Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl最新文献
Thomas G. Shepard, Eric D. Ruud, Henry Kinane, D. Law, Kohl Ordahl
Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.
{"title":"Bubble Formation From Porous Plates in Liquid Cross-Flow","authors":"Thomas G. Shepard, Eric D. Ruud, Henry Kinane, D. Law, Kohl Ordahl","doi":"10.1115/FEDSM2018-83221","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83221","url":null,"abstract":"Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"128 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87639539","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}
Majid Abbasian, M. Shams, Ziba Valizadeh, A. Moshfegh, Ashkan Javadzadegan
Wall shear stress (WSS) distribution in stenosed arteries has been known as an important hemodynamic factor to correlate with atherosclerosis and associated disturbances in blood flow. WSS depends on various factors such as geometric complexity and tortuosity of the artery, stenosis severity and morphology as well as blood rheological properties. We conducted a numerical simulation of blood flow using Ansys CFX software in 9 patient-specific coronary artery models with 3 classes of stenosis severity: mild, moderate and severe. For this purpose, we compared some numerical results between two non-Newtonian models and Newtonian blood flow viscosity using 9 patient-specific coronary artery models including the full range of real (physiological) stenosis, reconstructed from 3DQCA (quantities coronary angiography). Incompressible and steady state form of Navier-Stokes equations were used as governing equations. Flow was considered laminar and artery walls were assumed to be rigid. Results showed that the magnitude of WSS usually increases by decreasing the cross-section area of arteries. Despite the difference in the WSS magnitude between different models in each artery, the trend of variation of WSS along the artery was the same in all three models. The local peak point of WSS along the artery occurs at the stenosis location, same for all models.
{"title":"Effect of Non-Newtonian Blood Flow on Coronary Artery Hemodynamics in a Cohort of Patients With Stenosed Artery","authors":"Majid Abbasian, M. Shams, Ziba Valizadeh, A. Moshfegh, Ashkan Javadzadegan","doi":"10.1115/FEDSM2018-83381","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83381","url":null,"abstract":"Wall shear stress (WSS) distribution in stenosed arteries has been known as an important hemodynamic factor to correlate with atherosclerosis and associated disturbances in blood flow. WSS depends on various factors such as geometric complexity and tortuosity of the artery, stenosis severity and morphology as well as blood rheological properties. We conducted a numerical simulation of blood flow using Ansys CFX software in 9 patient-specific coronary artery models with 3 classes of stenosis severity: mild, moderate and severe. For this purpose, we compared some numerical results between two non-Newtonian models and Newtonian blood flow viscosity using 9 patient-specific coronary artery models including the full range of real (physiological) stenosis, reconstructed from 3DQCA (quantities coronary angiography). Incompressible and steady state form of Navier-Stokes equations were used as governing equations. Flow was considered laminar and artery walls were assumed to be rigid. Results showed that the magnitude of WSS usually increases by decreasing the cross-section area of arteries. Despite the difference in the WSS magnitude between different models in each artery, the trend of variation of WSS along the artery was the same in all three models. The local peak point of WSS along the artery occurs at the stenosis location, same for all models.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88878498","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 use of in-class demonstrations and videos in an introductory fluid mechanics can have many positive outcomes in regards to student learning and engagement. However, the face-to-face class time an instructor has during lecture is a valuable commodity which can disappear all too quickly given the amount of topics to be covered, example problems, exams, etc. Thus, there is a balance to be struck amongst the various in-class activities, which must also factor in the amount of preparation time demanded of the instructor. This paper examines the utility of in-class demonstrations and videos using student surveys and feedback from both the instructor and students. Survey results reveal that students see the benefits of videos and in-class demonstrations differently and generally agree on the balance to be struck in the how class time is allocated. The results further reveal how students view in-class time in light of the opportunity to have a flipped, or partially flipped course whereby students watch lecture content outside of class. Student recall for relevant fluid mechanic concepts highlighted during demos is discussed. Additionally, the paper describes some of the specific fluid mechanics demonstrations and videos while providing references to other resources.
