Convective Situations Research Articles

Radiative flow of temperature-dependent viscosity power-law nanofluids over a truncated cone saturated heat generating, porous media: Impacts of Arrhenius energy

In this paper, the coupled flow of the pseudo-plastic, dilatant/Newtonian nanofluids along truncated cones is treated using a set of non-similar solutions. The dynamic viscosity is assuming to be a variable and depending on flow region temperature. The non-Darcy model where the quadratic drag is significant is applied to formulate this situation and the medium's permeability is varied according to the modified Ostwald-de-Waele power law model. Both of the Arrhenius activation energy and non-linear radiation flux impacts are assumed. The converted system is treated using the effective finite differences analyses with Blottner scheme. The major outcomes disclosed that the temperature and nanoparticles distributions are higher in case of the pseudo-plastic nanofluids while the dilatant nanofluids types gives the higher rates of the heat and mass transfer. The Darcy flow case causes higher values of the Nusselt number comparing to the non-Darcy case. Further, presence of the activation energy supports the convective situation and enhances the Nusselt and Sherwood coefficient.

A Novel Method for Diagnosing Land–Atmosphere Coupling Sensitivity in a Single-Column Model

Abstract The response of boundary layer properties and cloudiness to changes in surface evaporative fraction (EF) is investigated in a single-column model to quantify the locally coupled impact of subgrid surface variations on the atmosphere during summer. Sensitive coupling days are defined when the model atmosphere exhibits large variations across a range of EFs centered on the analyzed value. Coupling sensitivity exists as both positive feedback (cloudiness increases with EF) and negative feedback (clouds increase with decreasing EF) regimes. The positive regime manifests in shallow convection situations, which are capped by a strengthened inversion and subsidence, restricting the vertical extent of convection to just above the boundary layer. Surfaces with larger EF (greater surface latent heat flux) can inject more moisture into the vertically confined system, lowering the cloud base and an increasing cloud liquid water path (LWP). Negative feedback regimes tend to manifest when large-scale deep convection, such as from mesoscale convective systems and fronts, is advected through the domain, where convection strengthens over surfaces with a lower EF (greater surface sensible heat flux). The invigoration of these systems by the land surface leads to an increase in LWP through strengthened updrafts and stronger coupling between the boundary layer and the free atmosphere. These results apply in the absence of heterogeneity-induced mesoscale circulations, providing a one-dimensional dynamical perspective on the effect of surface heterogeneity. This study provides a framework of intermediate complexity, lying between parcel theory and high-resolution coupled land–atmosphere modeling, and therefore isolates the relevant first-order processes in land–atmosphere interactions. Significance Statement Cloud formation, distribution, and other properties may be sensitive to heterogeneous surfaces depending on the strength and location of such heterogeneities and the background atmospheric state. This may drive differences in the cloud population depending on which part of the domain one is located. This may also lead to mesoscale circulations, which may strengthen or weaken this effect. Currently, climate models act on scales (∼100 km) that are too large to explicitly represent these processes, which are strongest at smaller scales (around 5–40 km). Therefore, subgrid-scale heterogeneity is neglected, and any predictability and model fidelity it may provide is lost. We use a simple model to diagnose sensitivity of the local atmosphere to surface variations meant to represent possible subgrid heterogeneity, providing a first-order estimate of its effect. We conclude that preferentially sensitive atmospheric states exist that lead to positive and/or negative feedback between land and atmosphere. This information is valuable to future climate model parameterizations aimed at improving the representation of these feedbacks.

Effect of window-glass type on solar heat gain and velocity and temperature distributions inside air-conditioned rooms – A conjugate numerical analysis

Conjugate mixed-convection numerical analysis is conducted in order to investigate effect of employing different types of window glass on solar heat gain in air-conditioned rooms using mixing air-distribution system. ANSYS Fluent and RNG k-ε turbulence model are utilized. Single- and double-pane clear and tinted window glass are considered with window-to-wall ratio of 0.33. The rate of air change per hour (ACH) is varied in range 5–20. Part of solar radiation absorbed by glass is conducted indoor while solar radiation transmitted through glass heats portion of floor and is released as a heat source to inner space. The numerical model is validated against measurements available under simpler conditions. Results of model application show that airflow pattern and temperature distribution are sensitive to the solar heat gain and, hence, to the type of glass used. It is found that air-conditioning load due to window glass heat gain is reduced by 55% by using double-pane tinted glass compared to using single-pane clear glass. A criterion to distinguish between forced and mixed convection situations in terms of ACH is also developed. In addition, further calculations are made using standard k-ω turbulence model and satisfactory agreement with RNG k-ε model results is obtained.

