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Manual welding operations are performed inside the engine room of a liquefied natural gas carrier under construction. The welders are at risk of exposure to welding fumes in case of poor ventilation. Therefore, ventilation fans are installed at shipbuilding sites to improve indoor air quality. Although ensuring the respiratory health of welders is important, studies focusing on ventilation in the ship engine room have not been conducted. Therefore, the ventilation efficiency was evaluated herein based on the placement of ventilation fans to alleviate air stagnation using a computational fluid dynamic (CFD) model operating on Fluent. The mean age of air (MAA) was computed to assess the ventilation efficiency. In addition, particles with size and physical properties similar to welding fumes were sourced assuming 30 welders in the engine room. Results revealed that ventilation fan and/or exhaust in enclosed spaces contributes significantly to alleviating the MAA level. MAA and particle distribution did not correlate well due to the different properties of air and the iron oxide particle. Therefore, to determine the optimal ventilation fan displacement, particle motion should be studied along with performing MAA analysis. The proposed CFD model potentially guides to improvement of the working environments and respiratory health of welders.

Cone coils have a larger surface area and produce more turbulence, which enhances the heat exchange rate, making them a more efficient option for improved heat transfer than simple coils in shell-and-coil heat exchangers. In addition to reducing fouling and the requirement for maintenance, the cone shape may also provide the benefit of a self-cleaning action. Ensuring a more even flow distribution maximizes the heat exchanger's surface area use and reduces poor-flow zones. Applications needing compact solutions without compromising performance significantly benefit from this design's versatility, allowing customization to meet unique operational demands. This work evaluates numerically the impact of employing a cone-shaped coil tube in a shell-and-coil tube heat exchanger, considering various configurations and coil pitches. A commercial CFD code is used to perform the numerical simulations based on the finite volume approach. The present study has two sections. In the first part, three different coil configurations were considered. The best case was considered according to the numerical results obtained from the first section. Then, in the second part, the impact of the cone coil pitch on the hydrothermal characteristics was analyzed. The obtained numerical outcomes revealed that the best performance evaluation criteria factor belongs to the cone-shaped coil with divergent configuration by about 64.1 % and 57.45 % more than the cone-shaped coil with convergent configuration at De = 1,000 and De = 2,500, respectively. Moreover, the cone-shaped coil with a divergent configuration displayed higher JF values by approximately 61.54 % and 58.06 % than a cone-shaped coil with a convergent configuration at De = 1,000 and De = 2,500, respectively. Among different evaluated cone coil pitches, the maximum performance evaluation criteria factor belongs to the case with pitch values of 40 mm. Moreover, the JF value increases by approximately 4.76 % and 5.56 %, respectively, at De = 1,000, when the pitch value grows by around 60 % and 100 %. Furthermore, when the pitch value climbs by 60 % and 100 %, at De = 2,500, the JF value rises by roughly 12.16 % and 19.59 %, respectively.

The present study aims to propose a coupled numerical model for analyzing the influence of the configuration of the vapor-cooled shield tubes on insulation performance. The numerical model is developed to calculate the effective thermal conductivity of multi-layer insulation (MLI) and rigorously evaluated. Specifically, the tank evaporation simulation software BoilFAST is manually coupled with the CFD commercial software of ANSYS FLUENT (2020 R2) to accurately determine the mass flow rate and temperature of boil-off gas in a tank, which is then used as inputs for the CFD simulations. This coupling methodology can be used for reliable calculations of boil-off losses for liquid hydrogen and heat transfer inside the MLI structures. Results demonstrate that the estimated effective thermal conductivity agrees with the earlier published data and that increasing the diameter and number of tubes enhances heat exchange between the VCS tubes and MLI structures. Also, the heat flux into the tank is relatively reduced by 32.04 % by increasing the diameter of the tube and 49.14 % by adding the number of tubes. Moreover, the maximum temperature difference of the VCS is estimated to be less than 1 K, indicating nearly uniform distributions of the VCS.

This research thoroughly examines heat transfer and fluid flow in a passage flow system, highlighting the difficulties posed by different geometric arrangements and temperature conditions that may affect the system's performance. The main aim is to evaluate the impacts of different geometric characteristics on the velocity, pressure, and temperature profiles inside the flow route. These factors encompass cavity dimensions, tube diameter, and input conditions. An inclusive comparison of three different geometric designs at controlled temperatures is conducted using computational fluid dynamics (CFD) simulations. The findings indicate that the optimal geometric parameters improve thermal performance, with certain arrangements displaying improvements in heat transfer rates up to 30 %. In this regard, the higher cavity dimensions and suitable input velocities are exposed as advantages. The first sample exhibited a higher velocity of 0.024 m s-1 due to its simpler geometry and favorable heating conditions, while the third sample demonstrated a higher temperature of 465 K due to its complex cavity shape and multiple heating sources. This study suggests that enhancing efficiency in heat management applications necessitates a strategic design approach for passage flow systems, which must account for flow characteristics and geometric specifications. This research would provide insightful information for designers and engineers looking at enhancing fluid flow systems across a range of industrial applications.

Fluid flows containing dispersed particles are abundant in both nature and industry. Simulating such flows, especially with high volumetric fractions of the dispersed solid phase, is challenging due to the complexity of solid–fluid and solid–solid interactions. In this paper, we introduce OpenHFDIB-DEM, an open-source software that couples computational fluid dynamics (CFD) with hybrid fictitious domain immersed boundary method (HFDIB) and discrete element method (DEM). The software is developed as an extension of the OpenFOAM library. The main contribution lies in a custom DEM implementation that is fully integrated in the OpenFOAM framework and allows for CFD-DEM simulations of various flows with arbitrarily shaped solids defined by triangulated surfaces in stereolithographic (STL) format.

One of the most expensive power system components is transformer. The correct use and health of the transformer increase the reliability of the power network.The transformer health is depend on careful planning for it. Therefore, hot spot temperature must be calculated for accurate transformer planning. Also, in order to increase the accuracy of transformer hot spot temperature estimation, the dynamic thermal model is used. On the other hand, the use of meta-heuristic algorithms has been less considered by researchers to calculate the transformer hot spot temperature. Thus, in this paper, the grey wolf, imperialist competitive and artificial bee colony algorithms are used to estimate the transformer hot spot temperature. Besides, electromagnetic analysis of the transformer is investigated using ANSYS-MAXWEL software. On the other hand, conjugate heat transfer modeling in the transformer is presented to compare the results with the grey wolf optimization algorithm. The results show that the grey wolf optimization algorithm can be a good alternative for transformer hot spot temperature estimation.

