International Journal of Numerical Methods for Heat & Fluid Flow最新文献

{"title":"Study of thermal convection in liquid metal using modified lattice Boltzmann method","authors":"Runa Samanta, Himadri Chattopadhyay","doi":"10.1108/hff-08-2024-0621","DOIUrl":"https://doi.org/10.1108/hff-08-2024-0621","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>This study aims to extend the application of the lattice Boltzmann method (LBM) to solve solid-to-liquid phase transition problems involving low Prandtl number (<em>Pr</em>) materials. It provides insight about the flow instability in a cavity undergoing melting. This work further report interface development and thermal transport against the Boussinesq number.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>This study modifies the lattice Bhatnagar–Gross–Krook model by including correction components in the energy and density distribution functions. To prevent numerical instability, a tuning parameter in the flow domain is set in the range of 0.15–0.7 for the range of Rayleigh number and Prandtl number. To the best of the authors’ knowledge, the modified LBM is being used for the first time to examine the low <em>Pr</em> domain melting behavior of liquid metals.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>The interaction with complicated flow structure with natural convection, studied in a square enclosure, has a significant impact on the melting of metals in the low <em>Pr</em> range. Results show that the melting rate and the length of the interface between two phases are significantly influenced by the Boussinesq number (<em>Bo</em>), the product of <em>Pr</em> and Rayleigh number (<em>Ra</em>). For changing <em>Ra</em>, the maximum interface length is almost constant in the in the Boussinesq number range up to 100 and beyond this range the interface length increases with <em>Bo</em>.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>The effects of <em>Pr</em> on melting rate, <em>Ra</em> and <em>Pr</em> together on the length of the solid–liquid interface and the thermofluidic behavior in the melt zone are explained. This work also includes mapping the maximum melt interface size with <em>Bo</em>.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"17 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143582628","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}

{"title":"Comparative analysis of microchannel heat sinks for different values of the Prandtl and Reynolds numbers","authors":"Evans Joel Udom, Marcello Lappa","doi":"10.1108/hff-11-2024-0884","DOIUrl":"https://doi.org/10.1108/hff-11-2024-0884","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>This study aims to perform a comprehensive comparative analysis of the performance of microchannel heat sinks (MCHS) across a wide range of operating conditions. It investigates the interplay between heat transfer efficiency, frictional effects and flow dynamics in different channel configurations and fluid types.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>The analysis is conducted through numerical simulations, solving the governing equations for mass, momentum and energy conservation. Multiple channel geometries are evaluated, each incorporating specific strategies to disrupt the thermal boundary layer along the heated channel surface. The study also considers the influence of transverse vorticity effects arising from abrupt or smooth geometric variations. The performance is assessed for three distinct fluids – mercury, helium and water – to examine the complex interplay between fluid properties (e.g. viscosity and thermal diffusivity), momentum losses and heat transfer gains. Key parameters, including the Reynolds number and Prandtl number, are systematically varied to uncover their impact on heat transfer coefficients, vorticity distribution and flow stability.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>The study reveals that microchannels with wavy geometries and double internal bifurcations consistently deliver superior thermal performance compared to other configurations, regardless of the working fluid. The results highlight that variations in the Prandtl number significantly influence the dimensional convective heat transfer coefficient, vorticity patterns and the onset of fluid-dynamic instabilities for a fixed Reynolds number and geometry. The authors introduce a correlation for the Nusselt number with the exponents for the Reynolds and Prandtl numbers being ½ and ¼, respectively; the authors also show that, in agreement with existing literature, the friction factor is primarily affected by the Reynolds number and channel shape, demonstrating no dependence on the Prandtl number.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>This research provides novel insights into the non-linear scaling of heat transfer and momentum loss with fluid properties in MCHS. The systematic exploration of fluid and geometric interactions enriches the current understanding of microchannel heat transfer mechanisms, presenting actionable recommendations for real-world applications.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"15 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143575395","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}

