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

Purpose

In the framework of GN-II theory, this paper aims to address the plane wave propagation in a two-dimensional homogeneous, transversely isotropic magneto-thermoelastic medium with rotation and voids.

Design/methodology/approach

To investigate the problem, the fundamental governing equations are modified in the purview of Green-Naghdi theory without energy dissipation. These equations are converted to non-dimensional form using dimensionless quantities and are further solved to obtain four quasi plane waves travelling with different phase speeds in the considered medium. Amplitude ratios and energy ratios have been provided in explicit form after implementing the proper boundary conditions.

Findings

Numerical calculations are carried out using MATLAB software. For graphical representation of the expressions for phase velocities, reflection coefficients and energy ratios, a particular material is chosen to demonstrate the effects of magnetic field, rotation and void parameter.

Originality/value

The reflection coefficients are strongly affected by rotation, void parameter and magnetic field, as evidenced by conceptual and numerical findings. For validation of this study, the outcomes have also been compared to earlier published studies. In addition, it has also been established that the energy conservation law is also justified during the reflection phenomena. In the current research, the authors have included rotation and magnetic field in a transversely isotropic thermoelastic medium having voids, which has not yet been addressed in the published research. The results of current problem are very useful in a number of fields, such as soil dynamics, geophysical processes, chemical engineering and petroleum sector.

Purpose

This study aims to develop a neurocomputational approach using the Levenberg–Marquardt artificial neural network (LM-ANN) to analyze flow and heat transfer characteristics in mixed convection involving radiative magnetohydrodynamic hybrid nanofluids. The focus is on the influence of morphological nanolayers at the fluid–nanoparticle interface, which significantly impacts coupled heat and mass transfer processes.

Design/methodology/approach

This research simplifies a complex system of higher-order nonlinear coupled partial differential equations governing the flow between orthogonal coaxially porous disks into ordinary differential equations via similarity transformations. These equations are solved using the shooting method, and parametric studies are conducted to observe the impact of varying important parameters. The resulting data sets are used to train, validate and test the LM-ANN model, which ensures high predictive accuracy. Machine learning and curve-fitting techniques further enhance the model’s capability to generate detailed visualizations.

Findings

The findings of this study indicate that increased nanolayer thickness (0.4–1.6) significantly improves thermal performance, while changes in the chemical reaction parameter (0.2–1) have a notable effect on enhancing the Sherwood number. These results highlight the critical role of morphological nanolayers in optimizing thermal and mass transfer efficiency in MHD nanofluids.

Originality/value

This research provides a novel neurocomputational framework for understanding the thermal and mass transfer dynamics in MHD nanofluids by incorporating the effects of interfacial nanolayers, an aspect often overlooked in conventional studies. The use of LM-ANN trained on computational data sets enables high-fidelity predictive analysis, offering new insights into the enhancement of thermal and mass transfer efficiency in hybrid nanofluid systems.

Purpose

This study aims to address the low thermal conductivity and suboptimal performance of phase change materials (PCMs) by examining the impact of geometric adjustments on their melting rate.

Design/methodology/approach

A two-dimensional numerical model was created to investigate the effect of different positions and angular inclinations of the inside heating surface (IHS) on the melting rate of PCM within a latent heat thermal energy storage system. The model analysed the IHS at the centre and below the centre at various positions (10, 20, 30 and 40 mm) and inclinations (0°, 15°, 30°, 45°, 60°, 75° and 90°).

Findings

The 90° inclination (vertical) significantly reduced the melting time by 75% compared to the 0° inclination (horizontal). The best melting performance was recorded with the IHS positioned 20 mm below the centre. At a 30° inclination, the maximum reduction in melting time was observed with the IHS at 30 and 40 mm placements. The system demonstrated the highest energy storage capacity of 307.72 kJ/kg at a 75° inclination with the IHS positioned 10 mm laterally, and the lowest capacity of 255.02 kJ/kg at a 0° inclination with the IHS at a 30 mm lateral position.

Practical implications

To address the deficient part of PCM like low thermal conductivity and below level performance characteristics, a structural (geometrical) adjustment was developed to study the effect on the melting rate of PCM without any cost addition. Using the computational model, an optimised thermal energy storage system is developed that can play a pivotal role in improving the applicability of thermal energy storage systems.

Originality/value

This research is novel in simultaneously investigating the numerical characteristics of PCM melting behaviour with different lateral positions and angular orientations of the IHS. A unique design modification was introduced, using a 2D numerical model and simulations to explore the effects under isothermal conditions.

