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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Fluid Science and Technology".

Deadline for manuscript submissions: closed (20 January 2025) | Viewed by 6274

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Prof. Dr. Antonio Castelo Filho

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Department of Applied Mathematics and Statistics, Institute of Mathematics and Computational Sciences, University of Sao Paulo, Av. Trabalhador Sao-carlense 400, CP 668, Sao Carlos 13560-970, SP, Brazil
Interests: geometric processing; mesh generation; numerical methods; computational fluid dynamics
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Dr. Alexandre M. Afonso

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CEFT-Transport Phenomena Research Center, Department of Mechanical Engineering, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal
Interests: theoretical and computational rheology; complex flows of complex fluids; electrokinetics; multiphase flow; micro-combustion
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Dr. Luís Lima Ferrás

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Center of Mathematics, University of Minho, 4710-057 Braga, Portugal
Interests: applied mathematics; fluid mechanics; fractional calculus; numerical analysis; machine learning
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Special Issue Information

Dear Colleagues,

This Special Issue on "Theoretical, Computational and Experimental Fluid Dynamics: Methods and Advanced Applications" aims to summarize new developments in the following areas: theory of fluid dynamics (nem models, analytical solutions and fundamentals); numerical solution of the equations that govern simple and complex flows (finite volume methods, finite element methods, finite difference methods, meshless methods, etc.); experimental studies that involve simple, complex and mixed flows.

All researchers working in these areas are invited to submit their work. All submissions will be subject to a rapid and thorough review.

Prof. Dr. Antonio Castelo Filho
Dr. Alexandre M. Afonso
Dr. Luís L. Ferrás
Guest Editors

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Keywords

computational fluid dynamics
numerical methods
experimental work
theoretical works on fluids
fluid flow

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Published Papers (5 papers)

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Research

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19 pages, 8205 KiB

Open AccessArticle

Large-Eddy Simulation of Droplet Deformation and Fragmentation Under Shock Wave Impact

by Viola Rossano and Giuliano De Stefano

Appl. Sci. 2025, 15(3), 1233; https://doi.org/10.3390/app15031233 - 25 Jan 2025

Viewed by 477

Abstract

This study employs the large-eddy simulation (LES) approach, together with the hybrid volume of fluid—discrete phase model, to examine the deformation and breakup of a water droplet impacted by a traveling shock wave. The research investigates the influence of Weber number on transient deformation and breakup characteristics. Particular focus is given to the detailed analysis of sub-droplet-size distributions, which are frequently overlooked in existing studies, providing a novel insight into droplet fragmentation dynamics. The predicted deformation and breakup patterns of droplets in the shear breakup regime align well with experimental data, validating the computational approach. Notably, LES is able to reproduce the underlying physical mechanisms, highlighting the significant role of recirculation zones and the progression of Kelvin–Helmholtz instabilities in droplet breakup. Additionally, it is shown that higher Mach numbers significantly amplify both cross-stream and streamwise deformations, leading to earlier breakup at higher airflow pressures. Increasing the Weber number from 205 to 7000 results in 25% reduction in the average size of the sub-droplets, indicating the strong influence of aerodynamic forces on droplet fragmentation. This comprehensive analysis, while aligning with experimental observations, also provides new insights into the complex dynamics of droplet breakup under post-shock conditions, highlighting the robustness and applicability of the proposed hybrid Eulerian–Lagrangian formulation for such advanced applications in fluid engineering. Full article

(This article belongs to the Special Issue Theoretical, Computational and Experimental Fluid Dynamics: Methods and Advanced Applications)

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31 pages, 5369 KiB

Open AccessArticle

Evaluation of the Effects of Body Forces and Diffusion Mechanisms on Droplet Separation in a Two-Phase Annular–Mist Flow

by Oktawia Dolna

Appl. Sci. 2024, 14(23), 10793; https://doi.org/10.3390/app142310793 - 21 Nov 2024

