A simple approach for the design of supersonic nozzles of complex 3D shapes is presented. The Method of characteristics is primarily applied to compute the axisymmetric flow field of the supersonic section of the de-Laval nozzle. Two-dimensional simulations are performed for the axisymmetric flow fields. The 3D configuration is then generated from the desired exit axisymmetric cross-sectional shape chosen through tracing its geometrical parameters back.to the throat. Elliptical, corrugated and two-dimensional wedge nozzles were designed using this approach. Preliminary results show a smooth geometrical transition from the throat to the exit cross section. Further three-dimensional analyses of the obtained geometries along with cold flow testing constitute the next steps to be performed.
{"title":"A Simple Method for the Design of Supersonic Nozzles of Arbitrary Cross Section Shape","authors":"N. Boughazi, A. Haddad","doi":"10.1115/fedsm2020-20197","DOIUrl":"https://doi.org/10.1115/fedsm2020-20197","url":null,"abstract":"\u0000 A simple approach for the design of supersonic nozzles of complex 3D shapes is presented. The Method of characteristics is primarily applied to compute the axisymmetric flow field of the supersonic section of the de-Laval nozzle. Two-dimensional simulations are performed for the axisymmetric flow fields.\u0000 The 3D configuration is then generated from the desired exit axisymmetric cross-sectional shape chosen through tracing its geometrical parameters back.to the throat. Elliptical, corrugated and two-dimensional wedge nozzles were designed using this approach. Preliminary results show a smooth geometrical transition from the throat to the exit cross section. Further three-dimensional analyses of the obtained geometries along with cold flow testing constitute the next steps to be performed.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126237265","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}
Ayesha Almheiri, L. Khezzar, M. Alshehhi, Saqib Salam, A. Goharzadeh
Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.
{"title":"Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe","authors":"Ayesha Almheiri, L. Khezzar, M. Alshehhi, Saqib Salam, A. Goharzadeh","doi":"10.1115/fedsm2020-20064","DOIUrl":"https://doi.org/10.1115/fedsm2020-20064","url":null,"abstract":"\u0000 Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116845266","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}
For homogenous two-phase bubbly flows, the theoretical speed of sound is dramatically reduced at moderate void fractions to speeds much lower than the speed of sound for either single phase. This theoretical speed of sound would suggest a propensity for bubbly flows to reach choked conditions when traveling through a convergent nozzle. However, for a bubbly flow to be considered homogenous requires assumptions that may not be realized in practical applications. In this experimental study, a bubbly flow was sent through a convergent nozzle before entering a large chamber. By setting steady flow conditions upstream and then reducing the chamber pressure via a vacuum pump, the transient response in terms of gas and liquid flow rates and upstream channel pressure was determined. The bubble size was carefully varied from ∼0.3–1 mm while holding gas and liquid flow rates constant in order to study how bubble size affects the transient flow characteristics. High-speed imaging was used for measuring the bubbles. Experiments were also conducted at two gas-liquid mass flow ratios. Results are presented to demonstrate the impact of bubble size and gas-liquid ratio on the transient response of upstream gas and liquid flow rates, upstream pressure and exit Mach number to the lowering of pressure downstream of the convergent nozzle. Results are presented both for flows that remained in the bubbly regime and for flows that transitioned to an annular flow regime during a trial.
