Fluids最新文献

{"title":"Editorial Summary: Boundary Layer Processes in Geophysical/Environmental Flows","authors":"Joseph Kuehl","doi":"10.3390/fluids8100279","DOIUrl":"https://doi.org/10.3390/fluids8100279","url":null,"abstract":"Boundary layer processes play a crucial role in establishing the circulation patterns of the oceans and atmosphere, significantly affecting both regional and global climate, as well as the distributions of heat, nutrients, species, pollutants and more [...]","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135730368","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":"Surface Roughness in RANS Applied to Aircraft Ice Accretion Simulation: A Review","authors":"Kevin Ignatowicz, François Morency, Héloïse Beaugendre","doi":"10.3390/fluids8100278","DOIUrl":"https://doi.org/10.3390/fluids8100278","url":null,"abstract":"Experimental and numerical fluid dynamics studies highlight a change of flow structure in the presence of surface roughness. The changes involve both wall heat transfer and skin friction, and are mainly restricted to the inner region of the boundary layer. Aircraft in-flight icing is a typical application where rough surfaces play an important role in the airflow structure and the subsequent ice growth. The objective of this work is to investigate how surface roughness is tackled in RANS with wall resolved boundary layers for aeronautics applications, with a focus on ice-induced roughness. The literature review shows that semi-empirical correlations were calibrated on experimental data to model flow changes in the presence of roughness. The correlations for RANS do not explicitly resolve the individual roughness. They principally involve turbulence model modifications to account for changes in the velocity and temperature profiles in the near-wall region. The equivalent sand grain roughness (ESGR) approach emerges as a popular metric to characterize roughness and is employed as a length scale for the RANS model. For in-flight icing, correlations were developed, accounting for both surface geometry and atmospheric conditions. Despite these research efforts, uncertainties are present in some specific conditions, where space and time roughness variations make the simulations difficult to calibrate. Research that addresses this gap could help improve ice accretion predictions.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136185075","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":"Using Computation Fluid Dynamics to Determine Oil Droplet Breakup Parameters during Emulsion Atomization with Pressure Swirl Nozzles","authors":"Miguel Ángel Ballesteros Martínez, Volker Gaukel","doi":"10.3390/fluids8100277","DOIUrl":"https://doi.org/10.3390/fluids8100277","url":null,"abstract":"A wide range of commercial powdered products are manufactured by spray drying emulsions. Some product properties are dependent on the oil droplet size, which can be affected by fluid mechanics inside the spray nozzle. However, most of the key flow parameters inside the nozzles are difficult to measure experimentally, and theoretical estimations present deviations at high shear rates and viscosities. Therefore, the purpose of this study was to develop a computational model that could represent the multiphase flow in pressure swirl nozzles and could determine the deformation stresses and residence times that oil droplets experience. The multiphase flow was modelled using the Volume-of-Fluid method under a laminar regime. The model was validated with experimental data using the operating conditions and the spray angle. The numerically calculated shear stresses were found to provide a better prediction of the final oil droplet size than previous theoretical estimations. A two-step breakup mechanism inside of the nozzle was also proposed. Additionally, some of the assumptions used in the theoretical estimations could not be confirmed for the nozzles investigated: No complete air core developed inside of the nozzle during atomization, and the shear stress at the nozzle outlet is not the only stress that can affect oil droplet size. Elongation stresses cannot be neglected in all cases.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135804380","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":"Numerical Study of the Influence of the Critical Reynolds Number on the Aerodynamic Characteristics of the Wing Airfoil","authors":"Anna Utkina, Andrey Kozelkov, Roman Zhuchkov, Dmitry Strelets","doi":"10.3390/fluids8100276","DOIUrl":"https://doi.org/10.3390/fluids8100276","url":null,"abstract":"The paper reports the results of a study concerned with the influence of the size of the leading edge laminar bubble on the aerodynamic characteristics of the HGR01 airfoil. The completely turbulent and transient flows are considered. The mechanism of the appearance and interaction of laminar and turbulent flow separation near the leading and trailing edges of the airfoil is studied in detail. In the paper, the dependence of aerodynamic forces on the critical Reynolds number for the HGR01 airfoil is discussed. It has been established that the separation bubble at the leading edge can only be obtained using the laminar–turbulent transition model. Fully turbulent models are not able to show this feature of the airfoil flow. Graphs of the lift coefficient as a function of the critical Reynolds number, as well as the pressure distribution as a function of the size of the laminar bubble, are shown.