Indoor air quality (IAQ) in confined spaces like bank vaults and basements is influenced by complex factors such as building layout and HVAC systems. This study examines how mechanical ventilation impacts IAQ in a bank building's occupied basement vault, addressing significant challenges posed by pollutant exposure in these air-tight environments. This study advances safe IAQ in confined spaces, crucial for occupant health and safety, using CFD (ANSYS Fluent Workbench 16.0) and CONTAM 3.2 software for multi-zone ventilation and air quality analysis. It analysed three indoor pollutants: Radon (Rn), Carbon dioxide (CO2), and Particulate Matter (PM2.5), enhancing the reliability and applicability of the findings. The findings indicated that the simulated indoor pollutants concentrations did not exceed the indoor air quality guideline levels. The CFD simulations predicted average steady-state values of 27.2 Bq/m3 for Radon, 574.80 ppm for CO2, and 69.36 µg/m3 for PM2.5 in the basement. For different outdoor air floor rates, an optimal ventilation rate of 4.7 ACH and a cooling load of 17 kW were determined to maintain Radon concentrations below 15 Bq/m3. This provides a practical and actionable solution for maintaining safe IAQ in confined spaces, which is a significant step forward compared to similar studies. These results align with other experimental research, validating the use of numerical techniques in indoor air quality studies. By optimizing HVAC systems to maintain IAQ and minimize energy consumption, the study supports SDG 7 (Affordable and Clean Energy) by enhancing energy efficiency, SDG 3 (Good Health and Well-being) by reducing exposure to indoor pollutants, and SDG 11 (Sustainable Cities and Communities) by improving air quality management in confined spaces. The findings are particularly relevant for Africa, offering practical solutions, informing policy direction, and supporting the African Union's Agenda 2063 and SDGs 3, 7, and 11.

Boiling flow presents a significant concern, especially when a liquid surpasses its boiling point, potentially leading to catastrophic consequences. This research utilizes a two-phase code in the OpenFOAM software to investigate bubble formation during flow boiling. The well-established empirical models for calculating wall heat components were selected based on the operating conditions. The study incorporates experimental data from high-pressure boiling flow (10–30 bars) with variable properties of refrigerant R-12. The predictions reveal underpredictions in void fraction and liquid temperature compared to experimental observations. Significantly, the impact of the subcooling degree on void fraction behaviour is emphasized, and a potential underprediction of the evaporation portion is highlighted, particularly near the wall. Challenges in modelling bubble size distribution are evident through discrepancies in bubble diameter and velocity data, indicating the necessity for further advancements in the code. In summary, this numerical study provides valuable insights into the intricate dynamics of high-pressure subcooled boiling flow, especially when considering variable working fluid properties. Future efforts will focus on refining models for nucleation site density, bubble departure size, and lift-off frequency to enhance prediction accuracy.

A transient transport flow model is adopted in a renal bifurcated artery with different stenosis cases to examine the flow phenomena when the non-Newtonian blood flow regime within the three-dimensional space domain is chosen as a pulsatile nature. The nonlinear governing equations are solved using the Finite Element Method with suitable initial-boundary conditions. During numerical computation, distinct hemodynamic parameters including Wall shear stress, Reynolds number, power law index are evaluated based on different stenosis severities (0%, 25%, and 50%) and stenosis lengths (0mm, 0.5mm, and 1mm). For 0%, 25%, and 50% stenosis, the approximate values of velocity and pressure profiles are estimated at t = 5s at various positions, and achieved the highest velocities that were around 0.07m/s, 0.08m/s, and 0.13m/s respectively. The unsteady response of the stress due to stenosis-induced shear on the outside wall is described as a result of stenosis at t = 0.1s, 0.2s, 5s. The flow is severely restricted by constriction, which increases wall movement and produces stress, depending on the amount of stenosis. As pulsatile flow time increases due to the presence of stenosis, the wall shear stress decreases gradually. The impact of Reynolds numbers on pressure profiles and velocity profiles are displayed for Re = 100, 300, 500, and 700, and found that both velocity and pressure outlines increase significantly. In order to identify the flow phenomena, the influences of the power law index for n = 0.1, 0.3568, 0.5 are presented on the velocity and pressure profiles. Shear-thinning flow occurs for 0

Objectives: This study aims to delineate the specific impact of using computational fluid dynamics (CFD) and 3D virtual surgery techniques in otolaryngology surgery, focusing on their roles in enhancing the precision of nasal surgery and optimizing future patient outcomes. The central objective was to assess whether these advanced technologies could reduce variability in surgical approaches and decision-making among specialists, thereby improving the consistency and efficacy of patient care in cases of nasal obstruction. Methods and results: Our methodology involved a detailed analysis of pre- and post-operative scenarios using CFD feedback. Six otolaryngologists participated, employing virtual surgery techniques on two patients with diagnosed nasal obstruction. The CFD analysis focused on quantifying key airflow parameters: right nasal flow rate (QR), left nasal flow rate (QL), flow symmetry (Ф), and bilateral nasal resistance (R). These parameters were meticulously compared before and after the application of CFD feedback to evaluate changes in surgical planning and outcomes. Quantitative analysis revealed a notable decrease in the standard deviation of the measured parameters among the specialists post-CFD feedback, indicating reduced variability in surgical approaches. Specifically, for Patient #1 the standard deviation for QR values dropped from 0.694 L/min to 0.602 L/min, and for QL values from 0.676 L/min to 0.584 L/min, and for Patient #2, the standard deviation for QR values decreased from 2.204 L/min to 0.958 L/min, and for QL values from 2.295 L/min to 1.014 L/min. Moreover, the variability range, represented by the differences between the maximum and minimum values for Ф and R, diminished significantly. Post-operative average values for all parameters showed a convergence towards ideal basal levels, suggesting a more uniform and effective surgical strategy across different surgeons. Conclusions: Both integration of CFD and 3D virtual surgery techniques in otolaryngology can substantially reduce variability in surgical planning and decision-making, ultimately leading to improved patient outcomes. These advanced tools have the potential to standardize the diagnosis and treatment of nasal pathologies, contributing to more effective and consistent care. Future research in this area should focus on larger patient cohorts and further exploration of the potential benefits and applications of CFD and virtual surgery in otolaryngology.

Background: Contrast retention (CR) is an important predictor of left atrial appendage thrombus (LAAT) and stroke in patients with non-valvular atrial fibrillation (AF). We sought to explore the underlying mechanisms of CR using computational fluid dynamic (CFD) simulations. Methods: A total of 12 patients with AF who underwent both cardiac computed tomography angiography (CTA) and transesophageal echocardiography (TEE) before left atrial appendage occlusion (LAAO) were included in the study. The patients were allocated into the CR group or non-CR group based on left atrial appendage (LAA) angiography. Patient-specific models were reconstructed to evaluate time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and endothelial cell activation potential (ECAP). Additionally, the incidence of thrombosis was predicted using residence time (RT) at different time-points. Results: TAWSS was lower [median (Interquartile Range) 0.27 (0.19–0.47) vs 1.35 (0.92–1.79), p

In this paper, phase change material (PCM) based hybrid thermal management strategies are proposed for cylindrical Lithium-ion battery modules. Experimental and numerical studies are conducted to analyze the proposed strategies at a high discharge rate of 7 C. Three different types of thermal management configurations are developed. In all the configurations primary coolant is the PCM and secondary coolants are liquid and air. In one of the configuration vertical liquid coolant channels are placed between the PCM and airflow at the top of the cells. Whereas, in the two configurations different designs of cold plates are utilized in place of liquid channels. The experimental studies are conducted to obtain the temperature and heat flux profiles of the battery module. Moreover, a numerical model is developed and validated using the experimental data obtained. Using the numerical model, the thermal performance of the battery module was obtained for the proposed strategies. Based on the results, the maximum temperature of the battery module was limited to 29.1 °C and a high temperature uniformity was achieved by the end of the discharge cycle with the temperature difference limited to 1.2 °C. Additionally, the proposed hybrid thermal management strategy was capable of maintaining the required optimal thermal operating conditions without changing the phase of the PCM. Furthermore, it eliminates the requirement of a pump and reservoir since there is no flow of liquid within the battery module. This reduces the energy required for the operation of the thermal management system, thereby increasing the available energy for propulsion. Additionally, the developed strategy also increases the safety of the battery modules as it is capable of maintaining the required thermal environment in high discharge rates up to 7 C.

