Pub Date : 2024-10-15DOI: 10.1016/j.euromechflu.2024.10.006
Ian G.B. Adams , Julian Simeonov , Carley Walker
Euler–Lagrange simulations of particle-laden flow require hydrodynamic models of drag and lift forces for individual particles. Our goal is to develop models that can prescribe these forces for arbitrarily orientated shell objects. Here, we use computational fluid dynamics simulations of steady bottom-boundary layer flow over a series of spherical triangle shell fragments to calculate the hydrodynamic forces. The simulations explicitly resolve the wall boundary layers using grid resolution on the order of at the shell fragment surface and use the SST k-omega turbulence closure model. These fragments cover a range of aspect ratio and flatness characteristics. The shell fragments are generated as triangular selections of a spherical shell with azimuthal and longitudinal angles proscribed based on elongation and flatness parameters (varying between 1 to 5, and 0.02 to 0.2 respectively), while characteristic length of the fragment is held constant to define the overall fragment size. Fragment orientations are considered with independently varying pitch, roll, and yaw each ranging from 0 to 180 degrees. The numerical estimates for the forces from all simulations were used to develop robust parameterizations of the drag and lift as a function of aspect ratio and flatness characteristics, as well as orientation of the shell fragments.
{"title":"Hydrodynamic force coefficients for spherical triangle shell fragments: Dependence on the aspect ratio and flatness","authors":"Ian G.B. Adams , Julian Simeonov , Carley Walker","doi":"10.1016/j.euromechflu.2024.10.006","DOIUrl":"10.1016/j.euromechflu.2024.10.006","url":null,"abstract":"<div><div>Euler–Lagrange simulations of particle-laden flow require hydrodynamic models of drag and lift forces for individual particles. Our goal is to develop models that can prescribe these forces for arbitrarily orientated shell objects. Here, we use computational fluid dynamics simulations of steady bottom-boundary layer flow over a series of spherical triangle shell fragments to calculate the hydrodynamic forces. The simulations explicitly resolve the wall boundary layers using grid resolution on the order of <span><math><mrow><msub><mrow><mi>y</mi></mrow><mrow><mo>+</mo></mrow></msub><mo>=</mo><mn>1</mn></mrow></math></span> at the shell fragment surface and use the SST k-omega turbulence closure model. These fragments cover a range of aspect ratio and flatness characteristics. The shell fragments are generated as triangular selections of a spherical shell with azimuthal and longitudinal angles proscribed based on elongation and flatness parameters (varying between 1 to 5, and 0.02 to 0.2 respectively), while characteristic length of the fragment is held constant to define the overall fragment size. Fragment orientations are considered with independently varying pitch, roll, and yaw each ranging from 0 to 180 degrees. The numerical estimates for the forces from all simulations were used to develop robust parameterizations of the drag and lift as a function of aspect ratio and flatness characteristics, as well as orientation of the shell fragments.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 213-224"},"PeriodicalIF":2.5,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present research aims to study cavitating flow around a CLARK-Y 11.7 % hydrofoil with variable angles of attack (α) while maintaining controlled levels of dissolved air in the operating fluid, which is water. A series of experiments were conducted using a water tunnel facility, where the cavitation characteristics were measured and observed using sensors and high-speed imaging techniques. The variables studied in the present work are cavitation number (1 ≤ σ ≤ 2.2) and angle of attack (α = 4°, 6°, 8°, 10°, and 12°), with dissolved air levels (DAL) in the range of 9.3 ppm to 13.1 ppm. The dimensionless cavity length decreases significantly with increasing values of σ/α, indicating an inverse relationship where higher cavitation numbers or lower angles of attack result in shorter cavities. The cavity length follows a power-law scaling relationship, with the empirical equation .Increasing the angle of attack transitions the cavitation nature from stable (Mode I) to dynamic (Mode II) and highly oscillating (Mode III). Larger cavities result in lower Strouhal numbers, which indicates reduced vortex shedding activity. The relationship between the Strouhal number and the normalized cavitation number σ/α is characterized by the power-law equation . The pressure coefficient at the leading-edge increases with the angle of attack at low cavitation numbers, while higher cavitation numbers lead to greater pressure coefficient differences between the leading and trailing edges.