{"title":"Assessing the Value and Balance of In-Class Demos and Videos in Fluid Mechanics Lecture","authors":"Thomas G. Shepard","doi":"10.1115/FEDSM2018-83276","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83276","url":null,"abstract":"The use of in-class demonstrations and videos in an introductory fluid mechanics can have many positive outcomes in regards to student learning and engagement. However, the face-to-face class time an instructor has during lecture is a valuable commodity which can disappear all too quickly given the amount of topics to be covered, example problems, exams, etc. Thus, there is a balance to be struck amongst the various in-class activities, which must also factor in the amount of preparation time demanded of the instructor. This paper examines the utility of in-class demonstrations and videos using student surveys and feedback from both the instructor and students. Survey results reveal that students see the benefits of videos and in-class demonstrations differently and generally agree on the balance to be struck in the how class time is allocated. The results further reveal how students view in-class time in light of the opportunity to have a flipped, or partially flipped course whereby students watch lecture content outside of class. Student recall for relevant fluid mechanic concepts highlighted during demos is discussed. Additionally, the paper describes some of the specific fluid mechanics demonstrations and videos while providing references to other resources.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83360933","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}
Immersed boundary method has got increasing attention in modeling fluid-solid interaction using computational fluid dynamics due to its robustness and simplicity. It simulates fluid-solid interaction by adding a body force in the momentum equation without a body conforming mesh generation involved. Different immersed boundary methods have been presented and applied to solve fluid flow with immersed solid bodies. The main difference between these immersed boundary methods is how the body force is calculated. In this paper, a new immersed boundary method is proposed. The body force is calculated based on the volume fraction of the solid body immersed in fluid. Compared to the existing and similar methods, the new method develops a mechanism to calculate the body force and thereby more accurately resolve the physics on the solid-fluid interface. The solid body is represented using a level set that facilitates the calculation of the solid volume fraction. The body force derivation is presented and the method is validated against the test cases with existing analytical solutions or well established numerical solutions. A good match was reached.
{"title":"An New Immersed Boundary Method With Level Set Based Geometry Representation and Volume Fraction Based Body Force Calculation","authors":"G. Yao","doi":"10.1115/FEDSM2018-83011","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83011","url":null,"abstract":"Immersed boundary method has got increasing attention in modeling fluid-solid interaction using computational fluid dynamics due to its robustness and simplicity. It simulates fluid-solid interaction by adding a body force in the momentum equation without a body conforming mesh generation involved. Different immersed boundary methods have been presented and applied to solve fluid flow with immersed solid bodies. The main difference between these immersed boundary methods is how the body force is calculated. In this paper, a new immersed boundary method is proposed. The body force is calculated based on the volume fraction of the solid body immersed in fluid. Compared to the existing and similar methods, the new method develops a mechanism to calculate the body force and thereby more accurately resolve the physics on the solid-fluid interface. The solid body is represented using a level set that facilitates the calculation of the solid volume fraction. The body force derivation is presented and the method is validated against the test cases with existing analytical solutions or well established numerical solutions. A good match was reached.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83691570","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 study, we have applied and compared two active flow control (AFC) mechanisms on a pitching NACA0012 airfoil at Reynolds number of 1 × 106 using 2-D computational fluid dynamics (CFD). These mechanisms are continuous blowing and suction which are applied separately on the airfoil which pitches around its quarter-chord in a sinusoidal motion. The location for suction and blowing was determined in our previous study based on the formation of a counter clock-wise vortex near the leading-edge. In our current study, we have compared the effectiveness of pure blowing and pure suction in suppressing the dynamic stall vortex (DSV) which is the main contributor to the drag increase, particularly near the maximum angle of attack (AOA) and in early downstroke motion. The blowing/suction slot is considered as a dent on the airfoil surface which enables the AFC to perform in a tangential manner. This configuration would allow blowing jet to penetrate further downstream and was shown to be more effective compared to a cross-flow orientation. We have compared the two aforementioned mechanisms in terms of hysteresis loops of lift and drag coefficients and have demonstrated the dynamics of flow in controlled and uncontrolled situations.
