Abstract Information on bubble distributions in liquids is required for various applications. Employment of inverse acoustic scattering is the usual path to determine these distributions. This path is based on solving a Fredholm first kind integral equation leading to an ill-posed mathematical problem. The usual regularization methods for such a problem are quite complex and require introduction of some tuning parameters. Meanwhile, as shown in this paper, another method works well for media, where acoustic waves propagate with the small losses. This method is based on extraction of a singular Cauchy integral in the above-mentioned equation and of the further inversion of this integral. Such a regularization via inversion is a simple operation that gives numerically stable solutions. Here this regularization is described, verified using the method of manufactured solutions and validated with the well-known already published experimental data.
{"title":"A Method to Determine Bubble Distribution in Liquid Using Data of Inverse Acoustical Scattering","authors":"Eduard Amromin","doi":"10.1115/1.4064005","DOIUrl":"https://doi.org/10.1115/1.4064005","url":null,"abstract":"Abstract Information on bubble distributions in liquids is required for various applications. Employment of inverse acoustic scattering is the usual path to determine these distributions. This path is based on solving a Fredholm first kind integral equation leading to an ill-posed mathematical problem. The usual regularization methods for such a problem are quite complex and require introduction of some tuning parameters. Meanwhile, as shown in this paper, another method works well for media, where acoustic waves propagate with the small losses. This method is based on extraction of a singular Cauchy integral in the above-mentioned equation and of the further inversion of this integral. Such a regularization via inversion is a simple operation that gives numerically stable solutions. Here this regularization is described, verified using the method of manufactured solutions and validated with the well-known already published experimental data.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135432119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The fluidic behaviours and interactions present in a setup utilising perforated blockages and downstream pin-fin are elucidated: specifically, the role of jet curvature in flow interactions and the interaction of end-wall flows around the pin-fins subjected to impinging jet. To this end, a combination of particle image velocimetry based measurements and oil-dye surface flow visualization technique is utilised. Two different configurations of jet flows, with or without flanking jets, and three different distances between the pin-fins and blockages were considered. Jet curvature can result in flow inclinations of as much as 45° - 60° interacting with the pin-fins and the majority of the jet flow skewed towards the inner side of the pin-fin. At the end-wall, the interaction with nearby structures, being blockages or pin-fins, alter the shape and profile of the flows. This alteration is in contrast to those around conventional pin-fin arrays which remain largely unaltered in the presence of nearby pin-fins.
{"title":"Orifice Jet Curvature And Its Interaction With A Row Of Short Pin-Fins","authors":"Sjouke Schekman, Tongbeum Kim","doi":"10.1115/1.4064008","DOIUrl":"https://doi.org/10.1115/1.4064008","url":null,"abstract":"Abstract The fluidic behaviours and interactions present in a setup utilising perforated blockages and downstream pin-fin are elucidated: specifically, the role of jet curvature in flow interactions and the interaction of end-wall flows around the pin-fins subjected to impinging jet. To this end, a combination of particle image velocimetry based measurements and oil-dye surface flow visualization technique is utilised. Two different configurations of jet flows, with or without flanking jets, and three different distances between the pin-fins and blockages were considered. Jet curvature can result in flow inclinations of as much as 45° - 60° interacting with the pin-fins and the majority of the jet flow skewed towards the inner side of the pin-fin. At the end-wall, the interaction with nearby structures, being blockages or pin-fins, alter the shape and profile of the flows. This alteration is in contrast to those around conventional pin-fin arrays which remain largely unaltered in the presence of nearby pin-fins.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135433009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The effects of perforation on the characteristics of the downstream vortex of a micro-vortex generator (MVG) mounted on a flat plate, are numerically investigated in this paper. A single rectangular MVG with circular and square perforation, at different locations on the MVG, is mounted on a flat plate at 16 degree installation angle with respect to the flow direction. The MVG is placed inside a turbulent boundary layer at Reynolds number of 16293 based on MVG height and free-stream velocity. Analysis is conducted using the Reynolds Averaged Navier-Stokes (RANS) modeling. The results of the analysis show that the MVG vortex is most effective when the perforation is located at the center and lower side of the MVG. The vortex strength for MVG with this perforated location is found to be much higher than the MVG without any perforation.
