SSP3-7.0 and SSP5-8.5, respectively.

Numerical Simulation of Wave–Current Force Characteristics of Horizontal Floating Cylinder in Heave Motion

This paper presents the characteristics of the heave motion responses and hydrodynamic forces of a horizontal floating circular cylinder during a wave–current interaction. A two-dimensional numerical model based on the CFD (Computational Fluid Dynamics) method for modeling wave flow is validated and verified. The hydrodynamic characteristics of the horizontal floating cylinder during heave motion were calculated and analyzed under the conditions of different k values (stiffness of spring), wave amplitudes, submerged depths, and flow rates. The results show that, with the increase in the k value, the vibration amplitude of the cylinder first increases and then decreases. The vibration amplitude peak is achieved, the vibration frequency is consistent with the wave frequency, and a resonant motion takes place. When the wave amplitude and flow rate are fixed, the maximum vibration amplitude decreases as the wave period increases. When the cylinder is half-submerged, the effect of the current on motion is significant; the vibration amplitude is less than the wave amplitude. When a quarter is submerged, the vibration amplitude is larger than that of the half-submerged cylinder at each k. The maximum amplitude is greater than the wave amplitude, and the vibration amplitude reaches the minimum at the moderate flow rate for each k.

Thermal control of lithium-ion batteries for electric cars by metal foam partially filled with Phase Change Material

A viable solution to environmental problems related to pollutant emissions from internal combustion engine vehicles is electric cars. The main problem with electric vehicles, which also limits their widespread use, is due to lithium batteries and in particular their thermal control. Thermal control of lithium batteries is an extremely topical issue since it is not only related to the performance of the vehicles on which they are mounted, but also to the safety of the vehicles and drivers. For this purpose, both factors internal to the battery itself and external causes such as environmental conditions must be considered.In this work, a thermal control system based on metal foams partially filled by the phase change material (PCM) was numerically investigated as a possible application for cooling lithium batteries. For this purpose, a two-dimensional numerical model was constructed in which the PCM partially fills the metal foam. The finite volume method used through the ANSYS Fluent code was used for the governing equations, which are written assuming local thermal equilibrium. Several cases were simulated for different values of the external convective heat transfer coefficient. The results obtained, are reported in terms of temperatures and liquid fractions. Comparisons with partially filled and totally filled cases by PCM in the thermal control system are reported to show the advantage obtained, in terms of thermal control, with a composite system of metal foam and PCM.

CFD modelling of spatiotemporal evolution of detailed tar species in a downdraft gasifier

The rising demand for renewable energy around the world has sparked interest in biomass gasification. However, the technology greatly suffers because of tar species produced during the gasification process, which limits direct use of the produced gas. To address this issue, the paper presents a novel piece of work that focuses on the formation and evolution of tar species consisting of benzene, naphthalene, toluene, and phenol. A two-dimensional numerical model for a downdraft biomass gasifier is developed with a total of 20 thermochemical kinetic reactions to investigate the formation of tar species in the gasifier with the effect of residence time. The model's predictions are validated with the experimental and kinetic data and found to be in good agreement. Besides, the model's ability to simulate the producer gas production from a downdraft gasifier is examined. Reaction rates for volatiles decomposition, combustion, and gasification reactions under different working conditions are investigated. Overall, benzene has the highest concentration of the selected tar species, followed by naphthalene, and with relatively modest amounts of phenol and toluene.

Accuracy of Seismic Response Evaluation of Two-Dimensional Analysis Model with Rigid Joints for RC Frame Buildings.

Three- or two-dimensional (2D) numerical models are used for the evaluation of the seismic performance of reinforced concrete (RC) buildings. This study examines a 2D numerical model for a specimen used in a full-scale four-story RC shaking-table test and evaluates the accuracy of the seismic response of the 2D numerical model, which is composed of a square fiber section model for the columns, a T-shape fiber section model for the beam and slab, and a rigid joint model for the beam-column joint. A parametric analysis of the effective slab width is performed to analyze its effects on the modal shape and natural period. The results suggest that the primary natural period of the considered model is almost identical to that associated with the experimental results. The applicability of the 2D numerical model for estimating the seismic response of the structure is established. By comparing the results of the seismic analysis and the experiment in the 50% amplitude of the JMA-Kobe wave, which corresponds to slightly exceeding VII on the modified Mercalli intensity scale, the root-mean-square percentage error of the 2D numerical model is 1.03% for the floor acceleration and 4.7% for the inter-story drift. Thus, the analytical model used in this study has sufficient accuracy in evaluating the seismic performance of buildings constructed in regions with a maximum seismic intensity of VII.