The present study offers an extensive dataset and empirical correlations that may serve as a benchmark framework, which facilitates the validation of computational and experimental models of cavitating flow under similar conditions.
{"title":"Benchmark experimental study on cavitating flow around Clark-Y 11.7 % hydrofoil at various angles of attack under controlled levels of dissolved air","authors":"Emad Hasani Malekshah , Włodzimierz Wróblewski , Mirosław Majkut","doi":"10.1016/j.euromechflu.2024.10.007","DOIUrl":"10.1016/j.euromechflu.2024.10.007","url":null,"abstract":"<div><div>The present research aims to study cavitating flow around a CLARK-Y 11.7 % hydrofoil with variable angles of attack (α) while maintaining controlled levels of dissolved air in the operating fluid, which is water. A series of experiments were conducted using a water tunnel facility, where the cavitation characteristics were measured and observed using sensors and high-speed imaging techniques. The variables studied in the present work are cavitation number (1 ≤ σ ≤ 2.2) and angle of attack (α = 4°, 6°, 8°, 10°, and 12°), with dissolved air levels (DAL) in the range of 9.3 ppm to 13.1 ppm. The dimensionless cavity length decreases significantly with increasing values of σ/α, indicating an inverse relationship where higher cavitation numbers or lower angles of attack result in shorter cavities. The cavity length follows a power-law scaling relationship, with the empirical equation <span><math><mrow><mrow><msub><mrow><mi>L</mi></mrow><mrow><mi>max</mi></mrow></msub></mrow><mo>/</mo><mrow><mi>C</mi></mrow></mrow><mo>=</mo><mn>4.78</mn><mo>×</mo><msup><mrow><mfenced><mrow><mrow><mi>σ</mi></mrow><mo>/</mo><mrow><mi>α</mi></mrow></mrow></mfenced></mrow><mrow><mo>−</mo><mn>0.76</mn></mrow></msup></math></span>.Increasing the angle of attack transitions the cavitation nature from stable (Mode I) to dynamic (Mode II) and highly oscillating (Mode III). Larger cavities result in lower Strouhal numbers, which indicates reduced vortex shedding activity. The relationship between the Strouhal number and the normalized cavitation number σ/α is characterized by the power-law equation <span><math><mrow><mi>St</mi><mo>=</mo><mn>0.041</mn><mo>×</mo><msup><mrow><mfenced><mrow><mrow><mi>σ</mi></mrow><mo>/</mo><mrow><mi>α</mi></mrow></mrow></mfenced></mrow><mrow><mn>0.3</mn></mrow></msup></mrow></math></span>. The pressure coefficient at the leading-edge increases with the angle of attack at low cavitation numbers, while higher cavitation numbers lead to greater pressure coefficient differences between the leading and trailing edges.</div><div>The present study offers an extensive dataset and empirical correlations that may serve as a benchmark framework, which facilitates the validation of computational and experimental models of cavitating flow under similar conditions.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 162-169"},"PeriodicalIF":2.5,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.euromechflu.2024.10.003
Saniya Suhail , Koushik Kanti Barman , Sunanda Saha , Chia-Cheng Tsai
The present study deals with the problem of oblique wave scattering by a finite floating elastic plate over a thick porous bed. A potential flow-coupled thin-elastic plate model has been developed, and the wave flow model resembling the physical scenario is framed into a boundary value problem (BVP). A semi-analytical method has been employed to obtain the hydrodynamic coefficients following the numerical and physical illustrations by varying different geometrical parameters. Prior to wave interaction, dispersive roots are thoroughly analyzed, and a critical frequency is observed above which the group velocity is negative. Within this range, minimum reflection and maximum transmission occur due to the high porosity of the seabed. A discontinuous pattern in the reflection coefficient is observed within the blocking range, which mainly exists for high compression. The findings of this work may be highly valuable for Very Large Floating Structures in marine settings, particularly in situations where interactions are primarily influenced by the thick porous beds.
