Convection Parameter Research Articles

Influence of activation energy and multidiffusive quadratic convective nanoliquid flow past a cone and wedge

The present problem aims to examine the impact of quadratic buoyancy-driven flow nanofluid flow on two specific geometries such as cone and wedge in the presence of binary chemical reactions with activation energy, using liquid hydrogen species. This analysis is relevant for various industrial applications and are widely used in thermal energy storage devices for cooling or heating processes. The fluid flow model's governing equations are numerically solved using a fifth-order boundary value approach in matrix laboratory (MATLAB). In order to obtain the numerical solution, we initially transformed the coupled equations of the flow model and the partial differential equations into ordinary differential equations using similarity variables. The graphs and tables illustrate the importance of different physical factors that impact fluid flow and heat transfer. The quadratic combined convection parameter leads to an augmentation in fluid velocity while also inducing an elevation in frictional forces between the object's surface and the fluid. The increased in values of Schmidt number cause a decrease in mass diffusivity, which in turn leads to lower concentration profiles and improved mass transport efficiency. The activation energy is directly proportional to the decreased amplitude of the concentration profiles of liquid hydrogen species.

Realistic Precipitation Diurnal Cycle in Global Convection‐Permitting Models by Resolving Mesoscale Convective Systems

AbstractAccurately representing the precipitation diurnal cycle has long been a challenge for global climate models (GCMs). Here we evaluate the precipitation diurnal cycle in the DYAMOND global convection‐permitting models (CPMs) and CMIP6 HighResMIP models. Comparison of the high‐ (25–50 km) and low‐resolution (100–250 km) models with parameterized convection in HighResMIP shows that simply increasing model resolution does not noticeably improve the precipitation diurnal cycle. In contrast, CPMs can better capture the observed amplitude and timing of precipitation diurnal cycle. However, the simulated spatial variation of timing in CPMs is smaller than observed, leading to an exaggeration of the spatially averaged diurnal amplitude. The better‐simulated precipitation diurnal cycle in the CPMs is tied to mesoscale convective systems (MCSs), which contribute about half of the total precipitation. The observed life cycle of MCSs, including initiation and mature stages, is well captured in the CPMs, leading to a more realistic precipitation diurnal cycle.

Numerical simulation for MHD slip flow with heat transfer over a stretching bullet‐shaped object

AbstractThis paper investigates magnetohydrodynamic (MHD) boundary layer slip flow with heat transfer over a bullet shaped object. The study addresses a significant problem in fluid dynamics and heat transport with applications in various engineering and industrial domains, including aerospace, material processing, and energy systems. The governing equations are resolved using the bvp4c, an inbuilt MATLAB tool, and the arithmetic computation for the momentum and thermotic equations are executed. The results are exhibited graphically. Numerical outcomes are graphically depicted with the aid of velocity and temperature profiles for several model variables. The achieved results exhibit a promising agreement with the previously established findings available in the open literature. The heat transfer processes and fluid flow are remarkably influenced by means of the ratio of surface thickness and stretching potential. The results obtained designated that the Mixed convection parameter λ increases momentum BL thickness, whereas the temperature profile diminishes. Furthermore, momentum and temperature profile improve for surface thickness parameter . The current investigation highlights the potential utility of heat transport rate and friction factor in the industrial divisions for regulating cooling rates and enhancing the quality of end products.

On thermal non-equilibrium (TNE) model for heat transfer in ternary ferro-nanofluid with rectangular porous fin

The heat transmission in a rectangular porous fin affected by a thermal non-equilibrium model with radiation and magnetic field influences is studied in this study. A ferrofluid containing ferroparticles (Fe3O, CoFe2O4, and Cu) and a mixture of 50 % water and 50 % ethylene glycol coats the fin. Dimensionless form is later achieved by formulating the governing equations for both the solid and ferrofluid phases. In order to get the answer, the Runge–Kutta–Fehlberg (RK-45) scheme is used. Visual and tabular representations are used to investigate the effect on heat transmission of the Biot and Rayleigh numbers as well as the porous and convective parameters. The results show that the solid phase temperature profile is inferior for lower Hartmann numbers (H) and Rayleigh numbers (Ra). The disparity in temperature between the solid and ferrofluid phases decreases in proportion to the Ra. Applications for this type of device include heat exchangers, air conditioners, and cooling towers.

