Pub Date : 2025-12-26DOI: 10.1016/j.ijheatfluidflow.2025.110207
Ziyang Zhou , Stéphane Moreau , Marlène Sanjosé
To evaluate installation effects on velocity statistics and its influence on farfield noise, three Direct Numerical Simulations (DNS) have been run using the Lattice-Boltzmann Method with the PowerFLOW software on the Controlled-Diffusion (CD) airfoil at a Reynolds number of 150 000 and 8 degrees angle of attack installed in the Universite de Sherbrooke (UdeS) wind tunnel. Differences in setup between these DNS simulations are the addition of voxel refinements and turbulent trips to the simulation setup for better capturing of the jet shear layer downstream of the wind tunnel nozzle lip. Results show that the airfoil boundary layer displacement thickness, momentum thickness and shape factor are slightly increased after jet shear layer refinement due to an increase in mean angle of attack caused by a change in shear layer state. Despite these changes caused by the mixing layer state, maximum Reynolds stress magnitude near the trailing edge of the airfoil was changed by only 6%. This indicates that adjustments to the wall pressure statistics which are relevant to trailing edge noise generation was only marginal. As such, changes to boundary layer statistics had limited impact on far-field noise in the mid-frequency range in this operating state.
{"title":"Direct numerical simulation of installation effects on airfoil noise","authors":"Ziyang Zhou , Stéphane Moreau , Marlène Sanjosé","doi":"10.1016/j.ijheatfluidflow.2025.110207","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110207","url":null,"abstract":"<div><div>To evaluate installation effects on velocity statistics and its influence on farfield noise, three Direct Numerical Simulations (DNS) have been run using the Lattice-Boltzmann Method with the PowerFLOW software on the Controlled-Diffusion (CD) airfoil at a Reynolds number of 150 000 and 8 degrees angle of attack installed in the Universite de Sherbrooke (UdeS) wind tunnel. Differences in setup between these DNS simulations are the addition of voxel refinements and turbulent trips to the simulation setup for better capturing of the jet shear layer downstream of the wind tunnel nozzle lip. Results show that the airfoil boundary layer displacement thickness, momentum thickness and shape factor are slightly increased after jet shear layer refinement due to an increase in mean angle of attack caused by a change in shear layer state. Despite these changes caused by the mixing layer state, maximum Reynolds stress magnitude near the trailing edge of the airfoil was changed by only 6%. This indicates that adjustments to the wall pressure statistics which are relevant to trailing edge noise generation was only marginal. As such, changes to boundary layer statistics had limited impact on far-field noise in the mid-frequency range in this operating state.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110207"},"PeriodicalIF":2.6,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145938999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-24DOI: 10.1016/j.ijheatfluidflow.2025.110214
Yoon Hoo Shin , Hyo Jun Sim , Jong Jin Hwang , Seung Jae Moon
This study aims to enhance the performance of an ion implanter by improving temperature control through a heating tube integrated within the bushing. In an ion implanter, gases such as PH3, AsH3, BF3, and GeF4 are ionized by applying high voltages of up to 80 kV. Consequently, an ion beam is extracted from the electrode. However, residual gases are deposited inside the bushing under relatively low operating temperatures. Consequently, a leakage current flows through the bushing due to the deposited residual gas layer. This results in arcing from the potential differences across the bushing. To address this issue, this study designs and implements a heating tube within the bushing and circulates a heating fluid via the tube to increase the bushing’s temperature. The proposed heating system prevents gas deposition and enhances the efficiency of the deposition process. The optimal condition—defined as achieving a bushing wall temperature of 60°C with minimal energy input—was determined as a FC-3283 flow rate of 24 LPM with an inlet temperature of 100°C. The effectiveness of this solution is evaluated through a combination of experiments and computational fluid dynamics simulations. The experimental results corroborate the simulation outcomes. This integrated experimental–simulation approach is expected to significantly enhance deposition process efficiency. These findings offer valuable insights for optimizing ion implantation performance and reducing the frequency of bushing replacements.