{"title":"Effect of Perforation on Vortex Characteristics of a Micro-Vortex Generator Mounted on a Flat Plate","authors":"Abhishek Khare, Shashank Khurana","doi":"10.1115/1.4064009","DOIUrl":"https://doi.org/10.1115/1.4064009","url":null,"abstract":"Abstract The effects of perforation on the characteristics of the downstream vortex of a micro-vortex generator (MVG) mounted on a flat plate, are numerically investigated in this paper. A single rectangular MVG with circular and square perforation, at different locations on the MVG, is mounted on a flat plate at 16 degree installation angle with respect to the flow direction. The MVG is placed inside a turbulent boundary layer at Reynolds number of 16293 based on MVG height and free-stream velocity. Analysis is conducted using the Reynolds Averaged Navier-Stokes (RANS) modeling. The results of the analysis show that the MVG vortex is most effective when the perforation is located at the center and lower side of the MVG. The vortex strength for MVG with this perforated location is found to be much higher than the MVG without any perforation.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135432378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract It has been confirmed that the passive obstacles would substantially depress the leading-edge cavitation in a waterjet pump. Combined with the experiments and numerical simulations, this work revisits blade cavitation evolutions to demonstrate the stabilizing effects of obstacles on cavitation unsteadiness. The multiscale POD (mPOD) and EEMD are adopted to study the energy contributions regarding the cavitation-induced loading and thrust. The mPOD modes illuminate that the leading-edge loading oscillations of the obstacle blade are consequently eliminated where the cavitation is completely depressed and the obstacle cavitation wakes greatly contribute to loading excitation. The thrust statistics demonstrate that the thrust extremes and standard deviation in some revolutions can be well reduced as the large-scale leading-edge cavity depression. The adaptive spectrums obtained by EEMD further illuminate that both the tonal and broadband components of blade thrust would be reasonably degraded to some degree. The pump with only one obstacle implementation, as an improvement strategy, is comparatively studied and indicates that single obstacle configuration presents positive effects on the leading-edge cavity depression owing to the pressure-raising effects and can reduce the unnecessary energy loss compared with two obstacles.
{"title":"Energy Contribution Study Of Blade Cavitation Control By Obstacles In A Waterjet Pump Based On mPOD And EEMD","authors":"Guoshou Zhao, Ning Liang, Qianqian Li, Wei Dong, Linlin Cao, Dazhuan Wu","doi":"10.1115/1.4064006","DOIUrl":"https://doi.org/10.1115/1.4064006","url":null,"abstract":"Abstract It has been confirmed that the passive obstacles would substantially depress the leading-edge cavitation in a waterjet pump. Combined with the experiments and numerical simulations, this work revisits blade cavitation evolutions to demonstrate the stabilizing effects of obstacles on cavitation unsteadiness. The multiscale POD (mPOD) and EEMD are adopted to study the energy contributions regarding the cavitation-induced loading and thrust. The mPOD modes illuminate that the leading-edge loading oscillations of the obstacle blade are consequently eliminated where the cavitation is completely depressed and the obstacle cavitation wakes greatly contribute to loading excitation. The thrust statistics demonstrate that the thrust extremes and standard deviation in some revolutions can be well reduced as the large-scale leading-edge cavity depression. The adaptive spectrums obtained by EEMD further illuminate that both the tonal and broadband components of blade thrust would be reasonably degraded to some degree. The pump with only one obstacle implementation, as an improvement strategy, is comparatively studied and indicates that single obstacle configuration presents positive effects on the leading-edge cavity depression owing to the pressure-raising effects and can reduce the unnecessary energy loss compared with two obstacles.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135432118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Most of the oil transportation industries deal with liquid-liquid flow considering the adiabatic situation. In such applications, film thickness measurement plays a very significant role in understanding the flow characteristics. The distribution of phases for efficient wall treatment and to understand the phase distribution, measurement of film thickness is very important. Among different flow patterns, stratified flow is most common for low and medium viscous oil-water flow. At lower oil velocities, stratified flow is observed downstream of singularity whereas in the upstream section, stratified flow is observed for low to medium oil velocities and high-water superficial velocity. Variation of oil film thickness for stratified flow has been analyzed in the present study. Results show that oil film thickness decreases with the increase in the superficial velocity of water (Us-Water) for a constant oil superficial velocity (Us-Oil). With the increase in the volume fraction of one phase, the film thickness of that phase increases. As Us-Oil increases, the film thickness of oil also increases for a constant Us-Water. Oil film thickness is directly proportional to the viscosity of oils. This means, the more the viscosity of the oil, the more will be the oil film thickness.
