WSEAS TRANSACTIONS ON FLUID MECHANICS最新文献

{"title":"Computing a Class of Blow-up Solutions for the Navier-Stokes Equations","authors":"C. Boldrighini, S. Frigio, P. Maponi, A. Pellegrinotti","doi":"10.37394/232013.2024.19.23","DOIUrl":"https://doi.org/10.37394/232013.2024.19.23","url":null,"abstract":"The three-dimensional incompressible Navier-Stokes equations play a fundamental role in a large number of applications to fluid motions, and a large amount of theoretical and experimental studies were devoted to it. Our work is in the context of the Global Regularity Problem, i.e., whether smooth solutions in the whole space R3 can become singular (“blow-up”) in a finite time. The problem is still open and also has practical importance, as the singular solutions would describe new phenomena. Our work is mainly inspired by a paper of Li and Sinai, who proved the existence of a blow-up for a class of smooth complex initial data. We present a study by computer simulations of a larger class of complex solutions and also of a related class of real solutions, which is a natural candidate for evidence of a blow-up. The numerical results show interesting features of the solutions near the blow-up time. They also show some remarkable properties for the real flows, such as a sharp increase of the total enstrophy and a concentration of high values of velocities and vorticity in small regions.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"28 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141926124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Wavy Interface on Natural Convection in Square Cavity Partially Filled with Nanofluid and Porous Medium using Buongiorno Model","authors":"Cherifa Benygzer, M. Bouzit, Abderrahem Mokhefi","doi":"10.37394/232013.2024.19.22","DOIUrl":"https://doi.org/10.37394/232013.2024.19.22","url":null,"abstract":"nvective heat transfer improvement from wavy surfaces presents a new solution in industrial engineering for composite materials, including porous medium, and nanofluids to address the wavy irregular surfaces in heat transfer devices such as a wavy solar collector, energy absorption and filtration, thermal insulation, and geothermal power plants. This technique enables the performance of engineering applications. The numerical study is performed to examine the effects of a wavy interface separating two layers in the enclosure on heat exchange rates. This paper investigates numerically the natural convection flow in a square cavity partially filled with nanofluid-porous layers separated by a wavy horizontal interface. The left and right walls of the cavity are maintained at constant hot and cold temperatures, whereas the other walls are adiabatic. The Buongiorno model is used to describe nanofluid motion, taking into account the brownian and thermophoresis effects in the cavity. The Galerkin finite element method was applied to solve the differential governing equations. The dynamic, thermal field and heat transfer have been analyzed for various parameters such as Rayleigh number (10^3 ≤ Ra ≤ 10^6), the amplitude of interface (0 ≤ A ≤ 0.1), and undulation number (0 ≤ n ≤ 9). The results reveal that the flow intensity induced by buoyancy forces is more significant in the nanofluid layer than in the porous layer, since the heat transfer is enhanced while the flow is not sensitive to variations in amplitude and number undulation, and accordingly, the decline of average Nusselt and Sherwood numbers is insignificant. The effects of controlled parameters on the structure of nanofluid flow, heat, and mass transfer rate are insignificant.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"4 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141268011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improvement of Aerodynamic Performance of NACA 2412 Airfoil using Active and Passive Control Techniques","authors":"Paramesh T., Tshering Tenzin, Mohammad Sarwar, Ahmad Mujeeb Azizi, Habte Getaneh, Tamal Jana","doi":"10.37394/232013.2024.19.20","DOIUrl":"https://doi.org/10.37394/232013.2024.19.20","url":null,"abstract":"The study of aerodynamic characteristics plays a crucial role in the design and performance evaluation of various airfoil profiles. In this study, a comprehensive investigation of the modified NACA 2412 airfoil has been carried out, focusing on its aerodynamic characteristics and performance. To improve the aerodynamic characteristics and to delay the stall, active and passive control techniques are introduced. The computational investigation is carried out using commercial software Ansys Fluent. Especially, the Reynolds-Averaged Navier Stokes (RANS) equation is numerically computed employing the K-omega SST turbulence model. The active control is implemented using four microjets, each having diameters of 