{"title":"Increasing bushing temperature via a heating tube for performance enhancement of ion implanters","authors":"Yoon Hoo Shin , Hyo Jun Sim , Jong Jin Hwang , Seung Jae Moon","doi":"10.1016/j.ijheatfluidflow.2025.110214","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110214","url":null,"abstract":"<div><div>This study aims to enhance the performance of an ion implanter by improving temperature control through a heating tube integrated within the bushing. In an ion implanter, gases such as PH<sub>3</sub>, AsH<sub>3</sub>, BF<sub>3</sub>, and GeF<sub>4</sub> are ionized by applying high voltages of up to 80 kV. Consequently, an ion beam is extracted from the electrode. However, residual gases are deposited inside the bushing under relatively low operating temperatures. Consequently, a leakage current flows through the bushing due to the deposited residual gas layer. This results in arcing from the potential differences across the bushing. To address this issue, this study designs and implements a heating tube within the bushing and circulates a heating fluid via the tube to increase the bushing’s temperature. The proposed heating system prevents gas deposition and enhances the efficiency of the deposition process. The optimal condition—defined as achieving a bushing wall temperature of 60°C with minimal energy input—was determined as a FC-3283 flow rate of 24 LPM with an inlet temperature of 100°C. The effectiveness of this solution is evaluated through a combination of experiments and computational fluid dynamics simulations. The experimental results corroborate the simulation outcomes. This integrated experimental–simulation approach is expected to significantly enhance deposition process efficiency. These findings offer valuable insights for optimizing ion implantation performance and reducing the frequency of bushing replacements.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110214"},"PeriodicalIF":2.6,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-24DOI: 10.1016/j.ijheatfluidflow.2025.110224
Shao-Fei Zheng , Jia-Xing Meng , Hua-Dong Shi , Yi-Feng Wang , Shu-Rong Gao , Yan-Ru Yang , Bo Gao , Xiao-Dong Wang
In gas turbine engines, efficient heat transfer following less friction loss is extremely preferable for the cooling of turbine blades, because of the limited supply of the cooling air. To maximize the cooling effect of the commonly utilized ribbed channel, the back propagation neural network (BPNN) model and the genetic algorithm (GA) are combined to construct an optimization tool by exactly modeling the complex nonlinear relationship between the influencing factors and cooling performance. The coupling influences of the channel aspect ratio (W/H = 0.5 ∼ 4.0), the pitch ratio of ribs (P/e = 20 ∼ 5), and the Reynolds number (Re = 20, 000 ∼ 100, 000) are comprehensively analyzed using the Nusselt number and overall performance factor as the target function. The results state that using the Nusselt number as the target function, the relatively large aspect ratio and small pitch ratio are recommended due to the heat transfer enhancement of the flow impingement effect with the rib-induced flow separation. Considering both the heat transfer enhancement and the increased friction loss, the overall performance factor presents a highly nonlinear relationship with those influencing parameters, and the relatively small aspect ratio and large pitch ratio are suggested to improve the comprehensive cooling performance. Using the GA-BPNN optimization method, a great increase of 16.98 %∼30.67 % is achieved for the overall performance factor in the current operating conditions. Finally, the GA-BPNN method is demonstrated as powerful and efficient for improving the ribbed cooling channel.
