Reynolds-averaged Navier-Stokes Approach Research Articles

Numerical analysis of a parallel triple-jet of liquid-sodium in a turbulent forced convection regime

In the present study, we have applied a combined wall-resolving dynamic Large-Eddy Simulation (LES) (for the velocity field) and Direct Numerical Simulation (DNS) (for the temperature field) approach for mixing of parallel triple-jets with different temperatures of liquid sodium in a turbulent forced convection regime. Because of the high thermal conductivity of sodium (a low-Prandtl fluid), we adopted the dynamic Smagorinsky subgrid closure for the unresolved velocity scales, while the thermal scales are fully resolved. Furthermore, the Time-dependent Reynolds-Averaged Navier-Stokes (T-RANS) approach with the high-Reynolds number variant (i.e. with the wall functions as boundary conditions along solid boundaries) of the four-equation eddy viscosity model (k−ε−kθ−εθ) was applied. The fine-mesh LES/DNS provided a close agreement with the experimental data for both velocity and temperature fields (for both first- and second-moments). In contrast, the coarse-mesh LES/DNS overestimated the turbulent kinetic energy profiles at different distances from the inlet plane. The T-RANS results confirmed a good agreement with the mean streamwise velocity and turbulent kinetic energy, as well as the mean temperature profiles. Finally, the analysis of power spectral density distributions of the temperature signal revealed that all simulation techniques captured a dominant flow frequency originating from the induced Kelvin-Helmholtz instabilities between the side and central jets. The presented combined dynamic LES/DNS approach is recommended for future simulations of the turbulent forced convection flows of low Prandtl fluids, especially if thermal fatigue effects need to be predicted correctly.

Integrating NSGA-II and CFD for enhanced urban airflow prediction: Recalibration of closure coefficients for a nonlinear eddy viscosity model

Accurately predicting urban environmental airflows using the Reynolds-averaged Navier‒Stokes (RANS) approach presents significant challenges due to unsolved closure issues. Previous attempts to address these limitations through coefficient adjustments were constrained by isotropic assumptions, resulting in limited generalizability and reliability, especially for complex building configurations. In this study, we proposed a recalibration approach within a multi-objective optimization framework. Nondominant sorting genetic algorithm-II (NSGA-II) and computational fluid dynamics (CFD) numerical computations were utilized to optimize the closure coefficients of a nonlinear eddy viscosity (NLEV) model, with a focus on improving the accuracy of the mean velocity, turbulent kinetic energy, and airflow characteristic predictions. To ensure the robustness of the model, appropriate objective functions were carefully defined. The proposed approach was evaluated using three-dimensional (3D) building cases related to urban prototypes, and the results demonstrated the necessity of multi-objective optimization. Our findings indicated that the trade-off solution on the Pareto front consistently outperformed the baseline and single-objective optimal versions across different types of urban airflow, demonstrating superior generalizability. The simulation results of this solution exhibited closer agreement with the wind tunnel experimental data and provided more accurate distributions of the time-averaged values and airflow characteristics. The normalized root mean square errors are reduced by about 33 %, 52 %, 35 % and 9 % in velocity, and 31 %, 25 %, 24 % and 11 % in turbulent kinetic energy, respectively. These results underscore the effectiveness of the multi-objective optimization framework in addressing closure issues and improving the prediction accuracy of complex urban environmental airflows.

Comparison between DNS and RANS approaches for liquid metal flows around a square rod bundle

The thermal-hydraulic characteristics of liquid metal flows around rod bundles are of great interest for the research and design of fourth generation nuclear reactors. Currently, a large research effort is aimed at the development of accurate numerical models for low Prandtl number fluid flows, since the data available in the literature are quite scarce. Direct Numerical Simulation (DNS) is undoubtedly the most accurate approach, but its large requirements of computational resources and time make it less practical than other simplified methods such as the Reynolds-Average Navier Stokes (RANS) approach. The present paper provides a comparison between numerical results of a flow of liquid Lead-Bismuth Eutectic (LBE) at Pr=0.031 around four vertical cylindrical rods arranged in a square lattice, obtained by DNS and RANS. Several turbulence models are considered, including the standard k−ε, k−ω SST, and two Reynolds stress models, namely the ones by Launder, Reece and Rodi (LRR), and Speziale, Sarkar and Gatski (SSG). The accuracy of these models is assessed by comparing the mean Nusselt number, the pressure drop, and local field distributions with those obtained by DNS.

