Pub Date : 2025-02-17DOI: 10.1016/j.ijheatfluidflow.2025.109766
Yuan Wang
Numerical simulation is conducted to investigate the heat transfer enhancement characteristics of channel surface modifications. Two-dimensional Inconel 718 mini-channels with modified triangular surface protrusions are used, employing supercritical-pressurized n-decane as the working fluid at an outlet pressure of 3.0 MPa and an inlet mass flow rate of 1 kg/s. A set of 76 test cases are designed to examine the influence of protrusion geometry, distribution, and varying channel surface heat flux ranging from 0.5 MW/m2 to 1.0 MW/m2. Structural temperature, average heat transfer coefficient havg, and friction factor f are calculated. Effects of the protrusion location and geometric parameters are discussed. It is found that protrusion height positively dominates both havg and f, with Pearson’s correlation coefficient r of 0.78085 and 0.78316, respectively. The protrusion leading length x1 has a slightly higher impact on havg compared to the trailing length x2, with rhavg-x1 = 0.35053 and rhavg-x2 = 0.30534. An increase in x2 shows a more profound impact on f compared to x1. Lower inter-convexity distance, increased convexity height and convexity leading length are recommended for heat transfer enhancement. The outcomes of the present study provide valuable insights for optimizing cooling channels in thermal protection systems under high heat flux and supercritical conditions.
{"title":"Numerical investigation of heat transfer enhancement in mini-channels with modified surface protrusions","authors":"Yuan Wang","doi":"10.1016/j.ijheatfluidflow.2025.109766","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109766","url":null,"abstract":"<div><div>Numerical simulation is conducted to investigate the heat transfer enhancement characteristics of channel surface modifications. Two-dimensional Inconel 718 mini-channels with modified triangular surface protrusions are used, employing supercritical-pressurized n-decane as the working fluid at an outlet pressure of 3.0 MPa and an inlet mass flow rate of 1 kg/s. A set of 76 test cases are designed to examine the influence of protrusion geometry, distribution, and varying channel surface heat flux ranging from 0.5 MW/m<sup>2</sup> to 1.0 MW/m<sup>2</sup>. Structural temperature, average heat transfer coefficient <em>h</em><sub>avg</sub>, and friction factor <em>f</em> are calculated. Effects of the protrusion location and geometric parameters are discussed. It is found that protrusion height positively dominates both <em>h</em><sub>avg</sub> and <em>f</em>, with Pearson’s correlation coefficient <em>r</em> of 0.78085 and 0.78316, respectively<em>.</em> The protrusion leading length <em>x</em><sub>1</sub> has a slightly higher impact on <em>h</em><sub>avg</sub> compared to the trailing length <em>x</em><sub>2</sub>, with <em>r<sub>h</sub></em><sub>avg-</sub><em><sub>x</sub></em><sub>1</sub> = 0.35053 and <em>r<sub>h</sub></em><sub>avg-</sub><em><sub>x</sub></em><sub>2</sub> = 0.30534. An increase in <em>x</em><sub>2</sub> shows a more profound impact on <em>f</em> compared to <em>x</em><sub>1</sub>. Lower inter-convexity distance, increased convexity height and convexity leading length are recommended for heat transfer enhancement. The outcomes of the present study provide valuable insights for optimizing cooling channels in thermal protection systems under high heat flux and supercritical conditions.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"113 ","pages":"Article 109766"},"PeriodicalIF":2.6,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427765","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 : 2025-02-17DOI: 10.1016/j.ijheatfluidflow.2025.109777
Hussam Sadique, Samsher, Qasim Murtaza
With the fast integration and shrinkage of electronic equipment, managing heat has emerged as a key roadblock to developing microelectromechanical systems. This investigation presents a bio-inspired fractal microchannel heat sink (FMCHS) design featuring ribs and cavities, which is motivated by the natural mass and energy transfer capabilities found in fractal structures. For an in-depth understanding of the thermal–hydraulic performance of an FMCHS, the branching ratios in successive tree-like structures are chosen via a parameter optimization process that prioritizes minimizing flow resistance. Different thermal and flow characteristics were analyzed numerically using Ansys Fluent, and these results were compared with a plain FMCHS (FMCHS-P). The outcomes suggest that incorporating variable cross-sectional structures can enhance the thermal performance of the FMCHS. FMCHS with ribs (FMCHS-R) and FMCHS with diagonally positioned ribs (FMCHS-DR) have the highest heat transfer performance, followed by FMCHS with cavities (FMCHS-C) and FMCHS with diagonally positioned cavities (FMCHS-DC), but at the same time, ribbed-configured FMCHS has the highest pressure drop. FMCHS models were optimized using ANN and the moth flame optimization (MFO) algorithm with the objective of maximizing Nusselt number and minimizing pumping power and thermal resistance. This research suggests that a model with FMCHS with ribs has an optimal geometrical configuration. The optimal input value is found to be 26 % of the rib radius along all the paths of FMCHS with ribs (FMCHS-R) at a flow rate of 200 ml/min.