{"title":"Gravity wave interaction with compressive VLFS in the presence of thick porous bed","authors":"Saniya Suhail , Koushik Kanti Barman , Sunanda Saha , Chia-Cheng Tsai","doi":"10.1016/j.euromechflu.2024.10.003","DOIUrl":"10.1016/j.euromechflu.2024.10.003","url":null,"abstract":"<div><div>The present study deals with the problem of oblique wave scattering by a finite floating elastic plate over a thick porous bed. A potential flow-coupled thin-elastic plate model has been developed, and the wave flow model resembling the physical scenario is framed into a boundary value problem (BVP). A semi-analytical method has been employed to obtain the hydrodynamic coefficients following the numerical and physical illustrations by varying different geometrical parameters. Prior to wave interaction, dispersive roots are thoroughly analyzed, and a critical frequency is observed above which the group velocity is negative. Within this range, minimum reflection and maximum transmission occur due to the high porosity of the seabed. A discontinuous pattern in the reflection coefficient is observed within the blocking range, which mainly exists for high compression. The findings of this work may be highly valuable for Very Large Floating Structures in marine settings, particularly in situations where interactions are primarily influenced by the thick porous beds.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 180-198"},"PeriodicalIF":2.5,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-07DOI: 10.1016/j.euromechflu.2024.10.001
Abhishek Kundu , Murugan Thangadurai
The interaction of high peak overpressure blast waves with a circular object placed at two different axial locations from the shock tube exit is studied through numerical simulation using an in-house developed multi-component Navier–Stokes solver. The driver and driven sections of the shock tube were 0.8 m and 6 m, respectively. Helium is used in the driver section, while atmospheric air is used in the driven section and outside the shock tube. The evolution of blast waves inside an open-ended shock tube and its interaction with a rectangular object is reported in Murugan et al.. (2022). Here, the blast wave interacting with a circular object is examined for diaphragm pressure ratios of 13 and 57 by placing the objects at 250 mm and 500 mm from the shock tube exit. The flow field is evaluated through numerical Schlieren, vorticity, density, pressure plots, and the enstrophy plot, which shows the vortical structures that originated in the flow field. The blast load acting on the circular object is calculated for two diaphragm pressure ratios and axial locations. This study helps understand the reflection and diffraction of blast waves and associated flow fields around circular objects used in blast wave attenuation.
{"title":"A Study on the interaction of shock tube-generated blast waves with a circular object at different pressure ratios","authors":"Abhishek Kundu , Murugan Thangadurai","doi":"10.1016/j.euromechflu.2024.10.001","DOIUrl":"10.1016/j.euromechflu.2024.10.001","url":null,"abstract":"<div><div>The interaction of high peak overpressure blast waves with a circular object placed at two different axial locations from the shock tube exit is studied through numerical simulation using an in-house developed multi-component Navier–Stokes solver. The driver and driven sections of the shock tube were 0.8 m and 6 m, respectively. Helium is used in the driver section, while atmospheric air is used in the driven section and outside the shock tube. The evolution of blast waves inside an open-ended shock tube and its interaction with a rectangular object is reported in Murugan et al.. (2022). Here, the blast wave interacting with a circular object is examined for diaphragm pressure ratios of 13 and 57 by placing the objects at 250 mm and 500 mm from the shock tube exit. The flow field is evaluated through numerical Schlieren, vorticity, density, pressure plots, and the enstrophy plot, which shows the vortical structures that originated in the flow field. The blast load acting on the circular object is calculated for two diaphragm pressure ratios and axial locations. This study helps understand the reflection and diffraction of blast waves and associated flow fields around circular objects used in blast wave attenuation.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 145-161"},"PeriodicalIF":2.5,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-02DOI: 10.1016/j.euromechflu.2024.09.006
Adrien Poupardin , Philippe Heinrich
This study investigates the effect of porous coral reef on the tsunami propagation in terms of experimental and numerical modelling. It aims at quantifying the influence of several input parameters on the wave attenuation and at adjusting Manning coefficients to reproduce experimental results. The density and the surface of individual reefs are fixed as well as the width and length of the coral barrier. Results show that the reef height is the most sensitive parameter. This latter affects the tsunami propagation with an attenuation of the first wave reaching 15 % compared to the case with a smooth reef. Wave breaking occurs on the reef flat for each test but, as expected, its location depends greatly on the reservoir depths difference. Numerical simulations show that the Manning coefficient must be adjusted both by considering the coral reef height and the spatial grid resolution. It varies from 0.01 (for lowest reef with highest grid resolution) to 0.058 (for higher reefs with coarsest grid resolution).