Laser cladding with coaxial shroud protection offers the possibility to process reactive metals in an open environment. The numerical analysis was performed on the thermal field and dynamics of molten pool with the aim of clarifying the mechanism of the complex effects of the applied extra shielding gas on the resultant microstructure and surface quality of cladding layers of Ti6Al4V. A three-dimensional (3D) computational fluid dynamics (CFD) model was first developed to investigate the extra shielding gas effect on the molten pool. The simulation shows that the extra shielding gas influences both the surface and internal flow field characteristics of the molten pool. The predicted solidification parameters imply fully columnar microstructure in the entire cladding layer. Comparative analysis was then carried out between the numerical simulation and experiments. The electron backscattering diffraction (EBSD) examination reveals that the high cooling rate due to the extra shielding gas inhibits the formation of grain boundary α phase and simultaneously refines the microstructure. The extra shielding gas reduces the surface roughness of cladding layers, and its bunching effect improves the powder utilization. The multi-track cladding experiments reveal that the extra shielding gas can effectively suppress crack formation with a large overlap ratio. This study provides a better understanding of the effect of extra shielding gas flow on molten pool, which helps control and improve the quality of cladding layers.

Based on computational fluid dynamics and large-eddy simulation technologies, a numerical simulation method of a moving thunderstorm field is established by considering the impinging jet model. In addition, the influence of movement speed of the storm center and jet velocity changes on the characteristics of the wind field is presented. By drawing horizontal wind speed radial profile curves, the vertical profile curves of horizontal wind velocity, radial wind profile curves of vertical wind speed, and transient wind speed characteristics of a moving thunderstorm downburst are illustrated. The results demonstrate that the wind field of a moving thunderstorm exhibits clear asymmetric characteristics. As the height from the ground increases, the horizontal wind speed first increases and then decreases. The extreme value of the horizontal wind speed appears at the position of (0.01–0.03) Djet (where Djet is the jet spout diameter) near the ground, which is consistent with the characteristics of a static thunderstorm wind field. Simultaneously, the distribution characteristics of wind pressure on the surface of wind turbines under moving thunderstorms is further studied. By considering variations of the wind attack angle, jet velocity, and moving speed, the results of wind pressure on the tower and blades of the wind turbine are presented. The coupling of the moving speed and jet velocity has a significant influence on the wind field and pressure on the wind turbine surface.

Dissimilar metal welding poses a significant challenge for researchers in the welding and materials science communities due to the different properties of the metals involved. In this study, we present a novel approach for determining the optimal processing parameters for continuous laser welding (CLW) of dissimilar metals, specifically aluminum and copper, using a circular strategy. The approach utilizes computational fluid dynamics (CFD) simulations to model the welding process and predict joint quality. We validated a CFD-based numerical model for predicting the melt-pool shape across a range of laser power and circular welding speed values. Additionally, we developed artificial neural network (ANN) models that can predict melt pool interface width, penetration depth, and copper concentration for any combination of processing conditions. Using surrogate modeling, we identified the optimal values of laser power and welding speed that result in the highest quality joint. Our results showed that the optimal processing conditions were a laser power of 2950W and a circular speed of 55 mm/s, which resulted in a high-quality Al–Cu joint with maximum shear strength of 2200 N. Microstructural analysis and tensile-shear strength testing confirmed that the optimal conditions resulted in a low degree of intermixing and the absence of large intermetallic compounds (IMCs) in the weld seam. Overall, study offers a valuable contribution to the welding and materials science communities by presenting a novel approach to address a common challenge in dissimilar metal welding. Our approach can be applied to other types of dissimilar metal welding and may inform the development of new welding techniques in the future.

The shape of the slit that injects the jet from the surface of the propeller was optimized through numerical computations. The high-pressure drop on the propeller surface caused by jet injection could be improved by modifying the hydrofoil geometry of the propeller. As the cover length increased and the slit was located at the center of the propeller, the volume of jets leading to the trailing edge increased, and the propulsion performance was improved. As the height of the slit increased, the thrust increased due to the Coanda effect, and the torque decreased because of the thrust of the jet. The jet injection pattern differed according to the area of the slit and tunnel, which caused a difference in the propeller performance. The jet pattern changed according to the area of the slit and tunnel, leading to a change in propeller performance. It was effective in improving the efficiency by injecting from as wide an area as possible, and the efficiency was improved by approximately 2 % considering the pump efficiency through optimization of the slit shape.

In general, the resistance of a real ship is estimated using an extrapolation method after doing experimental tests or numerical simulations with a model scale ship. Since the only Froude similarity is applied in the model test and simulation, the flow characteristics between the model and real ships could be different due to the inconsistency of Reynolds number. However, in the Computational Fluid Dynamics (CFD), the Froude and Reynolds numbers can be satisfied simultaneously because a fluid with virtual properties can be applied. This study investigated the effect of turbulence models and scales for a flat plate. And then the hydrodynamic feasibility of using a virtual fluid was investigated through numerical analysis. The resistance performance and flow structure of the ship were analysed by applying the virtual fluid, and they were confirmed how well these values and flow characteristics simulate the full-scale with a real fluid. This study shows that the results of a full-scale can be obtained at model scale by applying a virtual fluid instead of full-scale numerical simulations that require more computational resources.

Efforts to improve the hydrodynamic performance of high-speed ships have been underway for a long time. There are different approaches, one of which is to take advantage of an interceptor. Conventionally, the interceptor blades are mounted vertically on the ship's bottom transom, oriented at a zero-degree angle of attack (AoA). This study comprehensively explores high-speed ships' hulls with and without interceptor configurations, encompassing both negative and positive AoA of the interceptor, conducted through experimental and numerical methods using a fully captive model. The interceptors are strategically positioned and configured. Each configuration was examined under varying AoA settings, with uniform interceptor depths and systematic trim angle adjustments. The Computational Fluid Dynamics (CFD) approach simulates the local flow dynamics around the hull, thoroughly analyzing resistance, pressure distribution, lift force, wave profile, and trim moment. The results indicate that interceptor placement near the keel with AoA adjustments significantly reduces hydrodynamic resistance, while AoA changes have limited impact in other positions. Lift force analysis shows interceptors improve lift compared to the bare hull, but this improvement is not linear across positions. Furthermore, it is observed that adjustments in AoA influence lift, with a negative AoA generally being considered favorable. In summary, carefully considering placement, AoA, and height-to-length ratio is necessary to maximize interceptor advantages.