FEM treatments for MHD highly mixed convection flow within partially heated double-lid driven odd-shaped enclosures using ternary composition nanofluids

A highly mixed convection due to the movements of two perpendicular walls of odd-shaped enclosures is examined. The upper and right boundaries are partially heated, and several heating situations based on the positions of the active parts are considered. Also, several directions of the lid-walls movements are examined. The inner medium is a heat generating and the considered Lorentz force is inclined with angle Φ. The mathematical formulations are based on the Brinkman-extended non-Darcy model. The containers are filled with ternary composition nanofluids. The components of the ternary nanofluids are spherical Al2O3 nanoparticles, MWCNT cylindrical nanoparticles and platelet graphene nanoparticles and suitable correlations for the thermophysical properties are introduced. The numerical simulations are carried out using the finite element method (FEM) based on the characteristics–based split (CBS) algorithm. The major outcomes revealed that the ternary composition nanofluids cause an enhancement in the heat transfer rate by 17.65% comparing to the mono-nanofluids. Also, to get the best mixed convection situation, it is recommended to locate the heat sources in the middle of the outer perpendicular walls, set Re≥100 and make the lower perpendicular walls move in anticlockwise direction to get the best mixed convection situation.

Analysis of free and forced convections in the flow of radiative viscous fluid with oxytactic microorganisms

The prime intend behind the current effort is to explicate flow attributes of magnetically influenced Newtonian fluids toward a stretchable sheet under the novel physical impact of oxytactic microorganisms in a comparative manner for free and forced convections. In addition, modified Fourier and Fick’s laws are implemented to examine the change in temperature and concentration distributions in a more realistic manner by accounting thermal and mass relaxation parameters in the flow. The obtained PDEs are reduced into the non-linear ODEs by employing similarity variables. Due to the complexity of parametrically based differential equations, a numerical scheme based on a finite-difference approach is implemented via the MATLAB built-in routine known as BVP4C. Flow-controlling parameter effects on associated distributions are evaluated through graphs and tables. Subsequently, the influence of flow-controlling parameters on associated distributions is revealed through pictures in a comparative manner for different convection regimes. Additionally, the quantities such as heat and mass fluxes along with the density of motile microorganisms are also illustrated. From the thorough analysis of the current investigation, it is inferred that velocity distribution enhances for free and forced convections, whereas the temperature of the fluid diminishes against the mentioned convective regimes. It is manifested that the Nusselt number is more in the situation of free convection instead of the forced convection situation. The magnitude of the skin friction factor is more in case of free convection as compared to the forced convection regime. It is also reported that by uplifting the magnitudes of concentration and thermal relaxation parameters, depreciation in associated heat and mass transfer rate arises. In addition, it is also reported that with the increment in the magnetic field, buoyancy ratio, bioconvection parameters, and Rayleigh number skin friction accelerate, while the behavior is quite opposite in case of stretching the ratio parameter.

Evaporation characteristics of ethanol droplet in different gases under force convection condition

Ethanol is recognized as one of the finest alternative bio-fuels due to its natural characteristics. Fundamental studies on ethanol droplet evaporation process are mainly either in stagnant environment or using some semi-empirical co-relations. Here, a fully numerical model based on the first principle is solved to investigate the effects of various atmospheric gases (Ar, N2, O2 and CO2) on droplet evaporation phenomenon under force convective situation. Two-dimensional governing equations of species, momentum and energy transfer of spherical coordinate system are solved, and the simulation is validated quantitatively with the literature. Uniform convective strength (Re = 100) is maintained for all cases examined at T∞ = 500 K and P∞ = 0.1 MPa. From the simulation results, it is observed that the viscosity ratio (liquid to gas) has effect on droplet life time. The ethanol droplet life time increases in less viscous atmospheric gases. The ethanol droplet life time is shorter in Ar gas, but heat-up period, wet-bulb temperature, and the surface blowing effect are higher in Ar compared to other atmospheric gases. The heat-up periods of the ethanol droplet in Ar, CO2, N2 and O2 atmosphere occupy around 30%, 20%, 17% and 16.5% of the total life time of the droplet, respectively. It is also noticed that, the heat-up period increases with increase in the thermal conductivity ratio (liquid to gas) and vice versa. Furthermore, the flow pattern of both gas- and liquid-phase in terms of streamline and the internal temperature distributions of the droplet are visualized at various time instants.