Entanglement Kinetics in Polymer Melts Are Chemically Specific.

We investigate the universality of entanglement kinetics in polymer melts. We compare predictions of a recently developed constitutive equation for disentanglement to molecular dynamics simulations of both united-atom polyethylene and Kremer-Grest models for polymers in shear and extensional flow. We confirm that entanglements recover on the retraction time scale, rather than the reptation time scale. We find that the convective constraint release parameter β is independent of molecular weight, but that it increases with the ratio of Kuhn length bK to packing length p as β ∼ (bK/p)α, with an exponent α = 1.9, which may suggest that disentanglement rate correlates with an increase in the tube diameter. These results may help shed light on which polymers are more likely to undergo shear banding.

The Impact of the Explicit Representation of Convection on the Climate of a Tidally Locked Planet in Global Stretched-mesh Simulations

Convective processes are crucial in shaping exoplanetary atmospheres but are computationally expensive to simulate directly. A novel technique of simulating moist convection on tidally locked exoplanets is to use a global 3D model with a stretched mesh. This allows us to locally refine the model resolution to 4.7 km and resolve fine-scale convective processes without relying on parameterizations. We explore the impact of mesh stretching on the climate of a slowly rotating TRAPPIST-1e-like planet, assuming it is 1:1 tidally locked. In the stretched-mesh simulation with explicit convection, the climate is 5 K colder and 25% drier than that in the simulations with parameterized convection(with both stretched and quasi-uniform meshes). This is due to the increased cloud reflectivity—because of an increase in low-level cloudiness—and exacerbated by the diminished greenhouse effect due to less water vapor. At the same time, our stretched-mesh simulations reproduce the key characteristics of the global climate of tidally locked rocky exoplanets, without any noticeable numerical artifacts. Our methodology opens an exciting and computationally feasible avenue for improving our understanding of 3D mixing in exoplanetary atmospheres. Our study also demonstrates the feasibility of a global stretched-mesh configuration for LFRic-Atmosphere, the next-generation Met Office climate and weather model.

A Climatology of Convective Precipitation over Europe

Abstract The annual, seasonal, and diurnal spatiotemporal heavy convective precipitation patterns over a pan-European domain are analyzed in this study using a combination of datasets, including the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM) (IMERG) precipitation rate product, E-OBS ground-based precipitation gauge data, European climatological gauge-adjusted radar precipitation dataset (EURADCLIM), Operational Programme for the Exchange of Weather Radar Information (OPERA) ground-based radar-derived precipitation rates, and fifth major global reanalysis produced by ECMWF (ERA5) total and convective precipitation products. Arrival Time Difference Network (ATDnet) lightning data are used in conjunction with IMERG and EURADCLIM precipitation rates, with an imposed threshold of 10 mm h−1 to classify precipitation as convective. Annually, the largest convective precipitation accumulations are over the European seas and coastlines. In summer, convective precipitation is more common over the European continent, though relatively large accumulations exist over the northern coastal waters and the southern seas, with a seasonal localized maximum over the northern Adriatic Sea. Activity shifts southward to the Mediterranean and its coastlines in autumn and winter, with maxima over the Ionian Sea, the eastern Adriatic Sea, and the adjacent coastline. Over the continent, 1%–10% of the total precipitation accumulated is classified as convective, increasing to 10%–40% over the surrounding seas. In contrast, 30%–50% of ERA5 precipitation accumulations over land is produced by the convective parameterization scheme and 40%–60% over the seas; however, only 1% of ERA5 convective precipitation accumulations are from rain rates exceeding 10 mm h−1. Regional analyses indicate that convective precipitation rates over the inland mountains follow diurnal heating, though little to no diurnal pattern exists in convective precipitation rates over the seas and coastal mountains.