Early fire detection is essential for preventing catastrophic events, and fire detectors play a critical role in ensuring fire safety. Among the various types of fire detectors, photoelectric smoke detectors are widely used because of their ability to detect smoke at an early stage. The present study investigates the effects of changes in flow directions and inlet size on the smoke detection ability of a photoelectric smoke detector by conducting computational fluid dynamics (CFD) simulations. The results indicated that when the flow direction changes, the components in the optical chamber may hinder the smoke inflow and increase the detector activation time. Moreover, the smoke inlet size was found to affect the carbon monoxide concentration inside the chamber. The velocity magnitude distributions confirmed the correlation between the smoke velocity in the labyrinth structures entering the optical chamber and the detection ability of the smoke detector. These findings suggested that when optimizing the performance of a smoke detector, flow direction, inlet size, and amount of smoke introduced into the optical chamber should be considered. The current study suggested the modified design of the smoke detector to have superior detection ability in both directions compared to the base case in terms of activation time.

The flow velocity in compound open channels is greatly affected by the geometry of both the main channel (MC) and floodplain (FP). In this study, a numerical investigation of the joint effect between the FP divergence angle and the size of suspended sediment particles on sediment transport and flow depth-averaged velocity (DAV) in non-prismatic diverging compound channels was conducted. In addition, the influence of relative flow depth on the DAV in different flow directions (i.e., stream-wise and span-wise) was examined. Three divergence angles of 4.0, 6.3 and 11.3°, four sediment particle sizes of 1, 5, 50 and 500 µm and two relative depths of the FP with respect to the MC of 0.20 and 0.40 were considered during simulations. A Computational Fluid Dynamics (CFD) software ANSYS-Fluent was used to perform the required simulation scenarios and the DAV was expressed in terms of a dimensionless velocity (i.e., relative depth-averaged velocity; RDAV) to generalize the use of the obtained results. Results revealed that the span-wise RDAV gradient between the MC and FP at the middle and the end sections of the divergence reach is much larger in the case of higher divergence angle. Moreover, the presence of coarse sediment particles in the sediment-laden flow resulted in an augmentation in the fluctuations of span-wise and stream-wise RDAVs as compared to those obtained in the case of fine sediment particles. Results also showed that the span-wise RDAV gradient between the two subsections (MC and FP) increases with decreasing the relative flow depth. Sediment particle size had a considerable impact on the span-wise RDAV values, especially in the case of lower relative depth. As the sediment particle size increases, the distortion in the span-wise RDAV distribution curves increases. However, the stream-wise RDAV along the MC and FP decreases, as the sediment particle size decreases, especially in the case of higher relative depth. Based on the results, it can be concluded that the span-wise DAV gradient was greatly affected by the FP divergence angle and sediment particle size. The fluctuations in the span-wise DAV gradient were more pronounced in the case of higher divergence angles and coarser sediment particles. The stream-wise DAV distribution along the MC and FP was mainly influenced by the relative depth and sediment particle size. The stream-wise DAV dip along the MC and FP was more explicit in the case of higher relative depths and finer sediment particles.

The LabPET II detection module serves as the fundamental component within Positron Emission Tomography (PET) scanners designed for achieving ultra-high-resolution imaging of small to medium-sized animals as well as the human brain. To ensure peak performance, it is imperative that this module operates consistently at a stable temperature. In this paper, we present an automatic and real-time method to improve the thermal control of the scanner LabPET II by evacuating the heat to reduce the overall temperature and maintain the thermal stability of the system. Based on the Thermo-Electric Cooler (TEC) process, our method applies two numerical techniques, Computational Fluid Dynamics (CFD) and Heat Transfer Analysis (HTA). The Dirichlet Boundary Conditions (DBC) method is applied for the Application-Specific Integrated Circuit (ASIC) at 25∘ C. The real measurements confirm and validate the simulation results with the Finite Element Method (FEM) based on the software COMSOL Multiphysics™. Field-Programmable Gate Array (FPGA) implementation on the Development and Education (DE1) board is performed with comparative results study. The proposed method is both simple and practical, and ensures thermal stability at 35∘C for the duration of operation of the scanner, which has a complex structure.

A rotary excitation control valve is proposed in this paper. In order to study the interaction of the valve core groove parameters on the output flow velocity and pressure of the rotary excitation control valve, a dynamic simulation of the internal flow field of the rotary excitation control valve is carried out based on the Multiple Reference Frame Model (MRF), and the simulation results are experimentally verified. Based on the quadratic regression orthogonal test method, a significant non-lossy regression model of the groove parameters with the output flow velocity and pressure is established, and the response surface of the groove parameter interaction is obtained. The results show that the influence of groove parameters on flow velocity is in the order of width > depth > length, and the interaction between length and depth is the most significant; the influence of groove parameters on pressure is in the order of width > depth > length, and the interaction between width and depth is the most significant. The Response Surface Methodology (RSM) is used to optimize the groove parameters, and the best combination of groove parameters obtained is 20.00 mm in length, 5.65 mm in width and 8.00 mm in depth.

Due to health concerns, a device that separates soot particles based on their size is commonly used to monitor the concentration of soot particles in ambient air. This numerical study aimed to observe particle flow characteristics in low-volumetric separators and assess their performance under recommended operating conditions. The Computational Fluid Dynamics (CFD) technique, specifically the Discrete Particle Model (DPM) approach, was utilized to analyze the behavior of particles and calculate their velocities. The investigation focused on small harmful particles with sizes of 1 µm, 10 µm, and 20 µm. Three volumetric flow rates close to the manufacturer's suggestion, 10 l/min, 15 l/min, and 20 l/min, were examined to evaluate particle separation efficiency in the low-volumetric impact separator. The study revealed that the operating flow rate and the Stokes numbers of the particles significantly impacted the particle behavior, vorticity strength, and the efficiency of particle classification within the separator. The residence time of particles inside the impact chamber was identified as an important factor for assessing separation performance, as it is crucial to monitor and control the key parameters to optimize the separation process. The investigation recommended a flow rate of 15 l/min for efficient impact separation of the particles (PM1, PM10, PM20). The current classifying percentage for particles smaller than PM10 was approximately 70%. Therefore, future work will investigate the effects of the impact chamber's internal configurations to enhance the separator's efficiency, where the modified structure could be explored and recommended.