Purpose

High surface area-to-volume ratios make nanoparticles ideal for cancer heat therapy and targeted medication delivery. Moreover, ternary nanofluids (TNFs) may possess superior thermophysical properties compared to mono- and hybrid nanofluids due to their synergistic effects. In light of this information, the objective of this article is to examine the blood-based TNF flow within convergent/divergent channels under velocity slip and temperature jump.

Design/methodology/approach

Leading partial differential equations corresponding to the problem are transformed into a system of nonlinear ordinary differential equations by using similarity variables. The bvp4c code that uses the finite difference method is used to obtain a numerical solution.

Findings

The effect of nanoparticles may change depending on the characteristics of flow near the wall. The properties and proportions of the used nanoparticles become important to control the flow. When TNF was used, an increase in the Nusselt number between 4.75% and 6.10% was observed at low Reynolds numbers. At high Reynolds numbers, nanoparticles reduce the Nusselt number and skin friction coefficient values under some special flow conditions. Importantly, the effects of second-order slip on engineering parameters were also investigated. Furthermore, the Nusselt number increases with increasing shape factor.

Research limitations/implications

Obtained results of the study can be beneficial in both nature and engineering, especially blood flow in veins.

Originality/value

The main innovations of this study are the usage of blood-based TNF and the examination of the effect of shape factor in convergent/divergent channels with second-order velocity slip.

Purpose

The purpose of this study is to investigate the impact of swirling jet flow on the cooling performance of a heated rectangular prism placed within a channel. The primary aim is to explore the influence of varying aspect ratios (AR) of the prism and different fluid Reynolds numbers (Re) on the cooling efficiency.

Design/methodology/approach

The numerical analysis is performed using a finite volume-based solver, which incorporates the large eddy simulations (LES) turbulence model. The setup consists of twin 45° swirling jets directed at isothermally heated bodies, with water used as the cooling medium. The rectangular prism is oriented perpendicularly to the channel flow direction, positioned one unit distance from the inlet. This study examines three distinct aspect ratios (AR = 0.5, 1 and 1.5) and a range of Reynolds numbers (6000 = Re = 20000).

Findings

The results indicate that cooling efficiency improves as the aspect ratio decreases and the Reynolds number increases. Higher Reynolds numbers enhance jet impingement and turbulent mixing, which are crucial for efficient heat transfer. Conversely, lower Reynolds numbers lead to diminished impingement and reduced cooling efficiency. Increasing the Reynolds number from 6000 to 20000 elevates the average Nusselt number by 35% (for AR = 0.5) and up to 45% (for AR = 1.5). It was observed that lower aspect ratios produce superior cooling effects due to intensified localized jet interactions.

Originality/value

This research significantly contributes to the fields of fluid dynamics and thermal engineering by elucidating the influence of swirling jet flows on the cooling of heated surfaces. The findings offer valuable insights for optimizing the design and performance of cooling systems across various industrial applications.

Purpose

This paper aims to design and analyze implicit/explicit/semi-implicit schemes and a universal error estimator within the Generalized Single-step Single-Solve computational framework for First-order transient systems (GS4-I), which also fosters the adaptive time-stepping procedure to improve stability, accuracy and efficiency applied for fluid dynamics.

Design/methodology/approach

The newly proposed child-explicit and semi-implicit schemes emanate from the parent implicit GS4-I framework, providing numerous options with flexible and controllable numerical properties to the analyst. A universal error estimator is developed based on the consistent algorithmic variables and it works for all the developed methods. Applications are demonstrated by merging the developed algorithms into the iterated pressure-projection method for incompressible Navier–Stokes equations.

Findings

The child-explicit GS4-I has improved solution accuracy and stability properties, and the most stable option is the child explicit GS4-I(0,0)/second-order backward differentiation formula/Gear’s methods, which is new and novel. Numerical tests validate that the universal error estimator emanating from implicit designs works well for the newly proposed explicit/semi-implicit algorithms. The iterative pressure-correction projection algorithm is efficiently fostered by the error estimator-based adaptive time-stepping.

Originality/value

The implicit/explicit/semi-implicit methods within a unified computational framework are easy to implement and have flexible options in practical applications. In contrast to traditional error estimators, which work only on an algorithm-by-algorithm basis, the proposed error estimator is universal. They work for the entire class of implicit/explicit/semi-implicit linear multi-step methods that are second-order time accurate. Based on the accurately estimated local error, balance amongst stability, accuracy and efficiency can be well achieved in the dynamic simulation.

