Computational Fluid Dynamics Methodology Research Articles

Sustainable Fishing Livelihoods: Exploring the Potential of Sail Technology Using Computational Fluid Dynamic in Traditional Fishing Boats

The potential of using sails and Computational Fluid Dynamics (CFD) to improve the sustainability of traditional fishing boats in the Maluku region. This study highlights the importance of cost-effectiveness and environmental sustainability in the fishing industry. This study shows that Computational Fluid Dynamics (CFD) is effective in simulating the thrust force generated by sails. Sails were used to generate thrust forces on conventional fishing vessels by implementing CFD methodology with three different models. Various sail shapes were incorporated into the modelling process to assess their impact on the thrust force. Subsequently, a comprehensive analysis was conducted to evaluate the sail thrust force under typical operating conditions, focusing specifically on the average speed of the vessel at 15 knots in the waters surrounding the Maluku Islands. The results reveal that sail model 1 has the highest thrust force, amounting to 240.2 N. Sail models 3 and 2 generate thrust forces of 238.9 N and 227.9 N, respectively. The fluid flow conditions around sail model 1 and screen model 2 provide valuable insights into how the sail interacts with the fluid environment to produce thrust. By understanding and optimizing these fluid dynamics, designers and engineers can enhance the performance of sail models and improve their efficiency in harnessing wind power for propulsion. This study highlights the importance of ship science and technology in the design of appropriate propulsion systems for traditional fishing vessels.

Prediction of gas-solid nozzle performance based on CFD and response surface methodology

In this work, structural parameters and performance prediction of fan nozzles for powder spraying are investigated. Computational Fluid Dynamics (CFD) was used to simulate the working process of the grooved fan nozzle. A Box-Behnken experimental model was developed to analyze the effects of the structural parameters on the nozzle air flow stability and working performance, taking the nozzle structural parameter contraction angle (α), the ratio of outlet to inlet diameter (d/D), the ratio of outlet diameter to length (L2/d), and the half angle of the “V”– shaped groove (β). The air flow stability and working performance of nozzle were evaluated through coefficient of variation (Cv) and standard deviation (SD). Using multiple regression analysis, the prediction model of Cv and SD on the structural parameters is established. It was obtained that: with the increase of the diameter and length of the nozzle outlet, the spray angle of the nozzle decreases. As the “V”– shaped groove angle increases, the powder spray angle decreases. The effects of structural parameters on Cv are d/D, α, β, and L2/d in ascending order, and on SD are d/D, α, β, and L2/d in ascending order. In addition, the influence of the interaction of each structural parameter on Cv and SD was obtained. This study can provide a reference for the design and structural optimization of fan nozzles for powder spraying.

Wave and straight plenum effects on thermal management system performance

The need to offset heat generated by batteries in electric vehicles (EVs) necessitated the design and development of battery thermal management systems (BTMS), one of which adopt air cooling technique. The redesign of plenums of the BTMS has been beneficial in the enhancement of the BTMS's performance. In view of these, this study considered wave and straight design of plenums in an attempt to enhance the performance of the system. The proposed designs were investigated using Computational Fluid Dynamics (CFD) methodology. The CFD methodology was validated by first investigating the conventional Z-design of BTMS with straight plenums and the results were compared with existing results from experiments in literature. Findings from the study revealed that by replacing straight-horizontal plenum with straight-inclined plenum, maximum temperature (Tmax), and maximum temperature difference (ΔTmax) of the Z-design was reduced by 3.47 K and 6.82 K, respectively, with increase in pressure drop (ΔP) by 2.24 Pa and pumping power (Pp) by 0.01 W.Furthermore, by adopting wave-inclined plenum design, Tmax, and ΔTmax were reduced by 4.61 K and 8 K, respectively when compared with the conventional Z-design BTMS. More so, the pressure drop (ΔP) and pumping power (Pp) increased by 3.17 Pa and 0.0133 W, respectively. The study generally revealed that careful redesign of divergence plenum with inclined straight and wave-like structure will enhance the thermal performance of BTMS.