This study demonstrates the characteristics of two model packing configurations: 3D printed (3DP) catalyst monoliths on the one hand, and their conventional counterparts, packed beds of spheres, on the other. Cobalt deposited on alumina is selected as a convenient model system for this work, due to its wide spread use in many catalytic reactions. 3DP constructs were produced from alumina powder impregnated with cobalt nitrate while the alumina spheres were directly impregnated with the same cobalt nitrate precursor. The form of the catalyst, the impregnation process, as well as the thermal history, were found to have a significant effect on the resulting cobalt phases. Probing the catalyst bodies in situ by XRD-CT indicated that the level of dispersion of identified Co phases (Co3O4 reduced to CoO) across the support is maintained under reduction conditions. The packed bed of spheres exhibits a non-uniform distribution of cobalt phases, including a core-shell morphology with an average crystallite size of 10–14 nm across the sphere, while the 3DP monolith exhibits a uniform distribution of cobalt phases with an average crystallite size of 5–12 nm upon reduction from Co3O4 to CoO. Computational Fluid Dynamics (CFD) modelling was carried out to develop digital twins and assess the effect of the geometry of both configurations on the pressure drop and velocity profiles. Finally, the activity of both Cobalt-based catalyst geometries was assessed in terms of their conversion, selectivity and turn over frequencies under model multiphase (selective oxidation) reaction conditions, which showed that the desired 3D printed monolithic geometries can offer distinct advantages to the reactor design.

CFD of convective heat transfer remains a challenge, especially in channels with irregular rough walls due to the complex fluid dynamics over and between these roughness elements. This study investigates the performance of four commonly utilised RANS CFD models, namely Spalart-Allmaras (SA), Realisable k-ε, SST k-ω, and Reynolds Stress Model (RSM) in estimating the velocity and temperature profile as well as the skin friction coefficient and Nusselt number in smooth and rough channels. The CFD results were compared with DNS and experimental data in the literature. The roughness-resolving approach was used for all models to resolve the realistic geometry of irregular roughness in channel flows. The smooth-channel flow study was conducted at Reτ = 500, 1000, 2000, and 5000 and Pr = 0.71. Over this range, compared to smooth-wall DNS data from literature, the RSM showed consistent and satisfactory performance in estimating the velocity and temperature profiles within 2.54% and 4.21%, respectively; leading to the skin friction coefficient and Nusselt number in the smooth channels being predicted very well within 1.94% and 2.03%, respectively. The rough-channel flow study was performed at Reτ = 240, 360, 540, 720, 1000 and Pr = 1, with computational cells 7.8 times that of the smooth channel to resolve the irregular roughness geometry. Over this range, the Realisable k-ε showed the best performance in estimating the roughness function within 6.85%, while the results of the other models were wider at uncertainty levels of up to 36.9%. Similarly, the Realisable k-ε demonstrated the best performance in estimating the skin friction and Nusselt number in rough channels within 2.76% and 9.50%, respectively, while the performance of the other models was to a wider latitude ranging between 15.62% to 26.34%. In the present study, the Realisable k-ε with enhanced wall treatment showed the best capabilities in capturing the mean flow characteristics of both smooth and rough channels; however, its usage should be approached with caution in flows at higher Reynolds numbers. RANS models are also discussed for forced convection heat transfer at high Reynolds numbers. The results of this study should be useful in CFD studies on the effects of roughness in complex geometries without the need for LES and DNS.

In thermal systems, combination of PCMs with porous fillers with high thermal conductivity is a proper method to improve their performance. In photovoltaic thermal (PVT) systems, as porous fillers are introduced to the collector tube and PCM bulk, the thermal efficiency increases. Moreover, since the temperature of the PV unit has dropped, the electrical efficiency has improved too. However, the properties of the porous insertion, i.e., permeability and porosity, might affect the pumping work, and consequently, electrical efficiency. In the present study, the effect of metal foam insertions on thermal and electrical performances is analyzed using a computational fluid dynamics (CFD) method. The results show that installing metal foams with porosities of 0.70–0.94 inside the collector and PCM container of a PVT system improves the thermal efficiency without any considerable decrement in electrical efficiency. When copper foam with a porosity of 0.705 is installed within the collector and PCM tank, the highest thermal efficiency of 66.70% is achieved; while, when copper foam with a porosity of 0.94 is used, the maximum electrical efficiency of 13.24% is resulted.

This article demonstrates how to create a reliable Computational Fluid Dynamic (CFD) model of a 250 kW Internal Permanent Magnet Synchronous Motor (IPMSM), used in a dynamometer bench for testing electric motors, to address its overheating problems. The purpose is to investigate the rotor's high temperature levels and to propose mitigation strategies. Firstly, a literature review is conducted to highlight key difficulties and identify overlooked factors. Therefore, various novel aspects of the developed numerical model are outlined, such as an alternative way to treat rotating boundaries, how to model the presence of resins in the actual motor and the importance of mesh resolution in the air gap. Additionally, a novel procedure to accurately account for friction losses is presented. Following the model validation against experimental data, CFD predictions lead to the identification of the main cooling problem, related to air flow losses through vents in the air conveyor and in other components of the motor. Two solutions are then proposed, which allow for operating temperature reductions ranging from 25 K to 120 K.

The paper reports on the behaviour and dynamics of direct current electric arc in an industrial electric arc furnace. Electric arcs are intense energy sources involved in many industrial processes. The behaviour of electric arc is simulated in a 2D axisymmetric geometry. A 40 kA current flows between two electrodes with a gap of 0.25 cm. The flow of current creates a very powerful jet up to km/s. Such speeds pose the question of the importance of compressibility and what is the extent of the effects of compressibility on arc behaviour. To assess the effect of compressibility, two different simulations are performed: an incompressible and a compressible simulation. The first simulation considers a temperature-dependent density based on experimental measurement whereas the latter adopts the ideal gas law to calculate the density variation of the plasma. The incompressible results were previously validated and compared to the well-known results predicted by the literature. The numerical results of the two models are reported and compared in terms of flow, thermal fields, and voltage drop. The results show that compressibility affects several aspects of the arc. As expected, the velocity drops when compressibility is present, however, the voltage drop increase significantly. Additionally, compressibility introduces a repetitive pattern of voltage drop over time which also depicted in the arc dynamics. The pattern is divided into three distinctive dynamics: (1) High-frequency low amplitude instabilities, followed by (2) low low-frequency high amplitude instabilities region, and finally, a relatively (3) stable interval of voltage with a bell-shaped arc.

The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator, and thus a Eulerian multi-fluid volume of fluid (VOF) model was first proposed to describe the particulate flow in spiral separators. In order to improve the applicability of the model in the high solid concentration system, the Bagnold effect was incorporated into the modelling framework. The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature. Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model, and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature. Furthermore, the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator. When the Bagnold lift force model was considered, predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data. In the initial development stage, the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force. Thus, a better predicted vertical stratification between quartz and hematite particles was obtained, which provided favorable conditions for subsequent radial segregation.

The mechanisms of abdominal aortic aneurysm (AAA) formation and rupture are controversial in the literature. While the intraluminal thrombus (ILT) plays a crucial role in reducing oxygen flux to the tissue and therefore decreasing the aortic wall strength, other physiological parameters such as the vasa vasorum (VV) oxygen flow and its consumption contribute to altered oxygenation responses of the arterial tissue as well. The goal of this research is to analyse the importance of the aforementioned parameters on oxygen delivery to the aneurysmal wall in a patient-specific AAA. Numerical simulations of coupled blood flow and mass transport with varying levels of VV concentration and oxygen reaction rate coefficient are performed. The hypoperfusion of the adventitial VV and high oxygen consumption are observed to have critical effects on reducing aneurysmal tissue oxygen supply and can therefore exacerbate localized oxygen deprivation.

