S. Shiraghaee, J. Sundström, M. Raisee, Michel J. Cervantes
The present paper investigates the rotating vortex rope (RVR) mitigation on an axial turbine model by the radial protrusion of four cylindrical rods into the draft tube. RVR mitigation is of particular interest due to the unfavorable pressure pulsations it induces in the hydraulic circuit that can affect turbine life and performance. The protrusion lengths, which were the same among the four rods, were varied according to a pre-defined sequence. The experiments were performed under four part-load regimes ranging from upper part load to deep part load. Time-resolved pressure measurements were conducted at two sections on the draft tube wall along with high-speed videography and efficiency measurement to investigate the effect of the mitigation technique on the RVR characteristics and turbine performance. The recorded pressure data were decomposed and studied through spectral analyses, phase-averaging, and statistical analyses of the RVR frequency and peak-to-peak pressure amplitude distributions. The results showed different levels of pressure amplitude mitigation ranging from approximately 10% to 85% depending on the operating condition, protrusion length, and the method of analysis. The hydraulic efficiency of the turbine decreased by a maximum of 3.5% that of the best efficiency point (BEP) with the implementation of the mitigation technique. The variations in the obtained mitigation levels and efficiencies depending on protrusion length and operating condition indicate the need for the implementation of a feedback-loop controller. Thus, the protrusion length can be actively optimizes based on the desired mitigation target.
{"title":"Experimental Investigation of Part Load Vortex Rope Mitigation with Rod Protrusion in an Axial Turbine","authors":"S. Shiraghaee, J. Sundström, M. Raisee, Michel J. Cervantes","doi":"10.1115/1.4064610","DOIUrl":"https://doi.org/10.1115/1.4064610","url":null,"abstract":"\u0000 The present paper investigates the rotating vortex rope (RVR) mitigation on an axial turbine model by the radial protrusion of four cylindrical rods into the draft tube. RVR mitigation is of particular interest due to the unfavorable pressure pulsations it induces in the hydraulic circuit that can affect turbine life and performance. The protrusion lengths, which were the same among the four rods, were varied according to a pre-defined sequence. The experiments were performed under four part-load regimes ranging from upper part load to deep part load. Time-resolved pressure measurements were conducted at two sections on the draft tube wall along with high-speed videography and efficiency measurement to investigate the effect of the mitigation technique on the RVR characteristics and turbine performance. The recorded pressure data were decomposed and studied through spectral analyses, phase-averaging, and statistical analyses of the RVR frequency and peak-to-peak pressure amplitude distributions. The results showed different levels of pressure amplitude mitigation ranging from approximately 10% to 85% depending on the operating condition, protrusion length, and the method of analysis. The hydraulic efficiency of the turbine decreased by a maximum of 3.5% that of the best efficiency point (BEP) with the implementation of the mitigation technique. The variations in the obtained mitigation levels and efficiencies depending on protrusion length and operating condition indicate the need for the implementation of a feedback-loop controller. Thus, the protrusion length can be actively optimizes based on the desired mitigation target.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"24 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139686518","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}
Centrifugal pumps with guide vanes are widely used in pump as turbine, energy storage pump station and water diversion project. In this work, a theoretical prediction model based on fluid governing equation and Oseen vortex model is proposed to predict the velocity moment downstream the impeller of centrifugal pump. Then, an optimization design method is established to optimize the impeller of centrifugal pump with guide vanes. A centrifugal pump with specific speed of 127 is used to validate the theoretical prediction model, results of velocity moment show that the deviation between predicted and simulated results is below 0.5% in average. Finally, the optimization design method is applied, results show that the average efficiency of optimal pump under the working conditions is 1.04% higher than that of baseline pump, which validates the reliability of proposed optimization method by theoretical prediction based on Oseen vortex. Analysis on velocity distribution and turbulence eddy dissipation shows that the optimization design method based on Oseen vortex can effectively improve the flow pattern and pump performance.