{"title":"Membrane-driven flow and heat transfer of viscoelastic fluids: MHD and entropy generation analysis","authors":"Abhishesh Pandey, Ashvani Kumar, Dharmendra Tripathi, Kalpna Sharma","doi":"10.1108/hff-11-2024-0898","DOIUrl":"https://doi.org/10.1108/hff-11-2024-0898","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>The complex behavior of viscoelastic fluids and its flow analysis under the impact of transverse magnetic field are becoming increasingly important in numerous emerging applications including biomedical engineering, aerospace engineering, geophysics and industrial applications. Additionally, the thermal analysis and fluid flow driven by propagating membranes will aid significant applications for microscale transport in bio-thermal systems. This study aims to investigate the thermal effects of viscoelastic fluids driven by membrane-induced propagation and transverse magnetic field.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>The propagation of the membranes will work as pump which pushes the fluids from bottom to top against the gravitation force; however, there is backflow due to compression and expansion phases of membrane propagation. The Jeffrey fluid model is employed to analyze the viscoelastic fluid flow, with entropy generation examined and equations solved analytically under low Reynolds number and long-wavelength assumptions.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>The findings reveal that an increase in magnetic field strength impedes fluid flow, while higher values of the Grashof number, heat source parameter and Jeffrey fluid parameter enhance fluid motion. The study’s findings have significant implications for optimizing magnetohydrodynamic systems in various emerging applications, including biomedical engineering, aerospace, geophysics and industrial processes.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>This study aims to investigate the impact of a transverse magnetic field on the flow and heat transfer characteristics of viscoelastic fluids driven by membrane propagation.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"10 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143575396","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}

{"title":"Experimental and numerical study of a solar still with external solar heating: comparing internal condensation and air-pump-assisted external condensation in prism structures","authors":"Faraz Afshari","doi":"10.1108/hff-11-2024-0881","DOIUrl":"https://doi.org/10.1108/hff-11-2024-0881","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>The purpose of this study is to develop and evaluate a novel solar still system integrating external solar heating and condensation units, comparing its performance with traditional methods through experimental and numerical analyses to optimize clean water production and energy efficiency.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>This study involved designing a novel solar still system with an external solar heating unit and a prism-type condensation chamber. Two configurations were tested experimentally: one with internal condensation inside the prism and another with an air pump extracting vapor for external condensation. computational fluid dynamics (CFD) simulations were conducted to analyze temperature distributions and airflow dynamics in the system. Energy and exergy analyses were performed to evaluate the thermal performance and efficiency of both configurations, comparing clean water production rates and system effectiveness.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>This study found that the solar still system using an air pump with external condensation significantly enhanced water production, achieving approximately 144.7% more clean water compared to the internal condensation method. Scenario 2, with the external condensation configuration, demonstrated a slight improvement in thermal efficiency (12.84%) over Scenario 1 (12.36%) and higher exergy efficiency (5.86% compared to 4.83%). CFD simulations provided insights into the temperature and air velocity distributions, highlighting the effectiveness of the external heating and condensation setup. The results demonstrate the potential of the novel system to improve clean water production while maintaining energy efficiency.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>This study introduces a novel solar still design that integrates an external solar heating unit and an air pump-driven external condensation system, demonstrating a significant improvement in clean water production. By combining experimental results, CFD simulations and energy-exergy analyses, it provides valuable insights for optimizing solar-powered desalination systems with enhanced efficiency and sustainability.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"96 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143532862","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}