Prediction and comparison of aerodynamic performance and flow control for smooth and wavy tube banks in crossflow at subcritical Reynolds numbers using a 3D RANS approach

This paper investigates the effects of introducing wavy cylinders of appropriate wavelength into tube bundles for the passive control of flow-induced vibration. The Reynolds-averaged Navier–Stokes approach RANS was used to study the turbulent flow characteristics within staggered tube bundles having transverse and longitudinal pitch-to-diameter ratios of 3.8 and 2.1, respectively. Two wavy models are tested with different wavelength-to-mean diameter ratios, namely: Model-A with [Formula: see text] and Model-B with [Formula: see text], and their performances are compared with those of a smooth circular tube bundle Model-C ([Formula: see text]), in a range of subcritical Reynolds numbers [Formula: see text]. Mean velocity and pressure fields as well as aerodynamic coefficients are presented and compared. According to the obtained results, the wavy tube bundle with [Formula: see text] exhibits the best performance, with slightly smaller [Formula: see text] values than the smooth tube bundle. However, results show that the wavy model with [Formula: see text] is clearly the worst with an increase of [Formula: see text] up to 40%. Numerical outcomes also reveal that the interaction of neighboring rows and columns affects the fluctuation of [Formula: see text] values relative to each tube position. Moreover, [Formula: see text] evolutions depend significantly on the variation of Re as well, where drag reduction is more substantial by increasing Re. Thus, wavy-shaped tubes with optimum parameters could be more suitable for flow control by enhancing the secondary flow, turbulence and fluid mixing.

A Flow Structure Interaction Method for Towed Cable System

Abstract: The ocean towed cable system is a classic example of fluid-structure interaction (FSI). This interaction can exhibit stability or oscillation between a highly deformable moving cable and the surrounding turbulent flow. However, in dynamic simulations of towed cable systems, a constant drag coefficient for an infinite circular cylinder is often used based on experimental data. An innovative fluid-structure interaction method is introduced to obtain accurate drag distribution along cable to couple with towed system dynamics. A modified nodal position finite element method (NPFEM) coupled with Reynolds-averaged Navier-Stokes (RANS) approach has been utilized to predict hydrodynamic forces along the cable. A data exchange algorithm has been developed specifically for fluid-structure interaction within the towed cable system where the cable profile is transferred to construct the flow domain while hydrodynamics is interpolated for NPFEM analysis. A topology partition around cable is applied. A multiblock grid is generated around cable. The simulation results of the fluid-structure interaction of the towing system are verified. This FSI scheme reveals how strongly hydrodynamics determine cable dynamics and induce vortex structure vibrations around a towed cable system. Parametrically controlled structured grid generation and their applicability for complex flow fields have also been discussed. Detailed descriptions of boundary layer separation evolution around spatially distributed cable are provided. This FSI scheme reveals a real strongly hydrodynamic determined cable dynamics and vortex structure induced vibrations around a towed cable system. The proposed method enhances predictive accuracy of the towed system dynamics response.

Efficient control of the fully passive oscillating foil in 2D confined flows with adjustment of the heave damping

A foil that is free to pitch and heave in an upstream flow can oscillate very regularly and with large amplitudes given that its inertial properties and support stiffness in pitch and heave are well adapted to the flow velocity. Useful energy can be extracted from these oscillations via an appropriate damping in heave that models the presence of an electric generator. In recent years, the structural parameters of such a fully passive oscillating-foil turbine (OFT) have been optimized, yielding a maximum energy extraction efficiency of 51.0% under the assumptions of 2D and unconfined flow. However, the turbine is normally deployed in channels with finite cross-sectional area, thus impacting the flow rate passing through the turbine via the blockage effect. In this work, we extend the applicability of the 2D optimized structural parameters to 2D confined scenarios with a simple tuning of the viscous heave damping coefficient. Performance is determined via a fluid-structure interaction solver based on an unsteady Reynolds-averaged Navier–Stokes approach. As expected, confining the turbine increases the heave amplitude and the power, up to a point where the motions become chaotic, and thus require an increase in the heave damping coefficient. This study shows that in all confined 2D scenarios, reasonably good performances of the fully passive OFT can be maintained when using its optimal structural parameters obtained in 2D unconfined conditions, given that the generator is adjusted accordingly.