{"title":"Numerical Studies On the Oil Film Thickness in the Case of Stratified Flow with Different Oil-Water Flow Combinations Through Sudden Contraction Tube","authors":"Mushtaque Momin, Soham Mahindar, Faisal Rahmani, Mukesh Sharma","doi":"10.1115/1.4064007","DOIUrl":"https://doi.org/10.1115/1.4064007","url":null,"abstract":"Abstract Most of the oil transportation industries deal with liquid-liquid flow considering the adiabatic situation. In such applications, film thickness measurement plays a very significant role in understanding the flow characteristics. The distribution of phases for efficient wall treatment and to understand the phase distribution, measurement of film thickness is very important. Among different flow patterns, stratified flow is most common for low and medium viscous oil-water flow. At lower oil velocities, stratified flow is observed downstream of singularity whereas in the upstream section, stratified flow is observed for low to medium oil velocities and high-water superficial velocity. Variation of oil film thickness for stratified flow has been analyzed in the present study. Results show that oil film thickness decreases with the increase in the superficial velocity of water (Us-Water) for a constant oil superficial velocity (Us-Oil). With the increase in the volume fraction of one phase, the film thickness of that phase increases. As Us-Oil increases, the film thickness of oil also increases for a constant Us-Water. Oil film thickness is directly proportional to the viscosity of oils. This means, the more the viscosity of the oil, the more will be the oil film thickness.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135432994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Plunging liquid jets are a multiphase flow studied to understand how gas is entrained in a liquid and the resulting mixing capabilities. From existing literature, it has been hypothesized that rising bubbles play a noticeable role in the multiphase hydrodynamics of the plunging liquid jet bubble plume, and that separating the rising bubbles from the incoming liquid jet can result in a significant increase in the depth of the bubble plume. This study explores the effects of separating the incoming liquid jet from the rising bubble plume through floor interactions and compression effects due to a finite tank depth. This configuration is found in many natural and industrial systems, but not within published literature. Using existing theoretical models of infinite depth plunging liquid jet systems, which align reasonably well with captured baseline data, two models are developed for when floor interactions are present, one theoretical and one empirical. The models show a correlation between plume spread and floor interaction with the incoming plunging liquid jet bubble plume. Data acquired through stereographic backlit imaging over a range of flow rates show a reasonable agreement with the proposed models.
