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Influence of pulsating flow on droplet flow characteristics in cathode channel of proton exchange membrane fuel cell using multiple-relaxation time lattice Boltzmann method

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JOURNAL OF POWER SOURCES 2025年 634卷

作者： Wang, Hao You, Jiaqi Yang, Guogang Huang, Naibao Dalian Maritime Univ Dalian 116026 Peoples R China

The production and discharge balance of water significantly affects the reaction efficiency and system stability of the proton exchange membrane fuel cells (PEMFCs). Efficient water management is crucial for improving PEMFC performance. In this paper, the two-phase and multiple-relaxation time lattice Boltzmann (LB) model is developed to investigate the influence of waveform, frequency, amplitude and temperature on droplet removal in cathode channel of a PEMFC. The droplet morphology is characterized by analyzing the dynamic coverage and height of the droplets. The results indicate that pulsating flow enhances droplet removal, with square wave flow being the most effective. Additionally, the efficiency of droplet removal improves as the frequency and amplitude of the pulsating flow increase. The dynamic behavior of droplets at 353 K and 296 K is compared, and the lower surface tension of the droplet at high temperature leads to a drastic morphological variation during purging, resulting in decreased efficiency of droplet removal. This study elucidates the mechanism of pulsating flow on liquid droplet removal in the channel and determines the influence of various pulsating flow parameters on this process. It provides valuable insights for enhancing the water management strategy of PEMFCs.

关键词： Proton exchange membrane fuel cell Lattice Boltzmann method pulsating flow flow characteristics

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PERFORMANCE IMPROVEMENT OF TRANSIENT pulsating flow IN ROOT CANAL IRRIGATION AND flow MECHANISM ANALYSIS

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JOURNAL OF MECHANICS IN MEDICINE AND BIOLOGY 2024年第7期24卷

作者： Tan, Youwei Sun, Xiaoyu Liu, Ruirui Li, Ping Xi An Jiao Tong Univ Key Lab Thermo Fluid Sci & Engn Minist Educ Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Key Lab Shaanxi Prov Craniofacial Precis Med Res Xian 710049 Shaanxi Peoples R China

Inflow conditions dominate the process of root canal irrigation, and the application of pulsating inflow in dentistry is necessary to be explored due to its mass transfer enhancement capability. A prepared root canal model with a 30G side-vented needle is numerically investigated under pulsating inflow with different frequencies and amplitudes. Root canal apical pressure, extending depth, and effective cleaning area are adopted to evaluate the safety, mass transfer capacity, and clean efficiency of the irrigation system. Time-averaged results show that the irrigation performance is improved with pulsating flow maintaining safety. Compared with steady cases, the extending depth and effective cleaning area are increased by up to 43.6% and 11.42%, respectively. Three typical cases with significant improvement are selected for transient analysis. Transient results show that the apical pressure and extending depth have instant response features, while the effective cleaning area has a time-lag response characteristic. It is convinced that the transient characteristic of the system results from the coupling effects of the pulsating effect, instantaneous flow rate, and Coanda effect. The internal flow distribution of root canal system is prompted under the optimal parameters combinations of pulsating conditions, in which mass transfer capacity and clean efficiency are enhanced with guaranteed safety.

关键词： Root canal irrigation pulsating flow mass transfer capacity clean efficiency

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Numerical simulation of JAG-type corrugated plate structure optimization and enhanced heat transfer by pulsating flow

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CASE STUDIES IN THERMAL ENGINEERING 2024年 60卷

作者： Liu, Yuechan Pu, Yongdong Sun, Chao Ai, Shiqin Harbin Univ Sci & Technol Sch Measurement & Commun Engn Harbin 150080 Peoples R China Harbin Engn Univ Postdoctoral Res Mobile Stn Power Engn & Engn Ther Harbin 150001 Heilongjiang Peoples R China