Experimental and numerical analysis of the physical characteristics of natural and ventilated supercavitating flows

In this experimental and numerical study, we investigate the physical characteristics of a supercavitating flow generated behind a disk-shaped cavitator under both natural and ventilated conditions, an area of research that has not been thoroughly examined. Initially, the experiment is conducted within a cavitation tunnel employing a forward-facing model, complemented by high-speed visualization techniques. Subsequently, an unsteady Reynolds-averaged Navier–Stokes approach is adopted to conduct numerical simulations along with the k–ε turbulent model and Ffowcs Williams–Hawkings (FW–H) methods. The outcomes of the study demonstrate that when considering fixed cavitation numbers, the profiles of natural and ventilated cavities are consistent. Under constant flow conditions, the introduction of ventilating air leads to a discernible reduction in hydroacoustic characteristics in the high-frequency spectrum and has the potential to improve flow stability behind the cavitator. The numerical results offer insight into the behaviors of the water, vapor, and ventilation air. In the foamy cavity stage, all the considered phases (water, vapor, and ventilation air) coexist inside the cavity. Upon the formation of a transparent supercavity, the ventilation air primarily gathers around the ventilation holes and the surrounding gas-leakage region. Meanwhile, the vaporous gas is dominant and is concentrated predominantly in the central region of the supercavity. The findings extracted from this study represent a significant advancement in our understanding of the intricacies of supercavities under ventilated and vaporous conditions. These insights hold the potential to drive groundbreaking innovations in the design and control of supercavitating vehicles.

Experimental assessment of modelling VOC emissions from particleboard into a ventilated chamber

The interactions between the emission of Volatile Organic Compounds (VOCs) and airflow play a key role in determining indoor pollutant concentrations. In the framework of Indoor Air Quality (IAQ) prediction, numerical models based on fluid dynamics are useful tools to address typical cases and then make decisions to improve both public and occupational health. This requires an accurate description of VOC emission processes from building materials, products and furniture, taking into account the diffusion of VOCs into these materials instead of using constant surface emission rates. A predictive model combining Computational Fluid Dynamics (CFD) for airflow and kinetics modelling for VOC emissions is described. The validation of airflow and VOC transfer models is carried out by comparing experimental and simulation results into a 128 L ventilated experimental chamber.Our results show that the Reynolds-Averaged Navier Stokes (RANS) approach, together with a standard k-ω turbulence model, provide good agreement between numerical and experimental airflows regarding both air velocity and age of air profiles. The overall VOC dynamics is also reproduced by numerical simulation for the eight VOCs monitored. The predicted absolute VOC concentrations are in agreement with experimental data for acetone, formaldehyde, hexanal and terpenes. However, numerical simulations underestimate the concentration of pentanal, propanal, butanal, acetaldehyde, which is discussed in terms of representativeness of emission parameters. Our results highlight that CFD simulations combined with VOC emission kinetics modelling is a promising tool for IAQ prediction, but it requires further investigation to fully understand the observed behaviour for some VOCs. This finally demonstrates the crucial need of tracking various VOCs simultaneously in the framework of assessing an IAQ prediction model.

Ressalto hidráulico submergido: uma análise em diferentes escalas

ABSTRACT Advancements in computational capabilities have enabled engineers and scientists to numerically model complex turbulent phenomena such as hydraulic jumps. This research assesses the capability of numerically simulating a hydraulic jump that occurs in the UHE Porto Colômbia's stilling basin at a flow rate of 4,000 m3/s. To achieve this, simulation results were compared with data from three hydraulic physical models (scales 1:32, 1:50, and 1:100) and full-scale measurements. The simulations employed the Ansys CFX solver, utilizing a Reynolds-Averaged Navier-Stokes (RANS) approach, the RNG κ-ε turbulence model, and the Volume of Fluid (VOF) method for air-water interactions. Various variables were analyzed, with satisfactory results for mean pressures, conjugated depths, roller length, water profile in less aerated areas, and mean velocity at the submerged hydraulic jump upstream section, with errors below 10%. However, the submerged hydraulic jump's start position and the representation of the water surface profile in the region near the jump toe yielded more disparate results. In conclusion, the methods and conditions applied in the simulations are apt for representing variables less impacted by aeration phenomena, establishing CFD simulations as a valuable tool for hydraulic jump analysis.