Investigating the convective flow of ternary hybrid nanofluids and single nanofluids around a stretched cylinder: Parameter analysis and performance enhancement

Within this research, we examined the convective flow of a blend of ternary hybrid nanofluids and single nanofluids with a stagnation point caused by a stretched cylinder. The purpose of this study is to investigate the effect of using a ternary hybrid nanofluid instead of a single nanofluid. Water is used as the base fluid in this investigation. The single nanofluid is made of copper and the ternary hybrid nanofluid is made of Molybdenum disulfide, copper, and silver. The impact of the curvature parameter, nanoparticle volume fraction, mixed convection parameter, velocity ratio, shape factor, conjugate number and Eckert number parameters on temperature and velocity profiles has been investigated. Differential equations with partial derivatives were transformed to equations of ordinary differential type. The ODEs were then solved using the RK5th method. The ternary hybrid nanofluid has greater advantages than the single nanofluid and enhances the velocity and temperature compared to the single nanofluid, according to this study. Furthermore, the results showed that when curvature parameter, volume fraction and shape factor improved, so did the velocity and temperature profile. The results showed that moving from a single nanofluid to a ternary hybrid nanofluid at shape factor equal to 16.2 (Lamina) boosts the velocity by 20 %. Also, in Eckert number equal to 0.45, and substituting the ternary hybrid nanofluid boosts the temperature tenfold.

Mixed Convection Boundary Layer Flow over a Solid Sphere in AL203-Ag/Water Hybrid Nanofluid with Viscous Dissipation Effects

The current study aims to investigate how heat transfer and skin friction develop by modifications in the fundamental advantages of fluids in the presence of mixed convection boundary layer flow over on a sphere in hybrid nanofluids. The numerical solutions for the reduced Nusselt number, local skin friction coefficient temperature profile, and velocity profiles are discovered and clearly presented. The Eckert number, the mixed convection parameter λ, and the nanoparticle volume fraction are all investigated and described. It is found that increasing the volume percentage of nanomaterial in nanofluid enhanced the value of the skin friction coefficient. The low density of nano oxides in hybrid nanofluids, such as alumina, also contributes to reduced friction between fluid and body surface. The findings of a computational investigation demonstrate that the use of a hybrid nanofluid, composed of nanometal and nano-oxide in the form of , has the potential to decrease skin friction while maintaining heat transfer characteristics comparable to that of Ag/water nanofluid. The findings in this publication are new and will be useful to boundary layer flow researchers. It can also be applied as a guideline for experimental investigations with the goal of reducing the cost of operation

Fast and Slow Crystallization-driven Convection in White Dwarfs

We investigate crystallization-driven convection in carbon–oxygen white dwarfs. We present a version of the mixing length theory that self-consistently includes the effects of thermal diffusion and composition gradients, and provides solutions for the convective parameters based on the local heat and composition fluxes. Our formulation smoothly transitions between the regimes of fast adiabatic convection at large Peclet number and slow thermohaline convection at low Peclet number. It also allows for both thermally driven and compositionally driven convection, including correctly accounting for the direction of heat transport for compositionally driven convection in a thermally stable background. We use the MESA stellar evolution code to calculate the composition and heat fluxes during crystallization in different models of cooling white dwarfs, and determine the regime of convection and the convective velocity. We find that convection occurs in the regime of slow thermohaline convection during most of the cooling history of the star. However, at the onset of crystallization, the composition flux is large enough to drive fast overturning convection for a short time (∼10 Myr). We estimate the convective velocities in both of these phases and discuss the implications for explaining observed white dwarf magnetic fields with crystallization-driven dynamos.