Many issues have emerged more clearly than before in multi-storey residential buildings during quarantine and lockdown caused by the global pandemic COVID-19. Among these problems is the deterioration in people’s mental and physical health inside the home caused by quarantine and closure. This deterioration is due to inadequate passive ventilation, natural lighting, and the lack of green open spaces in and around traditional multi-storey residential buildings. Also, one of the most severe problems is the airborne infection transmission from a positive covid-19 person to others due to the lack of control in the entrance of buildings against an infected person. In this paper, we modified the shape of a traditional multi-storey residential building. Using Design-Builder and Autodesk CFD software, we create a simulation to compare the amount of natural ventilation and lighting before and after modifying the building’s shape. This work aims to increase the passive ventilation and daylight inside the building. Also, to achieve the biophilic concept to provide open spaces for each apartment to improve the mental and physical health of the residents. In addition, it protects the building users from infection with the virus. Through this study, we found that passive ventilation and daylight achieved more efficiency in the building that we have modified in its shape, which led to a 38% reduction in energy consumption. In summary, these findings suggest that by modifying the mass of the traditional multi-storey residential building with open green spaces provided for each apartment, the natural connection with the inhabitants of the building was sufficiently provided. Moreover, all this will significantly help improve residents’ mental and physical state, and it will also help prevent the spread of various diseases inside the homes.

The impact of rotor setting and relative arrangement on the individual and overall power performance and aerodynamics of double rotor vertical axis wind turbine (VAWT) arrays is investigated. Eight rotor settings are considered: two relative rotational directions (co-rotating, CO, and counter-rotating, CN), two relative positionings (downstream turbine positioned in the leeward, LW, and windward, WW, of the upstream rotor), and two phase lags (Δθ= 0° and 180°). For each of the eight rotor settings, 63 different relative arrangements are considered resulting in 504 unique cases. The arrangements are considered within 1.25d ≤ R ≤ 10d (d = rotor diameter) and 0° ≤Φ≤ 90°, where R and Φ are relative distance and angle of the rotors, respectively. Unsteady Reynolds-Averaged Navier–Stokes (URANS) CFD simulations, validated with experimental data, are employed. The results show that the power performance of the array is significantly influenced by the relative rotational direction and positioning, ∼8% in power coefficient (CP), while it is marginally dependent on relative phase lag. The different performance of the studied arrays is because of different parts of the downstream turbine revolution being affected by the wake of the upstream turbine and dissimilar strength/width of the shear layer created in the two rotors’ wake overlap. The preferred rotational direction for WW arrays is co-rotating while for LW arrays counter-rotating is favored. For the same arrangement, counter-rotating turbines with LW relative positioning have the highest CPdue to their downstream turbine blade moving along the flow direction in the wake overlap region resulting in little energy dissipation and weak shear layer. In contrast, counter-rotating arrays with WW relative positioning have the lowest CP, because the downstream turbine blade moves against the flow in the wake overlap region, resulting in extensive velocity deficit and a thick, strong shear layer.

Some recent studies show that the aerodynamic efficiency of the Savonius wind turbine can be improved by adding a properly designed deflector upstream of the rotor blade. However, these deflector designs can only improve the turbine efficiency in specific flow directions, which causes the loss of omnidirectionality. In this paper, a passive deflector is designed to solve this problem. The passive deflector can passively adjust its position with the change in wind direction so that the efficiency of the Savonius rotor is improved regardless of wind directions. For the sake of investigating the aerodynamic performance of the Savonius rotor with the new deflector, three-dimensional computational fluid dynamics simulations are performed at different operating conditions. The CFD method uses a set of high-quality structured grids and is validated with existing empirical data. The results show that the passive deflector can obtain a stable orientation adaptively according to the wind direction, and the maximum efficiency of the classical Savonius rotor is increased by 24.91% using the passive deflector.

As an alternative to a water-based cooling system for a sonoreactor, the present work presents for the first time the use of a phase change material for the management and storage of the dissipated heat within the sonicated water. The performance of the PCM is analyzed as a function of liquid height (LH = 5.1, 10.2, 15.3, and 20.4 cm) at a frequency of 300 kHz and two electric powers (PE = 20 and 60 W). The effective powers dissipated in the irradiated water were determined by the calorimetric technique. A computational fluid dynamics (CFD) model (implemented in ANSYS Fluent® software), was used for the analysis of the combined system (sonoreactor + PCM-thermal unit) at different operating conditions (liquid height and electric power). By analyzing the different outputs (variation of temperature, velocity, enthalpy, liquid fraction of PCM) of the used CFD model, more clarifications are provided about the behaviour of the combined system (sonoreactor + PCM-thermal unit) as function of the liquid height (5.1–20.4 cm) and electric power (20 and 60 W). In terms of temperature, velocity, enthalpy and liquid fraction of the PCM, promising results were obtained in spite of the low thermal conductivity of the employed PCM. The best performance of the combined system (sonoreactor and thermal unit) was obtained at the liquid height of 15.3 cm (corresponding to a water volume of 300 mL) with a similar behaviour (evolution of temperature, velocity, enthalpy, and liquid fraction of the PCM) at both electric powers (i.e., 20 and 60 W) with an intensified response at the PE = 60 W.

Based on the simulation of the fluid-structure interaction response, the cause of an overturning of a gantry crane induced by a downburst in Shenzhen is studied in this paper. According to the results, (1) Vicroy's downburst model could establish the steady-state wind field of the downburst more reasonably when there was only low-level wind speed observation data, and its simulation results were close to the two-dimensional downburst numerical simulation results; (2) Compared with the normal exponential vertical profile of wind speed, the disturbance caused by the front girder of the double-girder gantry crane structure under the downburst wind field was more severe, which increases the probability of the gantry crane overturning. (3) The downwind displacement of the main girder of the gantry crane under the condition of downburst is far greater than that under the normal condition. At the same time, under the condition of downburst, the pressure difference on the surface of the gantry crane was greater, and the distribution of the support reaction force was more uneven, resulting in a stronger overturning tendency of the gantry crane. (4) Under the condition of downburst, the overturning moment and the shearing force borne by the foundation of gantry crane exceeded the critical value to maintain the stability of the gantry crane by the gravity, resulting in the overturning of the gantry crane.

This paper presents an investigation into the behaviour of a Savonius wind turbine using Large Eddy Simulation (LES) through Computational Fluid Dynamics (CFD). The turbine was simulated for various Tip Speed Ratios (TSR) while calculating the predicted torque and power coefficients. The predicted torque and power coefficients were then compared with published data from wind tunnel testing. The results indicate that LES-based CFD simulations are a practical and reasonable approach for evaluating wind turbine performance. A validation study was conducted, and it was found that the accuracy was commensurate with data from the literature. This study demonstrates the potential of CFD simulations for optimizing wind turbine design.