3 mm, 4 mm, and 5 mm, placed upstream of the flow separation location of the uncontrolled airfoil. The jet exit velocity is maintained the same as the freestream flow velocity. For each case, the tangential orientations of the jets are varied from 2 to 10 degrees with an increment of 2 degrees. Besides, the impact of jet separation distance is also evaluated. On the other hand, the passive control method is introduced by deploying vortex generators (VG) with varying heights of 2 mm, 3 mm, and 4 mm, placed upstream of the separation location. Aerodynamic characteristics, including Lift, Drag, and Stall angle, are measured to assess performance. The study reveals that microjets with a diameter of 5 mm at a 2-degree tangential orientation perform best with a maximum of 11.33% increase in lift coefficient (Cl). For all the three sizes of microjets, the drag coefficients (Cd) are minimum for 2-degree tangential orientation. Besides, the vortex generator of height 2 mm demonstrates superior performance with a maximum of 4% increase in lift coefficient. For both cases, the stall angle of the airfoil is delayed by 28.57%. In addition, except 2mm height of the vortex generator, all other vortex generators lead to an increase in drag coefficient. Importantly, the microjets are proved to be more efficient than the vortex generator in delaying the flow separation thereby reducing the drag and increasing the aerodynamic efficiency of the airfoil.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"11 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140979992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bioinspired Genetic-Algorithm Optimized Ground-Effect Wing Design: Flight Performance Benefits and Aircraft Stability Effects","authors":"Karl Zammit, Howard Smith, Noel Sierra Lobo, Ioannis K. Giannopoulos","doi":"10.37394/232013.2024.19.19","DOIUrl":"https://doi.org/10.37394/232013.2024.19.19","url":null,"abstract":"This paper presents a bioinspired, genetic-algorithm evolutionary process for Ground-Effect vehicle wing design. The study made use of a rapid aerodynamic model generation and results evaluation computational fluid dynamics vortex lattice method software, supervised by a genetic algorithm optimization Python script. The design space for the aircraft wing parametric features drew inspiration from seabirds, under the assumption of their wings being naturally evolved and partially optimized for proximity flight over water surfaces. A case study was based on the A-90 Orlyonok Russian Ekranoplan, where alternative bioinspired wing variations were proposed. The study objective was to investigate the possible increased flight aircraft performance when using bioinspired wings, as well as verify the static and dynamic aircraft stability compliance for Ground-Effect flight. The methodology presented herein along with the study results, provided an incremental step towards advancing Ground-Effect aircraft conceptual designs using computational fluid dynamics.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"71 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141019207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Three-dimensional Effects on Gap-Resonances in Twin-Hull Vessels in Time-Harmonic Vertical Oscillations","authors":"G. Vernengo","doi":"10.37394/232013.2024.19.18","DOIUrl":"https://doi.org/10.37394/232013.2024.19.18","url":null,"abstract":"Three-dimensional effects induced by dimensional ratios on the gap resonances happening in twin hull vessels oscillating in forced vertical motion have been analyzed. They can lead to relevant consequences, such as the amplification of the inner radiated waves or the generation of standing waves in between the demi-hulls, that can have a direct effect on the operating profile of the vessel. The response of twin hull vessels in waves can be strongly affected by these resonant phenomena. Also, some of these behaviors can be exploited in the framework of wave energy conversion systems. The present analysis is carried out by using an open-source, linear, Boundary Element Method (BEM), based on the Green function approach. Mathematical backgrounds of the added mass and damping coefficients computation for a floating body under harmonic vertical oscillation are provided as well as details of the numerical discretization used in the BEM. A panel mesh sensitivity study is carried out and the numerical prediction is validated by comparison against available experimental data, another CFD solution obtained by a high-fidelity viscous solver based on the open-source libraries Open-FOAM and approximate analytic formulations. The effect of the beam ratio and the length-to-beam ratio on the resonant phenomena has been analyzed. This has been achieved by systematic variations of the geometric dimensions of the hull, focusing on the trends of the hydrodynamic coefficients, the amplitude of the radiated waves, and the location of the resonant frequencies over the analyzed range.