{"title":"Adjusting Manning coefficients to simulate tsunami propagation over porous coral reef","authors":"Adrien Poupardin , Philippe Heinrich","doi":"10.1016/j.euromechflu.2024.09.006","DOIUrl":"10.1016/j.euromechflu.2024.09.006","url":null,"abstract":"<div><div>This study investigates the effect of porous coral reef on the tsunami propagation in terms of experimental and numerical modelling. It aims at quantifying the influence of several input parameters on the wave attenuation and at adjusting Manning coefficients to reproduce experimental results. The density and the surface of individual reefs are fixed as well as the width and length of the coral barrier. Results show that the reef height is the most sensitive parameter. This latter affects the tsunami propagation with an attenuation of the first wave reaching 15 % compared to the case with a smooth reef. Wave breaking occurs on the reef flat for each test but, as expected, its location depends greatly on the reservoir depths difference. Numerical simulations show that the Manning coefficient must be adjusted both by considering the coral reef height and the spatial grid resolution. It varies from 0.01 (for lowest reef with highest grid resolution) to 0.058 (for higher reefs with coarsest grid resolution).</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 131-144"},"PeriodicalIF":2.5,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-26DOI: 10.1016/j.euromechflu.2024.09.005
Zhifei Cui , Mingliang Qi , Qiyu Ma , Diangui Huang
There are two modes of traveling wave motion, traveling wave propulsion and traveling wave energy absorption. In this paper, a two-dimensional flexible traveling wave plate is taken as the research object. The characteristic length and characteristic parameter of traveling wave motion are determined by numerical simulation, and the parametric study of the traveling wave motion in energy absorption mode is conducted. The effects of dimensionless amplitude and dimensionless wave velocity on the energy absorption characteristics of flexible traveling wave plate are analyzed, and the mechanism of traveling wave energy absorption is revealed. The results show that the larger the dimensionless amplitude is, the stronger the work capacity of the traveling wave plate becomes, while the absolute amplitude or absolute wavelength has little effect on the work capacity of the traveling wave plate. Under different waveforms, the work capacity of the traveling wave plate increases first and then decreases as the dimensionless wave velocity increases. Within the parameter range studied in this article, when the dimensionless amplitude is 0.2 and the dimensionless wave velocity is 0.5, the traveling wave plate can achieve an energy absorption efficiency of about 40 %.