{"title":"Numerical study and moth flame optimization of thermal–hydraulic performance of fractal microchannel heat sink with ribs and cavity","authors":"Hussam Sadique, Samsher, Qasim Murtaza","doi":"10.1016/j.ijheatfluidflow.2025.109777","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109777","url":null,"abstract":"<div><div>With the fast integration and shrinkage of electronic equipment, managing heat has emerged as a key roadblock to developing microelectromechanical systems. This investigation presents a bio-inspired fractal microchannel heat sink (FMCHS) design featuring ribs and cavities, which is motivated by the natural mass and energy transfer capabilities found in fractal structures. For an in-depth understanding of the thermal–hydraulic performance of an FMCHS, the branching ratios in successive tree-like structures are chosen via a parameter optimization process that prioritizes minimizing flow resistance. Different thermal and flow characteristics were analyzed numerically using Ansys Fluent, and these results were compared with a plain FMCHS (FMCHS-P). The outcomes suggest that incorporating variable cross-sectional structures can enhance the thermal performance of the FMCHS. FMCHS with ribs (FMCHS-R) and FMCHS with diagonally positioned ribs (FMCHS-DR) have the highest heat transfer performance, followed by FMCHS with cavities (FMCHS-C) and FMCHS with diagonally positioned cavities (FMCHS-DC), but at the same time, ribbed-configured FMCHS has the highest pressure drop. FMCHS models were optimized using ANN and the moth flame optimization (MFO) algorithm with the objective of maximizing Nusselt number and minimizing pumping power and thermal resistance. This research suggests that a model with FMCHS with ribs has an optimal geometrical configuration. The optimal input value is found to be 26 % of the rib radius along all the paths of FMCHS with ribs (FMCHS-R) at a flow rate of 200 ml/min.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"113 ","pages":"Article 109777"},"PeriodicalIF":2.6,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422711","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 : 2025-02-16DOI: 10.1016/j.ijheatfluidflow.2025.109773
Kinga Andrea Kovács, Esztella Balla
The identification of vortices remains a critical yet unresolved challenge in fluid mechanics, as no universally accepted definition of a vortex exists. This study compares several vortex detection methods applied to the simulation of three-dimensional fluid flows around a cylinder and a rectangular cuboid at various Reynolds numbers and angles of attack, including a highly turbulent flow case. The methods under investigation include traditional Eulerian local criteria – -criterion, -criterion, and -criterion – as well as more recent approaches such as the -method, Rortex method, Omega-Liutex method, and the Lagrangian-averaged vorticity deviation (LAVD). Classification metrics and visualization methods are used to quantify and compare the performance of each method. While traditional criteria and the Rortex method demonstrated accuracy only with carefully chosen parameters, the -, and Omega-Liutex methods achieved reliable results with consistent uncertainty using threshold values near the suggested value of 0.52. In highly three-dimensional turbulent flows, all methods encountered challenges with shear contamination, though the LAVD method was the most robust. However, the LAVD method’s reliance on two-dimensional plane-based analysis limits its ability to capture the full volumetric nature of vortices in such flows, which contributed to reduced accuracy. The LAVD method is threshold independent, and can provide accurate results, however, only on the cost of high computational time. It is concluded that for applications with limited computational resources, simpler methods like the -method may be preferable. However, in scenarios requiring high accuracy, the LAVD method, despite its longer processing time, could be more effective.