High level of noise limits the reliability of the lubricated journal bearing. In the current paper, the possibility of bearing design with a heterogeneous rough/smooth surface is explored using the computational fluid dynamics (CFD) approach to improve tribological and acoustic performance. A parametric analysis is conducted to determine the optimal surface roughness level, the cavitation pressure, and the ratio of length to the diameter of the journal. The effect of the presence of a roughened pattern on the thermal behavior of the lubricant, friction force, noise level, and cavitation phenomena was also studied in depth. The main finding of the present study is that when conventional journal bearing fails in generating the load support for concentric conditions, the heterogeneous rough/smooth bearing has a beneficial effect by increasing the load-carrying capacity. Furthermore, the high level of surface roughness can significantly increase the load-carrying capacity while decreasing frictional forces and acoustic power. However, the roughness does not dramatically change the maximum temperature (less than 1%). The numerical results also suggest that the variation in vapor saturation pressure has a negligible effect on the maximum temperature, friction force, and noise level.

In concentrating solar power plants, the mismatch between solar energy availability and energy demand requires the development of thermal storage systems. This study analyses a solid thermal energy storage module made of alumina. The block has a honeycomb pattern where the air flows through hexagonal channels. A transient 1D model, based on the finite difference method, is implemented and verified against CFD simulations. Such a simplified model considers the temperature dependence of thermodynamic properties for air and alumina. With the same boundary conditions, a 3D RNG k-ε turbulence CFD model is built, whose mesh and time step are assessed by means of sensitivity analyses. The average temperature difference between both models is as low as 14.8 K, even though the simplified one is around 300 times faster than the detailed CFD model.

The objective of this study was to improve the energy management of an overhead downward flow (ODF)-type data center (DC) using the evaporative cooling method. A computational fluid dynamics (CFD) approach was used to predict the optimal operating condition of an A1-grade DC exhibiting the smallest entropy generation rate of the ODF system. Experiments were performed to validate the predicted airflow speed at the inlet of each server and temperature distributions at the inlet and outlet of each server. Furthermore, three thermal performance metrics, namely rack cooling index (RCI), return temperature index (RTI), and supply heat index (SHI), were used to compare the numerical and experimental results, which were found to be consistent. The measured power usage effectiveness (PUE) reached 1.42, significantly lower than the global average PUE of 1.55 reported in 2022. Moreover, using the CFD method, water mist was added at the air supply port to reduce the temperature of air from 21.63 °C to 18 °C via evaporation and increase relative humidity from 50% to 70%. These results suggest that evaporative cooling has the potential to facilitate the supplied air to provide additional cooling capacity and lower the chiller load to reduce energy consumption in the DC.

The horizontal self-cleaning single-shaft kneader possesses excellent mixing performance and has many industrial applications in bulk polymerization, polycondensation and polymer devolatilization. Hence, the objective of this research is to investigate the hydrodynamics and mixing performance of different new types of self-cleaning single-shaft kneaders by using the finite element method (FEM) simulation and particle tracking technique. Both the distributive mixing process of randomly distributed material points between halves of kneaders and the local distributive mixing process of a cluster in selected positions were analyzed. The effect of kneader geometry structure on hydrodynamics and mixing performance was also analyzed. The FEM simulation were validated by using a small visual experimental device. There hardly exists the flow dead zone in the self-cleaning kneader. The area of region with high velocity magnitude increases with the number of dynamic kneading bars and decreases with the number of static kneading bars. The area with high shear rate increases with the number of both dynamic and static kneading bars due to small clearance. There exists the periodical intermeshing interaction between the static kneading bars on kneader wall and the dynamic kneading bars on rotating shaft. What counts is that the distributive mixing process and mixing efficiency can be enhanced and improved by the periodical intermeshing interaction.

Finite element method (FEM) simulation combined with the mesh superposition technique (MST) was adopted to investigate the flow field in a horizontal self-cleaning differential rotating twin-shaft kneader with a highly viscous Newtonian fluid. The distributive mixing process and mixing efficiency were investigated by using the particle tracking technique. The comparison of flow pattern, distributive mixing process and mixing efficiency for the opposite-rotating, co-rotating and back-rotating twin-shaft kneader was performed. For the opposite-rotating kneader, the material flow in the left and right region merges in the upper region of overlapping zone, moves towards the lower region and is split into two parts in the lower region of overlapping zone. For the co-rotating kneader, the main flow pattern that the material moves towards the right region from the left region. Besides, there exists the secondary flow and periodic cyclic vortex in the overlapping zone. For the back-rotating kneader, the material flow in the left and right region merges in the lower region of overlapping zone, moves towards the upper region and is split into two parts in the upper region of overlapping zone. The material exchange between the left and right part of flow domain in the co-rotating kneader is much more efficient than that in the opposite-rotating and back-rotating kneader. The mean length of stretch, instantaneous mixing efficiency and time averaged mixing efficiency of opposite-rotating kneader is very close to that of back-rotating kneader, which is much smaller than that of co-rotating kneader. Hence, the co-rotating kneader possesses much better mixing performance than the opposite-rotating and back-rotating kneaders.

A computational fluid dynamics (CFD) model for double-sided friction stir spot welding (FSSW) between AZ31 and ZK60 magnesium alloys using adjustable pins is proposed in this paper. Multiple phase flow theories are combined to track the metal interface and phase distribution using FLUENT software. The heat transfer and material flow for the 5 stages of the friction stir welding process, including the pre-heating, plunging, welding, rising and post-heating stages, are presented. For further evaluation, the calculated flow and thermal responses are compared with experimental data, which overall showed good agreement. The material between the upper and lower pins is softened after the pre-heating process and is then driven by the plunging pin to form a keyhole below the upper tool and a bulge region in the bottom of the plates. The welding interface between the pins is bowl-shaped after plunging, and grows uneven during the welding stage due to the extensive plastic material flow. The keyhole is then fully eliminated after the rising of the pins. After welding, the region between the tools is heated to a maximum temperature of 670 K and the welding interface slightly fluctuates and a phase mixing phenomenon occurs, suggesting that AZ31 and ZK60 plates are well joined by using the adjustable pins.

This study simulated the heat- and mass-transfer characteristics of fresh tomatoes by developing a computational fluid dynamics model. The root-mean-square error (RMSE) and mean absolute percentage error (MAPE) for the tomato temperature were 0.579 °C and 3.89%, respectively, and the RMSE and MAPE for the tomato mass loss were 0.737 g and 9.87%, respectively. Furthermore, the effect of different cold chain breaking (CCB) parameters on fluctuations in tomato temperature and mass loss were quantified by a sensitivity analysis. The results indicate that CCB increases the tomato temperature and moisture loss compared with an uninterrupted cold chain, especially for the tomato moisture loss during the second CCB because of the irreversibility and superposition of this negative effect. Furthermore, CCB would increase the inhomogeneity of the temperature distribution of packaged tomatoes but significantly reduce the inhomogeneity of tomato mass loss. Additionally, tomato temperature fluctuations are less sensitive to changes in relative humidity during the CCB process, and the sensitivity between them is almost two orders of magnitude less than the sensitivity of other CCB parameters. However, the loss of tomato mass proved to depend most strongly on variations in relative humidity and the least on variations in the CCB temperature.