{"title":"Plume Spreading Due to Floor Conditions of A Plunging Liquid Jet Using Stereographic Backlit Imaging","authors":"Roy Pillers, Theodore J. Heindel","doi":"10.1115/1.4064004","DOIUrl":"https://doi.org/10.1115/1.4064004","url":null,"abstract":"Abstract Plunging liquid jets are a multiphase flow studied to understand how gas is entrained in a liquid and the resulting mixing capabilities. From existing literature, it has been hypothesized that rising bubbles play a noticeable role in the multiphase hydrodynamics of the plunging liquid jet bubble plume, and that separating the rising bubbles from the incoming liquid jet can result in a significant increase in the depth of the bubble plume. This study explores the effects of separating the incoming liquid jet from the rising bubble plume through floor interactions and compression effects due to a finite tank depth. This configuration is found in many natural and industrial systems, but not within published literature. Using existing theoretical models of infinite depth plunging liquid jet systems, which align reasonably well with captured baseline data, two models are developed for when floor interactions are present, one theoretical and one empirical. The models show a correlation between plume spread and floor interaction with the incoming plunging liquid jet bubble plume. Data acquired through stereographic backlit imaging over a range of flow rates show a reasonable agreement with the proposed models.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135474886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Drew Safford, Junfeng Wang, Charles Liang, Kenneth Visser
Abstract An unsteady Reynolds-averaged Navier–Stokes model on body-fitted meshes in a commercial package (SimericsMP+) with a mismatched grid interface is used to study fluid dynamics around a ducted wind turbine. The model is validated by studying turbulent flow past a marine propeller. The nondimensional thrust and torque coefficients are compared against experimental data and results from a large eddy simulation model. Both coefficients are found to be within 3% of experimental results. Following this validation, the impact of different tip speed ratios on the ducted wind turbine's fluid dynamics is assessed. The optimal tip speed ratio is found to be the design value of 3.93 with a maximum power coefficient of 0.465 based on the duct exit area. The corresponding thrust coefficient is found to be 1.02 based on the rotor area. Lower tip speed ratios experience larger flow separation on the duct interior. Higher tip speed ratios decrease the size of the low-velocity region behind the hub. The ducted wind turbine's performance at design conditions is compared to an open rotor. The ducted wind turbine increases the power coefficient by 96% over the open rotor. The impact of hub size on the ducted wind turbine is also studied by simulating a smaller hub with 77% diameter. At the design tip speed ratio, the smaller hub has a power coefficient of 0.417. The maximum power coefficient is found to be 0.446 at a higher tip speed ratio of 4.5.
{"title":"Unsteady Reynolds-Averaged Navier-Stokes Simulations Of A Ducted Wind Turbine","authors":"Drew Safford, Junfeng Wang, Charles Liang, Kenneth Visser","doi":"10.1115/1.4063615","DOIUrl":"https://doi.org/10.1115/1.4063615","url":null,"abstract":"Abstract An unsteady Reynolds-averaged Navier–Stokes model on body-fitted meshes in a commercial package (SimericsMP+) with a mismatched grid interface is used to study fluid dynamics around a ducted wind turbine. The model is validated by studying turbulent flow past a marine propeller. The nondimensional thrust and torque coefficients are compared against experimental data and results from a large eddy simulation model. Both coefficients are found to be within 3% of experimental results. Following this validation, the impact of different tip speed ratios on the ducted wind turbine's fluid dynamics is assessed. The optimal tip speed ratio is found to be the design value of 3.93 with a maximum power coefficient of 0.465 based on the duct exit area. The corresponding thrust coefficient is found to be 1.02 based on the rotor area. Lower tip speed ratios experience larger flow separation on the duct interior. Higher tip speed ratios decrease the size of the low-velocity region behind the hub. The ducted wind turbine's performance at design conditions is compared to an open rotor. The ducted wind turbine increases the power coefficient by 96% over the open rotor. The impact of hub size on the ducted wind turbine is also studied by simulating a smaller hub with 77% diameter. At the design tip speed ratio, the smaller hub has a power coefficient of 0.417. The maximum power coefficient is found to be 0.446 at a higher tip speed ratio of 4.5.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In cycling races, overtaking is a crucial maneuver that involves drafting behind and moving to the side of another cyclist. The flow interaction between the cyclists has a very significant impact on the aerodynamic performance. Previous experimental and numerical studies have shown the aerodynamic drag changes at certain relative positions between cyclists. This study aims at providing a comprehensive aerodynamic power contour along a complete overtaking path, detailing the power at different relative positions to develop efficient overtaking strategies. The aerodynamic results are obtained with numerical simulations, the accuracy of which is validated against wind tunnel experiments. Improved sampling and data-fitting approaches are employed to enhance previous findings. The results show that starting the overtaking maneuver closest to the leading cyclist and overtaking with a larger lateral separation is the most aerodynamically efficient strategy. These findings provide valuable insights into developing optimal overtaking strategies in competitive cycling races.