Helicity evolution during the life cycle of tropical cyclones formed over the north Indian Ocean

Tropical cyclones (TCs) are violent multiscale convections occurring in the atmosphere. The destructive impact of the TCs is commensurate to the helicity associated with their evolution. The evolution of helicity of three TCs viz. Fani, Luban, and Ockhi formed over the north Indian ocean have been analyzed in this study. The analysis of kinetic energy density of primary (EP), secondary (ES) circulation and total helicity has shown that TCs showed helical features when the secondary overturning circulation knotted with primary tangential circulation in a moist convective situation. This condition can be considered a starting of the self-sustained helical feedback process. At this time, the core region became a rotation-dominated region that suppressed strain-dominated surroundings. The Okubo-Weiss parameter demonstrates the similar qualitative behavior of deep convection as total helicity. The local maximas in helicity time series are related with the changes in tropical cyclones' stages (intensification/dissipation). Therefore, consideration of helicity analysis is essential to analyze the TC intensification and dissipation.

Radar Reflectivity–Based Model Initialization Using Specified Latent Heating (Radar-LHI) within a Diabatic Digital Filter or Pre-Forecast Integration

Abstract A technique for model initialization using three-dimensional radar reflectivity data has been developed and applied within the NOAA 13-km Rapid Refresh (RAP) and 3-km High-Resolution Rapid Refresh (HRRR) regional forecast systems. This technique enabled the first assimilation of radar reflectivity data for operational NOAA forecast models, critical especially for more accurate short-range prediction of convective storms. For the RAP, the technique uses a diabatic digital filter initialization (DFI) procedure originally deployed to control initial inertial gravity wave noise. Within the forward-model integration portion of diabatic DFI, temperature tendencies obtained from the model cloud/precipitation processes are replaced by specified latent heating–based temperature tendencies derived from the three-dimensional radar reflectivity data, where available. To further refine initial conditions for the convection-allowing HRRR model, a similar procedure is used in the HRRR, but without DFI. Both of these procedures, together called the “Radar-LHI” (latent heating initialization) technique, have been essential for initialization of ongoing precipitation systems, especially convective systems, within all NOAA operational versions of the 13-km RAP and 3-km HRRR models extending through the latest implementation upgrade at NCEP in 2020. Application of the latent heat–derived temperature tendency induces a vertical circulation with low-level convergence and upper-level divergence in precipitation systems. Retrospective tests of the Radar-LHI technique show significant improvement in short-range (0–6 h) precipitation system forecasts, as revealed by reflectivity verification scores. Results presented document the impact on HRRR reflectivity forecasts of the radar reflectivity initialization technique applied to the RAP alone, HRRR alone, and both the RAP and HRRR. Significance Statement The large forecast uncertainty of convective situations, even at short lead times, coupled with the hazardous weather they produce, makes convective storm prediction one of the most significant short-range forecast challenges confronting the operational numerical weather prediction community. Prediction of heavy precipitation events also requires accurate initialization of precipitation systems. An innovative assimilation technique using radar reflectivity data to initialize NOAA operational weather prediction models is described. This technique, which uses latent heating specified from radar reflectivity (and can accommodate lightning data and other convection/precipitation indicators), was first implemented in 2009 at NOAA/NCEP and continues to be used in 2022 in the NCEP-operational RAP and HRRR models, making it a backbone of the NOAA rapidly updated numerical weather prediction capability.

Mixed convective cilia triggered stream of magneto ternary nanofluid through elastic electroosmotic pump: A comparative entropic analysis

Integration of ternary nanofluid with micro-pump heat sink is considered to be the incredible heat exclusion from thermal pumps/channels. The present work intends to present a theoretical thermal analysis of mixed convective transport of radiated magneto ternary fluid through an electroosmotic pump. To achieve efficient mixing and effective pumping, the inner surface of pump is embedded with bio-mimetic cilia. The cilia beat in synchronization to commence a train of metachronal waves along the elastic surface of micropump. The blood based ternary nanofluid is considered as working fluid in the pump by mixing trihybrid nanoparticles of TiO2, SiO2 and Al2O3 in blood. The mixed and forced convection situations are set with the help appropriate governing equations and solved analytically. A comparative exergy analysis between ternary, binary, unary nanofluid and conventional blood is also presented. In comparison the ternary hybrid nanofluid is observed be more thermally efficient then the unary and binary nanofluids and has significant ability to minimize heat losses. The ternary nanofluid shows an effective role in augmenting the heat transfer rate by lifting the rate up to 18.03% at smaller Hartmann number specifically at 0.5. It is further reported that thick EDL and high values of the Hartmann number dampens down the TiO2-SiO2-Al2O3/blood temperature.