Numerical Simulation of the Dovetail Tee and Hydraulic Optimization of the Height Difference for Pipeline in a Liquefied Natural Gas Filling Station

Certain configurations of liquefied natural gas refueling stations exhibit a deficiency in managing boil-off gas. Furthermore, the ill-conceived linkage between the submersible pump and the gas storage tank pipeline leads to impeded natural gas transmission. This study employed the computational fluid dynamics (CFD) methodology to scrutinize the hydrodynamic attributes of the T-type tee and dovetail tee configurations implemented in the pipeline design connecting the submersible pump and storage tank in a liquefied natural gas (LNG) filling station across diverse operational scenarios. The T-type tee induces detachment of the primary flow from the inner wall due to inertial forces, which results in vortex formation and heightened resistance, accompanied by increased energy dissipation. The transition of the rounded inner wall of the dovetail tee results in the reduction of eddy current generation and a smaller separation zone, thus minimizing resistance and energy loss. The maximum static differential pressure between the inlet and outlet of the dovetail tee is reduced by 52.52% compared to that of the T-type tee. In practical engineering applications, the use of dovetail tees leads to a reduction in the height difference for the pipeline by 17.58%, resulting in more uniform and stable flow rates and pressures in the flow field. These improvements contribute to engineering efficiency and environmental sustainability and are particularly evident in the design of LNG filling stations.

Effect of Entrainment on the Liquid Film Behavior in Pipe Elbows

Multiphase flow entrainment in natural gas engineering significantly influences the safety and efficiency of oil companies since it affects both the flow and the heat transfer process, but its mechanisms are not fully understood. Additionally, current computational fluid dynamics (CFD) methodologies seldom consider entrainment behavioral changes in pipe elbows. In this article, a verified CFD method is used to study the entrainment behavior, mechanism, and changes in an elbow. The results show that droplet diameter in a developed annular flow follows a negative skewness distribution; as the radial distance (from the wall) increases, the fluctuation in the droplets becomes stronger, and the velocity difference between the gas and the droplets increases linearly. Turbulence bursts and vortices sucking near the wall jointly contribute to droplet entrainment. As the annular flow enters the elbow, the secondary flow promotes the film expansion to the upper and lower parts of the pipe. Droplets re-occur near the elbow exit intrados, and their size is much smaller than those in the upstream pipe. Vortices sucking under low gas velocity play an important role in this process. These findings provide guidelines for safety and flow assurance issues in natural gas production and transportation and bridge the gap between multiphase flow theory and natural gas engineering.

A Comparative Analysis of Aerodynamic Performance: Straight Fin and Curved Fin Rockets using Computational Fluid Dynamics (CFD)

This investigation seeks to discern the aerodynamic differentials between rockets featuring straight fins and those with curved fins, focusing on the drag coefficient (cd), lift coefficient (cl), and moment coefficient (cm). Employing the computational fluid dynamics (CFD) methodology within ANSYS Fluent software, the research endeavors to provide comprehensive insights. The rockets under scrutiny share a common cylindrical body configuration, boasting a 70 mm diameter, a conical nose, and four symmetrically positioned fins along the lower body. The CFD analyses encompass subsonic Mach 0.6 and supersonic Mach 1.2 scenarios, with the angle of attack systematically varying from 0° to 25° at 5° intervals for each velocity setting. The outcomes of the simulations reveal notable trends: both cd and cl exhibit an upward trajectory, while cm experiences a decrement with escalating angles of attack and velocities. The culmination of Ansys CFD simulations for both rocket configurations unequivocally indicates superior flight performance for the straight fin rocket. This discernment is grounded in the observed amplification of drag and lift coefficients, coupled with the concomitant reduction in the moment coefficient, thus elucidating the nuanced aerodynamic distinctions between straight fin and curved fin rockets across varying flight conditions.

A Comprehensive Review of the Thermohydraulic Improvement Potentials in Solar Air Heaters through an Energy and Exergy Analysis

Supply disruptions, uncertainty, and unprecedented price rises of fossil fuels due to the recent pandemic and war have highlighted the importance of using renewable sources to meet energy demands. Solar air collectors (SACs) are major types of solar energy systems that can be utilized for space and water heating, drying, and thermal energy storage. Although there is sufficient documentation on the thermal analyses of SACs, no comprehensive reviews of the exergetic performance or qualitative insight on heat conversion are available. The primary objective of this article is to provide a comprehensive review on the optimum conditions at which the thermal performance of diverse types of solar air collectors is optimized. The effect of operating parameters such as temperature rise, flow rate, geometric parameters, solar radiation, and the Reynolds number on the thermal performance of SACs in terms of thermal hydraulic performance, energy, and exergy efficiencies has been reviewed adaptively. Beyond the operating parameters, a deep investigation is outlined to monitor fluid dynamics using analytical and computational fluid dynamics (CFDs) methodologies in the technology of SACs. In the third phase, thermodynamic irreversibility due to optical losses, thermal losses between absorber and environment, heat losses due to insulation, edge losses, and entropy generation are reported and discussed, which serve as the fundamental tools for optimization purposes.