{"title":"Design Method for Impeller of Centrifugal Pump with Guide Vanes Based On Oseen Vortex","authors":"Yangping Lu, Ming Liu, Lei Tan, Demin Liu","doi":"10.1115/1.4064607","DOIUrl":"https://doi.org/10.1115/1.4064607","url":null,"abstract":"\u0000 Centrifugal pumps with guide vanes are widely used in pump as turbine, energy storage pump station and water diversion project. In this work, a theoretical prediction model based on fluid governing equation and Oseen vortex model is proposed to predict the velocity moment downstream the impeller of centrifugal pump. Then, an optimization design method is established to optimize the impeller of centrifugal pump with guide vanes. A centrifugal pump with specific speed of 127 is used to validate the theoretical prediction model, results of velocity moment show that the deviation between predicted and simulated results is below 0.5% in average. Finally, the optimization design method is applied, results show that the average efficiency of optimal pump under the working conditions is 1.04% higher than that of baseline pump, which validates the reliability of proposed optimization method by theoretical prediction based on Oseen vortex. Analysis on velocity distribution and turbulence eddy dissipation shows that the optimization design method based on Oseen vortex can effectively improve the flow pattern and pump performance.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"42 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139813228","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}
“Double-loop” theory was determined by deriving a correlation between turbulent fluctuating kinetic energy and water vapor volume fraction from the momentum equation, which further logically revealed the mystery of cavitation breaking around a three-dimensional symmetry hydrofoil based on the numerical results of large eddy simulation and Zwart-Gerber-Belamri cavitation model. When the second-order fluctuation moment V'xV'x and the streamwise velocity Vx are depleted, a vortex is generated, leading to alternating cavitation interface fluctuations. In one state, cavitation naturally breaks outward from the inner zone, triggering an up-and-down fluctuation in the normal velocity in the gap vortex and transferring external energy to the inner zone. In another state, it triggers a rise in an upward normal velocity in the attached vortex, creating an exchange of energy through the wake. Cavitation collapse caused by a reentrant jet stagnates the reverse Vx so that V'xV'x tends to zero. The pressure implosion resulting from the Shrinkage of the “Like-Rayleigh-Plesset” cavity at cavitation onset is stronger than the pressure implosion created by the vortex field during cavitation breaking.
{"title":"Derivation of “double-loop” Theory and Mechanism of Cavitation-vortex Interaction in Turbulent Cavitation Boundary Layer","authors":"Weiwei Jin","doi":"10.1115/1.4064532","DOIUrl":"https://doi.org/10.1115/1.4064532","url":null,"abstract":"\u0000 “Double-loop” theory was determined by deriving a correlation between turbulent fluctuating kinetic energy and water vapor volume fraction from the momentum equation, which further logically revealed the mystery of cavitation breaking around a three-dimensional symmetry hydrofoil based on the numerical results of large eddy simulation and Zwart-Gerber-Belamri cavitation model. When the second-order fluctuation moment V'xV'x and the streamwise velocity Vx are depleted, a vortex is generated, leading to alternating cavitation interface fluctuations. In one state, cavitation naturally breaks outward from the inner zone, triggering an up-and-down fluctuation in the normal velocity in the gap vortex and transferring external energy to the inner zone. In another state, it triggers a rise in an upward normal velocity in the attached vortex, creating an exchange of energy through the wake. Cavitation collapse caused by a reentrant jet stagnates the reverse Vx so that V'xV'x tends to zero. The pressure implosion resulting from the Shrinkage of the “Like-Rayleigh-Plesset” cavity at cavitation onset is stronger than the pressure implosion created by the vortex field during cavitation breaking.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"12 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139596086","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}
It is extremely difficult, if not impossible, for existing force balances to capture very small skin-friction drag (SFD) in a perturbed turbulent boundary layer (TBL), which is characterized by the unpredictable, nonuniform distribution of static surface pressure. A novel force balance is proposed, which combines the level principle, as deployed in Cheng et al.'s (2020, “A High-Resolution Floating-Element Force Balance for Friction Drag Measurement,” Meas. Sci. Technol., 32, p. 035301) force balance, with a single-degree-of-freedom air bearing mechanism. This mechanism acts to eliminate disturbances, such as nonuniform static pressure on the wall associated with high Reynolds number TBL or a TBL under control. As a result, the developed balance may be used to accurately measure SFD in the order of 10−3 N in a TBL with or without control. This balance has been successfully applied to measure the drag reduction (DR) of a TBL manipulated using one array of streamwise microjets, at friction Reynolds number Reτ = 3340 ∼ 5480.