{"title":"Effect of impinging jet cooling and thermal radiation on magnetohydrodynamic mixed convection and entropy generation in a semicircular porous channel","authors":"Aniket Halder, Arabdha Bhattacharya, Mikhail A. Sheremet, Nirmalendu Biswas, Nirmal K. Manna, Dipak Kumar Mandal, Ali J. Chamkha","doi":"10.1108/hff-04-2024-0283","DOIUrl":"https://doi.org/10.1108/hff-04-2024-0283","url":null,"abstract":"&lt;h3&gt;Purpose&lt;/h3&gt;\u0000&lt;p&gt;This study aims to examine magnetohydrodynamic mixed convective phenomena and entropy generation within a semicircular porous channel, incorporating impinging jet cooling and the effects of thermal radiation. The present study analyzes the complex flow dynamics and heat transfer characteristics of a highly diluted 0.1% (volume) concentration Cu–Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/water hybrid nanofluid, based on findings from previous studies. The investigation is intended to support the development of effective thermal management systems across diverse industries, such as cooling of electronic devices and enhanced energy system applications.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Design/methodology/approach&lt;/h3&gt;\u0000&lt;p&gt;This study incorporates a heated curved bottom wall and a cooling jet of Cu–Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/water hybrid nanofluid impinging from the central top inlet, with two horizontal exit ports along the rectangular duct. Finite element-based simulations are conducted using COMSOL Multiphysics, using a single-phase homogeneous model justified by earlier works. This method uses experimental data of effective thermal conductivity and viscosity, emphasizing the evaluation of thermal performance in scenarios involving intricate geometries and multiphysical conditions. The study analyzes nondimensional variables such as Reynolds number (Re), modified Rayleigh number (Ra&lt;sub&gt;m&lt;/sub&gt;), Hartmann number (Ha), Darcy number (Da) and radiation parameter while maintaining a constant nanofluid volume fraction. A grid independence study and code validation were performed to ensure numerical accuracy.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Findings&lt;/h3&gt;\u0000&lt;p&gt;The analysis indicates that elevated Re contribute to a lessening in the thermal boundary layer thickness, prompting flow separation and significantly amplifying the average Nusselt number. The mixed convective heat transfer enhancement, coupled with an overall reduction in total entropy generation, diminishes with a rising Ha. However, optimized combinations of higher values for modified Ra&lt;sub&gt;m&lt;/sub&gt; and Da yield improved heat transfer performance, particularly pronounced with increasing Ha. Radiative heat transfer exerts a detrimental impact on both heat transfer and entropy production.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Practical implications&lt;/h3&gt;\u0000&lt;p&gt;While the single-phase model captures key macroscopic effects differentiating nanofluids from base fluids, it does not provide insights at the nanoparticle level. Future studies could incorporate two-phase models to capture particle-level dispersion effects. In addition, experimental validation of the findings would strengthen the study’s conclusions.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Originality/value&lt;/h3&gt;\u0000&lt;p&gt;This work represents innovative perspectives on the development of efficient hydrothermal systems, accounting for the influences of thermal radiation, porous media and hybrid nanofluids within a complex geometry. The results offer critical in","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"50 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143495564","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}

{"title":"Fisher’s information matrix approach for Fourier features physics-informed neural networks for two-dimensional local time-fractional anomalous diffusion equations with nonlinear thermal diffusivity","authors":"Navnit Jha, Ekansh Mallik","doi":"10.1108/hff-11-2024-0889","DOIUrl":"https://doi.org/10.1108/hff-11-2024-0889","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>This study aims to explore the influence of Fourier-feature enhanced physics-informed neural networks (PINNs) on effectively solving two-dimensional local time-fractional anomalous diffusion equations with nonlinear thermal diffusivity. By tackling the shortcomings of conventional numerical methods in managing fractional derivatives and nonlinearities, this research addresses a significant gap in the literature regarding efficient solution strategies for complex diffusion processes.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>This study uses a quantitative methodology featuring a feed-forward neural network architecture combined with a Fourier feature layer. Automatic differentiation is implemented to ensure precise gradient calculations for fractional derivatives. The effectiveness of the proposed approach is showcased through numerical simulations across various sub-diffusion and super-diffusion scenarios, with fractal space parameters adjusted to examine behavior. In addition, the training process is assessed using the Fisher information matrix to analyze the loss landscape.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>The results demonstrate that the Fourier-feature enhanced PINNs effectively capture the dynamics of the anomalous diffusion equation, achieving greater solution accuracy than traditional methods. The analysis using the Fisher information matrix underscores the importance of hyperparameter tuning in optimizing network performance. These findings support the hypothesis that Fourier features improve the model’s capacity to represent complex solution behaviors, providing the relationship between model architecture and diffusion dynamics.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>This research presents a novel approach to solving fractional anomalous diffusion equations through Fourier-feature enhanced PINNs. The results contribute to the advancement of computational methods in areas such as thermal engineering, materials science and biological diffusion modeling, while also providing a foundation for future investigations into training dynamics within neural networks.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"65 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477756","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}