Study on the effect of flow field optimization on flotation efficiency

ABSTRACT With the help of computational fluid dynamics (CFD) methodology, the Eulerian model was used for numerical simulation of XFD type flotation machine. By altering the flow field pattern, analyzing the internal flow characteristics of the flotation machine in terms of velocity field and turbulivity, and optimizing its structure, the relationship between turbulence intensity and turbulent energy dissipation rate in the flotation machine is investigated. The findings demonstrate that altering the flow field pattern enhances the turbulence in the flotation machine’s mixing zone, enhances the velocity distribution of the three-phase fluid at the bottom of the flotation tank, and fosters bubble-particle contact, collision, and adhesion. This can successfully reduce the clean coal ash content.

Design optimization of a cylindrical UV-C LED reactor for effective water disinfection with numerical simulations and test reactor fabrication

Ultraviolet C-band light-emitting diodes (UV-C LEDs) provide effective water disinfection and flexible reactor design. In this study, the disinfection performance of the cylindrical UV-C LED reactor was optimized using a new computational fluid dynamics (CFD) technique and validated experimentally with test reactors. The CFD technique provided UV doses for individual particles representing microorganisms, which were integrated along their trajectories using the discrete phase method within the radiation field acquired through the Monte Carlo method. Utilizing the minimum UV dose as a criterion, four key design parameters were evaluated: reactor aspect ratio (L/D) (in the range of 2.5−6), LED power angle (15−55°), wall reflectivity (0.6−0.94), and water flow rate (1−4 l/min). The optimal L/D of 4.2 was determined and subsequently applied to fabricate the test reactors. The polytetrafluoroethylene (PTFE) test reactor exhibited superior disinfection performance for E. coli O157:H7 compared to the one made of SUS304, due to its high wall reflectivity. Furthermore, a lower water flow rate enhanced disinfection performance by extending the residence time. The predicted log reductions exhibited a consistent trend with the measured values, confirming the efficacy of the CFD methodology applicable to various reactor designs and LED configurations.

Numerical investigation on boiling crisis in a full-length 5 × 5 fuel assembly under typical pressurized water reactor conditions

Critical heat flux (CHF) presents a research priority in the Pressurized Water Reactor (PWR) safety, as it can lead to the severe accidents and release radioactive materials. In this study, a wall heat flux partition model, proposed by Demarly [1], was employed within the two-fluid model by Computational Fluid Dynamics (CFD) methodology to investigate the characteristics of CHF under typical PWR conditions. A multi-scale interface model was coupled to consider the interfacial transfers in bulk flow during flow regime transition. The models were validated by using experimental data on subcooled flow boiling, boiling crisis in vertical tubes, and rod bundles. The PWR sub-channel and bundle test (PSBT) benchmark, comprising a full-length 5 × 5 fuel assembly with three different types of spacers, was simulated in this study. The CHF value was evaluated, demonstrating an acceptable accuracy compared to the experimental data, with a deviation of less than 10 % in the selected conditions. The CHF location in the cross section was successfully predicted by CFD approach, while the axial location of CHF was underestimated than experimental measurement. Besides, the impacts of mixing vanes with different deflection angles on boiling heat transfer characteristics were analyzed, revealing the crucial role of mixing vanes in the distribution of vapor and dry-patch area fraction in both the circumferential and flow directions.