RETRACTED: Effects of wavy porous fins on the flow, thermal fields, and entropy of the magnetic radiative non-Newtonian nanofluid confined inclined enclosures

In this paper, the numerical investigation on the micropolar non-Newtonian nanofluid transient flow within inclined enclosures containing wavy porous fins is carried out. Electromagnetic forces together with thermal radiation are taken into account. Also, the impacts of the Brownian motion and thermophores on the suspension flow are surveyed. The finite volume method is employed to solve nonlinear coupled partial differential equations. The enclosure is partially heated from below and the second law of the thermodynamic is analyzed. The cases where the microelements close to the boundaries are unable to rotate are assumed and a heat source/sink is taken place within the flow domain. The main outcomes revealed that the presence of the radiation enhances the convection situation while the heat generation and vortex parameters reduce the heat transfer rate. Also, there is a diminishing in the rate of the heat transfer up to 5.62% when the Hartmann number is altered from 0 to 50. This numerical investigation is germane to the engine lubricants, paint rheology, turbulent shear flows, direct absorption of the sunlight in solar collectors, cement slurries, and combustion chambers.

Estimating the urban atmospheric boundary layer height from remote sensing applying machine learning techniques

This study proposes a new methodology to estimate the Atmospheric Boundary Layer Height (ABLH), discriminating between Convective Boundary Layer and Stable Boundary Layer heights, based on the machine learning algorithm known as Gradient Boosting Regression Tree. The algorithm proposed here uses a first estimation of the ABLH derived applying the gradient method to a ceilometer signal and several meteorological variables to obtain ABLH values comparable to those derived from a microwave radiometer. A deep analysis of the model configuration and its inputs has been performed in order to avoid the model overfitting and ensure its applicability. The hourly and seasonal values and variability of the ABLH values obtained with the new algorithm have been analyzed and compared with the initial estimations obtained using only the ceilometer signal. Mean Relative Errors (MRE) between the ABLH estimated with the new algorithm and microwave radiometer show a daily pattern with their highest values during the night-time (stable situations) and their lowest values along the day-time (convective situations). This pattern has been observed for all the seasons with MRE ranging between −5% and 35%. This result notably improves those ABLH values derived by applying the gradient method to ceilometer data during convective situations and enables the Stable Boundary Layer height detection at night and early morning, instead of only Residual Layer top height. Finally, the model performance has been directly validated in three particular cases: clear-sky day, presence of low-clouds and dust outbreak event. In these three particular situations, ABLH values obtained with the new algorithm follow the pattern obtained with the microwave radiometer presenting very similar values, thus confirming the good model performance. In this way it is feasible by the combination of the proposed method with gradient method, to estimate Convective, Stable and Residual Boundary Layer height from ceilometer data and surface meteorological data in extended network that include ceilometer profiling.

Radiation and heat generation aspects on MHD convection of nanofluids in inclined wavy porous double lid-driven enclosures having obstacles: local thermal non-equilibrium

The present contribution focuses on the thermal non-equilibrium handling of an unsteady mixed convection nanofluid flow within two-sided wavy and two-sided lid-driven porous enclosures due to the impact of the thermal radiation and inclined magnetic field. The forced convection situation is due to the movements of the left irregular and top regular boundaries. This pattern accounts for such impacts as the inter-phase heat transfer factor impact, the modified conductivity ratio and the thermal radiation aspects. The cavity includes apart heated wall of length b subjected to external Cu water (with particle diameter less than 100 nm) nanofluid. The governing equations have been solved utilizing Galerkin finite element (GFE) approach with CBS algorithm. Numerical outcomes for the flow and heat transfer for the fluid and solid phases are determined for miscellaneous combinations of the physical factors. Graphical and tabular outcomes pointing out interesting features of the physics of the problem are presented and discussed. The forced convection mode is dominance at higher values of and low values of Hartmann number Ha. Furthermore, the considered range of the nanoparameter () gives an augmentation in the rate of the heat transfer up to 14.54%.