Study of the time dependent MHD convective couple stress nanofluid flow across bidirectional periodically stretched frame using the homotopy analysis method

AbstractThe current study presents a time dependent couple stress nanofluid flow across a bidirectional periodically stretched surface under magnetic effects. The effects of nonuniform heat source and variable thermal conductivity on the convective heat transfer are analyzed. The effect of the chemical reaction, nonlinear mixed convection, and activation energy are also considered. Adequate dimensional quantities are utilized to entertained the problem in simplified from. Then, a series of solutions are obtained via homotopic analysis method. Tables and graphs are organized to evaluates the physical dynamic of problem. The archived observations convey that the nonlinear convective parameters cause a rise in horizontal velocity component. It is determined that flow intensity and skin friction have an increasing behavior with most of the governing parameters. Current investigation emphasized that the temperature increases by imposing variable thermal conductivity. The concentration values become higher by increasing the activation energy but decrease with the reaction rate.

Analysis of the influence of heating temperature on the convective drying process

The study examines the influence of heating temperature during the convective drying of fruits on the mass fraction of moisture in the finished product. Convective drying is a promising method for preserving products, allowing the production of dried fruits that can provide essential nutrients year-round. The experiments detailed in this article aim to establish optimal fruit drying modes. Standard methods were used to analyze the experiments according to regulatory documents in force in Kazakhstan. The authors proposed diagrams of convective drying of the fruits in the south of Kazakhstan. According to the constructed schemes, it can be seen that the heating temperature during the drying process affects the final product. According to the analysis, an increase in heating temperature results in a decreased drying time. At the specified time, the highest conversion rate of the relative mass of the dried product is detected. Additionally, it was obtained that the temperature, size, and structure of fresh raw materials affect the period of maximum moisture volatilization rate. The authors carried out a sensory evaluation of the main quality indicators: taste, color, odor and consistency. The optimal characteristics of the indicators were determined. They were extracted at a heating temperature of 50 ....65 °C. Numerous experiments have shown that it is necessary to offer such convective drying parameters. Convective drying temperature for apples is 50-55 °C, for apricots - 55-65 °C, for prune plums - 60-65 °C. Such results will be useful in the technology of fruit and vegetable processing.

Bimodality in simulated precipitation frequency distributions and its relationship with convective parameterizations

Bimodality in precipitation frequency distributions is often evident in atmospheric models, but rarely in observations. This study i) proposes a metric to objectively quantify the bimodality in precipitation distributions, ii) evaluates model simulations contributed to the Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5), phase 6 (CMIP6), and the DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains (DYAMOND) project by comparing them to satellite-based and reanalysis precipitation products, and iii) investigates possible origins of bimodal precipitation distributions. Our results reveal that about 83% (20 out of 24) of CMIP5 and 70% (21 out of 30) of CMIP6 models used in this study exhibit bimodal distributions. The few DYAMOND models that use a deep convective parameterization also show bimodal distributions, while most DYAMOND models do not. Predictably, the bimodality originates from the separation of precipitation process between resolved grid-scale and parameterized subgrid-scale. However, in a larger number of models bimodality arises from the parameterized subgrid-scale convective precipitation alone.

Temperature distribution in stretching/shrinking fin with variable parameters

AbstractIn this paper, we consider a mathematical model, which has a unique mechanism of heat transfer in the stretching/shrinking straight fin with an exponential profile. The thermal conductivity, internal heat generation, and heat transfer coefficient are considered temperature‐dependent. Heat is exposed to the surroundings by convection and radiation. The governing differential equation and boundary conditions are presented in a dimensionless form. In our study, we considered variable surface emissivity, that is, a constant, and the linear function of a temperature. The convective heat transfer parameter is considered a power‐low type. The novelty of this work is the application of temperature‐dependent surface emissivity, and the problem is solved by the Legendre wavelet collocation method. A comparative analysis of the present results in the context of previous findings is presented in the form of a table for validation and found exactly the same. The impacts of distinct variables are presented in the form of figures and discussed in detail. The present analysis is focused on real‐world applications and offers valuable insights for improving the design of fins.