Transitional Delayed Detached-Eddy Simulation for a Compressor Cascade: A Critical Assessment

The accurate prediction of transitional flows is crucial for the industrial turbomachinery design process. While a Reynolds-averaged Navier–Stokes approach inherently brings conceptual weaknesses, large-eddy simulation will still be too expensive in the near future to affordably analyze complex turbomachinery configurations. We introduce a transitional delayed detached-eddy simulation (DDES) model, namely, DDES-γ, and analyze the numerical results of the compressor cascade V103. A comparison with the fully turbulent DDES approach emphasizes the benefit of coupling DDES with a transition model. Issues with undesired decay of modeled turbulent kinetic energy in the freestream are improved when running DDES-γ in combination with the synthetic turbulence generator method. The best results for DDES-γ are obtained when changing the inviscid flux solver blending from dynamic to constant mode. We show that DDES-γ is capable of predicting the transitional flow through a linear compressor cascade, but we also critically discuss the general concept and results.

An extended [formula omitted] model for wake-flow simulation of wind farms

The Reynolds-averaged Navier–Stokes approach coupled with the standard k−ɛ model is widely utilized for wind-energy applications. However, it has been shown that the standard k−ɛ model overestimates the turbulence intensity in the wake region and, consequently, overpredicts the power output of the waked turbines. This study focuses on the development of an extended k−ɛ model by incorporating an additional term in the turbulent kinetic energy equation. This term accounts for the influence of turbine-induced forces, and its formulation is derived through an analytical approach. To assess the effectiveness of the proposed model, we begin by analyzing the evolution of normalized velocity deficit and turbulence intensity in the wake region, and the normalized power of the waked turbines. This investigation involves a comparison of the predictions against results from large-eddy simulations in three validation cases with different layouts. We then simulate a wind farm consisting of 30 wind turbines and conduct a comparative analysis between the model-predicted normalized streamwise velocity and wind-tunnel measurements. Finally, to conclude our assessment of the proposed model, we apply it to the operational wind farm of Horns Rev 1 and evaluate the obtained normalized power with the results from large-eddy simulations. The comparisons and validations conducted in this study prove the superior performance of the extended k−ɛ model compared to the standard version.

Free fall drag estimation of small-scale multirotor unmanned aircraft systems using computational fluid dynamics and wind tunnel experiments

New European Union (EU) regulations for UAS operations require an operational risk analysis, which includes an estimation of the potential danger of the UAS crashing. A key parameter for the potential ground risk is the kinetic impact energy of the UAS. The kinetic energy depends on the impact velocity of the UAS and, therefore, on the aerodynamic drag and the weight during free fall. Hence, estimating the impact energy of a UAS requires an accurate drag estimation of the UAS in that state. The paper at hand presents the aerodynamic drag estimation of small-scale multirotor UAS. Multirotor UAS of various sizes and configurations were analysed with a fully unsteady Reynolds-averaged Navier–Stokes approach. These simulations included different velocities and various fuselage pitch angles of the UAS. The results were compared against force measurements performed in a subsonic wind tunnel and provided good consistency. Furthermore, the influence of the UAS`s fuselage pitch angle as well as the influence of fixed and free spinning propellers on the aerodynamic drag was analysed. Free spinning propellers may increase the drag by up to 110%, depending on the fuselage pitch angle. Increasing the fuselage pitch angle of the UAS lowers the drag by 40% up to 85%, depending on the UAS. The data presented in this paper allow for increased accuracy of ground risk assessments.

Effects of turbulence and flamelet combustion modelling on the CFD simulation of a dual inlet ramjet combustor

Abstract This manuscript presents Computational Fluid Dynamics simulation of a ramjet combustor using Reynolds Averaged Navier–Stokes approach for turbulence with flamelet combustion modelling. In the approach a one-dimensional premixed flame simulation is performed to cover a wide range of mixture fraction space. After a mesh study, effects of turbulence, Realizable k-ε and SST k-ω, and combustion modelling, Steady Laminar Flamelet and Flamelet Generated Manifold, are investigated in detail. The Flamelet Generated Manifold model that offers a reaction delay by employing an additional progress variable, shows there are no reactions taking place in the vicinity of jet inlets, hence the unrealistic temperature rise that is seen in the case of using Steady Laminar Flamelet is not observed. A study on the choice of progress variable based on the combustion products is carried out. The present study readily demonstrates good predictability of Flamelet Generated Manifold combustion modelling in such a dual inlet ramjet combustion chamber.