{"title":"Quantitative comparison of vortex identification methods in three-dimensional fluid flow around bluff bodies","authors":"Kinga Andrea Kovács, Esztella Balla","doi":"10.1016/j.ijheatfluidflow.2025.109773","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109773","url":null,"abstract":"<div><div>The identification of vortices remains a critical yet unresolved challenge in fluid mechanics, as no universally accepted definition of a vortex exists. This study compares several vortex detection methods applied to the simulation of three-dimensional fluid flows around a cylinder and a rectangular cuboid at various Reynolds numbers and angles of attack, including a highly turbulent flow case. The methods under investigation include traditional Eulerian local criteria – <span><math><mi>ω</mi></math></span>-criterion, <span><math><mi>Q</mi></math></span>-criterion, and <span><math><msub><mrow><mi>λ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>-criterion – as well as more recent approaches such as the <span><math><mi>Ω</mi></math></span>-method, Rortex method, Omega-Liutex method, and the Lagrangian-averaged vorticity deviation (LAVD). Classification metrics and visualization methods are used to quantify and compare the performance of each method. While traditional criteria and the Rortex method demonstrated accuracy only with carefully chosen parameters, the <span><math><mi>Ω</mi></math></span>-, and Omega-Liutex methods achieved reliable results with consistent uncertainty using threshold values near the suggested value of 0.52. In highly three-dimensional turbulent flows, all methods encountered challenges with shear contamination, though the LAVD method was the most robust. However, the LAVD method’s reliance on two-dimensional plane-based analysis limits its ability to capture the full volumetric nature of vortices in such flows, which contributed to reduced accuracy. The LAVD method is threshold independent, and can provide accurate results, however, only on the cost of high computational time. It is concluded that for applications with limited computational resources, simpler methods like the <span><math><mi>Ω</mi></math></span>-method may be preferable. However, in scenarios requiring high accuracy, the LAVD method, despite its longer processing time, could be more effective.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"113 ","pages":"Article 109773"},"PeriodicalIF":2.6,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this investigation, we present a novel Meshfree method for addressing nonlinear steady natural convection equations, leveraging the Radial Point Interpolation Method (RPIM) for discretization and a high-order continuation procedure for solution computation. The proposed approach is validated through examples involving two-dimensional air-filled cavities with diverse geometries and different boundary conditions, considering constant fluid properties except density. The numerical simulations demonstrate good agreement with Finite Element Method (FEM) and literature data. Various parameters, such as Rayleigh number, angular position of the inner elliptic and hexagonal cylinders, and radius of the inner circular cylinder, are systematically analyzed. Results, including streamlines, isotherms, and average equivalent conductivity, are presented graphically, establishing the effectiveness and accuracy of the proposed method.
{"title":"Nonlinear steady-state analysis of natural convection using a high-order continuation approach","authors":"Boutayna Laasl , Youssef Hilali , Said Mesmoudi , Oussama Bourihane","doi":"10.1016/j.ijheatfluidflow.2025.109770","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109770","url":null,"abstract":"<div><div>In this investigation, we present a novel Meshfree method for addressing nonlinear steady natural convection equations, leveraging the Radial Point Interpolation Method (RPIM) for discretization and a high-order continuation procedure for solution computation. The proposed approach is validated through examples involving two-dimensional air-filled cavities with diverse geometries and different boundary conditions, considering constant fluid properties except density. The numerical simulations demonstrate good agreement with Finite Element Method (FEM) and literature data. Various parameters, such as Rayleigh number, angular position of the inner elliptic and hexagonal cylinders, and radius of the inner circular cylinder, are systematically analyzed. Results, including streamlines, isotherms, and average equivalent conductivity, are presented graphically, establishing the effectiveness and accuracy of the proposed method.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"113 ","pages":"Article 109770"},"PeriodicalIF":2.6,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422709","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 : 2025-02-13DOI: 10.1016/j.ijheatfluidflow.2025.109774
Nan Zhang , Yibo Wang , Zhifeng Lou , Xiaona Huang , Shijing Wu , Yanan Yue
The temperature distribution of both the nanotip and the substrate during thermal scanning probe lithography processing is a critical factor that significantly influences the processing outcomes. The nanotip and the contact area both exhibit a relatively small spatial scale, which presents a significant challenge in accurately measuring the temperature distribution during thermal processing. In this study, finite element simulations are carried out to investigate the thermophysical process between the laser-irradiated nanotip and the PMMA substrate. The temperature distributions of the nanotip and substrate at different contact thermal resistances, apex radii, and vertical loads are investigated. The findings reveal that as the thermal contact resistance rises, the average temperature of the interface between the nanotip and the PMMA substrate diminishes, while it increases with the rise in the vertical load. The maximum average temperature reaches 669.51 K when the laser power and apex radius are 20 mW and 20 nm, respectively. Furthermore, the effective area of heat conduction, delineated by temperatures surpassing the glass transition temperature of PMMA, exhibits a similar trend to the average temperature. The results obtained under various conditions provide theoretical insights for optimizing the process settings of laser-assisted precise fabrication.