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135858824","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":"Pipe Flow of Suspensions of Cellulose Nanocrystals","authors":"Saumay Kinra, Rajinder Pal","doi":"10.3390/fluids8100275","DOIUrl":"https://doi.org/10.3390/fluids8100275","url":null,"abstract":"The pipeline flow behavior of suspensions of cellulose nanocrystals (CNCs) was investigated over the CNC concentration range of 0.24 to 3.65 wt% in different diameter pipelines. The CNC suspensions were Newtonian below the CNC concentration of 1 wt%. At higher concentrations, the CNC suspensions were non-Newtonian power-law fluids. For Newtonian CNC suspensions, the experimental friction factor–Reynolds number data were obtained only in the turbulent regime, and the data followed the Blasius equation closely. For power-law CNC suspensions, the experimental data of friction factor–Reynolds number covered both laminar and turbulent regimes. The experimental data followed the friction factor–Reynolds number relationships for power-law fluids reasonably well.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135967745","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":"Evaluation of Turbulence Models in Unsteady Separation","authors":"Claire Yeo MacDougall, Ugo Piomelli, Francesco Ambrogi","doi":"10.3390/fluids8100273","DOIUrl":"https://doi.org/10.3390/fluids8100273","url":null,"abstract":"Unsteady separation is a phenomenon that occurs in many flows and results in increased drag, decreased lift, noise emission, and loss of efficiency or failure in flow devices. Turbulence models for the steady or unsteady Reynolds-averaged Navier–Stokes equations (RANS and URANS, respectively) are commonly used in industry; however, their performance is often unsatisfactory. The comparison of RANS results with experimental data does not clearly isolate the modeling errors, since differences with the data may be due to a combination of modeling and numerical errors, and also to possible differences in the boundary conditions. In the present study, we use high-fidelity large-eddy simulation (LES) results to carry out a consistent evaluation of the turbulence models. By using the same numerical scheme and boundary conditions as the LES, and a grid on which grid convergence was achieved, we can isolate modeling errors. The calculations (both LES and RANS) are carried out using a well-validated, second-order-accurate code. Separation is generated by imposing a freestream velocity distribution, that is modulated in time. We examined three frequencies (a rapid, flutter-like oscillation, an intermediate one in which the forcing and the flow have the same timescales, and a quasi-steady one). We also considered three different pressure distributions, one with alternating favorable and adverse pressure gradients (FPGs and APGs, respectively), one oscillating between an APG and a zero-pressure gradient (ZPG), and one with an oscillating APG. All turbulence models capture the general features of this complex unsteady flow as well or better than in similar steady cases. The presence, during the cycle, of times in which the freestream pressure-gradient is close to zero affects significantly the model performance. Comparing our results with those in the literature indicates that numerical errors due to the type of discretization and the grid resolution are as significant as those due to the turbulence model.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135253242","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":"Unveiling the Potential of Cavitation Erosion-Induced Heavy Crude Oil Upgrading","authors":"Gadel F. Baimukhametov, Aydar A. Kayumov, Aleksey V. Dengaev, Alexander F. Maksimenko, Denis A. Marakov, Vladimir A. Shishulin, Ilya M. Drozdov, Larisa V. Samuylova, Andrey A. Getalov, Firdavs A. Aliev, Alexey V. Vakhin","doi":"10.3390/fluids8100274","DOIUrl":"https://doi.org/10.3390/fluids8100274","url":null,"abstract":"The application of ultrasonic waves in the processing of hydrocarbons is a new promising technology that has developed rapidly in recent years. However, the acoustic-induced cavitation erosion phenomenon is poorly studied. In this paper, a comparison study of cavitation erosion was carried out in water and oils with different viscosities produced from Ashal’cha and North Komsomol using an ultrasonic reactor operating at an industrial frequency of 20 kHz. The acoustic spectra obtained from hydrophones during the ultrasonic treatment of fluids can be characterized by using subharmonics of the main frequency and a continuous white noise level. Moreover, the cavitation erosion of aluminum foil under various ultrasound irradiation times and power levels was thoroughly investigated. It has been found that the process of ultrasonic cavitation has a less erosive impact on metal foil in oil due to its high viscosity. In addition, the formation of microflows in the oil phase, which also intensify the erosion process, is hindered. Cavitation erosion in the Ashal’cha oil sample exhibited a higher intensity compared to that in the North Komsomol oil sample. It was found that upon increasing ultrasound intensity in the case of the viscous (Ashal’cha) oil sample, cavitation stability was disrupted. In turn, this led to a reduction in the collapse energy of the cavitation bubbles. The results we obtained enable the assessment of cavitation erosion in crude oil and could be used to improve methodologies for monitoring and optimizing cavitation processes in crude oil.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135593795","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":"Blood Flow Simulation of Aneurysmatic and Sane Thoracic Aorta Using OpenFOAM CFD Software","authors":"Francesco Duronio, Andrea Di Mascio","doi":"10.3390/fluids8100272","DOIUrl":"https://doi.org/10.3390/fluids8100272","url":null,"abstract":"Cardiovascular diseases still represent one of the most deadly pathologies worldwide. Knowledge of the blood flow dynamics within the cardio-vascular system is crucial in preventing these diseases and analysing their physiology and physio-pathology. CFD simulations are highly effective in guiding clinical predictions and, more importantly, allow the evaluation of physical and clinical parameters that are difficult to measure with common diagnostic techniques. Therefore, in particular, this study is focused on investigating the hemodynamics of the thoracic aorta. Real aortic geometries