Concrete ablation depth analysis of OPR1000 NPP during top flooding ex-vessel cooling

This study assesses the integrity of OPR1000 nuclear power plant (NPP) containment during top flooding ex-vessel cooling in the event of a postulated severe accident. Maintaining containment integrity during ex-vessel cooling is critical for preventing substantial release of radioactive materials to the environment. To analyze the feasibility of top flooding ex-vessel cooling of the OPR1000 NPP, the spread of molten corium in the dry reactor cavity is first calculated, followed by calculating the concrete ablation depth according to the reactor cavity flooding delay time. It is judged whether the leak-tightness integrity of the containment during ex-vessel cooling is maintained based on whether the containment liner plate (CLP) is damaged or not. In the first step analysis, the spread of molten corium in the dry reactor cavity is calculated using computational fluid dynamics (CFD) methodology for various cases, and results indicate a uniform deposition of approximately 143 tonnes of molten corium, with a thickness of about 33 cm, meaning that the thermal load is distributed uniformly in the reactor cavity. In the second step analysis, concrete ablation depths are calculated base on the delay time for flooding the reactor cavity. For the postulated severe accident, injecting coolant into the reactor cavity one hour after breach of the reactor vessel results in a concrete ablation depth of about 0.74 m, indicating no damage to the CLP and ensuring containment integrity. The maximum allowable delay time for flooding the reactor cavity for the postulated severe accident is evaluated to be 2.24 hours maintaining the leak-tightness integrity of the OPR1000 NPP containment. The research methodology and findings presented in this study are expected to aid in assessing the feasibility of top flooding ex-vessel cooling and establishing appropriate accident management strategies for nuclear power plants like the OPR1000 NPP.

Computational Fluid Dynamics Analysis of Flow Characteristics and Heat Transfer Variabilities in Multiple Turbine Blade Cooling Channels

Abstract In the realm of gas turbine engine technology, turbine blades are persistently subjected to extreme thermal conditions due to prolonged exposure to high-temperature gases. Given this operating environment, devising effective cooling strategies is paramount for ensuring the turbine’s safety and longevity. Despite the critical nature of this issue, existing literature scarcely addresses cooling channels that incorporate factors like variable cross-sectional attributes and rotational effects. In this study, Computational Fluid Dynamics (CFD) and numerical methodologies were employed to analyze the flow mechanism and performance of three distinct cooling channels characterized by variable cross-sectional features. The results indicate a marginal thermal performance improvement of up to 3% for U-shaped cooling channels, specifically at a Reynolds number of 20,000, in comparison to Net cooling channels. Conversely, jet impingement channels outperform U-shaped channels by an impressive margin of over 11%. Additionally, at a Reynolds number of 60,000, jet impingement cooling channels manifest a significant upsurge of nearly 25% in the ratio between average Nusselt number, and the reference Nusselt number when compared with U-shaped and Net cooling channels.

Optimization of G1 Micromixer Structure in Two-Fluid Mixing Based on CFD and Response Surface Methodology

Optimizing the structure of micromixers to improve the mixing efficiency is of great significance for chemical engineering and biology fields. In this study, an optimization of the microchannel in two liquids mixing is carried out based on computational fluid dynamics (CFD) and response surface methodology. Firstly, CFD simulations were performed to investigate the mixing flow field and mixing efficiency in the microchannel by considering different process and structure parameters (e.g., feed pressure p, microchannel width w). The response surface methodology was adopted to construct a fitting surface by CFD discrete working conditions. Then, an optimized microchannel width w was searched using the parallel particle swarm optimization (PPSO) algorithm from the response surface. Lastly, the searched optimum was validated by CFD simulation again, and the final result showed that the predicted mixing efficiency from the response surface model is well confirmed by CFD simulation. On average, the new optimized microchannel width of 1.634 mm performs higher flow flux and mixing efficiency than the original width of 1.5 mm, increasing 13.51% and 2.45%, respectively.

Numerical and Experimental Investigation of the Dynamics of a U-Shaped Sloshing Tank to Increase the Performance of Wave Energy Converters

In this investigation, a comprehensive study was conducted on a U-shaped sloshing tank, based on reversing the classical treatment of such devices as motion stabilizers and using them instead to improve the performance of wave energy converters. The modeling encompasses a comparative analysis between a linear model and Computational Fluid Dynamics (CFD) simulations. The validation of the CFD methodology was rigorously executed via a series of experimental tests, subsequently enhancing the linear model. The refined linear model demonstrates a notable alignment with rigorously verified results, thus establishing itself as a reliable tool for advanced research, indicating promise for various applications. Furthermore, this novelty is addressed by simulating the integration of a U-tank device with a pitch-based wave energy converter, displaying a broadening of the operational bandwidth and a substantial performance improvement, raising the pitch motion of the floater to about 850% in correspondence with the new secondary peak over extended periods, effectively addressing previously identified limitations. This achievement contributes to the system’s practical relevance in marine energy conversion.