{"title":"Numerical studies on thermophysical process in laser-assisted thermal probe fabrication of nanostructures","authors":"Nan Zhang , Yibo Wang , Zhifeng Lou , Xiaona Huang , Shijing Wu , Yanan Yue","doi":"10.1016/j.ijheatfluidflow.2025.109774","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109774","url":null,"abstract":"<div><div>The temperature distribution of both the nanotip and the substrate during thermal scanning probe lithography processing is a critical factor that significantly influences the processing outcomes. The nanotip and the contact area both exhibit a relatively small spatial scale, which presents a significant challenge in accurately measuring the temperature distribution during thermal processing. In this study, finite element simulations are carried out to investigate the thermophysical process between the laser-irradiated nanotip and the PMMA substrate. The temperature distributions of the nanotip and substrate at different contact thermal resistances, apex radii, and vertical loads are investigated. The findings reveal that as the thermal contact resistance rises, the average temperature of the interface between the nanotip and the PMMA substrate diminishes, while it increases with the rise in the vertical load. The maximum average temperature reaches 669.51 K when the laser power and apex radius are 20 mW and 20 nm, respectively. Furthermore, the effective area of heat conduction, delineated by temperatures surpassing the glass transition temperature of PMMA, exhibits a similar trend to the average temperature. The results obtained under various conditions provide theoretical insights for optimizing the process settings of laser-assisted precise fabrication.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109774"},"PeriodicalIF":2.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403195","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 : 2025-02-11DOI: 10.1016/j.ijheatfluidflow.2025.109754
Ahmed Saieed, Jean-Pierre Hickey
The clustering of heated particles is known to increase with the rise in local gas viscosity, even at particle Stokes number . Despite being a dominant effect that holds in two-way coupling (TWC), this rise in clustering has been only probed in a triply periodic box via direct numerical simulations (DNS), in which the flow evolves temporally and the total volume (and mean fluid density) is fixed. We conduct DNS to study the dispersion of heated polydispersed particles in a spatially developing subsonic confined jet flow, where energy and momentum are modeled with TWC. Although there is only a increase in gas viscosity in the heated particle-laden simulation, it is sufficient to limit the particles within the central hot region of the jet. The particles traveling laterally start clustering at a thermal front created at the outer periphery of the jet. Thus, their lateral dispersion is also limited. Despite starting with the same values as their unheated counterparts, the heated particles yield more concentrated clusters within the jet as the number of heated particles declines sharply in the lateral direction. This is a compounding effect, where the presence of particles within the jet can produce more significant thermal changes inside the jet, which can further restrict the lateral movement of the particles. Experiencing identical eddies inside the jet causes particles of all sizes in the heating case to cluster at similar locations in the domain. These findings can considerably aid applications such as targeted drug delivery and cold spray coating techniques.