{"title":"Impact of Bubble Size on Flow Response to Transient Pressure Drop Through Converging Nozzle","authors":"Aleksey Garbaly, Thomas G. Shepard","doi":"10.1115/fedsm2020-20278","DOIUrl":"https://doi.org/10.1115/fedsm2020-20278","url":null,"abstract":"\u0000 For homogenous two-phase bubbly flows, the theoretical speed of sound is dramatically reduced at moderate void fractions to speeds much lower than the speed of sound for either single phase. This theoretical speed of sound would suggest a propensity for bubbly flows to reach choked conditions when traveling through a convergent nozzle. However, for a bubbly flow to be considered homogenous requires assumptions that may not be realized in practical applications. In this experimental study, a bubbly flow was sent through a convergent nozzle before entering a large chamber. By setting steady flow conditions upstream and then reducing the chamber pressure via a vacuum pump, the transient response in terms of gas and liquid flow rates and upstream channel pressure was determined. The bubble size was carefully varied from ∼0.3–1 mm while holding gas and liquid flow rates constant in order to study how bubble size affects the transient flow characteristics. High-speed imaging was used for measuring the bubbles. Experiments were also conducted at two gas-liquid mass flow ratios. Results are presented to demonstrate the impact of bubble size and gas-liquid ratio on the transient response of upstream gas and liquid flow rates, upstream pressure and exit Mach number to the lowering of pressure downstream of the convergent nozzle. Results are presented both for flows that remained in the bubbly regime and for flows that transitioned to an annular flow regime during a trial.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123958387","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}
In support of the digital transformation of our programs, simulation assignments are embedded in undergraduate fluid mechanics and heat transfer lecture-based courses, as well as in the Computational Engineering technical electives. Each course integrates simulations, application building, and inquiry-based learning (IBL) with ten assignments performed outside the class and documented in technical reports. FEA and CFD tools are employed to teach thermo-fluids, and in turn, course material is used to teach CFD and FEA. This new, high-impact practice facilitates a deeper understanding of theoretical concepts, exposes students to modern engineering tools, and develops students’ research capacity while the ‘lecture’ time is dedicated for the fundamental theoretical topics only. The main goal of this study was to expand on the implementation of simulations and IBL in undergraduate thermo-fluids courses and create a template to do so in other topical threads. This was accomplished by: (1) strategically balancing step-by-step instructions supporting skill-building, with inquiry-based tasks guiding discovery process and developing higher order thinking skills; (2) providing clear and detailed grading criteria guiding students both in the process of gaining skills and performing IBL; (3) designing strategies for the assessment of student work that are easily transported across the curriculum; and (4) assessing students’ understanding and the effect of the overall digital transformation effort based on quantitative and qualitative data indicative of the achievement of learning outcomes. This study builds on the authors’ previously reported work in the area of simulations and IBL that covered individual courses as well as course sequences. While quantitative data includes assessment of students’ understanding and confidence in comprehension of select concepts using grades, student surveys, and course evaluations, the impact of the described approach is illustrated with qualitative data including several examples of student work and its influence on their professional development.
{"title":"Unified Assessment Approach for Courses With Simulation Component [And Professors in Hurry]","authors":"I. Milanović, T. Eppes, Kamau C. Wright","doi":"10.1115/fedsm2020-20161","DOIUrl":"https://doi.org/10.1115/fedsm2020-20161","url":null,"abstract":"\u0000 In support of the digital transformation of our programs, simulation assignments are embedded in undergraduate fluid mechanics and heat transfer lecture-based courses, as well as in the Computational Engineering technical electives. Each course integrates simulations, application building, and inquiry-based learning (IBL) with ten assignments performed outside the class and documented in technical reports. FEA and CFD tools are employed to teach thermo-fluids, and in turn, course material is used to teach CFD and FEA. This new, high-impact practice facilitates a deeper understanding of theoretical concepts, exposes students to modern engineering tools, and develops students’ research capacity while the ‘lecture’ time is dedicated for the fundamental theoretical topics only.\u0000 The main goal of this study was to expand on the implementation of simulations and IBL in undergraduate thermo-fluids courses and create a template to do so in other topical threads. This was accomplished by: (1) strategically balancing step-by-step instructions supporting skill-building, with inquiry-based tasks guiding discovery process and developing higher order thinking skills; (2) providing clear and detailed grading criteria guiding students both in the process of gaining skills and performing IBL; (3) designing strategies for the assessment of student work that are easily transported across the curriculum; and (4) assessing students’ understanding and the effect of the overall digital transformation effort based on quantitative and qualitative data indicative of the achievement of learning outcomes.\u0000 This study builds on the authors’ previously reported work in the area of simulations and IBL that covered individual courses as well as course sequences. While quantitative data includes assessment of students’ understanding and confidence in comprehension of select concepts using grades, student surveys, and course evaluations, the impact of the described approach is illustrated with qualitative data including several examples of student work and its influence on their professional development.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116699434","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}
The performance of multi-stage Electrical Submersible Pumps (ESPs) under different flow conditions and its life span with sand production are commonly predicted by the Computational Fluid Dynamics (CFD) simulations. The mesh generation methodology and optimum grid number are usually validated by pump water catalog curves. Then, the validated mesh geometry is adopted in high viscosity, multiphase flow, and sand erosion simulations to study the effects including but not limited to: discrete phase bubble diameter, turbulence model, body forces, and erosion models. However, the mesh validation by pump water curves is not enough in complex flow conditions, especially in the erosion simulations. Different from the pump hydraulic performance simulation, the accuracy of the erosion simulation can be affected by mesh boundary and inner layer grid thickness, especially for small particles. In addition, the mesh-type (hexahedral and tetrahedral) and size of the inner domain can also significantly affect the particle trajectory. A comprehensive mesh independent study is conducted for water, oil, and gas-liquid conditions of a mixed type ESP in this paper. Then the near-wall inflation layer thickness and inner domain grid size effect to ESP erosion simulation are well analyzed. The mesh generation methodology can be applied to other turbomachinery simulations to improve accuracy.