Viewed by 540

Abstract

For decades, studies have been conducted on the efficiency of gas purification processes with wet scrubbers, including the Venturi scrubbers, and this is the most commonly addressed issue in the field literature. The Venturi scrubber consists of a Venturi nozzle and a cyclone. The article addresses the empirical and analytical studies on the annular–mist flow regime that exists in the throat of the Venturi nozzle with a square cross-section. The uniform distribution of droplets over the cross-section area of the Venturi’s throat strongly correlates with the efficiency of the gas cleaning process using Venturi scrubbers. Due to the above, studies on the physics of the phenomena that affect the quantity of small droplets present in the core of the flow are highly justified. The influence of body forces and diffusive mechanisms impacting the number of droplets in the core flow were investigated to tackle the problem in question. Consequently, the fractions of droplets susceptible to turbulent or inertial–turbulent diffusion mechanisms can now be predicted using the outcomes of the research carried out. The droplets were divided into three fractions that differed by their sizes as follows: airborne droplets I confirm thar italic can be removed in all cases.

(d_{d} \leq

10 µm), medium-sized droplets

(d_{d} \leq

20 µm), and largest droplets

(d_{d}

= (50–150) µm). The estimation of diffusion coefficients

(ε_{d, M}, ε_{d, r e f})

and stopping distances

(s_{M}, s_{r e f})

of all fractions of droplets was carried out with the inclusion

(ε_{d, M}, s_{M})

and exclusion

(ε_{d, r e f}, s_{r e f})

of the Magnus lift force

(M)

in equations of both the droplet’s stopping distance and its diffusion coefficient. The outcomes revealed that the inclusion of the M force translates significantly to the growth in values of

ε_{d, M}, s_{M}

compared to

ε_{d, r e f}, s_{r e f}

. Hence, it was concluded that the M force impacts the increase in the speed of the diffusion of the droplets with

d_{d} \geq

16.45 µm, which is favorable. Hence, the inertial–turbulent diffusion of larger droplets and the turbulent diffusion of medium ones seem to be supported by the M force. The local velocity gradient, which varied within the region of the flow’s hydraulic stabilization also impacted the mass content of droplets with diameter

d_{d} \leq

10 µm in the core of the flow. As the flow development progressed, the number of droplets measured at n = 5 Hz varied nonlinearly up to the point where the boundary layer thickness reached the channel radius. The quantity of small droplets in the main flow was significantly influenced by turbulence intensity

(T u)

. The desired high number of small droplets in the core of the flow (mist flow) was estimated empirically, and it was achieved when gas flows at high speed and has a mean value of Tu. The former benefits the efficiency of gas purification. Investigations on the effects of body forces of inertia of the continuous phase on the separation of droplets with diameters of a few microns and sub-microns from the flow were performed by employing two channel elbows, namely

e_{4}

and

e_{1}

. The curved channels were subsequently mounted at the end of the straight channel (

S C h_{2}

). The curvature angle (

α

) of the

e_{4}

and

e_{1}

equaled 90 °C and 30 °C, respectively. The number of droplets existing in the mist flow was higher in value, as desired, when the

e_{4}

was used, unlike

e_{1}

. Two-dimensional flow fields of the mist have been obtained using the Particle Imaging Velocimetry (PIV) technique and analyzed further. Topas LAP 332 Aerosol Spectrometer was used for the determination of droplet (

d_{d} \leq

40 µm) size distribution (DSD) and particle concentrations, while the Droplet Size Analyzer D Kamika Instruments (DSA) was exploited to ascertain DSD of droplets with diameter

d_{d} > 40

µm. Full article

(This article belongs to the Special Issue Theoretical, Computational and Experimental Fluid Dynamics: Methods and Advanced Applications)

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23 pages, 2445 KiB

Open AccessArticle

Numerical Coupling between a FEM Code and the FVM Code OpenFOAM Using the MED Library

by Giacomo Barbi, Antonio Cervone, Federico Giangolini, Sandro Manservisi and Lucia Sirotti