在燃气涡轮发动机中，由于冷却空气的供应有限，在摩擦损失较小的情况下，高效的传热对于涡轮叶片的冷却是极其可取的。为了使常用的肋形通道冷却效果最大化，将反向传播神经网络（BPNN）模型与遗传算法（GA）相结合，通过精确建模影响因素与冷却性能之间复杂的非线性关系，构建了优化工具。耦合通道宽高比的影响(0.5 W / H = ∼ 4.0),肋骨的螺距比(P / e = 20 ∼ 5),和雷诺数(Re = 000 ∼ 100年,000年)进行了全面分析使用努塞尔特数和整体性能因素作为目标函数。结果表明，以Nusselt数为目标函数，由于肋诱导流动分离强化了流动冲击效应的传热，建议采用较大的展弦比和较小的节距比。考虑到传热增强和摩擦损失的增加，综合性能因子与这些影响参数呈高度非线性关系，建议采用较小的展弦比和较大的节距比来提高综合冷却性能。使用GA-BPNN优化方法，在当前运行条件下，总体性能因子实现了16.98 % ~ 30.67 %的大幅提高。最后，验证了GA-BPNN方法对肋形冷却通道的改进效果。
{"title":"Optimization of the cooling performance of ribbed channels by combining neural networks and genetic algorithms","authors":"Shao-Fei Zheng , Jia-Xing Meng , Hua-Dong Shi , Yi-Feng Wang , Shu-Rong Gao , Yan-Ru Yang , Bo Gao , Xiao-Dong Wang","doi":"10.1016/j.ijheatfluidflow.2025.110224","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110224","url":null,"abstract":"<div><div>In gas turbine engines, efficient heat transfer following less friction loss is extremely preferable for the cooling of turbine blades, because of the limited supply of the cooling air. To maximize the cooling effect of the commonly utilized ribbed channel, the back propagation neural network (BPNN) model and the genetic algorithm (GA) are combined to construct an optimization tool by exactly modeling the complex nonlinear relationship between the influencing factors and cooling performance. The coupling influences of the channel aspect ratio (<em>W</em>/<em>H</em> = 0.5 ∼ 4.0), the pitch ratio of ribs (<em>P</em>/<em>e</em> = 20 ∼ 5), and the Reynolds number (<em>Re</em> = 20, 000 ∼ 100, 000) are comprehensively analyzed using the Nusselt number and overall performance factor as the target function. The results state that using the Nusselt number as the target function, the relatively large aspect ratio and small pitch ratio are recommended due to the heat transfer enhancement of the flow impingement effect with the rib-induced flow separation. Considering both the heat transfer enhancement and the increased friction loss, the overall performance factor presents a highly nonlinear relationship with those influencing parameters, and the relatively small aspect ratio and large pitch ratio are suggested to improve the comprehensive cooling performance. Using the GA-BPNN optimization method, a great increase of 16.98 %∼30.67 % is achieved for the overall performance factor in the current operating conditions. Finally, the GA-BPNN method is demonstrated as powerful and efficient for improving the ribbed cooling channel.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110224"},"PeriodicalIF":2.6,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-24DOI: 10.1016/j.ijheatfluidflow.2025.110221
Srirama Chandra Murthy Rampally, Navneet Kumar
This study explores the influence of varying cross-sectional geometries on the capillary-driven wicking of water in vertically suspended Whatman filter paper strips. By extending the classical Lucas–Washburn framework through a Darcy-based model with spatially varying cross-sectional area , we analyze how geometry impacts both penetration length and advancing front velocity. The empirical power-law relationship was used to quantify penetration kinetics. Experimentally, the exponent increased from in rectangular strips to and in exponential and hyperbolic geometries, respectively, demonstrating improved wicking due to shape-induced modulation of viscous resistance. Velocity comparisons show that at a height of , front velocities in exponential and hyperbolic cases were and higher than trapezoidal, while at , the trapezoidal geometry outperformed others by and over exponential and hyperbolic shapes, respectively. A central element of this enhancement is the dimensionless viscous resistance term , which captures how geometry influences the wicking. Unlike the constant in rectangular strips, exponential and hyperbolic profiles exhibit a smooth, monotonic increase in , reducing cumulative resistance and supporting sustained wicking. In contrast, the trapezoidal geometry displays a peak in at for an aspect ratio of , leading to a transient benefit. These findings not only align with theoretical predictions but also demonstrate how strategic geometric tapering can substantially enhance capillary transport. The work holds practical significance for wick design in microfluidic diagnostics, passive cooling, and liquid delivery systems.