The paper presents a numerical investigation of the structural optimization of a JAG-type corrugated plate and enhanced heat transfer under pulsating flow based on the research results that have been achieved. Firstly, the corrugation pitch, corrugation depth, and corrugation inclination of the corrugated plate were optimized using Taguchi method to obtain the best heat transfer performance. Secondly, a detailed study is carried out on the flow and heat transfer characteristics under different pulsation velocities (0.01 m/s similar to 0.1 m/s), frequencies (0.4Hz -3.2Hz), and amplitudes (0.1 -0.9). Additionally, the relationship between the flow variation at the contact tail of the corrugated channel and enhanced heat transfer is elucidated in combination with the field synergy theory. The results demonstrate that the application of pulsation characteristics to fluid flow enhances heat transfer efficiency under different working conditions, with significantly superior heat transfer performance observed at low flow rates compared to high flow rates. Moreover, the modification of amplitude has a greater impact on heat transfer performance compared to changes in frequency and speed conditions. Changing the amplitude can produce a better synergistic effect. The research results can provide important reference for the engineering application of enhanced heat transfer by pulsating flow.

关键词： JAG-Type corrugated plate Taguchi method pulsating flow Field synergy theory Enhanced heat transfer Numerical simulation

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Numerical simulation of the fluoride salt flow and heat transfer in the pebble bed under pulsating flow conditions

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APPLIED THERMAL ENGINEERING 2025年 269卷

作者： Zhang, Jiaming Liu, Limin Liu, Ziying Cong, Tenglong Gu, Hanyang Shanghai Jiao Tong Univ Sch Nucl Sci & Engn Shanghai Peoples R China

The thermal-hydraulic characteristics of high-Prandtl number fluoride salt flow in a pebble bed channel under the influence of pulsating flow are investigated through numerical simulations. The pebble bed channel is simulated with the body-centered cubic (BCC) structure, and the applied turbulence model is the DDES model. The flow regime transition criteria have been determined through analysis of characteristics of the flow field. For the transition process, the critical Reynolds number between the laminar regime and the transition regime under different pulsating parameters is approximately 160 to 200, and the critical Reynolds number between the transition regime and the turbulent regime is approximately 210-245. The transition Reynolds number increases with the increase of Womersley number. flow resistance and convective heat transfer characteristics were also obtained. Within a pulsation cycle, the variation trends of the flow and heat transfer characteristics under different flow regimes exhibit significant differences. In most pulsating conditions, the average pressure drop and the average friction factor are approximately 50 % and 10 % higher, respectively, than their corresponding steady-state values. However, in cases with smaller pulsation amplitudes where the pulsation process has not transitioned into the turbulent regime, the average friction factor is lower than that under steady-state conditions. Similarly, under most pulsating conditions, the average Nusselt number is approximately 10 %-15 % higher than that of the corresponding steady-state conditions. The enhancement in convective heat transfer also results in a reduction in wall temperatures for these conditions compared to the steady-state values. In contrast, for cases with smaller amplitudes that do not enter the turbulent regime, the average Nusselt number decreases compared to steady-state conditions, leading to an increase in instantaneous average wall temperature. This indicates deteriorat

关键词： Floating FHR pulsating flow flow transition flow and heat transfer characteristics Pebble bed reactor core

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Exergy-Based Aerothermodynamic Evaluation of a Turbocharger Turbine Under pulsating flow: An Experimental Power-Based Approach

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ENERGIES 2025年第7期18卷 1714-1714页

作者： Bakhshmand, Sina Kazemi Biet, Clemens Tech Univ Berlin Integrated Modeling Energy Efficient Vehicle Power Salzufer 17-19 D-10587 Berlin Germany

This experimental study investigates the aerothermodynamic performance of a turbocharger turbine under steady and pulsating flow conditions across various turbine inlet temperatures (TITs) and pulsation frequencies. A power-based approach was implemented to quantify turbine heat transfer for diabatic scenarios over a range of operating turbocharger speeds. The results reveal that higher TITs significantly increase heat transfer under steady flow, driven by enhanced thermal gradients;while pulsating flow amplifies heat transfer by up to 63.6% due to intensified turbulence and frequent boundary layer disruptions. The exergy analysis shows that pulsating flow increases exergy destruction compared to steady flow, primarily due to pressure and velocity fluctuations that intensify flow friction and turbulence. At higher pulsation frequencies, exergy destruction decreases slightly, while heat transfer exergy loss becomes more prominent, reflecting a shift in the exergy balance. These higher frequencies, representative of real engine conditions, drive the flow toward quasi-steady behavior, further shaping the aerothermodynamic performance of the turbine. These findings provide valuable insights into the effects of pulsating flow on turbine heat transfer and exergy losses, offering practical implications for optimizing turbocharger turbine performance under realistic operating conditions.