{"title":"A Numerical Study Of Cyclist-Cyclist Aerodynamic Interaction Towards Efficient Overtaking Strategy","authors":"Sinforiano Cantos, Kwan Pui Mok, Peng Zhou, Hanbo Jiang, Xiaochen Mao, Siyang Zhong, Xin Zhang","doi":"10.1115/1.4063935","DOIUrl":"https://doi.org/10.1115/1.4063935","url":null,"abstract":"Abstract In cycling races, overtaking is a crucial maneuver that involves drafting behind and moving to the side of another cyclist. The flow interaction between the cyclists has a very significant impact on the aerodynamic performance. Previous experimental and numerical studies have shown the aerodynamic drag changes at certain relative positions between cyclists. This study aims at providing a comprehensive aerodynamic power contour along a complete overtaking path, detailing the power at different relative positions to develop efficient overtaking strategies. The aerodynamic results are obtained with numerical simulations, the accuracy of which is validated against wind tunnel experiments. Improved sampling and data-fitting approaches are employed to enhance previous findings. The results show that starting the overtaking maneuver closest to the leading cyclist and overtaking with a larger lateral separation is the most aerodynamically efficient strategy. These findings provide valuable insights into developing optimal overtaking strategies in competitive cycling races.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136103266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this study, the flow physics of the forward-facing (FF) and backward-facing (BF) trapezoidal cylinders (TC) subjected to two-dimensional, incompressible, and laminar flow is investigated using an in-house developed flexible forcing immersed boundary lattice Boltzmann solver [Dash et al. (2014)]. The Reynolds number (Re) is defined based on the cylinder's characteristic length D. For the steady and unsteady flow regimes, Re is varied in the ranges of 10-40 and 75-125, respectively. The TC's shape is varied by modifying its non-dimensional axial H/D and transverse Y/D length scales, between 0.5 to 2 and 0 to 1, respectively. Here, TC's horizontal central axis is always aligned along the incoming flow direction. It is observed that the flow separation points on the FF-TC and BF-TC are strongly influenced by the geometric (H/D and Y/D) and flow parameters (Re). Based on the boundary layer separation point, we have categorized the wake flow regimes behind the FF-TC and BF-TC into four types. In addition, the effect of the geometric and flow parameters on the drag coefficient (Cd), vortex shedding frequency, and steady and unsteady wake characteristics are thoroughly investigated here. Furthermore, by performing non-linear regression analysis, we have proposed a set of correlation equations for the Cd and Strouhal number (St), using which the aerodynamic characteristics of differently shaped TC can be derived in the considered Re range without performing rigorous numerical simulations or experiments.
在本研究中，使用自主开发的柔性强迫浸没边界晶格玻尔兹曼解算器研究了前面向(FF)和后面向(BF)梯形柱体(TC)在二维不可压缩层流下的流动物理特性[Dash et al.(2014)]。雷诺数(Re)是根据气缸的特征长度d来定义的。对于定常流动和非定常流动，Re分别在10-40和75-125范围内变化。通过改变其无量纲轴向H/D和横向Y/D长度尺度，分别在0.5到2和0到1之间改变TC的形状。在这里，TC的水平中心轴总是沿着来流方向对齐。观察到，几何参数(H/D和Y/D)和流动参数(Re)对FF-TC和BF-TC上的流动分离点有强烈的影响。基于边界层分离点，我们将FF-TC和BF-TC后面的尾流流型分为四种类型。此外，还深入研究了几何参数和流动参数对阻力系数(Cd)、旋涡脱落频率以及定常和非定常尾迹特性的影响。此外，通过非线性回归分析，我们提出了一组Cd和Strouhal数(St)的相关方程，利用该方程可以在考虑的Re范围内推导出不同形状TC的气动特性，而无需进行严格的数值模拟或实验。
{"title":"An Investigation On The Steady And Unsteady Wake Flow Regimes And Aerodynamic Characteristics Of The Trapezoidal Cylinders Using Immersed Boundary-Lattice Boltzmann Method","authors":"Akash Bhunia, Prabir Sikdar, Sunil Manohar Dash","doi":"10.1115/1.4063933","DOIUrl":"https://doi.org/10.1115/1.4063933","url":null,"abstract":"Abstract In this study, the flow physics of the forward-facing (FF) and backward-facing (BF) trapezoidal cylinders (TC) subjected to two-dimensional, incompressible, and laminar flow is investigated using an in-house developed flexible forcing immersed boundary lattice Boltzmann solver [Dash et al. (2014)]. The Reynolds number (Re) is defined based on the cylinder's characteristic length D. For the steady and unsteady flow regimes, Re is varied in the ranges of 10-40 and 75-125, respectively. The TC's shape