{"title":"Geometry-induced enhancement of capillary wicking in porous strips: Experimental and analytical insights","authors":"Srirama Chandra Murthy Rampally, Navneet Kumar","doi":"10.1016/j.ijheatfluidflow.2025.110221","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110221","url":null,"abstract":"<div><div>This study explores the influence of varying cross-sectional geometries on the capillary-driven wicking of water in vertically suspended Whatman filter paper strips. By extending the classical Lucas–Washburn framework through a Darcy-based model with spatially varying cross-sectional area <span><math><mrow><mi>A</mi><mo>(</mo><mi>z</mi><mo>)</mo></mrow></math></span>, we analyze how geometry impacts both penetration length and advancing front velocity. The empirical power-law relationship <span><math><mrow><mi>h</mi><mo>=</mo><mi>a</mi><msup><mrow><mi>t</mi></mrow><mi>b</mi></msup></mrow></math></span> was used to quantify penetration kinetics. Experimentally, the exponent <span><math><mrow><mi>b</mi></mrow></math></span> increased from <span><math><mrow><mn>0.53</mn></mrow></math></span> in rectangular strips to <span><math><mrow><mn>0.59</mn></mrow></math></span> and <span><math><mrow><mn>0.54</mn></mrow></math></span> in exponential and hyperbolic geometries, respectively, demonstrating improved wicking due to shape-induced modulation of viscous resistance. Velocity comparisons show that at a height of <span><math><mrow><mn>20</mn><mi>m</mi><mi>m</mi></mrow></math></span>, front velocities in exponential and hyperbolic cases were <span><math><mrow><mspace></mspace><mn>14</mn><mo>%</mo></mrow></math></span> and <span><math><mrow><mspace></mspace><mn>27</mn><mo>%</mo></mrow></math></span> higher than trapezoidal, while at <span><math><mrow><mn>50</mn><mi>m</mi><mi>m</mi></mrow></math></span>, the trapezoidal geometry outperformed others by <span><math><mrow><mspace></mspace><mn>34</mn><mo>%</mo></mrow></math></span> and <span><math><mrow><mspace></mspace><mn>50</mn><mo>%</mo></mrow></math></span> over exponential and hyperbolic shapes, respectively. A central element of this enhancement is the dimensionless viscous resistance term <span><math><mrow><mi>f</mi></mrow></math></span>, which captures how geometry influences the wicking. Unlike the constant <span><math><mrow><mi>f</mi></mrow></math></span> in rectangular strips, exponential and hyperbolic profiles exhibit a smooth, monotonic increase in <span><math><mrow><mi>f</mi></mrow></math></span>, reducing cumulative resistance and supporting sustained wicking. In contrast, the trapezoidal geometry displays a peak in <span><math><mrow><mi>f</mi></mrow></math></span> at <span><math><mrow><msup><mrow><mi>z</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>=</mo><mn>1</mn><mo>-</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>-</mo><mn>1</mn></mrow></msup></mrow></math></span> for an aspect ratio of <span><math><mrow><mn>0.083</mn></mrow></math></span>, leading to a transient benefit. These findings not only align with theoretical predictions but also demonstrate how strategic geometric tapering can substantially enhance capillary transport. The work holds practical significance for wick design in microfluidic diagnostics, passive cooling, and liquid delivery systems.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110221"},"PeriodicalIF":2.6,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-23DOI: 10.1016/j.ijheatfluidflow.2025.110215
Siyu Gao, Xiaohong Hao, Yan Wang, Xiangsheng Zheng
Supercritical carbon dioxide (SCO2) has emerged as a novel working fluid in nuclear power generation systems due to its unique thermophysical properties and potential system efficiency advantages. In this study, numerical investigations of heat transfer characteristics of SCO2 in a vertical helical tube were conducted under conditions of pressures ranging from 15 to 20 MPa, inlet temperatures from 453 to 483 K, and mass fluxes from 297.16 to 866.44 kg/m2s. The SST k-ω turbulence model and pseudo-transient method were employed to simulate the heat transfer process. The effects of mass flux, inlet temperature, pressure drop, buoyancy, and flow acceleration on the heat transfer coefficient were analyzed. The results indicated that at high mass fluxes, the influence of vortices and secondary flows becomes more pronounced, decreasing heat transfer efficiency. Increasing the inlet temperature can reduce the fluid flow resistance, enhancing the heat transfer coefficient. As pressure increases, the fluid density increases and the fluid inertia force grows, offsetting part of the viscous force and reducing pressure drop and friction factor. Finally, to accurately predict the heat transfer of SCO2 in a spiral heat exchanger, a new heat transfer correlation was proposed.