{"title":"Comparison of Two Active Flow Control Mechanisms of Pure Blowing and Pure Suction on a Pitching NACA0012 Airfoil at Reynolds Number of 1 × 106","authors":"E. Asgari, M. Tadjfar","doi":"10.1115/FEDSM2018-83463","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83463","url":null,"abstract":"In this study, we have applied and compared two active flow control (AFC) mechanisms on a pitching NACA0012 airfoil at Reynolds number of 1 × 106 using 2-D computational fluid dynamics (CFD). These mechanisms are continuous blowing and suction which are applied separately on the airfoil which pitches around its quarter-chord in a sinusoidal motion. The location for suction and blowing was determined in our previous study based on the formation of a counter clock-wise vortex near the leading-edge. In our current study, we have compared the effectiveness of pure blowing and pure suction in suppressing the dynamic stall vortex (DSV) which is the main contributor to the drag increase, particularly near the maximum angle of attack (AOA) and in early downstroke motion. The blowing/suction slot is considered as a dent on the airfoil surface which enables the AFC to perform in a tangential manner. This configuration would allow blowing jet to penetrate further downstream and was shown to be more effective compared to a cross-flow orientation. We have compared the two aforementioned mechanisms in terms of hysteresis loops of lift and drag coefficients and have demonstrated the dynamics of flow in controlled and uncontrolled situations.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89871307","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 study was done to investigate how boundary layer tripping mechanisms can affect the ability of a permeable surface FW-H solver to predict the far field noise emanating from an airfoil trailing edge. The far field noise in a baseline airfoil as well as the baseline airfoil fitted with fin let fences was analyzed. Two numerical boundary layer tripping mechanisms were implemented. The results illustrated the importance of choosing a permeable integration surface that is outside any high frequency waves emanating from the trip region. The results also illustrated the importance of choosing a boundary layer tripping mechanism that minimizes any extraneous noise so that an integration surface can be taken close to the airfoil.
{"title":"Implementation of the Ffowcs Williams-Hawkings Equation: Predicting the Far Field Noise From Airfoils While Using Boundary Layer Tripping Mechanisms","authors":"Andrew Bodling, Anupam Sharma","doi":"10.1115/FEDSM2018-83385","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83385","url":null,"abstract":"A study was done to investigate how boundary layer tripping mechanisms can affect the ability of a permeable surface FW-H solver to predict the far field noise emanating from an airfoil trailing edge. The far field noise in a baseline airfoil as well as the baseline airfoil fitted with fin let fences was analyzed. Two numerical boundary layer tripping mechanisms were implemented. The results illustrated the importance of choosing a permeable integration surface that is outside any high frequency waves emanating from the trip region. The results also illustrated the importance of choosing a boundary layer tripping mechanism that minimizes any extraneous noise so that an integration surface can be taken close to the airfoil.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76846864","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}
Computational fluid dynamics (CFD) simulation results are presented for the canonical test case of flow over a backward facing step (BFS). The BFS case exhibits complex physics including turbulent separation, reattachment, and boundary layer restart. Results are obtained using two different turbulence models as representative examples of two classes of modeling: Reynolds-averaged Navier-Stokes (RANS) and hybrid RANS-LES (large-eddy simulation). The specific models used are k-ω SST and dynamic hybrid RANS-LES (DHRL). The objective of the study is to compare the performance of both turbulence models as implemented in three different flow solvers (Flow Psi, Loci-CHEM, and Ansys FLUENT) and using three different methods for numerical discretization of the convective terms in the governing equations. Results are compared to experimental data for validation purposes. Results show that both k-ω SST and DHRL models are capable of reproducing the mean flow physics with reasonable accuracy. The differences due to solver algorithm and convective discretization scheme are apparent for both models, but the DHRL model shows more sensitivity, as expected. Overall the results highlight the importance of considering all integrated aspects of a turbulent CFD simulation to ensure that an optimum combination of model and numerical method are employed.