THERMOPHYSICAL AND ENVIRONMENTAL ASSESSMENT OF NATURAL GAS UTILIZATION IN THE RECONSTRUCTION OF A PULVERIZED COAL-FIRED BOILER

Link for citation: Maltsev K.I., Gil A.V., Abramov N.V., Puzyrev S.A. Thermophysical and environmental assessment of natural gas utilization in the reconstruction of a pulverized coal-fired boiler. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 30-38 In Rus. The relevance of the investigation is caused by the need to assess the completeness of fuel combustion, harmful emissions, and temperature stress of the screen surfaces of a pulverized coal-fired boiler during its reconstruction for natural gas combustion. Currently, the conversion of solid fuel combustion installations to natural gas is highly relevant due to significantly lower emissions of carbon compounds. The main aim of this research is to study the physicochemical processes in the combustion chamber at various loads with flammable natural gas combustion and evaluate the effectiveness of combustion organization during the reconstruction of a pulverized coal-fired boiler. Objects: combustion chamber of a boiler unit with a steam capacity of 210 t/h, burners, parameters of the combustion chamber environment Methods: comparison of results obtained from analytical thermal calculations and numerical modeling. The numerical simulation of gas flare combustion was performed using the ANSYS Fluent software package. Reynolds Averaged Navier–Stokes approaches based on averaging the Navier–Stokes equations over the Reynolds number with additional equations for the turbulent kinetic energy k and the rate of turbulent kinetic energy dissipation ε were applied to describe the turbulent flow. Results. A numerical study of the physicochemical processes in the combustion chamber of a boiler unit was conducted after its reconstruction for natural gas combustion. Dependencies of temperature level changes, hydrodynamics, and concentrations of combustion products components in the volume of the combustion chamber at various loads were obtained. It was found that high-temperature combustion products are redistributed towards the front and rear walls, resulting in the formation of zones in the wall layer with a significant temperature gradient. The nozzles of the tertiary air contribute to the reduction of nitrogen oxide emissions in the combustion chamber by suppressing their formation due to oxygen deficiency in the combustion zone, as well as by lowering the temperature of the flame in the oxidizing zone.

Inter-room pollutant transmission routes in naturally ventilated street canyon buildings

Airborne transmission of pollutants is a significant concern in urban areas, especially since the recent pandemic. While previous studies have explored inter-room pollutant crossflow in highrise buildings and isolated scenarios, the ventilation characteristics within street canyon configurations have not received enough attention. Understanding ventilation characteristics in this layout will help limit the spread of pollutants along the street. This study investigates the wind-driven transmission characteristics of pollutants between the indoor rooms situated adjacent to a street canyon, subjected to perpendicular approach flow. Numerical simulations were performed using the 3D steady Reynolds-Averaged Navier-Stokes approach and validated against surface pressure measurements inside a wind tunnel. The impacts of seven building ventilation strategies were compared, each representing a window opening combination on the two buildings. Based on the set environmental conditions, the results indicate that the inter-room transmission is dependent on both the ventilation efficiency and the specific location of the room. Increasing the ventilation rate decreases the cross transmission between the rooms, while rooms at the centre of the canyon have an increased susceptibility of being contaminated. For instance, switching from cross to single-sided ventilation decreased the average air change rate from 42.3h-1 to 1.4h-1, coinciding with a rise in pollutant concentration by 114-fold and 12-fold at the canyon's centre and side, respectively. Rooms at the edge of the canyon were more contagious and could contaminate other rooms located further inside the street, albeit in small doses. Our findings present new insights within the domain of indoor-outdoor air interaction, shedding light on the interplay between room location and potential inter-unit pollutant transmission. In addition, the pressure measurement results from the wind tunnel experiment provide a valuable resource for other researchers aiming to validate numerical simulations for building engineering applications.

Analysis of turbulent mixing in a methane–oxygen recessed injector for space propulsion

Turbulent mixing in a methane–oxygen recessed injector is studied using direct numerical simulations. The operating point is chosen to be fuel-rich and at high pressure to recreate a representative environment for space propulsion applications. The results are used to investigate the transport of the turbulent mixture fraction statistics and the validity of conventional transport models. It is observed that molecular diffusion is only relevant near the boundary layer of the injection recess cavity and at the recirculation zone. Moreover, turbulent mixing in the axial direction is negligible as radial turbulent diffusion dominates. Radial turbulent diffusion near injection is driven by Kelvin–Helmholtz Instabilities (KHI) manifesting at large scales in the order of the injector geometry. The dominance of this process over microscale mixing originates negative turbulent diffusion, which produces a mixture resegregation and the appearance of lean pockets far from the oxidizer injection plane. Gradient models display poor capabilities for the prediction of this sort of phenomena. Closure models for the turbulent mixing transport terms are proposed and evaluated. An anisotropic gradient model is devised, providing performance improvements within the recess cavity and the recirculation region. In addition, a novel filtered Reynolds-averaged Navier Stokes approach based on the mixing state is proposed. This new methodology shows excellent prediction capabilities in the regions dominated by KHI, accurately predicting negative turbulent diffusivity. The challenges associated with this model are commented on, and strategies to enable its application are proposed.