{"title":"Determining local distribution of convective heat transfer coefficients on the tool during orthogonal cutting","authors":"Julius Wilker, Tim Göttlich, Thorsten Helmig, Rafael Solana Gómez, Hossein Askarizadeh, Reinhold Kneer","doi":"10.1108/hff-08-2024-0638","DOIUrl":"https://doi.org/10.1108/hff-08-2024-0638","url":null,"abstract":"&lt;h3&gt;Purpose&lt;/h3&gt;\u0000&lt;p&gt;Particularly during machining, large heat sources and thus high temperature gradients and mechanical stress occur in the cutting zone. By using cutting fluids, part of the heat generated can be dissipated, thereby reducing local temperatures. To quantify the cooling efficiency of the cutting fluid, the flow behaviour of the cutting fluid in vicinity of the cutting zone must be determined to derive the resulting convective heat transfer coefficients at the tool. The purpose of this paper is to investigate the local distribution of the convective heat transfer coefficient as a function of the flow boundary conditions, specifically evaluating the effects of Reynolds number, injection angle and nozzle radius.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Design/methodology/approach&lt;/h3&gt;\u0000&lt;p&gt;The geometries, temperature fields as well as the heat sources resulting during the machining process are extracted from a chip formation simulation using finite element method (FEM) and used to set up a three-dimensional computational fluid dynamics (CFD) flow simulation.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Findings&lt;/h3&gt;\u0000&lt;p&gt;On the tool rake face, the local distribution of the convective heat transfer coefficient can be divided into three regions. Firstly, the region where the liquid impinging jet initially strikes, then a region near the chip where the flow is strongly deflected and then the remaining region in the boundary layer region. For each region, a function is derived that describes its position, subsequently the mean convective heat transfer coefficient is determined and summarised in a Nusselt correlation as a function of the flow parameters.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Research limitations/implications&lt;/h3&gt;\u0000&lt;p&gt;Simulation results reveal that the distribution of the convective heat transfer coefficient on the tool rake face can be divided into three distinct regions: the impingement zone where the impinging jet first strikes, the deflection zone near the chip where the flow sharply redirects and the boundary layer zone covering the remaining surface. A geometric function is derived to describe the position and extent of each of these areas. In addition, the mean convective heat transfer coefficient can be determined for each of the regions using a Nusselt correlation based on the flow parameters.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Practical implications&lt;/h3&gt;\u0000&lt;p&gt;These correlations allow for simplified determination of the local convective heat transfer coefficient on the tool.&lt;/p&gt;&lt;!--/ Abstract__block --&gt;\u0000&lt;h3&gt;Originality/value&lt;/h3&gt;\u0000&lt;p&gt;This paper introduces an innovative approach for estimating the local distribution of the convective heat transfer coefficient at the tool rake face during orthogonal cutting under cutting fluid supply. The influence of the three-dimensional flow field of the cutting fluid jet of the convective heat transfer coefficient on the tool rake face is analysed in detail in the vicinity of the chip as a function of varying Rey","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"22 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143462759","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}

{"title":"A continuous adjoint cut‐cell formulation for topology optimization of bi‐fluid heat exchangers","authors":"Nikolaos Galanos, Evangelos Papoutsis-Kiachagias, Kyriakos Giannakoglou","doi":"10.1108/hff-08-2024-0642","DOIUrl":"https://doi.org/10.1108/hff-08-2024-0642","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>This paper aims to present a topology optimization (TopO) method for designing heat exchangers (HEx) with two working fluids to be kept apart. The introduction of cut–cells gives rise to the cut-cell TopO method, which computes the optimal distribution of an artificial impermeability field and successfully overcomes the weaknesses of the standard density-based TopO (denTopO) by computing the fluid–solid interface (FSI) at each cycle. This allows to accurately solve the flow and conjugate heat transfer (CHT) problem by imposing exact boundary conditions on the computed FSI and results to correct performances computed without the need to re-evaluate the optimized solutions on a body-fitted grid.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>The elements of an artificial impermeability distribution field defined on a background grid act as the design variables and allow topological changes to take place. Post-processing them yields two fields indicating the location of the two flow streams inside the HEx. At each TopO cycle, the FSIs computed based on these two fields are used as the cutting surfaces of the cut-cell grid. On the so-computed grid, the incompressible Navier–Stokes equations, coupled with the Spalart–Allmaras turbulence model, and the temperature equation are solved. The derivatives of the objective and constraint functions with respect to the design variables of TopO are computed by the continuous adjoint method, using consistent discretization schemes devised thanks to the “Think Discrete – Do Continuous” (TDDC) adjoint methodology.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>The effectiveness of the cut-cell–based TopO method for designing HEx is demonstrated in 2D parallel/counter flow and 3D counter flow HEx operating under both laminar and turbulent flow conditions. Compared to the standard denTopO, its ability to compute FSIs along which accurate boundary conditions are imposed, increases the accuracy of the flow solver, which usually leads to optimal, rather than sub-optimal, solutions that truly satisfy the imposed constraints.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>This work proposes a new/complete methodology for the TopO of two-fluid systems including CHT that relies on the cut-cell method. This successfully combines aspects from both TopO and Shape Optimization (ShpO) in a single framework thus overcoming the well-known downsides of standard denTopO regarding its accuracy or the need for a follow-up ShpO after TopO. Instead of adding the well-known Brinkman penalization terms into the flow equations, it computes the FSIs at each optimization cycle allowing the solution of the CHT problem on a cut-cell grid.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"12 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443216","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}