{"title":"A Numerical Study of Mesh Type, Size, and Near Wall Grid Thickness Effect on Performance and Erosion Simulations in an Electrical Submersible Pump (ESP)","authors":"Haiwen Zhu, Zimo Lin, Jianlin Peng, Hong-quan Zhang, Jianjun Zhu, Jun Zhang","doi":"10.1115/fedsm2020-20382","DOIUrl":"https://doi.org/10.1115/fedsm2020-20382","url":null,"abstract":"\u0000 The performance of multi-stage Electrical Submersible Pumps (ESPs) under different flow conditions and its life span with sand production are commonly predicted by the Computational Fluid Dynamics (CFD) simulations. The mesh generation methodology and optimum grid number are usually validated by pump water catalog curves. Then, the validated mesh geometry is adopted in high viscosity, multiphase flow, and sand erosion simulations to study the effects including but not limited to: discrete phase bubble diameter, turbulence model, body forces, and erosion models. However, the mesh validation by pump water curves is not enough in complex flow conditions, especially in the erosion simulations. Different from the pump hydraulic performance simulation, the accuracy of the erosion simulation can be affected by mesh boundary and inner layer grid thickness, especially for small particles. In addition, the mesh-type (hexahedral and tetrahedral) and size of the inner domain can also significantly affect the particle trajectory. A comprehensive mesh independent study is conducted for water, oil, and gas-liquid conditions of a mixed type ESP in this paper. Then the near-wall inflation layer thickness and inner domain grid size effect to ESP erosion simulation are well analyzed. The mesh generation methodology can be applied to other turbomachinery simulations to improve accuracy.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125374078","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}
In this article, loop like planar networks formed by circular cross sectioned conduits with possibly different geometric measurements are studied to supply the required amount of isothermal water within the optimal time and through the shortest path. The flow optimization procedure is controlled by time varying pressures at nodes throughout the network for given specifications about pressure value at multiple demanding and single supply nodes. The flow governing equation is solved analytically to correlate transient flow rate and pressure and then studied using analogous electrical circuit. For each possible path between source and demand node, minimum equivalent flow impedance criterion is considered to pick the optimum path. This sets a multi-objective dynamic flow optimization algorithm and the same is executed under the assumption of fully developed and laminar flow. The optimum flow impedance can further be used to measure the pumping power as the cost of flow of a particular path. The algorithm can be extended to reduce the water wastages by controlling pressures efficiently.