{"title":"Numerical investigation of heat transfer characteristics of supercritical carbon dioxide in a spiral heat exchanger","authors":"Siyu Gao, Xiaohong Hao, Yan Wang, Xiangsheng Zheng","doi":"10.1016/j.ijheatfluidflow.2025.110215","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110215","url":null,"abstract":"<div><div>Supercritical carbon dioxide (SCO<sub>2</sub>) has emerged as a novel working fluid in nuclear power generation systems due to its unique thermophysical properties and potential system efficiency advantages. In this study, numerical investigations of heat transfer characteristics of SCO<sub>2</sub> in a vertical helical tube were conducted under conditions of pressures ranging from 15 to 20 MPa, inlet temperatures from 453 to 483 K, and mass fluxes from 297.16 to 866.44 kg/m<sup>2</sup>s. The SST k-ω turbulence model and pseudo-transient method were employed to simulate the heat transfer process. The effects of mass flux, inlet temperature, pressure drop, buoyancy, and flow acceleration on the heat transfer coefficient were analyzed. The results indicated that at high mass fluxes, the influence of vortices and secondary flows becomes more pronounced, decreasing heat transfer efficiency. Increasing the inlet temperature can reduce the fluid flow resistance, enhancing the heat transfer coefficient. As pressure increases, the fluid density increases and the fluid inertia force grows, offsetting part of the viscous force and reducing pressure drop and friction factor. Finally, to accurately predict the heat transfer of SCO<sub>2</sub> in a spiral heat exchanger, a new heat transfer correlation was proposed.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110215"},"PeriodicalIF":2.6,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-23DOI: 10.1016/j.ijheatfluidflow.2025.110219
Xiaoming Zhou , Haocun Wang , Wang Leilei , Yanni Jiang
To analyze the oscillation and evolution characteristics of thermocapillary convection instability of non-Newtonian fluids, the effect of power-law index on the critical transition process and oscillation evolution is investigated systematically, in which the power-law model is adopted to describe the rheological properties of the fluid. It is found that the transition time from steady single vortex flow (SUF) to unsteady hydrothermal waves (HTW) varied with the power-law index, being initially governed by the effective viscosity. For the periodic oscillation regime, the number of vortical cells decreases and their size increases as power-law index decreases. The transient apparent viscosity of non-Newtonian fluids exhibits a clear periodic fluctuation with time. A decrease in the power-law index tends to destabilize the flow, whereas an increase in the consistency coefficient enhances flow stability. For Ma ≥ Macr (Ma, Marangoni number), thermocapillary convection manifests periodic oscillations with multiple evolving vortices, a lower power-law index diminishes the critical temperature difference, amplifies the amplitude of velocity oscillations, and induces larger time-series irregularity.