Effect of thermal manikin shape on thermal comfort parameters prediction uncertainties: a numerical study

The main goal of the study is to evaluate the effect of the thermal manikin shape on the uncertainty of thermal comfort parameters CFD prediction. Numerical simulation of the airflow and heat transfer was carried out in a model room with displacement ventilation where a standing heated thermal manikin is located (test by P.V. Nielsen et al.). Numerical modelling was carried out using three manikin shapes: the detailed one (close to the human body shape), the simplified (block) one, and the single-parallelepiped shape. The 3D calculations were carried out using the ANSYS Fluent CFD package. Turbulence modelling was performed using the Reynolds-Averaged Navier-Stokes (RANS) approach with the standard k-ε turbulence model. The uncertainties in the CFD-predicted draught rating (DR), percentage dissatisfied caused by vertical air temperature difference (PD), the predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD), are discussed. The main result of the paper is the quantitative evaluation of the changes in the local velocity, temperature and thermal comfort parameters due to the thermal manikin shape simplification. It was found that the shape simplifications are suitable if the goal of the study is to predict the integral parameters.

Numerical Investigation into Single and Double Gurney Flaps for Improving Airfoil Performance

The impact of single and double Gurney flaps of heights within the range of is determined for a typical symmetrical airfoil (NACA 0015) by numerical simulations using an unsteady Reynolds-averaged Navier–Stokes approach. The optimal scaling of the Gurney flap to maximize the lift-to-drag ratio of the airfoil is revisited and confirmed to depend on the boundary-layer thickness in the region where it is deployed. Appropriate scaling rules for both single and double Gurney flap are proposed. Studying the Gurney flap’s pressure distribution at a finely resolved level highlights its effect on the overall foil’s pressure distribution. Finally, the unsteady simulations carried out are harnessed to determine the shedding frequencies generated by the flaps and the flow structures associated with them, hinting at the physical mechanisms by which Gurney flaps may increase lift at a low drag cost, thus improving the lift-to-drag ratio of the airfoil.

Steady and unsteady flow characteristics of dual cavity in strut injection scramjet combustor

This study aims to understand the flow performance of a dual wall-mounted cavities in a strut-injector mounted scramjet combustor for steady-state and transient reacting conditions. Conventionally, two-dimensional Reynolds Averaged Navier-Stokes approach is adopted to compute the steady flow, whereas the current research employs Delayed Detached Eddy Simulation for predicting the unsteady flow characteristics as well. The calculated flow patterns, density, pressure, and temperature fields of dual cavities are compared with shadowgraph and wall pressure measurements from DLR experiments. The dual cavities position substantiates to explore the interplay between wave propagation and shear layer mixing characteristics. Employing a dual cavities arrangement accelerates toward the complete combustion relative to the baseline model. The combustion zone widens in the lateral direction as the dual cavities shift the shock train downstream of the strut injector owing to intense shock shear layer interactions. These cavities' existence significantly modifies the dominating frequencies and affects the strength of the diverging section's coherent flow structures.

A volume-of-fluid methodology for interfacial mass transfer

This study developed a novel interfacial mass transfer model for computational fluid dynamics (CFD) capable of handling a concentration jump of multiple orders of magnitude across the interface between two fluids. The interfacial mass transfer model uses a volume of fluid methodology. After establishing the mathematical foundation of the model, termed the Mass Fraction – Continuous Species Transfer (MF-CST) model, validation on a two-dimensional system was performed. Two different chemical systems were used: one system having the mass transfer resistance in only one phase and the other system having mass transfer resistance in both phases. For both validation cases, the MF-CST predictions agreed with the analytical solution to within 1 percent. A framework was also provided for combining a Reynolds-averaged Navier Stokes (RANS) approach with the MF-CST model. To demonstrate the use of the RANS and MF-CST models simultaneously, simulations were performed on a structured packing system.