{"title":"Parametric study of traveling wave motion in energy absorption mode","authors":"Zhifei Cui , Mingliang Qi , Qiyu Ma , Diangui Huang","doi":"10.1016/j.euromechflu.2024.09.005","DOIUrl":"10.1016/j.euromechflu.2024.09.005","url":null,"abstract":"<div><div>There are two modes of traveling wave motion, traveling wave propulsion and traveling wave energy absorption. In this paper, a two-dimensional flexible traveling wave plate is taken as the research object. The characteristic length and characteristic parameter of traveling wave motion are determined by numerical simulation, and the parametric study of the traveling wave motion in energy absorption mode is conducted. The effects of dimensionless amplitude and dimensionless wave velocity on the energy absorption characteristics of flexible traveling wave plate are analyzed, and the mechanism of traveling wave energy absorption is revealed. The results show that the larger the dimensionless amplitude is, the stronger the work capacity of the traveling wave plate becomes, while the absolute amplitude or absolute wavelength has little effect on the work capacity of the traveling wave plate. Under different waveforms, the work capacity of the traveling wave plate increases first and then decreases as the dimensionless wave velocity increases. Within the parameter range studied in this article, when the dimensionless amplitude is 0.2 and the dimensionless wave velocity is 0.5, the traveling wave plate can achieve an energy absorption efficiency of about 40 %.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 116-130"},"PeriodicalIF":2.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-24DOI: 10.1016/j.euromechflu.2024.09.004
L.M. Flores Ramírez, L.P.J. Kamp, H.J.H. Clercx, M. Duran-Matute
In this paper, we report on an investigation of the vertical transport of tracer particles released within a shallow, continuously-forced flow by means of numerical simulations. The investigation is motivated by the shallow flows encountered in many environmental situations and inspired by the laboratory experiments conducted in electromagnetically forced shallow fluid layers. The flow is confined to a thin fluid layer by stress-free top and no-slip bottom walls. The dynamics and the transport properties of the shallow flow are investigated under various flow conditions characterized by a Reynolds number related to the forcing, , and the aspect ratio of vertical and horizontal length scales . The forcing generates an array of vortices that becomes unsteady when . These vortices are accompanied by upwellings in their cores which are surrounded by narrower, stronger downwellings. Hence, upwellings occur where the horizontal flow is vorticity-dominated, while downwellings where it is strain-dominated. The magnitude of the asymmetry in strength and size of the vertical flows and their correlation with horizontal structures depends on the flow conditions and significantly influences the vertical spreading of particles within the fluid volume. Under conditions leading to a large asymmetry, particles within updrafts are transported slowly upwards, while particles within downdrafts rapidly move downwards. In addition, particles are trapped for longer within the updrafts than downdrafts because of their correlation with vorticity-dominated regions. However, when the flow becomes fully three-dimensional and highly unsteady for large values, this transport asymmetry subsides because the updrafts and downdrafts exhibit similar strength and size in such flow conditions. Consequently, similar amounts of particles are transported upwards and downwards at similar rates.
{"title":"Asymmetric vertical transport in weakly forced shallow flows","authors":"L.M. Flores Ramírez, L.P.J. Kamp, H.J.H. Clercx, M. Duran-Matute","doi":"10.1016/j.euromechflu.2024.09.004","DOIUrl":"10.1016/j.euromechflu.2024.09.004","url":null,"abstract":"<div><div>In this paper, we report on an investigation of the vertical transport of tracer particles released within a shallow, continuously-forced flow by means of numerical simulations. The investigation is motivated by the shallow flows encountered in many environmental situations and inspired by the laboratory experiments conducted in electromagnetically forced shallow fluid layers. The flow is confined to a thin fluid layer by stress-free top and no-slip bottom walls. The dynamics and the transport properties of the shallow flow are investigated under various flow conditions characterized by a Reynolds number related to the forcing, <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>F</mi></mrow></msub></mrow></math></span>, and the aspect ratio of vertical and horizontal length scales <span><math><mi>δ</mi></math></span>. The forcing generates an array of vortices that becomes unsteady when <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>F</mi></mrow></msub><msup><mrow><mi>δ</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≳</mo><mn>10</mn></mrow></math></span>. These vortices