{"title":"Exploration of the stability and evolution characteristics of thermocapillary convection of shear-thinning fluids in rectangular cavity","authors":"Xiaoming Zhou , Haocun Wang , Wang Leilei , Yanni Jiang","doi":"10.1016/j.ijheatfluidflow.2025.110219","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110219","url":null,"abstract":"<div><div>To analyze the oscillation and evolution characteristics of thermocapillary convection instability of non-Newtonian fluids, the effect of power-law index on the critical transition process and oscillation evolution is investigated systematically, in which the power-law model is adopted to describe the rheological properties of the fluid. It is found that the transition time from steady single vortex flow (SUF) to unsteady hydrothermal waves (HTW) varied with the power-law index, being initially governed by the effective viscosity. For the periodic oscillation regime, the number of vortical cells decreases and their size increases as power-law index decreases. The transient apparent viscosity of non-Newtonian fluids exhibits a clear periodic fluctuation with time. A decrease in the power-law index tends to destabilize the flow, whereas an increase in the consistency coefficient enhances flow stability. For Ma ≥ Ma<sub>cr</sub> (Ma, Marangoni number), thermocapillary convection manifests periodic oscillations with multiple evolving vortices, a lower power-law index diminishes the critical temperature difference, amplifies the amplitude of velocity oscillations, and induces larger time-series irregularity.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110219"},"PeriodicalIF":2.6,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.1016/j.ijheatfluidflow.2025.110212
Anupama Singh , Anand Kumar , Vinod K. Gupta
The current article explores the structure of chaotic convection and the rate of heat transfer in a Rivlin–Ericksen fluid layer with an internal heat source flowing through a highly permeable porous medium that is heated from below. The truncated Galerkin approximation has produced a low-dimensional system similar to the Lorenz model. To compute the numerical simulation for a Lorenz-like equation framework, we implemented the fourth-order Runge–Kutta method. We utilized MATHEMATICA software for quantitative analysis and MATLAB software for visualization. The influence of an internal heat content on chaotic convection has been investigated. Additionally, when comparing only the elasticity effect, we found that the Rayleigh number decreases by 8.09%. This indicates that the chaotic behavior predominates over the instability of the system. We discovered that both the level of internal heat and the elastic parameter enhance chaotic convection. We propose that the level of internal heat influences the transition from steady to chaotic convection.
{"title":"Insight into effect of internal heating on natural convection of Rivlin–Ericksen fluid with highly permeable porous medium: Dynamical system approach","authors":"Anupama Singh , Anand Kumar , Vinod K. Gupta","doi":"10.1016/j.ijheatfluidflow.2025.110212","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110212","url":null,"abstract":"<div><div>The current article explores the structure of chaotic convection and the rate of heat transfer in a Rivlin–Ericksen fluid layer with an internal heat source flowing through a highly permeable porous medium that is heated from below. The truncated Galerkin approximation has produced a low-dimensional system similar to the Lorenz model. To compute the numerical simulation for a Lorenz-like equation framework, we implemented the fourth-order Runge–Kutta method. We utilized MATHEMATICA software for quantitative analysis and MATLAB software for visualization. The influence of an internal heat content on chaotic convection has been investigated. Additionally, when comparing only the elasticity effect, we found that the Rayleigh number decreases by 8.09%. This indicates that the chaotic behavior predominates over the instability of the system. We discovered that both the level of internal heat and the elastic parameter enhance chaotic convection. We propose that the level of internal heat influences the transition from steady to chaotic convection.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110212"},"PeriodicalIF":2.6,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-20DOI: 10.1016/j.ijheatfluidflow.2025.110218
Zhen Xiang , Qilong Liu , Shaohua Han , Shizhen Qi , Tianyi Huo , Runsheng Zhang , Leping Zhou , Li Li , Hui Zhang , Xiaoze Du
Improving the cooling effectiveness of turbine blade squealer tip regions under high thermal loads remains a challenge in designing of gas turbines. This study numerically investigates the cooling performance of a novel protrusion-V-rib composite structure applied to the internal U-channel near the blade squealer tip. Eight configurations, including holed/hole free designs and combinations of V-ribs, protrusions and vanes, are evaluated at Re = 10,000–50,000. Key findings show that holed structures enhance heat transfer near holes due to accelerated fluid velocity and increased turbulence, resulting in higher Nusselt number. However, hole free configurations exhibit superior downstream heat transfer (up to 4.14 % improvement) by maintaining coolant mass flow. Complex geometries, particularly the V-Convex design, significantly suppress flow separation and reduce vortex size by promoting fluid disturbance and turbulence. The V-convex structure exhibits the highest Nusselt number and comprehensive thermal performance factor under both constant temperature and constant heat flux boundary conditions, confirming its robustness. The results highlight the trade-off between local heat transfer enhancement (holed structures) and downstream cooling effectiveness (hole-free designs), emphasizing the importance of geometric optimization for blade squealer tip cooling. This work helps understand the composite cooling structures and provides insights for efficient thermal management in applications of high-temperature turbines.