Hybrid carbon nanotubes flow and heat transfer over a vertical thin needle with suction effect: A numerical and optimisation analysis

The present study aims to provide a numerical and optimisation analysis of the hybrid carbon nanotubes flow over a vertical thin needle under the suction effect. The thin needle is suspended in water-based hybrid nanofluids containing a combination of single- and multi-walled carbon nanotubes. The heat is transported using the mixed convection flow. A mathematical model of partial differential equations (PDEs) is developed subject to boundary conditions. The PDEs system is converted to non-dimensional ordinal differential equations (ODEs) by using the similarity solution method. Then, the first order of the ODEs system is solved in a MATLAB bvp4c function. We innovatively carry out an optimisation process using response surface methodology (RSM) to enhance the efficiency of the numerical experiment data and fill a gap in the optimised analysis. To observe the variation solutions for the reduced skin friction and heat transfer coefficients, several parameters, such as the mixed convection and suction parameters, are altered into several values. The solutions are essential for accurately forecasting the occurrence of boundary layer separation, particularly in the case of dual solutions. Our analysis reveals that the model generates multiple solutions for the opposing flow, and the boundary layer separates slowly due to the suction effect. To complete the research, RSM reveals that the highest value of the nanoparticle volume fraction and suction parameters, as well as the smallest value of the needle size, generate the maximum transmitting heat through the slender needle. Furthermore, both the numerical and RSM results show that hybrid carbon nanotubes perform better than mono‑carbon nanotubes for better practical reference.

Non-similar analysis of suction/injection and Cattaneo-Christov model in 3D viscoelastic non-Newtonian fluids flow due to Riga plate: A biological applications

Bioconvective non-Newtonian fluids with motile microorganisms have diverse applications in biology and medicine, offering numerous research opportunities. This article presents a comprehensive investigation into the non-similar analysis of bio-convective micropolar flow induced by a Darcy-Forchheimer exponentially stretchable sheet, considering the effects of suction/injection and thermal radiation in a three-dimensional framework. The fluid under scrutiny is a viscoelastic tangent hyperbolic nanofluid, the impact of Cattaneo-Christov heat subjected to Riga plate is considered for novelty. The role of activation energy and heat source are also computed. The governing equations of viscoelastic tangent hyperbolic nanofluids are transformed into couple of ordinary differential equations via similarity approximations. The resulting ODEs are tackled numerically via bvp4c tool of MATLAB. The impression of appropriate parameters like magnetic parameter, bio-convection parameter, viscoelasticity parameter suction/injection parameter etc. on involved profiles are computed via graphical and tabulated trends. It is observed that velocity layer f′ is dwindled for growing value of Forchheimer number Fr, while reverse relation in velocity curve is noted for developing value of mixed convection parameter δ. Micropolar fluids find biomedical engineering applications in modeling blood flow in microvessels, understanding cerebrospinal fluid dynamics, and optimization of biomedical devices and therapies and simulating drug delivery in tissues.

A computational approach for 2D elliptic singularly perturbed weakly coupled systems of convection–diffusion type with multiple scales and parameters in the diffusion and the convection terms

In this work, we consider the efficient resolution of a 2D elliptic singularly perturbed weakly coupled system of convection–diffusion type, which has small parameters at both the diffusion and the convection terms. We assume that the diffusion parameters can be distinct at each equation of the system, and also, they can have different orders of magnitude, but the convection parameter is the same at both equations of the system. Then, in general, overlapping regular or parabolic boundary layers can appear in the exact solution. The continuous problem is approximated by using the standard upwind finite difference scheme, which is constructed on a special piecewise uniform Shishkin mesh. Then, the numerical scheme is an almost first‐order uniformly convergent method with respect to all the perturbation parameters. Some numerical results, obtained with the numerical algorithm for one test problem, are presented, which show the good performance of the proposed numerical method and also corroborate in practice the theoretical results.