{"title":"Optimal Control Strategy to Distribute Water Through Loop-Like Planar Networks","authors":"B. Soni, Utkarsh Aashu Mishra, A. Nayak","doi":"10.1115/fedsm2020-20097","DOIUrl":"https://doi.org/10.1115/fedsm2020-20097","url":null,"abstract":"\u0000 In this article, loop like planar networks formed by circular cross sectioned conduits with possibly different geometric measurements are studied to supply the required amount of isothermal water within the optimal time and through the shortest path. The flow optimization procedure is controlled by time varying pressures at nodes throughout the network for given specifications about pressure value at multiple demanding and single supply nodes. The flow governing equation is solved analytically to correlate transient flow rate and pressure and then studied using analogous electrical circuit. For each possible path between source and demand node, minimum equivalent flow impedance criterion is considered to pick the optimum path. This sets a multi-objective dynamic flow optimization algorithm and the same is executed under the assumption of fully developed and laminar flow. The optimum flow impedance can further be used to measure the pumping power as the cost of flow of a particular path. The algorithm can be extended to reduce the water wastages by controlling pressures efficiently.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123126829","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}
Non-equilibrium thermal fluctuations present as wave elements in a flow. A wave element is the wave interface between two molecule groups with different temperature; it is generated by density difference which results from temperature difference. Tiny temperature differences always exist everywhere in a fluid. When the fluid is in motion, wave elements are generated among molecule groups. Wave motion and Brownian motion may be the two basic forms of motion of molecules in flow. Brownian motion is controlled by temperature. Wave elements are caused by temperature differences and the motion of the fluid. Wave motion maybe the physical mechanism of convective heat transfer. Non-equilibrium thermal fluctuations exist everywhere among molecule groups in a flow. The theoretical analysis presents that a wave element presents oscillatory behavior along the space and time dimensions simultaneously. The experimental evidence for wave elements can not be directly established at present scientific testing capability because the temperature difference of two molecule groups adjoining to each other in a flow is very small. A series of “enlarged size” experiments of fouling to show the behaviors of wave elements by tracing the movement of molecules are conducted. The experimental study of fouling presents that oscillatory interface along the space and time dimensions simultaneously exists between two densities due to motion of the fluids. The experimental and theoretical analyses are supported to each other.
{"title":"Non-Equilibrium Thermal Fluctuation in Flow","authors":"Wei Li","doi":"10.1115/fedsm2020-20131","DOIUrl":"https://doi.org/10.1115/fedsm2020-20131","url":null,"abstract":"\u0000 Non-equilibrium thermal fluctuations present as wave elements in a flow. A wave element is the wave interface between two molecule groups with different temperature; it is generated by density difference which results from temperature difference. Tiny temperature differences always exist everywhere in a fluid. When the fluid is in motion, wave elements are generated among molecule groups. Wave motion and Brownian motion may be the two basic forms of motion of molecules in flow. Brownian motion is controlled by temperature. Wave elements are caused by temperature differences and the motion of the fluid. Wave motion maybe the physical mechanism of convective heat transfer. Non-equilibrium thermal fluctuations exist everywhere among molecule groups in a flow. The theoretical analysis presents that a wave element presents oscillatory behavior along the space and time dimensions simultaneously. The experimental evidence for wave elements can not be directly established at present scientific testing capability because the temperature difference of two molecule groups adjoining to each other in a flow is very small. A series of “enlarged size” experiments of fouling to show the behaviors of wave elements by tracing the movement of molecules are conducted. The experimental study of fouling presents that oscillatory interface along the space and time dimensions simultaneously exists between two densities due to motion of the fluids. The experimental and theoretical analyses are supported to each other.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124207305","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}
Use of active flow control techniques has become important in flow separation control. Continuous blowing jet is one of the most effective methods that can be used to improve aerodynamic performance of an airfoil. In the present work, different operational parameters of a continuous blowing jet were optimized to improve the aerodynamic performance of an oscillating NACA0012 airfoil. The airfoil underwent a sinusoidal motion about its quarter-chord between −5 and 25 degrees at the Reynolds number of 1.35 × 105. Unsteady Navier-Stokes equations were solved with k-ω SST turbulence model. Due to the time-consuming nature of large number of numerical simulations required during the optimization process, two neural networks were employed to reduce the number of simulations required. The optimization was carried out with the use of a genetic algorithm. The objective function was defined as the lift-to-drag ratio. In these networks, the relationship between the jet operational characteristics and the aerodynamic coefficients were trained. The jet operational parameters that were considered in this study, included jet location (at 1–60 percent of chord length), jet-opening length (0.05 to 0.3 percent of chord length), blowing jet velocity magnitude (0 to 5U∞), and blowing jet incident angle (0 to 180 degrees). Obtained results indicated that jet-opening length and blowing velocity magnitude have a greater effect on the aerodynamic performance when reached their upper values. Concerning the jet location, it was observed that the best jet location was about 2 to 5 percent of the chord Jet angle (θ) was found to results in the best performance when oriented at range 55 to 70 angle. Results indicated a significant improvement of the aerodynamic performance at the optimum blowing jet configuration.