{"title":"Enhanced cooling performance in turbine blade tip U-channel using protrusion-V-rib composite structure","authors":"Zhen Xiang , Qilong Liu , Shaohua Han , Shizhen Qi , Tianyi Huo , Runsheng Zhang , Leping Zhou , Li Li , Hui Zhang , Xiaoze Du","doi":"10.1016/j.ijheatfluidflow.2025.110218","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110218","url":null,"abstract":"<div><div>Improving the cooling effectiveness of turbine blade squealer tip regions under high thermal loads remains a challenge in designing of gas turbines. This study numerically investigates the cooling performance of a novel protrusion-V-rib composite structure applied to the internal U-channel near the blade squealer tip. Eight configurations, including holed/hole free designs and combinations of V-ribs, protrusions and vanes, are evaluated at Re = 10,000–50,000. Key findings show that holed structures enhance heat transfer near holes due to accelerated fluid velocity and increased turbulence, resulting in higher Nusselt number. However, hole free configurations exhibit superior downstream heat transfer (up to 4.14 % improvement) by maintaining coolant mass flow. Complex geometries, particularly the V-Convex design, significantly suppress flow separation and reduce vortex size by promoting fluid disturbance and turbulence. The V-convex structure exhibits the highest Nusselt number and comprehensive thermal performance factor under both constant temperature and constant heat flux boundary conditions, confirming its robustness. The results highlight the trade-off between local heat transfer enhancement (holed structures) and downstream cooling effectiveness (hole-free designs), emphasizing the importance of geometric optimization for blade squealer tip cooling. This work helps understand the composite cooling structures and provides insights for efficient thermal management in applications of high-temperature turbines.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110218"},"PeriodicalIF":2.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-20DOI: 10.1016/j.ijheatfluidflow.2025.110206
Sangdi Gu
This study, for the first time, systematically quantifies the specific impact of stagnation point boundary layer (BL) edge nonequilibrium on surface heating for arbitrary BLs by decoupling the problem. Stagnation point heat flux theory is used in conjunction with a quasi-one-dimensional stagnation streamline model, in which the BL edge state is precisely controlled: pressure, enthalpy, and velocity gradient are held constant while chemical composition is varied between the frozen and equilibrium limits. It is found that nonequilibrium at the edge has no effect on heat flux when the wall is super-catalytic, the flow is equilibrated, or the recombination rate is sufficiently fast to maintain the atomic mass fraction at the wall unchanged despite variations at the BL edge. If the Lewis number () is not equal to 1 in these scenarios, edge nonequilibrium may moderately influence the heat flux by up to approximately , although is likely a good approximation. In contrast, edge nonequilibrium can significantly affect the heat flux if the wall is non-catalytic and chemistry in the BL is slow, regardless of . These results contribute significantly to theoretical understanding of high-enthalpy stagnation-point heating and enable clearer interpretation of full-fidelity simulations under various scenarios.