Forced convective rate and pressure drop through a packed annulus: a numerical simulation

Porous materials are used in engineering and industry due to their heat transmission qualities. This study examined forced convection flow through an annular tube packed with sphere balls of various materials and sizes using numerical analysis. The sphere balls were permeable. Ceramic, plastic, and steel with spherical diameters of 3, 5, and 6 and porosity of 0.4 were tested for heat dissipated and fluid flow. Also, test the impact of steel balls of diameter 6mm with 0.6 and 0.8 porosity. The numerical simulation results are used to analyze the forced convection and fluid flow parameters of a three-dimensional annular tube with continuous heat flux in the Reynold number range (5000-14000). Steel balls had an 80% higher heat transfer coefficient than annular tubes without porous mediums. The simulation showed that inserting the porous media increased annular tube pressure loss. The maximum heat transfer coefficient improved by about 80% when the spherical diameter is 3 mm. Also, the result illustrated the heat transfer coefficient of steel balls Increased by about 79%, 69%, and 49%, with 0.4, 0.6, and 0.8 respectively

Mixed convective viscous dissipative flow of Casson hybrid nanofluid with variable thermal conductivity at the stagnation zone of a rotating sphere

AbstractMixed convection flows across the revolving bodies have eminent applications in science and technology, such as fibre coating, polymer deposition, centrifugal blood pumps, rotatory machinery, and so forth. In the current work, magnetohydrodynamic (MHD) flow and heat transfer characteristics of Casson hybrid nanofluid (Ag/MgO as nanoparticles) over the rotating sphere at the stagnation zone are being studied. Moreover, an analysis of heat transmission is conducted by considering the influence of thermal radiation, temperature‐dependent thermal conductivity, magnetic field, and viscous dissipation. The relevant partial differential equations are reformed into ordinary differential equations by appropriate transformations, which are solved using the successive linearization method (SLM). The thermal field, velocity components in x and z directions, heat transfer rate, and skin friction coefficient are computed for various physical quantities like rotation parameter mixed convection parameter, radiation parameter, Eckert number, Casson parameter, magnetic parameter, variable thermal conductivity parameter, and so forth. The current findings align well with the literature in a limiting sense. Thermal enhancement in hybrid nanofluid is observed for the viscous dissipation parameter (Ec), thermal conductivity parameter (), and radiation parameter (Rd). The degree of heat transfer rises from 12.8% to 20% when the Casson parameter's value () increases. Also, a decrease of approximately 33% is depicted between the peak values of the velocity magnitude with an increase in rotation parameter.

Computational analysis of microgravity and viscous dissipation impact on periodical heat transfer of MHD fluid along porous radiative surface with thermal slip effects

The current thermal slip and Magnetohydrodynamic analysis plays prominent importance in heat insulation materials, polishing of artificial heart valves, heat exchangers, magnetic resonance imaging and nanoburning processes. The main objective of the existing article is to deliberate the impact of thermal slip, thermal radiation and viscous dissipation on magnetized cone embedded in a porous medium under reduced gravitational pressure. Convective heating characteristics are used to increase the rate of heating throughout the porous cone. For viscous flow along a heated and magnetized cone, the conclusions are drawn. The simulated nonlinear partial differential equations are transformed into a dimensionless state by means of suitable non-dimensional variables. The technique of finite differences is implemented to solve the given model with Gaussian elimination approach. The FORTRAN language is used to make uniform algorithm for asymptotic results according to the boundary conditions. The influence of controlling parameters, such as thermal radiation parameter Rd, Prandtl number Pr, porosity parameter Ω, viscous dissipation parameter Ec, δ thermal slip parameter, Rg reduced gravity parameter and mixed convection parameter λ is applied. Graphical representations were created to show the consequences of various parameters on velocity, temperature and magnetic field profiles along with fluctuating skin friction, fluctuating heat and oscillatory current density. It is found that velocity and temperature profile enhances as radiation parameter enhances. It is noted that the amplitude and oscillations in heat transfer and electromagnetic waves enhances as magnetic Prandtl factor increases.