关键词： turbocharger exergy pulsating flow aerothermodynamic turbine power-based approach

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Particulate fouling characteristics of wing vortex generator under pulsating flow

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2025年 210卷

作者： Li, Jiang Han, Zhimin Liu, Wei Xu, Zhiming Northeast Elect Power Univ Sch Energy & Power Engn Jilin Jilin Province Peoples R China

With the rapid advancement of modern industry, heat exchangers often operate with fluids containing fine particulate impurities that easily deposit within heat exchange channels, forming particulate fouling. To address this issue, this study combines pulsating flow with wing vortex generators. First, particulate fouling and pulsating flow models were developed, and their accuracy was validated through experimental testing. Numerical simulations were then conducted to compare the anti-fouling performance of three types of wing vortex generators under pulsating flow conditions. Finally, a detailed analysis was carried out on the effects of the relative height and length of rectangular wing vortex generators on particulate deposition. The results indicate that, compared to smooth channels, the use of pulsating flow offers a certain degree of anti-fouling performance, and combining pulsating flow with wing vortex generators further enhances this effect. Among the three types of wing vortex generators, the rectangular wing vortex generator exhibited the most effective anti-fouling performance under pulsating flow conditions. As the relative length and height of the rectangular wing vortex generator increased, fouling resistance first decreased and then increased. The minimum fouling resistance occurred when the relative length and height were 0.1 and 0.45, respectively, resulting in an anti-fouling performance improvement of up to 42.1 %.

关键词： pulsating flow Wing vortex generator Particulate fouling Fouling resistance Numerical simulation Nomenclatures

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POD analysis of turbulent convective heat transfer of pulsating flow in a channel with teardrop-shaped dimples using LES

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APPLIED THERMAL ENGINEERING 2025年 259卷

作者： Yamamoto, T. Murata, A. Inokuma, K. Iwamoto, K. Tokyo Univ Agr & Technol Dept Mech Syst Engn 2-24-16 Nakacho Koganei Tokyo 1848588 Japan

This study investigated effects of flow pulsation on the heat transfer performance of the surface with teardropshaped dimples using Proper Orthogonal Decomposition (POD). Velocity and temperature data for POD was obtained from the Large Eddy Simulation (LES). LES was performed for the following conditions: teardropshaped dimples with 30 deg in-line arrangement, the Strouhal number of 0.3, half of peak-to-peak velocity amplitude normalized by bulk velocity of 0.2, and the bulk Reynolds number of 2.5 x 104. The POD results revealed the first mode of velocity corresponded to periodic flow separation at leading and trailing edges of dimples, and the second mode to periodic swirling flow-separation behind leading side-edges of dimples. It was confirmed that the dominant periodic flow-separation over dimples was reproduced by using only the first and second modes. On the other hand, the periodic temperature variation caused by the pulsating flow was reproduced by the second and forth modes: low temperature fluid was periodically introduced into the dimples by the swirling flow-separation behind the leading side-edges of dimples.

关键词： Gas Turbine Teardrop-Shaped Dimples pulsating flow Large Eddy Simulation Proper Orthogonal Decomposition

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Study of High-Frequency pulsating flow Control Valves

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APPLIED SCIENCES-BASEL 2024年第22期14卷 10177-10177页

作者： Zhang, Dongdong Wu, Yunchen Zhu, Kuankuan Shi, Ruiyi Ruan, Jian Ding, Chuan Zhejiang Univ Technol Key Lab Special Purpose Equipment & Adv Proc Techn Minist Educ & Zhejiang Prov Hangzhou 310023 Peoples R China

pulsating flow signals are widely used in the fields of dynamic calibration of flow meters and reliability testing of fluid transmission pipelines. A high-frequency pulsating flow control valve is proposed, its structure and working principle are introduced, and its mathematical model is also established. Finally, an experimental platform is built to experimentally verify the performance of the high-frequency pulsating flow signal generation of this flow control valve prototype. When applying sinusoidal flow signals of 1-25 Hz, the amplitude of the output flow starts to decay after 2 Hz, and the frequency corresponding to the decay to -3 dB is about 23.5 Hz. The experimental results show that the valve can effectively generate unidirectional sinusoidal flow with a maximum amplitude of 25 L/min and a frequency of 23.5 Hz.