{"title":"An Air-Bearing Floating-Element Force Balance for Friction Drag Measurement","authors":"Xiaohui Wei, Xin Zhang, Jiangang Chen, Yu Zhou","doi":"10.1115/1.4064294","DOIUrl":"https://doi.org/10.1115/1.4064294","url":null,"abstract":"\u0000 It is extremely difficult, if not impossible, for existing force balances to capture very small skin-friction drag (SFD) in a perturbed turbulent boundary layer (TBL), which is characterized by the unpredictable, nonuniform distribution of static surface pressure. A novel force balance is proposed, which combines the level principle, as deployed in Cheng et al.'s (2020, “A High-Resolution Floating-Element Force Balance for Friction Drag Measurement,” Meas. Sci. Technol., 32, p. 035301) force balance, with a single-degree-of-freedom air bearing mechanism. This mechanism acts to eliminate disturbances, such as nonuniform static pressure on the wall associated with high Reynolds number TBL or a TBL under control. As a result, the developed balance may be used to accurately measure SFD in the order of 10−3 N in a TBL with or without control. This balance has been successfully applied to measure the drag reduction (DR) of a TBL manipulated using one array of streamwise microjets, at friction Reynolds number Reτ = 3340 ∼ 5480.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"17 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139601648","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}
Brian T. Bohan, M. Polanka, Il J. Kim, Jeffrey M. Layng
Traditionally fluidic oscillators are designed to be planar. However, there are applications that may desire the exiting fluid to move in the third dimension. This could allow these oscillators to be more effective in applications such as fuel sprays, cooling flow, or flow control devices with its increase in effective spray area. This investigation designed a series of oscillators that curved the whole body and/or the exit nozzle to understand how to maximize out of plane motion. These configurations were compared to a baseline planar oscillator with no curved characteristics. Velocities were measured downstream of these oscillators within a data collection grid using a hot wire probe to determine the 3D shape of the exiting jet. Results show that configurations with only one of the two curved physical characteristics (i.e., only a curved body or a curved nozzle) produced the most curvature. Having both of the curved physical characteristics caused the nozzle width to decrease causing the axial spacing to decrease. Additionally, these curved exiting flows were only seen at mass flow rates below 40 standard liters per minute (SLPM). Higher mass flow rates caused the exiting flow to flatten, returning the flow to the baseline result of in-plane oscillations. This led to a decrease in jet spread.
{"title":"The Effect of Curved Geometry on Exiting Flow of Fluidic Oscillators","authors":"Brian T. Bohan, M. Polanka, Il J. Kim, Jeffrey M. Layng","doi":"10.1115/1.4064293","DOIUrl":"https://doi.org/10.1115/1.4064293","url":null,"abstract":"\u0000 Traditionally fluidic oscillators are designed to be planar. However, there are applications that may desire the exiting fluid to move in the third dimension. This could allow these oscillators to be more effective in applications such as fuel sprays, cooling flow, or flow control devices with its increase in effective spray area. This investigation designed a series of oscillators that curved the whole body and/or the exit nozzle to understand how to maximize out of plane motion. These configurations were compared to a baseline planar oscillator with no curved characteristics. Velocities were measured downstream of these oscillators within a data collection grid using a hot wire probe to determine the 3D shape of the exiting jet. Results show that configurations with only one of the two curved physical characteristics (i.e., only a curved body or a curved nozzle) produced the most curvature. Having both of the curved physical characteristics caused the nozzle width to decrease causing the axial spacing to decrease. Additionally, these curved exiting flows were only seen at mass flow rates below 40 standard liters per minute (SLPM). Higher mass flow rates caused the exiting flow to flatten, returning the flow to the baseline result of in-plane oscillations. This led to a decrease in jet spread.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"60 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139600793","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}
Exascale computing has extended the reach of resolved flow simulations in complex, heterogeneous systems far beyond conventional CFD capabilities. As a result, unprecedented pore and micro scale resolution has been achieved in domains that have been traditionally modeled by, and limited to, continuum, effective medium approaches. By making use of computational resources on the new exascale supercomputer, Frontier, at the Oak Ridge Leadership Computing Facility we performed flow simulations that have pushed the limits of domain-to-resolution ratios by several orders of magnitude for heterogeneous media. Our approach is an incompressible, Navier-Stokes CFD solver based on an adaptive, embedded boundary method supported by the Chombo software framework for applied PDEs. The computational workhorse in the CFD application code is an elliptic solver framework in Chombo for pressure-Poisson and viscous, Helmholtz terms that leverages a PETSc-hypre software interface tuned for accelerator-based platforms. We demonstrate scalability of our approach by replicating a unit cylinder packed with microspheres to achieve over 400 billion degrees of freedom simulated. These simulations model domain lengths of over 20 meters with channel volumes of over 400 cm^3 containing millions of packed spheres with 20 micron grid resolution, challenging current understanding of what it means to be a representative elementary volume of the continuum scale in heterogeneous media. We also simulate a range of Reynolds numbers to demonstrate wide applicability and robustness of the approach.