regarding a sane and diseased patient presenting an aneurysm were considered. CFD simulations were performed with the OpenFOAM C++ library using patient-specific pulsatile blood flow waveforms and implementing the Windkessel pressure boundary condition for the artery outflow. The adopted methodology was preliminarily verified for assessing the numerical uncertainty and convergence. Then, the CFD results were evaluated against experimental data concerning pressure and velocity of the thoracic aorta measured with standard diagnostic techniques. The normal aorta’s blood flow was also compared against the pattern regarding the patient-specific aortic aneurysm. Parameters such as wall pressure, wall shear stress (WSS) and velocity distribution were investigated and discussed. The research highlighted that the blood flow in the aorta is strongly affected by the aneurysm onset, with the growth of recirculation zones being potentially hazardous. The outcomes of the investigation finally demonstrate how CFD simulation tools, capturing the detailed physics of the aortic flow, are powerful tools for supporting clinical activities of the cardio-vascular system.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135895698","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":"Design of a Cryogenic Duplex Pressure-Swirl Atomizer through CFDs for the Cold Conservation of Marine Products","authors":"Eduardo Ayala, Diego Rivera, Julio Ronceros, Nikolai Vinces, Gustavo Ronceros","doi":"10.3390/fluids8100271","DOIUrl":"https://doi.org/10.3390/fluids8100271","url":null,"abstract":"The following article proposes the design of a bi-centrifugal atomizer that allows the interaction of sprays from two fluids (water and liquid nitrogen). The liquid nitrogen (LN2) is below −195.8 °C, a temperature low enough for the nitrogen, upon contact with the atomized water, to cause heat loss and bring it to its freezing point. The objective is to convert the water droplets present in the spray into ice. Upon falling, the ice particles can be dispersed, covering the largest possible area of the seafood products intended for cold preservation. All these phenomena related to the interaction of two fluids and heat exchange are due to the bi-centrifugal atomizer, which positions the two centrifugal atomizers concentrically, resulting in the inevitable collision of the two sprays. Each of these atomizers will be designed using a mathematical model and CFDs tools. The latter will provide a better study of the flow behavior of both fluids inside and outside the bi-centrifugal atomizer. Hence, the objective revolves around confirming the validity of the mathematical model through a comparison with numerical simulation data. This comparison establishes a strong correlation (with a maximum variance of 1.94% for the water atomizer and 10% for the LN2 atomizer), thereby ensuring precise manufacturing specifications for the atomizers. It is important to highlight that, in order to achieve the enhanced resolution and comprehension of the fluid both inside and outside the duplex atomizer, two types of meshes were utilized, ensuring the utilization of the optimal option. Similarly, the aforementioned meshes were generated using two distinct software platforms, namely ANSYS Meshing (tetrahedral mesh) and ANSYS ICEM (hexahedral mesh), to facilitate a comparative analysis of the mesh quality obtained. This comprehension facilitated the observation of water temperature during its interaction with liquid nitrogen, ultimately ensuring the freezing of water droplets at the atomizer’s outlet. This objective aligns seamlessly with the primary goal of this study, which revolves around the preservation of seafood products through cold techniques. This particular attribute holds potential for various applications, including cooling processes for food products.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135459344","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":"The Effects of Flexible Cylinder Structural Dynamics to the near Wake Turbulence","authors":"Sharul Sham Dol, Siaw Khur Wee, Tshun Howe Yong, Shaharin Anwar Sulaiman","doi":"10.3390/fluids8100270","DOIUrl":"https://doi.org/10.3390/fluids8100270","url":null,"abstract":"The utilization of a rigid and projecting surface, coupled with an agitator and vortex generator, frequently results in the dissipation of more energy than the production of turbulence that meets the required criteria. By contrast, a passively oscillating flexible protruding surface can generate a greater turbulence level. In the current study, a circular finite cylinder (cantilever) was used as the geometry of the rigid and protruding surface. Both the material and the aspect ratio were varied. Also, a local Reynolds number within the subcritical flow range (102 < ReD < 105) was considered. The results from the rigid protruding surface (finite cylinder) serve as a validation of the published results and a benchmark for the improvement of the turbulence generated by the flexible protruding surface. The results obtained via an ultrasonic velocity profiler have further demonstrated that the flexible cylinder is capable of generating greater turbulence by examining the turbulence intensity, the turbulence production term and the Reynolds stress. All the flexible cylinders that oscillate show an increase in turbulence production but at different percentages. The cylinders studied in this work ranged from the least structural stiffness (EVA) to moderate (aluminum) and the highest structural stiffness (carbon steel). Through studying the normalized amplitude responses graph for the flexible cylinders, it is found that the oscillating motion does indeed contribute to the increment. A further examination of the results shows that the increase is due to the structural velocity instead of just the oscillating motion.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135459596","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}