is varied by modifying its non-dimensional axial H/D and transverse Y/D length scales, between 0.5 to 2 and 0 to 1, respectively. Here, TC's horizontal central axis is always aligned along the incoming flow direction. It is observed that the flow separation points on the FF-TC and BF-TC are strongly influenced by the geometric (H/D and Y/D) and flow parameters (Re). Based on the boundary layer separation point, we have categorized the wake flow regimes behind the FF-TC and BF-TC into four types. In addition, the effect of the geometric and flow parameters on the drag coefficient (Cd), vortex shedding frequency, and steady and unsteady wake characteristics are thoroughly investigated here. Furthermore, by performing non-linear regression analysis, we have proposed a set of correlation equations for the Cd and Strouhal number (St), using which the aerodynamic characteristics of differently shaped TC can be derived in the considered Re range without performing rigorous numerical simulations or experiments.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136102691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The aerodynamics and flowfield of a rectangular semi-wing equipped with four four-bladed propellers and a 40%-chord full-span plain trailing-edge flap were investigated by using force balance and particle image velocimetry (PIV). The DEP (distributed electric propulsion) wing was tilted from zero to 90-deg angle of attack. The maximum lift coefficient, lift-curve slope, and stall angle of the DEP wing were found to increase significantly with increasing propeller rotation. The DEP wing also exhibited a gradual stall in contrast to the sudden stall of the baseline wing. The lift coefficient of the DEP wing positioned vertically at 90 deg was also found to be greatly increased with increasing propeller rotation. Regardless of the magnitude of propeller rotation, the general pattern and behavior of the lift curve was consistent. For the flapped DEP wing, the deployment of the flap led to a further increase in the maximum lift coefficient and lift-curve slope but an earlier wing stall and an increased drag as compared to the unflapped wing. The flap deflection also led to a lowered lift coefficient in the post-stall angle-of-attack regime as compared to the unflapped DEP wing. Gurney flap was also employed to further increase the lift generation of the DEP wing. The lift augmentation produced by the propeller slipstream was supplemented by the PIV flowfield measurements.
{"title":"Aerodynamics And Flowfield Of Dep Tiltwing During Transition With Deflected Trailing-Edge Flap","authors":"Timothy Lee, James Ni, Ge Lin","doi":"10.1115/1.4063934","DOIUrl":"https://doi.org/10.1115/1.4063934","url":null,"abstract":"Abstract The aerodynamics and flowfield of a rectangular semi-wing equipped with four four-bladed propellers and a 40%-chord full-span plain trailing-edge flap were investigated by using force balance and particle image velocimetry (PIV). The DEP (distributed electric propulsion) wing was tilted from zero to 90-deg angle of attack. The maximum lift coefficient, lift-curve slope, and stall angle of the DEP wing were found to increase significantly with increasing propeller rotation. The DEP wing also exhibited a gradual stall in contrast to the sudden stall of the baseline wing. The lift coefficient of the DEP wing positioned vertically at 90 deg was also found to be greatly increased with increasing propeller rotation. Regardless of the magnitude of propeller rotation, the general pattern and behavior of the lift curve was consistent. For the flapped DEP wing, the deployment of the flap led to a further increase in the maximum lift coefficient and lift-curve slope but an earlier wing stall and an increased drag as compared to the unflapped wing. The flap deflection also led to a lowered lift coefficient in the post-stall angle-of-attack regime as compared to the unflapped DEP wing. Gurney flap was also employed to further increase the lift generation of the DEP wing. The lift augmentation produced by the propeller slipstream was supplemented by the PIV flowfield measurements.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136104852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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