Entropy generation minimization E.G.M. analysis of free convective hybrid nanofluid flow in a corrugated triangular annulus with a central triangular heater

All heat transfer phenomena are always escorted with entropy production and hence destruct the available work and energy resources. One way to minimize valuable energy rescores, especially in convective heat transfer augmentation situations, is to develop a thermal design that reduces the temperature differences inside the system and thus the entropy generation. This study analyzes an optimal thermal design for an augmented free convective situation considering a hybrid nanofluid flow in a corrugated triangular annulus heated by an underneath partial heater. Three approaches are applied to reduce entropy production: the corrugated walls, an inner heater at a lower non-uniform temperature, and the magnetic field effects. A numerical solution is presented for the normalized governing equations by a finite element method. A comparison with previously published investigation confirms the validity of results. The study reveals the influential role of the presented design in reducing entropy production due to the higher thermal conductivity of hybrid nanofluid. It is noticed that if the inner triangular body is heated at uniform or non-uniform temperature, keeping the magnitude of temperature lesser than the bottom heat source, the overall entropy significantly reduces. Moreover, overall, entropy is minimized if, instead of flat walls, corrugated walls are considered.

Third Grade Fluid Flow in a Microchannel Crammed with Permeable Media Liable to Non-linear Thermal Radiation

This work unveils the impact of third-grade fluid flowing in microchannel placed vertically and packed by porous media. Walls facilitate injection/suction of concerned fluid. Slip and convective situations are employed. Active action of non-linear radiation and heat source are contemplated. Pressure gradient is the aspect that's responsible for the flow. The equations modeled consider the contribution of buoyancy forces on geometry with viscous dissipation. The outcomes of the customized equations for the above-narrated flow are assessed by the tactic of reducing the dimensions of equations to one. Owing to the flow and heat transport, entropy and Bejan number are effectually learned with the aid of the Runge Kutta Fehlberg method using graphical manifestation. The consequence of this scrutiny upholds that the rise of third-grade fluid parameter depletes the flow profile. Radiation parameter plummets temperature and entropy produced. The heat source parameter effect is reflected on thermal profile by boosting temperature.

Heat transfer for a single deformed evaporating droplet in the internal combustion engine

A droplet injected from the engine nozzle at high speed generally exhibits a non-spherical shape due to aerodynamic pressure on the droplet surface. The non-spherical shape of a droplet affects its convective heat transfer, heating, and evaporation. Droplet evaporation is critical in heat transfer. The effect of a droplet's non-sphericity on evaporation is investigated in this paper, under the assumption that droplet shapes are prolate or oblate spheroids. Analytical evaporation rates and heat transfer enhancement factors under forced convection for both prolate and oblate spheroidal droplets are derived. The effects of droplet aspect ratio, volume, and Reynolds number on the droplet evaporation under different conditions are numerically investigated. The results indicate that the evaporation conversion rates for both prolate and oblate spheroids are enhanced compared to a spherical droplet of the same volume. In addition, larger droplets show an increased enhancement effect on the evaporation process. Assuming that the droplet shrinkage reduces the dimension perpendicular to the droplet surface, the spheroidal droplet maintains its original aspect ratio during the evaporation process in a quiescent environment, while the nonspherical droplet tends to increase its sphericity under a forced convection situation.

3D magnetic buoyancy-driven flow of hybrid nanofluids confined wavy cubic enclosures including multi-layers and heated obstacle

This paper provides numerical simulations of the magnetic convective process based on buoyancy forces within three dimensional wavy cubic enclosures. The flow domain is partitioned into two layers specifically, a porous layer and a hybrid nanofluid layer. The upper and lower plans of the domain are adiabatic while the residual plans are mentioned to relatively low temperatures. The temperature disparity within the flow domain is a result of a rectangular heated area that is located in the bottom plane. The magnetic force is taken in the normal direction (Z-direction). As for the porous matrix, the Brinkman-extended non-Darcy model was chosen to simulate its effects. The method of solution is based on the Galerkin finite element, the outcomes are represented using various illustrations and tools. It is noticeable that changing the location of the heated area is a beneficial factor for this convective situation. Also, when Ha is altered from 0 to 100, a drop in values of the stream function is given up to 84.78%.