关键词： high-frequency flow signal pulsating flow flow control valve experimental study

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Heat transfer characteristics of pulsating flow in a straight channel with rhombic-shaped expanding chamber: A numerical study

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ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS 2024年第1期46卷 4608-4627页

作者： Akcay, Selma Cankiri Karatekin Univ Fac Engn Dept Mech Engn TR-18100 Cankiri Turkiye

The combination of passive and active heat transfer recovery techniques in channel flows has significant potential in terms of increasing thermal performance. Therefore, this study focused on the numerical examination of the flow and thermal behavior of pulsating flow in a straight duct containing a rhombus chamber. In the context of the study, iterations were solved using the finite volume method (FVM). The study was carried out for different pulsating amplitudes (A: 0.2, 0.4, 0.6, and 0.8), Strouhal numbers (St: 1, 2, 3, 4), and Reynolds numbers (200 <= Re <= 800). The surfaces other than the adiabatic lengths at the inlet and outlet of the duct were kept constant at Tw = 360 K. Results were compared with the results of the steady flow case. The effects of pulsating velocity and oscillatory parameters on Nusselt number, pressure drop, and performance factor were discussed. Velocity and temperature images were presented for different Reynolds numbers and pulsating components in the channel. The findings revealed that although the pulsating parameters significantly enhanced the heat transfer at increasing Reynolds numbers, they had a fairly low effect on heat transfer at the same Reynolds number. It was observed that at Re = 800, the Nusselt number formed a peak at St = 3 for all tested pulsating amplitudes. For the parameters of Re = 800, A = 0.6, and St = 2, heat transfer and performance factor in pulsating flow increased by 8.96 and 8.22 times, respectively, compared to steady flow conditions.

关键词： Rhombus chamber thermal recovery pulsating flow friction factor performance factor

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The impact of particle size and concentration on the characteristics of solid-fluid two-phase flow in vertical pipe under pulsating flow

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CHEMICAL ENGINEERING JOURNAL 2024年 500卷

作者： Ren, Wanlong Zhang, Xuhui Zhang, Yan Lu, Xiaobing Chinese Acad Sci Inst Mech Beijing 100190 Peoples R China Univ Chinese Acad Sci Sch Engn Sci Beijing 100049 Peoples R China Shanghai Jiao Tong Univ State Key Lab Ocean Engn Shanghai 200030 Peoples R China

Vertical pipe hydraulic conveying is currently considered the most promising method for deep-sea mining. The conveying velocity at the inlet of the vertical pipe is often close to a pulsating form due to the influence of the flexible pipe and the marine environment. This study employs a combined Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) approach to investigate the impact of various particle sizes and concentrations on the flow behavior of solid-fluid two-phase flow in a vertical pipe under pulsating flow. The study reveals that fluid velocities exhibit periodic fluctuations within the vertical pipe under pulsating inlet flow. Moreover, the periodic phenomenon of local increases in particle velocity and concentration becomes more pronounced as particle size and concentration increase. Larger particle sizes increase particle inertia, reducing the ability to follow the fluid and leading to more localized particle aggregation. Therefore, the flow pattern within the vertical pipe transitions from homogeneous flow to plug flow as particle size increases. Variations in fluid-solid interaction forces and particle collision forces are explored to explain this phenomenon. When the particle size exceeds a critical threshold, the collision force surpasses the fluid-solid interaction force, leading to the transition.

关键词： Solid-fluid two-phase flow flow pattern Hydraulic conveying pulsating flow Particle size

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