Purpose

This study aims to optimize the design of falling film heat exchangers by providing a deeper understanding of wave characteristics and capillary flow in laminar inclined falling films at low Reynolds numbers. The focus is on the effects of different Kapitza numbers, influenced by fluid properties and inclination, on the interfacial wave behavior.

Design/methodology/approach

A numerical investigation was conducted using the volume of fluid method within OpenFOAM’s interFoam solver. This study examined the effects of Kapitza number, inclination angle and inlet disturbances on wave formation and flow dynamics, analyzing how these factors influence interfacial wave amplitude, wavelength and flow in the capillary region.

Findings

The results revealed that higher Kapitza numbers lead to the formation of stronger capillary waves. Flow separation was observed in the capillary wave region for materials with high Kapitza numbers. An improved Nosoko correlation model was developed, incorporating the inclination angle to more accurately predict the relationship between wave peaks and wavelengths in inclined cases.

Originality/value

This research investigates the impact of low Kapitza number on inclined falling film flow, and a correlation model was derived that provides a broader range for evaluating wave behavior in inclined conditions, offering extended references for the design of falling film heat exchangers.

Purpose

This study aims to investigate the effects of thermal buoyancy and flow incidence angles on mixed convection heat transfer and vortex-induced vibration (VIV) of an elastically mounted circular cylinder. The focus is on understanding how varying these parameters influences the vibration amplitudes in both the x and y directions and the overall heat transfer performance.

Design/methodology/approach

The research involves a numerical simulation of thermal fluid-structure interactions by integrating rigid-body motion equations with heat and fluid flow solvers. The cylinder operates at a lower temperature than the mainstream flow, and flow incidence angles range from 0° (opposing gravity) to 90° (perpendicular to gravity). The methodology is validated by comparing the results with established data on VIV for a cylinder vibrating in one direction under thermal buoyancy effects.

Findings

The study reveals that, without buoyancy (Ri = 0), increasing the flow angle from 0° to 90° decreases the vibration amplitude along the x-direction (A_x) while increasing it along the y-direction (A_y) across various reduced velocities (U_r). When buoyancy effects are introduced (Ri = −1), A_x peaks at specific U_r values depending on the flow angle, with significant variations observed. The maximum increase in A_x at Ri = −1 is over 15 times at U_r = 9 for a 0° angle, and A_y shows a more than 10-fold increase at U_r = 8 for a 30° angle. Additionally, adjusting the flow angle results in up to an 8% increase in the mean Nusselt number at Ri = −1.

Originality/value

This research provides novel insights into the combined effects of flow incidence angles and thermal buoyancy on VIV and heat transfer in an elastically mounted cylinder.

Purpose

This paper aims to study boundary and interior layer phenomena in coupled multiscale parabolic convection–diffusion interface problems and to present their efficient numerical resolution and analysis.

Design/methodology/approach

This study includes cases in which the diffusion parameters are small, distinct and can differ in order of magnitude. The source term is considered to be discontinuous. The asymptotic behavior of the solution is examined. The layer structure is analyzed, leading to the development of a variant of layer-resolving Shishkin mesh. For efficient numerical resolution, two methods are developed by combining additive schemes on a uniform mesh to discretize in time and an upwind difference scheme away from the line of discontinuity and a specific upwind difference scheme along the line of discontinuity, defined on a variant of layer resolving Shishkin mesh, to discretize in space. The analysis of the numerical resolution is discussed using the barrier function approach. Numerical simulations provide a verification of the theory and efficiency of the approach.

Findings

The discontinuity in the source term, along with the inclusion of small and distinct diffusion parameters, results in multiple overlapping and interacting boundary and interior layers. The work demonstrates that the present approach is robust in resolving boundary and interior layers. From a computational cost perspective, the numerical resolution presented in the paper is more efficient than conventional approaches.

Originality/value

Efficient numerical resolution and analysis of boundary and interior layer phenomena in coupled multiscale parabolic convection–diffusion interface problems are provided. The discretization of the coupled system in the approach incorporates a distinctive feature, wherein the components of the approximate solution are decoupled at each time level, resulting in tridiagonal linear systems to be solved, in contrast to large banded linear systems with conventional approaches.