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"44 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141022468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational Simulation of Wind Loads on Three Curved Eave Models with Different Height-Width Relationships","authors":"Guilherme S. Teixeira, Leonardo G. Teodoro Júnior, Marco D. Campos","doi":"10.37394/232013.2024.19.12","DOIUrl":"https://doi.org/10.37394/232013.2024.19.12","url":null,"abstract":"This work deals with the effects of wind loads on two industrial shed models with curved eaves aspect of different height-to-width ratios. Using Ansys Workbench software, the external pressure coefficients for the entire roof by applying refinement levels were determined. Also were studied the quality of the unstructured and tetrahedral grid according to recommendations to ensure greater efficiency in the simulation results. The results generated provided evidence that the wind in the transverse direction is more damaging in the windward region: for a wind at 45º the most critical region appeared both windward and leeward in the model with a ratio of h/b=0.5 (Model 1) and to windward in the models with a ratio of h/b=1 (Model 2) and h/b=1.5 (Model 3). The leeward suctions increased due to the reduction in the height-width ratio considering a wind direction of 45º. The increase in this ratio intensified the values of the external pressure coefficients in the windward region for the 90º wind direction.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"93 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140250765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transient MHD Fluid Flow Past a Moving Vertical Surface in a Velocity Slip Flow Regime","authors":"Ighoroje W. A. Okuyade, T. M. Abbey","doi":"10.37394/232013.2024.19.10","DOIUrl":"https://doi.org/10.37394/232013.2024.19.10","url":null,"abstract":"The problem of unsteady MHD fluid flow past a moving vertical surface in a slip flow regime is presented. The model is built on the assumption that the flow is naturally convective with oscillating time-dependent and exponentially decaying suction and permeability, double-diffusion, viscous dissipation, and temperature gradient-dependent heat source, and non-zero tangential velocity at the wall; the fluid is viscous, incompressible, Newtonian, chemically reactive, and magnetically susceptible; the surface is porous, and electrically conductive, and thermally radiative. The governing partial differential equations are highly coupled and non-linear. For easy tractability, the equations are reduced to one-dimensional using the one-dimensional unsteady flow theory. The resulting equations are non-dimensionalized and solved using the time-dependent perturbation series solutions, and the Modified Homotopy Perturbation Method (MHPM). The solutions of the concentration, temperature, velocity, rates of mass and heat diffusion, and wall shear stress are obtained, computed, and presented graphically and quantitatively, and analyzed. The results among others, show that the increase in the: Schmidt number increases the fluid concentration, velocity, the rate of heat transfer to the fluid, and the stress on the wall, but decreases the rate of mass transfer to the fluid; Magnetic field parameter decreases the fluid velocity and stress on the wall; Slip parameter increases the flow velocity, but decreases the stress on the wall; Permeability parameter increases the flow velocity and the stress on the wall. These results are benchmarked with the reports in existing literature and they agree.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"16 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140260945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Propagation of Waves in a Fluid in a Thin Elastic Cylindrical Shell","authors":"Durdimurod Durdiyev, I. Safarov, M. Teshaev","doi":"10.37394/232013.2024.19.11","DOIUrl":"https://doi.org/10.37394/232013.2024.19.11","url":null,"abstract":"The oscillatory process of a viscoelastic shell of a cylindrical tipe filled with a liquid is considered. Unlike other works, this paper focuses on the viscoelastic properties of a cylindrical shell and a liquid. Differential equations for joint vibrations of a shell and liquid are obtained by the equations of a thin shell that satisfies the Kirchhoff–Love hypotheses, and the equations of motion of a viscous liquid obey the Navier–Stokes equation. After simple transformations, the integro-differential equations are reduced to ordinary differential equations and solved using Godunov's orthogonal run method combined with Muller's method. Based on the developed algorithm, natural frequencies and corresponding vibration modes were obtained. For steady-state oscillations, all eigenvalues and eigenmodes turned out to be complex. For the first time, it was found that the damping coefficient branches out after certain values of wave numbers. It was found that the motion in a cylindrical shell is localized on the surface of the shell. At slow localization, starting from a certain wave number, the natural oscillations become aperiodic.