The helical coil heat exchanger (HCHX) is one of the most popular heat transfer devices in heat pump water heaters. In this study, the Computational Fluid Dynamics (CFD) software, ANSYS FLUENT, was employed to predict the thermohydraulic performance of an HCHX, including the overall heat transfer coefficient and Fanning friction factor. Using different sizes of the HCHX, comparing the CFD results with experimental data or correlations available in the literature revealed that both results on thermohydraulic performance agreed well. The objective of this study was to choose the Taguchi method coupled with grey relational analysis (GRA) to optimize the HCHX design with the improvement of thermohydraulic performance. Among the selected three factors in the optimization process, it was found that the coil pitch and coil diameter were the two most important factors in influencing the thermohydraulic performance of HCHXs, while the outer diameter of the helical tube had little impact. Consequently, the optimal design of the HCHX increased the overall heat transfer coefficient by 131% and decreased the friction fanning factor by 6%, resulting in the increase of heat transfer rate by 47% and the reduction of pumping work by 72%. Moreover, the predicted optimal thermohydraulic performance was verified by the predictive formula of the Taguchi method.

Struts are attached to a submarine to maintain its submerged depth when conducting the model tests. While previous studies have mentioned that the attachment of the struts has a negligible effect on the performance of a submarine, it is difficult to find studies that clearly explain the effects of the struts. The present study examines the effect of struts with a circular cross-section on the resistance and propulsion performances of a submarine under both straight-ahead (β = 0°) and static-drift (β = 6° and 12°) conditions. For this analysis, the open-source computational fluid dynamics (CFD) toolkit OpenFOAM was utilized. A generic submarine Joubert BB2 was selected as a test model, which was modified by the Maritime Research Institute Netherlands (MARIN). Analyses of resistance were conducted in straight-ahead and static-drift conditions, and the flow characteristics such as pressure, velocity, vorticity, and turbulent kinetic energy were compared to identify differences caused by the struts on the BB2 submarine. The results showed that as the drift angle increased, the struts had a smaller effect on the submarine along the hull to the propeller plane. From the results, it was predicted that the effect of the struts should be considered during the design process for the submarine.

This study aims to present a practical practice to obtain a reliable numerical solution based on an Unsteady Reynolds Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) to estimate the forces acting on moored ships during a passage of a ship in a confined waterway. The motion of the passing ship is implemented using an overset-grid method. The convergence of the numerical solutions depending on the spatial and temporal discretization are systematically analyzed, and the computational results are validated with a recent benchmark test data. In particular, the effect of the initial state of the passing ship in the unsteady simulation is dealt with in-depth. The simulation results when the passing ship departs at a constant speed and when it accelerates from a standstill are compared, and the influence of undesirable wave radiation generated with the departure of the passing ship at a constant speed is discussed.

In the present study, the hull form of an 1,800 TEU containership was developed to reduce fuel consumption under real operation conditions. Contrary to the conventional hull form design practice in terms of the calm-sea performance, the hull form design in this study was aimed at improving the performance of a ship under in-service condition, which is closely associated with the added resistance due to waves. In order to reduce the added resistance due to waves, the bow hull form was modified to have sharper entrance with increased length between perpendicular. This enabled the waves to follow the bow part more smoothly. The added resistance of the developed hull was predicted by means of a series of CFD simulations in regular waves with wavelengths λ/Lpp=0.5∼2.0. The added resistance at irregular waves was calculated by frequency integration. The Daily Fuel Oil Consumption (DFOC) was subsequently calculated based on the wave statistics on the operating route. The significance of the present study lies in the point that the performance evaluation was carried out by means of the free-surface CFD simulation in the presence of regular waves. Final performance verification was made through a series of model tests. The resulting DFOC and daily CO2 emission for the optimal hull form under the in-service conditions was found to be reduced by 7.65%. Furthermore, the calm-sea DFOC and CO2 emission were also improved by 3.43%.

In this paper, a pseudo three-dimensional computational fluid dynamics model of Sandia’s 17-meter Vertical Axis Wind Turbine is implemented and validated against experimental data for a Tip Speed Ratio of 4.60. The Unsteady Reynolds Averaged Navier Stokes equations and the Shear Stress Transport turbulence model are used to assess the performance of the turbine in conjunction with ANSYS CFX’s rotating domain setup. The pressure coefficient, normal coefficient and tangential coefficient were used as validation metrics. The numerical results showed good agreement with the experimental data, with the normal force coefficient differing from the experimental data by 32% on average, and the tangential force coefficient differing by 51%. Discrepancies between the numerical and experimental data are likely associated with two sources: 1) the assumption of a fully turbulent boundary layer resulting in an over-prediction of drag; 2) the inherent deficiencies associated with two-equation turbulence models such as the stagnation point anomaly as well as the dissipative nature of Reynolds Averaged Navier Stokes based turbulence models. The model was also able to predict the asymmetric power generation associated with vertical axis wind turbines due to the blade-wake interaction during the downwind revolution.

While dealing with a solid-type ceramic breeding blanket for a fusion reactor, it is critical to determine the basic and thermal properties of the functional material in the form of a pebble bed. In the form of pebbles, lithium ceramics serve as the tritium breeder material in the fusion blanket. Effective thermal conductivity (keff) is one of the important thermal properties for the design and useful parameter to determine the performance of the blanket component. Artificial Neural Networks (ANN) are a popular machine learning technique for tuning between input and output parameters. These networks can learn from examples (data set) and apply them when a homogeneous event arises, making them able to work through genuine-time events. Hence, it can save a lot of time and money for doing repetitive experiments and high-end simulations. This will aid in the creation of a huge database on the pebble bed's keff, which will be useful in the design and development of fusion blankets. The findings of simulations and experiments are compared to those predicted by the ANN model for the pebble bed's thermal conductivity.At IPR, a test setup for experiments has been developed using the steady-state and axial heat flow approach. keff of Li2TiO3 has been measured for the pebbles of diameter of 0.8–1.2 mm having packing fraction of ∼62% and using helium environment at different temperatures ranging from 100 °C to 600 °C at constant atmospheric pressure. keff has been compared with pebble bed of stainless steel pebbles of different diameters (1, 2, 3, 1&3, & 2&3 mm) as well. DDPM-DEM model has been used to generate the pebble bed and ANSYS-CFD simulations using FLUENT have been performed to validate the results. The projected values using ANN are within 5% of the results obtained from simulations and experiments. The details of the DDPM-DEM and ANN models, FLUENT simulations, and experimental results will be discussed in this paper.

Pneumatic bioreactors are a class of reactors increasingly used in bioprocesses, since they provide adequate heat and mass transfer, rapid mixing and good suspension of solids. In this work, oxygen transfer from a square-cross section bubble column bioreactor was evaluated experimentally and numerically using computational fluid dynamics (CFD), and the results were compared with data obtained experimentally. Different specific air flow rates (1.0, 3.0 and 5.0 vvm) and drag and lift interfacial forces, were considered in the numerical simulations using the two-fluid Eulerian model. The simulations considering the presence of lift force showed results closer to the experimental data, with the highest values of kLa found for the higher specific air flow rate (5 vvm) analyzed in this study.