are accompanied by upwellings in their cores which are surrounded by narrower, stronger downwellings. Hence, upwellings occur where the horizontal flow is vorticity-dominated, while downwellings where it is strain-dominated. The magnitude of the asymmetry in strength and size of the vertical flows and their correlation with horizontal structures depends on the flow conditions and significantly influences the vertical spreading of particles within the fluid volume. Under conditions leading to a large asymmetry, particles within updrafts are transported slowly upwards, while particles within downdrafts rapidly move downwards. In addition, particles are trapped for longer within the updrafts than downdrafts because of their correlation with vorticity-dominated regions. However, when the flow becomes fully three-dimensional and highly unsteady for large <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>F</mi></mrow></msub><msup><mrow><mi>δ</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span> values, this transport asymmetry subsides because the updrafts and downdrafts exhibit similar strength and size in such flow conditions. Consequently, similar amounts of particles are transported upwards and downwards at similar rates.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 100-115"},"PeriodicalIF":2.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1016/j.euromechflu.2024.09.003
Pankaj Barman, Darbhasayanam Srinivasacharya
The objective of the present article is to explore the stability of micropolar fluid flow in a vertical channel in the presence of thermal radiation and a transverse magnetic field. The generalized eigenvalue problem is numerically solved by utilizing the Chebyshev spectral collocation method, which is obtained from the perturbed state using the normal mode technique. The numerical data were compared with previously published results for particular cases. The critical modified Grashof number () and the associated wave numbers () are calculated and displayed graphically for different values of the parameters. It is noticed that the boundaries of instability may be increased or decreased with the flow governing parameters because of the presence of a magnetic field and thermal radiation.
{"title":"Influence of radiation on the stability of MHD micropolar fluid in a vertical channel","authors":"Pankaj Barman, Darbhasayanam Srinivasacharya","doi":"10.1016/j.euromechflu.2024.09.003","DOIUrl":"10.1016/j.euromechflu.2024.09.003","url":null,"abstract":"<div><p>The objective of the present article is to explore the stability of micropolar fluid flow in a vertical channel in the presence of thermal radiation and a transverse magnetic field. The generalized eigenvalue problem is numerically solved by utilizing the Chebyshev spectral collocation method, which is obtained from the perturbed state using the normal mode technique. The numerical data were compared with previously published results for particular cases. The critical modified Grashof number (<span><math><mrow><mi>G</mi><msubsup><mrow><mi>r</mi></mrow><mrow><mi>c</mi></mrow><mrow><mo>′</mo></mrow></msubsup></mrow></math></span>) and the associated wave numbers (<span><math><msub><mrow><mi>α</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>) are calculated and displayed graphically for different values of the parameters. It is noticed that the boundaries of instability may be increased or decreased with the flow governing parameters because of the presence of a magnetic field and thermal radiation.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 80-91"},"PeriodicalIF":2.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142242299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1016/j.euromechflu.2024.09.001
Seungjun Baek , Yong Sung Park , Il Won Seo
We investigate the settling velocity change of weakly inertial particles, whose density ratio to fluid ranges from 1.35 to 1.38, in vertical water flow. To assess the effect of turbulence, we experimentally examine the dependence of modifications of velocity on physical scales, including time, velocity, and length, between particles and turbulence. It is observed that the settling velocity is either enhanced or hindered by the turbulence compared to stagnant conditions. The change in settling velocity is observed to be responsive to both the inertia of particles and the turbulence intensity. In cases of weak turbulence or with larger particles, the settling velocity exhibits small changes and even decreases. Conversely, the change in settling velocity is more pronounced for smaller particles and in more intense turbulence, reaching a maximum increase at . We compare our experimental results with existing studies conducted in solid–liquid two-phase flow, finding a consistent tendency. In both prior research and the present study, the length scale parameter, , has consistently been important in discerning inertial conditions that determine the change in settling velocity under turbulent conditions.