{"title":"Viscosity-driven clustering of heated polydispersed particles in subsonic jet flows","authors":"Ahmed Saieed, Jean-Pierre Hickey","doi":"10.1016/j.ijheatfluidflow.2025.109754","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109754","url":null,"abstract":"<div><div>The clustering of heated particles is known to increase with the rise in local gas viscosity, even at particle Stokes number <span><math><mrow><mi>S</mi><mi>t</mi><mo><</mo><mn>1</mn></mrow></math></span>. Despite being a dominant effect that holds in two-way coupling (TWC), this rise in clustering has been only probed in a triply periodic box via direct numerical simulations (DNS), in which the flow evolves temporally and the total volume (and mean fluid density) is fixed. We conduct DNS to study the dispersion of heated polydispersed particles in a spatially developing subsonic confined jet flow, where energy and momentum are modeled with TWC. Although there is only a <span><math><mrow><mn>16</mn><mtext>%</mtext></mrow></math></span> increase in gas viscosity in the heated particle-laden simulation, it is sufficient to limit the particles within the central hot region of the jet. The particles traveling laterally start clustering at a thermal front created at the outer periphery of the jet. Thus, their lateral dispersion is also limited. Despite starting with the same <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span> values as their unheated counterparts, the heated particles yield more concentrated clusters within the jet as the number of heated particles declines sharply in the lateral direction. This is a compounding effect, where the presence of particles within the jet can produce more significant thermal changes inside the jet, which can further restrict the lateral movement of the particles. Experiencing identical eddies inside the jet causes particles of all sizes in the heating case to cluster at similar locations in the domain. These findings can considerably aid applications such as targeted drug delivery and cold spray coating techniques.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109754"},"PeriodicalIF":2.6,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatfluidflow.2025.109756
Y.K. Song , J.G. Chen , Y. Zhou
This work investigates flow separation control and drag reduction (DR) of an axisymmetric body using six tangentially steady blowing jets placed around the periphery of the semi-spherical after-body. The Reynolds number (ReD) examined is from 1.2 × 104 to 5.4 × 105. Comprehensive measurements using hot-wire, force balance, pressure scanner, particle image velocimetry and flow visualization have been conducted with and without control. The unforced flow exhibits the characteristics of a sphere wake and may be divided into subcritical and supercritical regimes based on whether the separating boundary layer from the after-body is laminar or turbulent. The measured after-body pressure drag coefficient , which is linearly correlated to DR, depends on the volume flow rate ratio (Cm) of the jets and ReD. It is found that flow separation from the after-body can be completely suppressed, resulting in a maximum DR of 24.1 %. Furthermore, may be reduced to , where g1 and g2 are two different functions and is the after-body pressure drag coefficient in the absence of control. This scaling law may be divided into three distinct regions. The flow physics associated with the three regions is discussed in detail, along with its impact upon the DR and the control efficiency. A conceptual model is proposed for the control mechanisms.
{"title":"Control of flow separation from an axisymmetric body using tangentially steady bowing jets","authors":"Y.K. Song , J.G. Chen , Y. Zhou","doi":"10.1016/j.ijheatfluidflow.2025.109756","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109756","url":null,"abstract":"<div><div>This work investigates flow separation control and drag reduction (DR) of an axisymmetric body using six tangentially steady blowing jets placed around the periphery of the semi-spherical after-body. The Reynolds number (<em>Re<sub>D</sub></em>) examined is from 1.2 × 10<sup>4</sup> to 5.4 × 10<sup>5</sup>. Comprehensive measurements using hot-wire, force balance, pressure scanner, particle image velocimetry and flow visualization have been conducted with and without control. The unforced flow exhibits the characteristics of a sphere wake and may be divided into subcritical and supercritical regimes based on whether the separating boundary layer from the after-body is laminar or turbulent. The measured after-body pressure drag coefficient <span><math><mrow><msubsup><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mi>p</mi></mrow><mi>a</mi></msubsup></mrow></math></span>, which is linearly correlated to DR, depends on the volume flow rate ratio (<em>C<sub>m</sub></em>) of the jets and <em>Re<sub>D</sub></em>. It is found that flow separation from the after-body can be completely suppressed, resulting in a maximum DR of 24.1 %. Furthermore, <span><math><mrow><msubsup><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mi>p</mi></mrow><mi>a</mi></msubsup><mo>=</mo><msub><mi>g</mi><mn>1</mn></msub><mrow><mfenced><mrow><msub><mi>C</mi><mi>m</mi></msub><mo>,</mo><msub><mrow><mi>Re</mi></mrow><mi>D</mi></msub></mrow></mfenced></mrow></mrow></math></span> may be reduced to <span><math><mrow><msubsup><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mi>p</mi></mrow><mi>a</mi></msubsup><mo>/</mo><msubsup><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mi>p</mi></mrow><mrow><mi>a</mi><mo>,</mo><mn>0</mn></mrow></msubsup><mo>=</mo><msub><mi>g</mi><mn>2</mn></msub><mrow><mfenced><mrow><msub><mi>C</mi><mi>m</mi></msub></mrow></mfenced></mrow></mrow></math></span>, where <em>g<sub>1</sub></em> and <em>g<sub>2</sub></em> are two different functions and <span><math><mrow><msubsup><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mi>p</mi></mrow><mrow><mi>a</mi><mo>,</mo><mn>0</mn></mrow></msubsup></mrow></math></span> is the after-body pressure drag coefficient in the absence of control. This scaling law may be divided into three distinct regions<em>.</em> The flow physics associated with the three regions is discussed in detail, along with its impact upon the DR and the control efficiency. A conceptual model is proposed for the control mechanisms.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109756"},"PeriodicalIF":2.6,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377314","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 : 2025-02-05DOI: 10.1016/j.ijheatfluidflow.2025.109767
Qi Wang , Rui Yang , Yu-xin Zhao , Wei Liu
A novel quasi-one-dimensional mathematical model for time-averaged supersonic cavity flow arising from quasi-one-dimensional analysis is proposed. The fundamental inputs required for the model comprise the primary vortex center position and the aerodynamic parameters of the boundary. Specifically, the primary vortex center position serves to fix the contours of the quasi-one-dimensional model, while the total temperature, density, and velocity of the boundary provide definite conditions for the model. The assumptions regarding the inputs are proposed based on numerical investigation which has been validated through experiments on the n-regular-polygonal cavities. The model helps to reveal the intricate correlations between cavity flow characteristics and cavity geometry, as well as the relationship between cavity flow characteristics and freestream Mach number, and may be used for the prediction of mass flux within the cavity.
{"title":"Quasi-one-dimensional mathematical model of the two-dimensional supersonic cavity mean flow","authors":"Qi Wang , Rui Yang , Yu-xin Zhao , Wei Liu","doi":"10.1016/j.ijheatfluidflow.2025.109767","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109767","url":null,"abstract":"<div><div>A novel quasi-one-dimensional mathematical model for time-averaged supersonic cavity flow arising from quasi-one-dimensional analysis is proposed. The fundamental inputs required for the model comprise the primary vortex center position and the aerodynamic parameters of the boundary. Specifically, the primary vortex center position serves to fix the contours of the quasi-one-dimensional model, while the total temperature, density, and velocity of the boundary provide definite conditions for the model. The assumptions regarding the inputs are proposed based on numerical investigation which has been validated through experiments on the n-regular-polygonal cavities. The model helps to reveal the intricate correlations between cavity flow characteristics and cavity geometry, as well as the relationship between cavity flow characteristics and freestream Mach number, and may be used for the prediction of mass flux within the cavity.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109767"},"PeriodicalIF":2.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140625","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 : 2025-02-05DOI: 10.1016/j.ijheatfluidflow.2025.109765
Tong Ren , Mengzhuo Li , De Wang , Jia Yang , Lingbo Kong , Long He
Corridor ventilation is a crucial measure to provide good air quality for underground buildings, it is necessary to predict and study the variation law of the environment in the corridor. Theoretical analysis and numerical simulation of heat and humidity transfer were carried out and the equations to predict air temperature and moisture content are proposed for the underground corridor. Corridor structure (e.g. cross-section diameter, length) and environmental parameters (e.g. wall temperature, air velocity, inlet air temperature, and relative humidity) are discussed in detail. The corridor structure parameters have been found to have little impact on the cooling and dehumidification effect when the corridor length x/L > 0.1. The inlet air temperature and velocity are the most crucial parameters for the cooling and dehumidification efficiency. The inlet air relative humidity and wall temperature are the main factors of fog formation in the corridor. Therefore, reasonable design and matching of corridor parameters is very important for the environmental control in underground corridors.