Appl. Sci. 2024, 14(9), 3744; https://doi.org/10.3390/app14093744 - 27 Apr 2024

Viewed by 1227

Abstract

This paper investigates a numerical code-coupling technique to tackle multiphysics and multiscale simulations using state-of-the-art software packages that typically address some specific modeling domain. The coupling considers the in-house FEM code FEMuS and the FVM code OpenFOAM by exploiting the MED library from the SALOME platform. The present approach is tested on a buoyancy-driven fluid flow within a square cavity, where the buoyancy force constitutes the coupling term. In uncoupled scenarios, momentum and temperature equations are solved in both FEM and FVM codes without data exchange. In the coupled setting, only the OpenFOAM velocity and the FEMuS temperature fields are solved separately and shared at each time step (or vice versa). The MED library handles the coupling with ad hoc data structures that perform the field transfer between codes. Different Rayleigh numbers are investigated, comparing the outcomes of coupled and uncoupled cases with the reference literature results. Additionally, a boundary data transfer application is presented to extend the capabilities of the coupling algorithm to coupled applications with separate domains. In this problem, the two domains share interfaces and boundary values on specific fields as fluxes are exchanged between the two numerical codes. Full article

(This article belongs to the Special Issue Theoretical, Computational and Experimental Fluid Dynamics: Methods and Advanced Applications)

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26 pages, 11042 KiB

Open AccessArticle

Physics-Based Swab and Surge Simulations and the Machine Learning Modeling of Field Telemetry Swab Datasets

by Amir Mohammad, Mesfin Belayneh and Reggie Davidrajuh

Appl. Sci. 2023, 13(18), 10252; https://doi.org/10.3390/app131810252 - 13 Sep 2023

Cited by 2 | Viewed by 1605

Abstract

Drilling operations are the major cost factor for the oil industry. Appropriately designed operations are essential for successful drilling. Optimized drilling operations also enhance drilling performance and reduce drilling costs. This is achieved by increasing the bit life (minimizing premature bit wear), drilling more quickly, which reduces drilling time, and also reducing tripping operations. This paper is presented in two parts. The first part compares the parametric physics-based swab and surge simulation results obtained from the Bingham plastic, power law, and Robertson–Stiff models. The aim is to show how the model’s predictions deviate from each other. Two 80:20 oil/water ratio (OWR) oil-based drilling fluids and two 90:10 OWR oil-based drilling fluids, 1.96 sg and 2.0 sg, were considered in vertical and deviated wells. Analysis of the simulation results revealed that the deviations depend on the drilling fluid’s physical and rheological parameters as well as the well trajectory. Moreover, the model’s predictions were inconsistent. Data-driven machine learning (ML) modeling is the focus of the second section. Data-driven modeling was performed using both software-generated datasets and field datasets. The results show that the random forest regressor (RF), artificial neural network (ANN), long short-term memory (LSTM), LightGBM, XGBoost, and multivariate regression models predicted the training and test datasets with higher R-squared and minimum mean square error values. Deploying the ML model in real-time applications and the planning phase would lead to potential applications of artificial intelligence for well planning and optimization processes. Full article

(This article belongs to the Special Issue Theoretical, Computational and Experimental Fluid Dynamics: Methods and Advanced Applications)

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Review

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23 pages, 2095 KiB

Open AccessReview

Review of Mechanisms and Suppression Methods for Low-Frequency Pressure Fluctuations in Open-Jet Wind Tunnels

by Ling Jin, Xiao Bing Deng, Xunnian Wang, Junlong Zhang and Weiping Zeng

Appl. Sci. 2023, 13(19), 10808; https://doi.org/10.3390/app131910808 - 28 Sep 2023

Cited by 1 | Viewed by 1601

Abstract

Low-frequency pressure fluctuations are common in open-jet wind tunnels, affecting test accuracy and posing safety risks to the wind tunnels. These oscillations can be caused by different mechanisms in different wind tunnels, and it is often necessary to identify the specific mechanism responsible for the oscillation and develop appropriate control methods. This paper presents a comprehensive review of the current state of research on low-frequency pressure fluctuations in subsonic open-jet wind tunnels, with a particular emphasis on their generation mechanisms and control strategies. The primary source of excitation is attributed to the edgetone feedback formed by the impingement of the jet on the collector. The sound wavelength corresponding to the edgetone frequency is close to that of the plenum scale, facilitating resonance with both plenum-associated vibration modes and specific-order standing wave modes within the circuit loop, resulting in significant low-frequency pulsations. Passive control methods such as nozzle vortex generators and collector breathing gaps have been extensively employed due to their cost-effectiveness and efficiency. The concluding section highlights some unresolved issues that require further investigation in this field. Full article

(This article belongs to the Special Issue Theoretical, Computational and Experimental Fluid Dynamics: Methods and Advanced Applications)

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