Numerical Studies on Effects of Blade Number Variations on Performance of Sludge Pumps

The sedimentation of sludge in pangasius catfish ponds constitutes a notable challenge for the economic advancement of Vietnamese farmers. Sludge formation is the result of a composite process involving residual food, waste material, and algae, which undergo decomposition, thereby releasing hazardous gases such as hydrogen sulfide (H2S), ammonia (NH3), and nitrogen dioxide (NO2). These emissions subsequently diminish oxygen levels within the ponds, adversely affecting the growth of catfish. Removal of the accumulated sludge is deemed necessary every two months throughout the catfish cultivation cycle. A proficient sludge pump, designed to function effectively within the Vietnamese environmental context, becomes imperative to address this predicament. The primary objective of this research paper is to explore the influence of blade count on the performance metrics of a sludge pump. Given that pangasius ponds typically exhibit depths ranging from 2 to 4 meters, this study is predominantly centered on assessing pump performance within the specified head range of 2 to 4 meters. Employing the computational fluid dynamics (CFD) methodology, the research delves into the fluid dynamics of sludge pumps featuring impeller blades numbering 7, 8, 9, and 10. These pumps are modeled as semi-open impeller centrifugal pumps operating at a speed of 2200 revolutions per minute (rpm), with the k-e turbulence model and the time-averaged Navier-Stokes equation serving as the fundamental analytical framework.

CFD simulation of hydrodynamics and concentration polarization in osmotically assisted reverse osmosis membrane systems

Osmotically assisted reverse osmosis (OARO) has been recently suggested as an alternative to improve water recovery of reverse osmosis (RO) for applications in which RO has reached its limit. To elucidate the physics, a computational fluid dynamics (CFD) methodology is developed that describes all important physical phenomena occurring in the feed, porous and draw sides of OARO. The CFD model shows good agreement with the reported experimental data and predicts the water flux better than a simplified analytical model. This paper reveals that external concentration polarization (ECP) at the feed side is more important than internal concentration polarization (ICP) within the porous support layer, especially for a system with a high transmembrane pressure, Δp (≥40 bar). In contrast to conventional RO, where concentration polarization (CP) at the permeate side is negligible, OARO experiences a non-negligible ECP at the draw (permeate) side, particularly in cases with high Δp. This analysis also found that both counter-current and co-current configurations show similar flux performance at module scale.

Numerical Investigation on Interactive Hydrodynamic Performance of Two Adjacent Unmanned Underwater Vehicles (UUVs)

This study investigates the effectiveness of UUV formations during navigation to designated target areas. The research focuses on propeller-equipped UUVs and employs a computational fluid dynamics (CFD) methodology to analyze the hydrodynamic interactions among multiple UUV formations while en route to their targeted exploration areas. Utilizing the relative drag coefficients (rl and rf) and static thrust (Rfleets) as analytical parameters, this paper defines the relative distances (a and b) between UUVs within a formation and conducts a comparative analysis of the hydrodynamic performance between individual UUVs and formation configurations. The study establishes correlations between relative distances and the hydrodynamic performance of formations. The findings reveal the following: 1. For both the lead UUV and the following UUV within the formation, the rl and rf heatmaps exhibit two distinct regions: a thrust region and a drag region. Notably, these regions significantly overlap. The maximum rl is 31.23%, while the minimum rf is −20.9%, corresponding to relative distances of a = 0.12 and b = 1.5. Conversely, the minimum rl is −12.2%, while the maximum rf is 22.03%, with relative distances of a = 1.1 and b = 0.2; 2. An analysis of formation static thrust Rfleets reveals that it can be up to 7% greater than the drag experienced by self-propelled UUVs when relative distances a and b are set to 1.1 and 1, respectively. This highlights the enhanced performance achievable through formation navigation. The results presented in this paper offer valuable theoretical insights into the optimal design of relative distances within UUV formations, contributing to the advancement of UUV formation navigation strategies.