{"title":"Settling velocity of weakly inertial particles in vertical flow","authors":"Seungjun Baek , Yong Sung Park , Il Won Seo","doi":"10.1016/j.euromechflu.2024.09.001","DOIUrl":"10.1016/j.euromechflu.2024.09.001","url":null,"abstract":"<div><div>We investigate the settling velocity change of weakly inertial particles, whose density ratio to fluid ranges from 1.35 to 1.38, in vertical water flow. To assess the effect of turbulence, we experimentally examine the dependence of modifications of velocity on physical scales, including time, velocity, and length, between particles and turbulence. It is observed that the settling velocity is either enhanced or hindered by the turbulence compared to stagnant conditions. The change in settling velocity is observed to be responsive to both the inertia of particles and the turbulence intensity. In cases of weak turbulence or with larger particles, the settling velocity exhibits small changes and even decreases. Conversely, the change in settling velocity is more pronounced for smaller particles and in more intense turbulence, reaching a maximum increase at <span><math><mrow><mi>S</mi><mi>t</mi><mo>≈</mo><mi>O</mi><mrow><mo>(</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span>. We compare our experimental results with existing studies conducted in solid–liquid two-phase flow, finding a consistent tendency. In both prior research and the present study, the length scale parameter, <span><math><mrow><mi>S</mi><mi>t</mi><mi>S</mi><mi>v</mi></mrow></math></span>, has consistently been important in discerning inertial conditions that determine the change in settling velocity under turbulent conditions.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 92-99"},"PeriodicalIF":2.5,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142311061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-06DOI: 10.1016/j.euromechflu.2024.08.006
Pavel Procházka, Pavel Šnábl, Sony Chindada, Chandra Shekhar Prasad, Václav Uruba, Luděk Pešek
The experimental and numerical investigation of the flow instabilities acting on rigid blades and vice versa was conducted for both compressor and turbine configuration. The blade cascade consisted of five rectangular NACA 0010 blades, with three middle blades capable of performing harmonic motion with one degree of freedom (pitching) using force excitation. The base case (all blades fixed) and excited regime were examined. The influence of various angles of attack, harmonic frequency values, amplitude values, inter-blade phase angles and Reynolds numbers (Re) were tested. The mean flow properties as well as the fluid - structure interaction (FSI) were studied using Particle Image Velocimetry (PIV), Reynolds-averaged Navier-Stokes (RANS) CFD methods and using force measurement. Additionally, two different approaches, namely traveling wave mode (TWM) and aerodynamic influence coefficient (AIC), were adopted to estimate the aeroelastic stability of the blade cascade, and the results were compared. The results show significant aeroelastic coupling between the blades in both compressor and turbine configuration. However, the aerodynamic coupling effect for torsional flutter is more prominent in turbine configuration.
{"title":"The broad study of blade cascade under controlled torsional flutter: Dynamics of the flow and stability analysis","authors":"Pavel Procházka, Pavel Šnábl, Sony Chindada, Chandra Shekhar Prasad, Václav Uruba, Luděk Pešek","doi":"10.1016/j.euromechflu.2024.08.006","DOIUrl":"10.1016/j.euromechflu.2024.08.006","url":null,"abstract":"<div><p>The experimental and numerical investigation of the flow instabilities acting on rigid blades and vice versa was conducted for both compressor and turbine configuration. The blade cascade consisted of five rectangular NACA 0010 blades, with three middle blades capable of performing harmonic motion with one degree of freedom (pitching) using force excitation. The base case (all blades fixed) and excited regime were examined. The influence of various angles of attack, harmonic frequency values, amplitude values, inter-blade phase angles and Reynolds numbers (Re) were tested. The mean flow properties as well as the fluid - structure interaction (FSI) were studied using Particle Image Velocimetry (PIV), Reynolds-averaged Navier-Stokes (RANS) CFD methods and using force measurement. Additionally, two different approaches, namely traveling wave mode (TWM) and aerodynamic influence coefficient (AIC), were adopted to estimate the aeroelastic stability of the blade cascade, and the results were compared. The results show significant aeroelastic coupling between the blades in both compressor and turbine configuration. However, the aerodynamic coupling effect for torsional flutter is more prominent in turbine configuration.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 66-79"},"PeriodicalIF":2.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142167856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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