{"title":"Continuous Blowing Jet Flow Control Optimization in Dynamic Stall of NACA0012 Airfoil","authors":"M. Tadjfar, Saman Kasmaiee, S. Noori","doi":"10.1115/fedsm2020-20149","DOIUrl":"https://doi.org/10.1115/fedsm2020-20149","url":null,"abstract":"\u0000 Use of active flow control techniques has become important in flow separation control. Continuous blowing jet is one of the most effective methods that can be used to improve aerodynamic performance of an airfoil. In the present work, different operational parameters of a continuous blowing jet were optimized to improve the aerodynamic performance of an oscillating NACA0012 airfoil. The airfoil underwent a sinusoidal motion about its quarter-chord between −5 and 25 degrees at the Reynolds number of 1.35 × 105. Unsteady Navier-Stokes equations were solved with k-ω SST turbulence model. Due to the time-consuming nature of large number of numerical simulations required during the optimization process, two neural networks were employed to reduce the number of simulations required. The optimization was carried out with the use of a genetic algorithm. The objective function was defined as the lift-to-drag ratio. In these networks, the relationship between the jet operational characteristics and the aerodynamic coefficients were trained. The jet operational parameters that were considered in this study, included jet location (at 1–60 percent of chord length), jet-opening length (0.05 to 0.3 percent of chord length), blowing jet velocity magnitude (0 to 5U∞), and blowing jet incident angle (0 to 180 degrees). Obtained results indicated that jet-opening length and blowing velocity magnitude have a greater effect on the aerodynamic performance when reached their upper values. Concerning the jet location, it was observed that the best jet location was about 2 to 5 percent of the chord Jet angle (θ) was found to results in the best performance when oriented at range 55 to 70 angle. Results indicated a significant improvement of the aerodynamic performance at the optimum blowing jet configuration.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133473951","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}
A numerical study is proposed to analyze the turbulent flow structures. This paper aims to determine the effect of the series of the cavities. The configuration is similar to that represented by two walls with infinite width, one of which is mobile and the other is fixed. The series of cavity are placed on the fixed wall. The objectives are to study the aero acoustic capabilities of LBM and to build and to assess the efficiency of the Lattice Boltzmann Equation (LBE) as a new computational tool to perform the Large-Eddy Simulations (LES) for turbulent flows. In the first part, the background of LBM is presented and the construction of Navier-Stokes equations from Boltzmann equation is discussed. The LBM-LES model for solving transition is developed and turbulence modeling is implemented. In the second part, the dynamics of the flows in the vicinity of cavities with symmetric or asymmetric edges are considered, to then discuss the oscillation phenomenon. The effect of the geometric of the cavity and the Reynolds numbers were studied to investigate the fluid flow dynamics. We were focusing on the dynamics of asymmetric deep cavity flows, to put forward the topology of the cavity flow and to highlight the effects of dissymmetry and aspect ratio.
{"title":"Lattice Boltzmann Method Based on Large-Eddy Simulation (LES) Used to Investigate the Unsteady Turbulent Flow on Series of Cavities","authors":"Insaf Mehrez, R. Gheith, F. Aloui","doi":"10.1115/fedsm2020-20329","DOIUrl":"https://doi.org/10.1115/fedsm2020-20329","url":null,"abstract":"\u0000 A numerical study is proposed to analyze the turbulent flow structures. This paper aims to determine the effect of the series of the cavities. The configuration is similar to that represented by two walls with infinite width, one of which is mobile and the other is fixed. The series of cavity are placed on the fixed wall. The objectives are to study the aero acoustic capabilities of LBM and to build and to assess the efficiency of the Lattice Boltzmann Equation (LBE) as a new computational tool to perform the Large-Eddy Simulations (LES) for turbulent flows. In the first part, the background of LBM is presented and the construction of Navier-Stokes equations from Boltzmann equation is discussed. The LBM-LES model for solving transition is developed and turbulence modeling is implemented. In the second part, the dynamics of the flows in the vicinity of cavities with symmetric or asymmetric edges are considered, to then discuss the oscillation phenomenon. The effect of the geometric of the cavity and the Reynolds numbers were studied to investigate the fluid flow dynamics. We were focusing on the dynamics of asymmetric deep cavity flows, to put forward the topology of the cavity flow and to highlight the effects of dissymmetry and aspect ratio.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115552864","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}
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