{"title":"Exascale CFD in Heterogeneous Systems","authors":"David Trebotich","doi":"10.1115/1.4064534","DOIUrl":"https://doi.org/10.1115/1.4064534","url":null,"abstract":"\u0000 Exascale computing has extended the reach of resolved flow simulations in complex, heterogeneous systems far beyond conventional CFD capabilities. As a result, unprecedented pore and micro scale resolution has been achieved in domains that have been traditionally modeled by, and limited to, continuum, effective medium approaches. By making use of computational resources on the new exascale supercomputer, Frontier, at the Oak Ridge Leadership Computing Facility we performed flow simulations that have pushed the limits of domain-to-resolution ratios by several orders of magnitude for heterogeneous media. Our approach is an incompressible, Navier-Stokes CFD solver based on an adaptive, embedded boundary method supported by the Chombo software framework for applied PDEs. The computational workhorse in the CFD application code is an elliptic solver framework in Chombo for pressure-Poisson and viscous, Helmholtz terms that leverages a PETSc-hypre software interface tuned for accelerator-based platforms. We demonstrate scalability of our approach by replicating a unit cylinder packed with microspheres to achieve over 400 billion degrees of freedom simulated. These simulations model domain lengths of over 20 meters with channel volumes of over 400 cm^3 containing millions of packed spheres with 20 micron grid resolution, challenging current understanding of what it means to be a representative elementary volume of the continuum scale in heterogeneous media. We also simulate a range of Reynolds numbers to demonstrate wide applicability and robustness of the approach.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"35 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139603853","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. Thyagarajan, Gangchen Ren, Debjyoti Banerjee, Vijay K. Dhir
Experiments were performed for determining the efficacy of a swirl-flow apparatus for phase separation of a premixed two-phase air water mixture. In the experiments gas and liquid flow rates were parametrically varied. The goal of this study was to determine the ideal operating conditions for phase separation of an adiabatic mixture and to serve as a benchmark for future experiments involving dynamic flash evaporation. The novel swirl-flow apparatus enables the formation of a stable air core (lighter fluid) in the middle of the separator tube due to centrifugal force induced by strategically injecting the two-phase mixture tangentially into the tubular test section. Separated air is removed by tapping into the air core using a retrieval tube that is mounted in the center of the test section. Conditions under which maximum phase-separation efficiency is obtained in the swirl-flow apparatus were identified and a correlation for the phase separation efficiency is proposed for the range of experimental conditions explored in this study.
{"title":"Experimental Investigation of the Performance of a Novel Adiabatic Swirl-Flow Separation Apparatus in Air-Water Two-Phase Flow","authors":"A. Thyagarajan, Gangchen Ren, Debjyoti Banerjee, Vijay K. Dhir","doi":"10.1115/1.4064531","DOIUrl":"https://doi.org/10.1115/1.4064531","url":null,"abstract":"\u0000 Experiments were performed for determining the efficacy of a swirl-flow apparatus for phase separation of a premixed two-phase air water mixture. In the experiments gas and liquid flow rates were parametrically varied. The goal of this study was to determine the ideal operating conditions for phase separation of an adiabatic mixture and to serve as a benchmark for future experiments involving dynamic flash evaporation. The novel swirl-flow apparatus enables the formation of a stable air core (lighter fluid) in the middle of the separator tube due to centrifugal force induced by strategically injecting the two-phase mixture tangentially into the tubular test section. Separated air is removed by tapping into the air core using a retrieval tube that is mounted in the center of the test section. Conditions under which maximum phase-separation efficiency is obtained in the swirl-flow apparatus were identified and a correlation for the phase separation efficiency is proposed for the range of experimental conditions explored in this study.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"77 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139604059","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}
Aaron Lattanzi, William Fullmer, Andrew Myers, Jordan Musser
In the presence of large size disparities, single-grid neighbor search algorithms lead to inflated neighbor lists that significantly degrade the performance of Lagrangian particle solvers. If Eulerian--Lagrangian (EL) frameworks are to remain performant when simulating realistic systems, improved neighbor detection approaches must be adopted. To this end, we consider the application of a multi-grid neighbor search (MGNS) algorithm in the MFIX-Exa software package, an exascale EL solver built upon the AMReX library. Details regarding the implementation and verification of MGNS are provided along with speedup curves for a bidisperse mixing layer. MGNS is shown to yield up to 15 × speedup on CPU and 6 × speedup on GPU for the problems considered here. The MFIX-Exa software is then validated for a variety of polydisperse flows. Finally, a brief discussion is given for how dynamic MGNS may be completed, with application to spatially varying particle size distributions.