{"title":"Evaluation of Performance and Code-to-Code Variation of a Dynamic Hybrid RANS/LES Model for Simulation of Backward-Facing Step Flow","authors":"Olalekan O. Shobayo, D. K. Walters","doi":"10.1115/FEDSM2018-83160","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83160","url":null,"abstract":"Computational fluid dynamics (CFD) simulation results are presented for the canonical test case of flow over a backward facing step (BFS). The BFS case exhibits complex physics including turbulent separation, reattachment, and boundary layer restart. Results are obtained using two different turbulence models as representative examples of two classes of modeling: Reynolds-averaged Navier-Stokes (RANS) and hybrid RANS-LES (large-eddy simulation). The specific models used are k-ω SST and dynamic hybrid RANS-LES (DHRL). The objective of the study is to compare the performance of both turbulence models as implemented in three different flow solvers (Flow Psi, Loci-CHEM, and Ansys FLUENT) and using three different methods for numerical discretization of the convective terms in the governing equations. Results are compared to experimental data for validation purposes. Results show that both k-ω SST and DHRL models are capable of reproducing the mean flow physics with reasonable accuracy. The differences due to solver algorithm and convective discretization scheme are apparent for both models, but the DHRL model shows more sensitivity, as expected. Overall the results highlight the importance of considering all integrated aspects of a turbulent CFD simulation to ensure that an optimum combination of model and numerical method are employed.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81178758","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}
J. Degroote, Lucas Delcour, L. Moerloose, Henri Dolfen, J. Vierendeels
Flexible cylinders surrounded by a fluid flow that is dominantly aligned with the axis of the cylinders can be found in several applications. Examples with a flow confined to a narrow region around the cylinder(s) can be found in tube bundles of heat exchangers and reactor cores and also in air-jet weaving machines. This research analyses the flow-induced vibration of these two different cases with flexible cylinders in confined axial flow using numerical fluid-structure interaction (FSI) simulations. The FSI simulations of both cases use a partitioned framework, meaning that a computational fluid dynamics (CFD) solver is coupled with a finite element analysis (FEA) structural solver. The dynamic and kinematic equilibrium conditions at the contact surface between the fluid and the structure are satisfied by performing coupling iterations between both solvers in each time step. Convergence of these iterations is accelerated using quasi-Newton coupling techniques. For the case of the tube bundle, the modal characteristics have been identified for a tube bundle when they are submerged in an axial fluid flow. Furthermore, different types of flow-induced vibration have been studied. The flow speed has been increased in an FSI simulation of a single cylinder surrounded by an annular fluid domain, resulting first in static buckling and then in flutter at higher flow speeds. For the case of the air-jet weaving machines, the cylinder represents a smooth yarn which is accelerated by an air jet in the main nozzle of the machine, consisting of a long tube with small diameter. FSI simulations of a yarn clamped at the upstream end have been performed using the arbitrary Lagrangian-Eulerian formulation with deforming grids in the fluid domain. This work demonstrates the feasibility of analyzing and predicting flow-induced vibration of cylinders in confined axial flow by performing FSI simulations. The results of simulations are compared with those of experiments for tubes in axial flow and for a yarn in a nozzle of an air-jet weaving machine.