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"4 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140262251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unsteady Compressed Williamson Fluid Flow Behavior under the Influence of a Fixed Magnetic Field (Numerical Study)","authors":"A. El Harfouf, Rachid Herbazi, S. Mounir, H. Mes-Adi, A. Wakif","doi":"10.37394/232013.2024.19.8","DOIUrl":"https://doi.org/10.37394/232013.2024.19.8","url":null,"abstract":"A numerical investigation is conducted into a two-dimensional mathematical model of magnetized unsteady incompressible Williamson fluid flow over a sensor surface with fixed thermal conductivity and external squeezing accompanied by viscous dissipation effect. Based on the flow geometry under consideration, the current flow model was created. The momentum equation takes into consideration the magnetic field when describing the impact of Lorentz forces on flow behavior. The energy equation takes varying thermal conductivity into account while calculating heat transmission. The extremely complex nonlinear, unstable governing flow equations for the now under investigation are coupled in nature. Due to the inability of analytical or direct methods, the Runge-Kutta scheme (RK-4) via similarity transformations approach is used to tackle the physical problem under consideration. The physical behavior of various control factors on the flow phenomena is described using graphs and tables. For increasing values of the Weissenberg parameter and the permeable velocity parameter, the temperature boundary layer thickens. As the permeable velocity parameter and squeezed flow index increased, the velocity profile shrank. The velocity profile grows as the magnetic number rises. Squeezed flow magnifying increases the Nusselt number's magnitude. Furthermore, the extremely complex nonlinear complex equations that arise in fluid flow issues are quickly solved by RK-4. The current findings in this article closely align with the findings that have been reported in the literature.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"11 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140409919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A study for an Optimization of Cutting Fluids in Machining Operations by TOPSIS and Shannon Entropy Methods","authors":"Pankaj Prasad Dwivedi, Dilip Kumar Sharma","doi":"10.37394/232013.2024.19.9","DOIUrl":"https://doi.org/10.37394/232013.2024.19.9","url":null,"abstract":"Cutting fluids are used in machining processes to increase the quality of machined surfaces, extend the life of tools, and lessen the effect of friction and heat on contact surfaces. The least costly, least hazardous to the environment, and least poisonous lubricant would be the perfect choice. It should also be resistant to low temperatures, have high lubricating qualities, be recyclable, and have stability against oxidation, hydrolysis, and heat. Its viscosity should also fall between the ideal range and not exceed it. Taking the needed properties of the cutting fluids into consideration, for the machining process choosing the best cutting fluid is essential. Five types of cutting fluids are examined in this paper that are often used in machining operations: canola oil, mineral oil, synthetic ester, PAG (Polyalkylene Glycol), and TMPTO (trimethylolpropane trioleate). In this study, the Multicriteria decision-making (MCDM) techniques were used to identify the best choice of cutting fluids based on several parameters, such as low temperature, toxicity, lubricating ability, hydrolytic stability, thermal stability, viscosity index, oxidative stability, and cost. The most popular TOPSIS methods and Shannon's Entropy were utilized to choose these cutting fluids optimally. The TOPSIS approach is used to calculate the final ranking, and Shannon’s entropy method is utilized to calculate the weight of the criterion. According to the result with the more lucid rating, PAG cutting fluid was shown to be the most effective, followed by synthetic ester in second place, as well as last place achieved by vegetable-based canola oil.","PeriodicalId":510564,"journal":{"name":"WSEAS TRANSACTIONS ON FLUID MECHANICS","volume":"28 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140412358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}