{"title":"Isolating the specific contribution of boundary-layer edge chemical nonequilibrium to stagnation-point heating","authors":"Sangdi Gu","doi":"10.1016/j.ijheatfluidflow.2025.110206","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110206","url":null,"abstract":"<div><div>This study, for the first time, systematically quantifies the specific impact of stagnation point boundary layer (BL) edge nonequilibrium on surface heating for arbitrary BLs by decoupling the problem. Stagnation point heat flux theory is used in conjunction with a quasi-one-dimensional stagnation streamline model, in which the BL edge state is precisely controlled: pressure, enthalpy, and velocity gradient are held constant while chemical composition is varied between the frozen and equilibrium limits. It is found that nonequilibrium at the edge has no effect on heat flux when the wall is super-catalytic, the flow is equilibrated, or the recombination rate is sufficiently fast to maintain the atomic mass fraction at the wall unchanged despite variations at the BL edge. If the Lewis number (<span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>) is not equal to 1 in these scenarios, edge nonequilibrium may moderately influence the heat flux by up to approximately <span><math><mrow><mo>±</mo><mn>20</mn><mtext>%</mtext></mrow></math></span>, although <span><math><mrow><mi>L</mi><mi>e</mi><mo>≈</mo><mn>1</mn></mrow></math></span> is likely a good approximation. In contrast, edge nonequilibrium can significantly affect the heat flux if the wall is non-catalytic and chemistry in the BL is slow, regardless of <span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>. These results contribute significantly to theoretical understanding of high-enthalpy stagnation-point heating and enable clearer interpretation of full-fidelity simulations under various scenarios.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110206"},"PeriodicalIF":2.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-19DOI: 10.1016/j.ijheatfluidflow.2025.110213
Juhui Chen , Shuxiang Pang , Dan Li , Liwei Chen , Michael Zhurakov , Siarhei Lapatsin , Wenrui Jiang
Conventional microchannels typically exhibit limited heat transfer efficiency and suboptimal flow characteristics. This study investigates two fin-enhanced microchannel geometries, triangular ribbed and corrugated, using a moving-grid method to simulate periodic fin motion. Numerical simulations were conducted over a Reynolds number range of 50–250 at a fin oscillation frequency of 20 Hz. The results show that the triangular ribbed microchannel offers lower flow resistance and improved overall flowability due to its relatively smoother flow path, whereas the corrugated design produces stronger flow disturbances and secondary vortices, leading to enhanced heat transfer, especially at lower Reynolds numbers. However, the intensified flow mixing in the corrugated microchannel also increases flow-path tortuosity, resulting in a larger pressure drop. To evaluate the overall performance, the Performance Evaluation Criterion (PEC) was used. The triangular ribbed channel achieved a maximum PEC of 1.52 at Re = 200, indicating a balanced improvement in both heat transfer and flow resistance. These geometries are relevant for practical thermal management applications, such as compact heat sinks and miniaturized cooling devices, due to their manufacturability and effectiveness in enhancing thermo-fluidic performance.
{"title":"Effect of fin-enhanced microchannel structures on flow and heat transfer: comparison of triangular ribbed and corrugated designs","authors":"Juhui Chen , Shuxiang Pang , Dan Li , Liwei Chen , Michael Zhurakov , Siarhei Lapatsin , Wenrui Jiang","doi":"10.1016/j.ijheatfluidflow.2025.110213","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110213","url":null,"abstract":"<div><div>Conventional microchannels typically exhibit limited heat transfer efficiency and suboptimal flow characteristics. This study investigates two fin-enhanced microchannel geometries, triangular ribbed and corrugated, using a moving-grid method to simulate periodic fin motion. Numerical simulations were conducted over a Reynolds number range of 50–250 at a fin oscillation frequency of 20 Hz. The results show that the triangular ribbed microchannel offers lower flow resistance and improved overall flowability due to its relatively smoother flow path, whereas the corrugated design produces stronger flow disturbances and secondary vortices, leading to enhanced heat transfer, especially at lower Reynolds numbers. However, the intensified flow mixing in the corrugated microchannel also increases flow-path tortuosity, resulting in a larger pressure drop. To evaluate the overall performance, the Performance Evaluation Criterion (<em>PEC</em>) was used. The triangular ribbed channel achieved a maximum <em>PEC</em> of 1.52 at <em>Re</em> = 200, indicating a balanced improvement in both heat transfer and flow resistance. These geometries are relevant for practical thermal management applications, such as compact heat sinks and miniaturized cooling devices, due to their manufacturability and effectiveness in enhancing thermo-fluidic performance.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"118 ","pages":"Article 110213"},"PeriodicalIF":2.6,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号