{"title":"Theoretical and numerical studies of heat and humidity transfer in underground ventilation corridor","authors":"Tong Ren , Mengzhuo Li , De Wang , Jia Yang , Lingbo Kong , Long He","doi":"10.1016/j.ijheatfluidflow.2025.109765","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109765","url":null,"abstract":"<div><div>Corridor ventilation is a crucial measure to provide good air quality for underground buildings, it is necessary to predict and study the variation law of the environment in the corridor. Theoretical analysis and numerical simulation of heat and humidity transfer were carried out and the equations to predict air temperature and moisture content are proposed for the underground corridor. Corridor structure (e.g. cross-section diameter, length) and environmental parameters (e.g. wall temperature, air velocity, inlet air temperature, and relative humidity) are discussed in detail. The corridor structure parameters have been found to have little impact on the cooling and dehumidification effect when the corridor length x/L > 0.1. The inlet air temperature and velocity are the most crucial parameters for the cooling and dehumidification efficiency. The inlet air relative humidity and wall temperature are the main factors of fog formation in the corridor. Therefore, reasonable design and matching of corridor parameters is very important for the environmental control in underground corridors.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109765"},"PeriodicalIF":2.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140332","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}
Fractional order models are becoming a promising tool for modeling complex physical phenomena due to their non-local and memory-dependent properties. In this study, a novel fractional order double-diffusion model is proposed to analyze the transient nature of fluid flow, convective heat, and the solute transfer phenomena within a wavy porous cavity. The fractional time derivative is defined in the Caputo sense for an order of and is incorporated into the governing equations formulated using the Darcy-Brinkman-Forchheimer model, along with energy and mass transfer equations. The resulting coupled nonlinear fractional partial differential equations (FPDEs) are subjected to numerical simulation using a fully discrete scheme comprising an L1 finite difference scheme for temporal discretization and a penalty finite element scheme for spatial discretization. The double-diffusion process undergoes varying evolution phases for each . It is observed that a higher value of the fractional order parameter accelerates the evolution rate, leading to faster convergence towards steady-state conditions. Additionally, this study also explores the impacts of various parameters such as the Rayleigh number, buoyancy ratio, Darcy number, porosity, and Lewis number on thermal and solute transport processes.
{"title":"Numerical simulation of fractional order double diffusive convective nanofluid flow in a wavy porous enclosure","authors":"Deepika Parmar , S.V.S.S.N.V.G. Krishna Murthy , B.V. Rathish Kumar , Sumant Kumar","doi":"10.1016/j.ijheatfluidflow.2025.109749","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109749","url":null,"abstract":"<div><div>Fractional order models are becoming a promising tool for modeling complex physical phenomena due to their non-local and memory-dependent properties. In this study, a novel fractional order double-diffusion model is proposed to analyze the transient nature of fluid flow, convective heat, and the solute transfer phenomena within a wavy porous cavity. The fractional time derivative is defined in the Caputo sense for an order of <span><math><mrow><mn>0</mn><mo><</mo><mi>α</mi><mo><</mo><mn>1</mn></mrow></math></span> and is incorporated into the governing equations formulated using the Darcy-Brinkman-Forchheimer model, along with energy and mass transfer equations. The resulting coupled nonlinear fractional partial differential equations (FPDEs) are subjected to numerical simulation using a fully discrete scheme comprising an L1 finite difference scheme for temporal discretization and a penalty finite element scheme for spatial discretization. The double-diffusion process undergoes varying evolution phases for each <span><math><mrow><mi>α</mi><mo>∈</mo><mrow><mo>(</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>)</mo></mrow></mrow></math></span>. It is observed that a higher value of the fractional order parameter <span><math><mrow><mo>(</mo><mi>α</mi><mo>)</mo></mrow></math></span> accelerates the evolution rate, leading to faster convergence towards steady-state conditions. Additionally, this study also explores the impacts of various parameters such as the Rayleigh number, buoyancy ratio, Darcy number, porosity, and Lewis number on thermal and solute transport processes.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109749"},"PeriodicalIF":2.6,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140609","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}
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