Modeling the impact of the fuel injection strategy on the combustion and performance characteristics of a heavy-duty GCI engine

Gasoline compression ignition (GCI) is a promising strategy to achieve high thermal efficiency and low emissions with limited modifications to the conventional diesel engine hardware. It is a partially premixed concept, which derives its superiority from higher volatility and longer ignition delay of gasoline-like fuels combined with higher compression ratio typical of diesel engines. The present study investigates the combustion process in a GCI engine operating with different injection strategies using computational fluid dynamics (CFD). Simulations are carried out on a single cylinder of a multi cylinder heavy-duty compression ignition engine, which operates at a compression ratio of 17:1 and an engine speed of 1038 rev/min. Two different injection strategies viz., late injection (LI), and early pilot injection (EP) are investigated to understand their impact on combustion and performance of the engine. Renormalized group (RNG) k-ε model is used to describe in-cylinder turbulence and KH RT model is used to simulate the fuel spray breakup. The developed CFD methodology is validated against relevant experimental data under a wide range of operating conditions for each injection strategy. The developed CFD methodology was found to capture the engine combustion behavior quite well. Based on the validated CFD model, the differences in the progress of combustion event for the two injection strategies is highlighted. It was found that a larger pilot fuel mass fraction results in a steeper rise in the initial heat release rate which in turn influences the transition to mixing controlled combustion. In line with the experimental data, the study showed that the late pilot injection strategy with three injection pulses, results in higher performance compared to the other conditions.

High-Fidelity Simulations of Shield Assembly Mixed-Convection Flows with Applications Toward Reduced-Resolution Modeling

Flow circulation and heat removal through shield and reflector assemblies can have major impacts on safety in long transients for sodium fast reactors (SFRs). These transients are typically categorized by reduced flow rates and large-scale organized flow patterns, including potential intra-assembly circulation. Such low-flow cases can provide challenges for experiments because of complications in measuring the flow rates and temperatures with high accuracy in different areas. This consequently also raises the uncertainty of many modeling approaches for these phenomena. In an effort to address some of these issues, high-fidelity large eddy simulations are performed using the highly parallel solver NekRS. A 19-pin configuration of a tight-lattice wire-wrapped hexagonal bundle (pitch-to-diameter ratio = 1.07), representing a prototypical internal configuration of a shield assembly, was investigated. The sodium flow was set at a bundle Reynolds number of 2000, with simulations being performed for modified Richardson numbers of 0.0 (i.e., no buoyancy), 0.01, and 0.04, where mixed-convection effects are anticipated. The flow and temperature fields for these cases are discussed in detail. The high-fidelity data should prove useful as reference data for expanding and improving on various reduced-resolution approaches. A basic framework for combining subchannel and computational fluid dynamics methodologies in SFRs is also presented, with preliminary results from simulations of light water reactor bundles and a discussion of changes that need to be made for potential application to SFRs.

Numerical prediction of fire dynamics and the safety zone in large‐scale multiple pool fire in a dike using flamelet model

AbstractThis research aims to develop a computational fluid dynamics (CFD) methodology for estimating the safety zone around a dike with multiple pool fire (MPF). This study predicts the safety zone and burning characteristics of heptane MPF inside a square dike in calm wind and worst‐case crosswind situations using unsteady simulations. The heptane MPF is modelled using flamelet approach with large eddy simulation (LES) turbulence model incorporating the soot generation. Discrete ordinates and Moss–Brookes model estimate the effect of participating medium radiation on prediction of safety distance and soot production. The discretization is incorporated using an isotropic trimmed cell mesher with local refinement to resolve the flame characteristics in Simcenter STAR CCM+. An extensive grid‐independence study has been executed to find the optimal mesh. The flame temperature and O2 and CO2 mass fraction predictions in calm wind conditions are in good agreement with the experimental findings of Koseki and Yumoto and the maximum flame temperature predictions are within 2.8% error. The safety zone is predicted using the estimated radiative heat flux. The effect of different ordinate sets (angular discretization S4, S6, and S12) approach on safety distance prediction is investigated. The validated grid independent CFD model combined with flamelet generated manifold model and LES turbulence model is proposed to predict the safety zone for industrial MPF in crosswind scenarios, thereby preventing human fatalities and property loss.