{"title":"Isogeometric boundary element formulation to simulate droplets in microchannel confinement","authors":"Ozgur Can Gumus, Gokberk Kabacaoglu, Barbaros Cetin","doi":"10.1108/hff-08-2024-0641","DOIUrl":"https://doi.org/10.1108/hff-08-2024-0641","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>This study aims to present an isogeometric boundary element formulation that stably and accurately models the motion of a droplet with arbitrary viscosity in free flows and microchannel confinements.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>Like other numerical methods, isogeometric boundary element formulation also suffers from mesh distortion; therefore, volume correction and mesh relaxation are also required for efficient and stable simulations of deformable particles in Stokes flow with high accuracy. To improve the stability and accuracy of the proposed formulation, (i) volume correction and (ii) mesh relaxation algorithms to prevent mesh distortion are implemented.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>Several test cases for a droplet in free-space shear flow are demonstrated for different Ca and viscosity ratio values which determine the deformability of a droplet. The results reveal that the drift of the enclosed volume inside a droplet and the mesh distortion becomes severe at low viscosity ratios and high Ca values, i.e. in the high deformability regime. The proposed numerical method integrating the stabilization algorithm enables the simulations at low spatiotemporal resolutions, even in extreme cases. The proposed method provides more than 10× speed-up compared to high-fidelity simulations without mesh relaxation. Efficient and accurate 3D simulations of droplets are also presented for simulations in microfluidic confinement.</p><!--/ Abstract__block -->\u0000<h3>Practical implications</h3>\u0000<p>The current formulation can be applied for many different microfluidic applications, and can be extended to tackle multiphysics simulations of multiple droplets in microchannel confinement.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>The paper presents an isogeometric boundary element formulation with volume correction and mesh relaxation to model the motion of a droplet with arbitrary viscosity in free flows and microchannel confinements.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"12 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443217","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}

{"title":"Magnetohydrodynamic ternary hybrid nanofluid slip flow past a permeable shrinking sheet: boundary layer flow control and optimization using response surface methodology","authors":"Nur Syahirah Wahid, Shahirah Abu Bakar, Mohd Shafie Mustafa, Norihan Md Arifin, Ioan Pop","doi":"10.1108/hff-08-2024-0637","DOIUrl":"https://doi.org/10.1108/hff-08-2024-0637","url":null,"abstract":"<h3>Purpose</h3>\u0000<p>Magnetohydrodynamics (MHD) in nanofluids is crucial in boundary layer flow as it enables the manipulation of fluid motion through magnetic fields, which leads to improved stability and efficiency. This study aims to introduce a model and solutions for the boundary layer flow of a ternary hybrid nanofluid past a permeable shrinking sheet, integrating both magnetohydrodynamic and slip effects.</p><!--/ Abstract__block -->\u0000<h3>Design/methodology/approach</h3>\u0000<p>The model is firstly expressed as partial differential equations and subsequently converted into ordinary differential equations (ODEs) through a similarity transformation technique. A finite difference scheme with the Lobatto IIIa formula in MATLAB is applied to numerically solve the ODEs, where the respective outcomes provide insights into the skin friction coefficient, Nusselt number, velocity profiles and temperature profiles.</p><!--/ Abstract__block -->\u0000<h3>Findings</h3>\u0000<p>The results highlight the significance of enhancing magnetohydrodynamic effects and first-order velocity slip to reduce skin friction, improve heat transfer, delay boundary layer separation, increase flow velocity and lower fluid temperature. In addition, the stable numerical solution is scrutinized using response surface methodology (RSM) to validate and optimize flow control. The RSM optimization confirms that higher suction, magnetohydrodynamic effects and first-order slip levels are essential for minimizing skin friction and maximizing heat transfer simultaneously.</p><!--/ Abstract__block -->\u0000<h3>Originality/value</h3>\u0000<p>The presented model together with the numerical and statistical results can be used as a guidance to control the flow and heat transfer that occur within a related practical application, especially in engineering and industrial activities such as cooling technologies, energy harvesting or fluid transport in nanotechnology, where precise control of heat transfer and fluid dynamics is essential for optimizing performance and reducing energy consumption.</p><!--/ Abstract__block -->","PeriodicalId":14263,"journal":{"name":"International Journal of Numerical Methods for Heat & Fluid Flow","volume":"193 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143393571","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}