Soil-structure interaction of integral abutments

Integral abutment bridges (IABs) are pioneering structures that offer certain advantages over conventional bridges. The main difference is the ability of IABs to eliminate the necessity of utilizing bearings and expansion joints. This results in more economical construction and enhanced structural performance. However, the intricate soil-structure interactions of IABs under the influence of seasonal changes are not yet fully understood. This paper aims to improve the understanding of these innovative structures by utilizing comprehensive numerical models to investigate their geostructural performance under various conditions. The case study selected for this research was the Middlesex bridge in Vermont, USA. A full-scale monitoring program at this bridge measured and recorded the bridge acting pressures, deformations, and internal forces, making it possible to gain insight into the thermal response of such structures. For the numerical research, a comprehensive two-dimensional numerical model, developed by using the PLAXIS software, was verified against the available field measurements. Subsequently, parametric studies were conducted to investigate earth pressure and pile bending moment variations influenced by different model conditions. Key model parameters were varied, including the constitutive soil model, thermal loading, backfill stiffness, pile size and orientation, and span length. It was found that utilizing a linear constitutive soil model could lead to significant inaccuracies in the results. Increasing the backfill stiffness was seen to increase passive earth pressures and decrease pile bending moments. With smaller pile sections, oriented for weak-axis bending, pile bending moments decreased substantially and lateral earth pressures increased. Because dead load magnitudes were closely linked to span lengths, pile bending moments and backfill pressures increased when fewer and longer bridge spans were used.

Modeling the hydrodynamics of a tidal inlet during bay-side storms

Bay-side storms, defined here as storms with tracks on the landward side of barrier islands, may disturb the hydrodynamics of inner bays to a larger extent than on the ocean side. These storms are common in large-scale O(>100,000 m) estuarine systems and have the potential to modify the circulation in bays and within tidal inlets. Here, we provide an overview of the hydrodynamic response of a tidal inlet under forcings caused by bay-side storms and explore the role of waves in modulating the release of storm surge from the back-barrier regions into the ocean. A two-dimensional horizontal numerical model including wave-current interactions is calibrated and validated against field observations of water levels and depth-averaged velocities at Oregon Inlet, NC. The model is then used to investigate the effect of synthetic bay-side storms with varying wave conditions and water levels based on those generated by Hurricane Irene (2011), which is the strongest bay-side storm to hit the Outer Banks of North Carolina in the last two decades. Effect of timing of the peak storm surge during the ebb and flood phases of the tide is also explored.Results from synthetic storms indicate that, during bay-side storms, the water level gradient along the inlet favors ebbing flows regardless of the timing of the storms relative to tidal phase. These results suggest that waves might be responsible for any influx of volume to the bay during high bay-side surge events. Wave blocking effects were found to be stronger along the ebb shoal and only reached the flood delta when bay water levels were nearly the same as the ocean water levels. Reduction of currents by waves in the inlet have the potential to extend the duration of the inundation period in the back barrier region. Bay-side storms also caused flux enhancement over inlet shoals and channels in the flood delta, which could have implications for circulation patterns as well as the morphodynamics of the system.

Effects of Different Heat Transfer Conditions on the Hydrogen Desorption Performance of a Metal Hydride Hydrogen Storage Tank

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption.

Numerical investigation of solute transport into deformable marine sediments driven by ocean waves

Most existing studies do not consider the effect that the deformability of submarine sediments may have on solute transport under the action of ocean waves. In this study a two-dimensional numerical model based on Biot’s poro-elastic consolidation theory and an advection–dispersion equation is established to investigate the transport of non-reactive solute into a deformable porous seabed under the influence of ocean waves. The numerical model is then validated against experimental and analytical results in order to demonstrate its accuracy and robustness. The simulation results indicate that ignoring the deformability of seabed soil and associated seepage force due to ocean waves may lead to a significant underestimation of the rate of solute transport in shallow layers of marine sediment, particularly fine sand or silt. The effects of parameters such as the shear modulus, non-dimensional mechanical dispersion coefficient (related to particle size and permeability), dimensionless sediment thickness, wave steepness and the relative water depth have on solute transport into deformable sediments were investigated. The results indicate that the ratio of the longitudinal coefficient of mechanical dispersion between deformable and non-deformable sediments that can represent the enhancement of solute migration due to soil deformation may reach up to 85. This becomes more pronounced as the shear modulus and permeability of sediments decrease and the depth of water increases when the sediment thickness is less than 0.8 times the wavelength. The rate of solute transport in deformable sediments reaches its maximum when the sediment thickness is about 0.2 times the wavelength. In fact, as the relative water depth increases from 0.1 to 0.3, the enhancement of solute migration due to wave-induced soil deformation increases by about 60%-80%. In comparison to linear waves, shallow water waves, e.g., the first-order cnoidal waves, can increase the transport of solute more due to its strong non-linear behaviour, particularly in deformable seabed.