在存在较大尺寸差异的情况下，单网格邻域搜索算法会导致邻域列表膨胀，从而显著降低拉格朗日粒子求解器的性能。如果欧拉-拉格朗日（EL）框架要在模拟现实系统时保持高性能，就必须采用改进的邻域检测方法。为此，我们考虑在 MFIX-Exa 软件包中应用多网格邻域搜索（MGNS）算法，这是一种基于 AMReX 库的超大规模 EL 求解器。本文提供了有关 MGNS 实施和验证的详细信息，以及双分散混合层的加速曲线。对于本文所考虑的问题，MGNS 在 CPU 上的速度提高了 15 倍，在 GPU 上的速度提高了 6 倍。随后，MFIX-Exa 软件针对各种多分散流动进行了验证。最后，简要讨论了如何完成动态 MGNS，并将其应用于空间变化的粒度分布。
{"title":"Towards Polydisperse Flows with MFIX-Exa","authors":"Aaron Lattanzi, William Fullmer, Andrew Myers, Jordan Musser","doi":"10.1115/1.4064533","DOIUrl":"https://doi.org/10.1115/1.4064533","url":null,"abstract":"\u0000 In the presence of large size disparities, single-grid neighbor search algorithms lead to inflated neighbor lists that significantly degrade the performance of Lagrangian particle solvers. If Eulerian--Lagrangian (EL) frameworks are to remain performant when simulating realistic systems, improved neighbor detection approaches must be adopted. To this end, we consider the application of a multi-grid neighbor search (MGNS) algorithm in the MFIX-Exa software package, an exascale EL solver built upon the AMReX library. Details regarding the implementation and verification of MGNS are provided along with speedup curves for a bidisperse mixing layer. MGNS is shown to yield up to 15 × speedup on CPU and 6 × speedup on GPU for the problems considered here. The MFIX-Exa software is then validated for a variety of polydisperse flows. Finally, a brief discussion is given for how dynamic MGNS may be completed, with application to spatially varying particle size distributions.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"118 29","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139605519","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 direct numerical simulation (DNS) study was performed on turbulent flow in the involute channel geometry to develop a numerical database and determine the differences compared with a flat parallel channel. The varying channel curvature along the walls was studied for differences in mean profiles. Parameters of interest include streamwise velocity, turbulent kinetic energy (TKE), and turbulence dissipation rate, as well as Reynolds stresses and turbulence transport terms. Profile sampling was carried out at 10 locations along the span of the involute. Additional DNS studies were performed on smaller domains of comparable curvature to the involute domain: a high curvature channel (high circular), a low curvature channel (low circular), and a flat channel (flat). Each of these four cases were compared against each other and to other DNS studies performed on parallel flows. The results indicate that the bulk involute channel flow does not differ significantly from a flat parallel channel flow and that the curvature of the walls does not significantly alter the mean flow parameters. However, the regions of the involute channel near the side walls exhibit interesting flow patterns, which warrant further study.