Rainfall-induced attenuation correction for two operational dual-polarization C-band radars in the Netherlands

AbstractThe Royal Netherlands Meteorological Institute (KNMI) operates two operational dual-polarization C-band weather radars providing 2-D radar rainfall products. Attenuation can result in severe underestimation of rainfall amounts, particularly in convective situations that are known to have high impact on society. In order to improve the radar-based precipitation estimates, two attenuation correction methods are evaluated and compared: 1) Modified Kraemer (MK) method, i.e. Hitschfeld-Bordan where parameters of the power-law Zh–kh relation are adjusted such that reflectivities in the entire dataset do not exceed 59 dBZh and attenuation correction is limited to 10 dB; 2) using two-way path-integrated attenuation computed from the dual-polarization moment specific differential phase Kdp (Kdp method). In both cases the open-source Python library wradlib is employed for the actual attenuation correction. A radar voxel only contributes to the computed path-integrated attenuation if its height is below the forecasted freezing level height from the numerical weather prediction model HARMONIE-AROME. The methods are effective in improving hourly and daily quantitative precipitation estimation (QPE), where the Kdp method performs best. The verification against rain gauge data shows that the underestimation diminishes from 55% to 37% for hourly rainfall for the Kdp method when the gauge indicates more than 10 mm of rain in that hour. The improvement for the MK method is less pronounced, with a resulting underestimation of 40%. The stability of the MK method holds a promise for application to data archives from single-polarization radars.

Study of Laminar Naturel Convection in Partially Porous Cavity in the Presence of Nanofluids

The objective of this work is the mathematical modelling and the numerical simulation of the stationary, laminar, and natural convection, in a confined square cavity (H = L) filled with two fluids (a mixture of nanoparticles of aluminum oxide and Al2O3 water) in one partition and pure water in the other partition. A porous conductive wall of thickness w (w = L/e) and thermal conductivity Keff constitutes the exchange surface between these two partitions. The fluid movement is modeled by the Navier-Stokes equations in the two partitions, while the porous medium is modelled by the Darcy–Brinkman equation. Comsol Multiphysics software is used to solve the system of differential equations that is based on the finite element method. The results are discussed with particular attention to the mean and local Nusselt number (Nu), streamlines and isotherms. A parametric study for Rayleigh number Ra (102 to 106), volume fraction j (0% to 10%), and Darcy number Da (10-7 to 10-2) is performed. The obtained findings show that the increase in Ra, Da, and j intensifies the flow and improves the thermal exchange on the cold wall. For Da £ 10-5, Nu remains practically low and the natural convection is being dominated by conduction. For Da > 10-5, an increase in Nu is observed and the flows tend towards a purely convective situation. Furthermore, an increase in the heat transfer coefficients is observed with the raise of the porous layer permeability, volume fraction and Rayleigh number.

Magnetic micropolar nanofluids flow in double lid‐driven enclosures using two‐energy equation model

AbstractImpacts of an inclined electromagnetic force on a mixed convective process in two‐sided lid‐driven geometries using the two‐energy equation model are examined in this study. The flow domain is filled by a porous medium and the local thermal nonequilibrium model is applied. Magnetic micropolar nanofluids are assumed as working fluids consisting of water as a base fluid and CuO as nanoparticles. The forced convection situation is due to the moving of the upper and lower walls in the right direction with a constant velocity. The used methodology depends on the finite volume method, together with the SIMPLE algorithm. The obtained outcomes are visualized using contours of the streamlines, isotherms for the nanofluid phase, isotherms for the solid phase, and angular velocity. The main findings revealed that the increase in lengths of the heated parts and the Nield number reduces the Nusselt number for the nanofluid phase. Also, the average heat transfer rate for the nanofluid and solid phases are boosted with the increase in the vortex viscosity.

A Mixed Eulerian–Lagrangian scheme for scalar transport

The tracking of pollutants in gas and liquid is a major problem to address in atmospheric environment, air quality characterization, and industrial material processes. A Lagrangian scheme devoted to the approximation of the advection term in an advection–diffusion equation is proposed to deal with small diffusivity values or large Peclet numbers. The Lagrangian scheme is used in practice as an Eulerian method discretized on Lagrangian marker points. Advection and diffusion of a circular concentration spot in a vortex flow are considered for validation purpose. The resulting mixed Eulerian–Lagrangian scheme reduces the numerical diffusion to almost computer error and provides better results than other Eulerian classical schemes of the literature. The scheme is finally illustrated in a natural convection situation.