{"title":"Fluid-Structure Interaction Simulations of Flexible Cylinders in Confined Axial Flow","authors":"J. Degroote, Lucas Delcour, L. Moerloose, Henri Dolfen, J. Vierendeels","doi":"10.1115/FEDSM2018-83193","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83193","url":null,"abstract":"Flexible cylinders surrounded by a fluid flow that is dominantly aligned with the axis of the cylinders can be found in several applications. Examples with a flow confined to a narrow region around the cylinder(s) can be found in tube bundles of heat exchangers and reactor cores and also in air-jet weaving machines. This research analyses the flow-induced vibration of these two different cases with flexible cylinders in confined axial flow using numerical fluid-structure interaction (FSI) simulations.\u0000 The FSI simulations of both cases use a partitioned framework, meaning that a computational fluid dynamics (CFD) solver is coupled with a finite element analysis (FEA) structural solver. The dynamic and kinematic equilibrium conditions at the contact surface between the fluid and the structure are satisfied by performing coupling iterations between both solvers in each time step. Convergence of these iterations is accelerated using quasi-Newton coupling techniques.\u0000 For the case of the tube bundle, the modal characteristics have been identified for a tube bundle when they are submerged in an axial fluid flow. Furthermore, different types of flow-induced vibration have been studied. The flow speed has been increased in an FSI simulation of a single cylinder surrounded by an annular fluid domain, resulting first in static buckling and then in flutter at higher flow speeds.\u0000 For the case of the air-jet weaving machines, the cylinder represents a smooth yarn which is accelerated by an air jet in the main nozzle of the machine, consisting of a long tube with small diameter. FSI simulations of a yarn clamped at the upstream end have been performed using the arbitrary Lagrangian-Eulerian formulation with deforming grids in the fluid domain.\u0000 This work demonstrates the feasibility of analyzing and predicting flow-induced vibration of cylinders in confined axial flow by performing FSI simulations. The results of simulations are compared with those of experiments for tubes in axial flow and for a yarn in a nozzle of an air-jet weaving machine.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80985683","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}
Various technologies have been developed to enhance the heat transfer. Vortex generator (VG) is one of the passive techniques which can change the flow behavior and ultimately enhances the heat transfer performance. Delta winglet (DW) vortex generator can create longitudinal and horseshoe vortices which do not decay until further downstream and consequently increase heat transfer coefficient with comparatively lower pressure drop. With this vortex generator, it is expected to have higher Nusselt number with some increase of friction factor. Therefore, this study is to study the effect of pitch ratio (PR) and attack angle (B) of DW vortex generator to increase the thermal performance of heat exchanger. Four delta winglets are attached into a ring. Those rings attached with VGs will be used to investigate the influence of different parameters to heat transfer performance. In this study VGs were placed inside a circular copper tube and the heating coil was wrapped up around the outer surface of the copper tube to generate a constant heat flux condition. The experimental setup consists of a blower, orifice meter, flow straightener, calm/flow developing section and test section. The results show the friction factor, Nusselt number, and Thermal Performance Enhancement. It increases the thermal performance due to the formation of longitudinal vortex inside the circular tube. Pitch ratio and attack angle seem to have significant impact on the flow and heat transfer. The Pitch ratio of 1.6 have the highest impact on both (f/f0) and (Nu/Nuo) followed by attack angle. Smoke flow visualization technique was used to study flow behavior and flow structures.
{"title":"Heat Transfer Enhancement With Delta Winglets Vortex Generator for Different Arrangement in a Circular Tube","authors":"Islam, A. Nurizki, A. Kareem, A. Baba","doi":"10.1115/FEDSM2018-83244","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83244","url":null,"abstract":"Various technologies have been developed to enhance the heat transfer. Vortex generator (VG) is one of the passive techniques which can change the flow behavior and ultimately enhances the heat transfer performance. Delta winglet (DW) vortex generator can create longitudinal and horseshoe vortices which do not decay until further downstream and consequently increase heat transfer coefficient with comparatively lower pressure drop. With this vortex generator, it is expected to have higher Nusselt number with some increase of friction factor. Therefore, this study is to study the effect of pitch ratio (PR) and attack angle (B) of DW vortex generator to increase the thermal performance of heat exchanger. Four delta winglets are attached into a ring. Those rings attached with VGs will be used to investigate the influence of different parameters to heat transfer performance. In this study VGs were placed inside a circular copper tube and the heating coil was wrapped up around the outer surface of the copper tube to generate a constant heat flux condition. The experimental setup consists of a blower, orifice meter, flow straightener, calm/flow developing section and test section. The results show the friction factor, Nusselt number, and Thermal Performance Enhancement. It increases the thermal performance due to the formation of longitudinal vortex inside the circular tube. Pitch ratio and attack angle seem to have significant impact on the flow and heat transfer. The Pitch ratio of 1.6 have the highest impact on both (f/f0) and (Nu/Nuo) followed by attack angle. Smoke flow visualization technique was used to study flow behavior and flow structures.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82761316","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}
Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：