对渐开线水道几何形状中的湍流进行了直接数值模拟（DNS）研究，以开发一个数值数据库，并确定与平直平行水道相比的差异。研究了沿渠壁变化的渠曲，以确定平均剖面的差异。相关参数包括流向速度、湍流动能（TKE）、湍流耗散率以及雷诺应力和湍流传输项。沿渐开线跨度的 10 个位置进行了剖面取样。此外，还对曲率与渐开线域相当的较小域进行了 DNS 研究：高曲率通道（高圆）、低曲率通道（低圆）和平坦通道（平坦）。对这四种情况中的每一种进行了比较，并与其他针对平行流进行的 DNS 研究进行了比较。结果表明，大体积渐开线水道流动与平直平行水道流动没有明显区别，水道壁的曲率也不会明显改变平均流动参数。不过，渐开线通道靠近侧壁的区域表现出有趣的流动模式，值得进一步研究。
{"title":"Direct Numerical Simulation of Involute Channel Turbulence","authors":"Emilian Popov, Nicholas Mecham, I. Bolotnov","doi":"10.1115/1.4064496","DOIUrl":"https://doi.org/10.1115/1.4064496","url":null,"abstract":"\u0000 A direct numerical simulation (DNS) study was performed on turbulent flow in the involute channel geometry to develop a numerical database and determine the differences compared with a flat parallel channel. The varying channel curvature along the walls was studied for differences in mean profiles. Parameters of interest include streamwise velocity, turbulent kinetic energy (TKE), and turbulence dissipation rate, as well as Reynolds stresses and turbulence transport terms. Profile sampling was carried out at 10 locations along the span of the involute. Additional DNS studies were performed on smaller domains of comparable curvature to the involute domain: a high curvature channel (high circular), a low curvature channel (low circular), and a flat channel (flat). Each of these four cases were compared against each other and to other DNS studies performed on parallel flows. The results indicate that the bulk involute channel flow does not differ significantly from a flat parallel channel flow and that the curvature of the walls does not significantly alter the mean flow parameters. However, the regions of the involute channel near the side walls exhibit interesting flow patterns, which warrant further study.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"34 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139528470","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}
Abdolreza Raoufi, Andrew Williams, Craig Metcalfe, Paul-Emile Trudeau, Joshua R. Brinkerhoff, L. Warwaruk, Sina Ghaemi
The heat transfer and friction factor of turbulent pipe flows with different internal roughness are experimentally investigated. Three types of roughness in forms of a mesh, hemispherical elements, and a coil are added to the interior of pipes with a nominal diameter of two inches. The working fluid is air, and the Reynolds numbers varies from 20,000 to 90,000 in increments of 10,000. For investigating the heat-transfer properties the pipe wall is heated to 375°C while the inlet air remains at the room temperature. The measurements show that the mesh-type roughness results in a maximum Nusselt number, Nu, increase of approximately 6%, the pipes with hemispherical roughness increased the Nu by a maximum amount of 30%, and the coil increased Nu by up to 60% compared with the smooth pipe. The maximum increase of friction factor is 40% for the pipes with mesh-type roughness, 30% for pipes with hemispherical roughness, and 67% for pipes with coil roughness. The experimental results indicate that adding hemispherical and coil roughness to the internal surface of the pipe can lead to a significant improvement in the rate of heat-transfer while adding a mesh-type roughness can have marginal improvements and comes with a large frictional loss penalty. The analysis shows that the highest thermohydraulic performance is achieved using the hemispherical roughness elements.
{"title":"Comparison of Heat Transfer and Friction in Pipes with Various Internal Roughness","authors":"Abdolreza Raoufi, Andrew Williams, Craig Metcalfe, Paul-Emile Trudeau, Joshua R. Brinkerhoff, L. Warwaruk, Sina Ghaemi","doi":"10.1115/1.4064495","DOIUrl":"https://doi.org/10.1115/1.4064495","url":null,"abstract":"\u0000 The heat transfer and friction factor of turbulent pipe flows with different internal roughness are experimentally investigated. Three types of roughness in forms of a mesh, hemispherical elements, and a coil are added to the interior of pipes with a nominal diameter of two inches. The working fluid is air, and the Reynolds numbers varies from 20,000 to 90,000 in increments of 10,000. For investigating the heat-transfer properties the pipe wall is heated to 375°C while the inlet air remains at the room temperature. The measurements show that the mesh-type roughness results in a maximum Nusselt number, Nu, increase of approximately 6%, the pipes with hemispherical roughness increased the Nu by a maximum amount of 30%, and the coil increased Nu by up to 60% compared with the smooth pipe. The maximum increase of friction factor is 40% for the pipes with mesh-type roughness, 30% for pipes with hemispherical roughness, and 67% for pipes with coil roughness. The experimental results indicate that adding hemispherical and coil roughness to the internal surface of the pipe can lead to a significant improvement in the rate of heat-transfer while adding a mesh-type roughness can have marginal improvements and comes with a large frictional loss penalty. The analysis shows that the highest thermohydraulic performance is achieved using the hemispherical roughness elements.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"32 20","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139528504","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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