Abstract Fluid disinfection involving ultraviolet rays (UV) is a promising method due to its easy implementation and low cost compared to other methods. In the present work, fluid disinfection in a Taylor-Couette configuration operating with power-law fluids with different absorbance coefficients,and fluence rates were simulated using the Lattice Boltzmann Method. The effects of operating parameters such as Taylor and axial Reynolds numbers, power-law index behavior, and fluence rate were analyzed. Results show that the required UV dose decreases for an increase in absorbance coefficient, while it grows for increasing power-law indexes. For T a = 120 and Re = 3, the disinfection reaches 82.3% for pseudo-plastic fluids and is complete for dilatant fluids. Considering different absorbance coefficients, it was observed that a = 0.4 leads to complete disinfection regardless of the fluid. For a = 0.5, fluid disinfection is complete for the dilatant fluid only. A value of 0.6 leads to partial disinfection (~90%) for all fluids.
摘要与其他方法相比，采用紫外线(UV)进行液体消毒具有操作简单、成本低等优点，是一种很有前途的方法。在本工作中，使用格子玻尔兹曼方法模拟了具有不同吸光度系数和通量率的幂律流体在Taylor-Couette配置中的流体消毒。分析了泰勒雷诺数、轴向雷诺数、幂律折射率行为和流量等操作参数的影响。结果表明，随着吸光度系数的增加，所需紫外线剂量减小，而随着幂律指数的增加，所需紫外线剂量增大。当t_a = 120, Re = 3时，拟塑性流体消毒效果达到82.3%，膨胀流体消毒效果完全。考虑不同吸光度系数，无论采用何种液体，a = 0.4均可达到完全消毒。当a = 0.5时，仅对膨胀液消毒完成。值为0.6导致所有液体部分消毒(~90%)。
{"title":"Effect Of Power-Law Fluids Flow Structures On Germicides Disinfection Through Taylor-Couette Configuration","authors":"Feriel Hasballaoui, Samir Khali, Rachid Nebbali, Abderrahmane Zidane","doi":"10.1115/1.4063851","DOIUrl":"https://doi.org/10.1115/1.4063851","url":null,"abstract":"Abstract Fluid disinfection involving ultraviolet rays (UV) is a promising method due to its easy implementation and low cost compared to other methods. In the present work, fluid disinfection in a Taylor-Couette configuration operating with power-law fluids with different absorbance coefficients,and fluence rates were simulated using the Lattice Boltzmann Method. The effects of operating parameters such as Taylor and axial Reynolds numbers, power-law index behavior, and fluence rate were analyzed. Results show that the required UV dose decreases for an increase in absorbance coefficient, while it grows for increasing power-law indexes. For T a = 120 and Re = 3, the disinfection reaches 82.3% for pseudo-plastic fluids and is complete for dilatant fluids. Considering different absorbance coefficients, it was observed that a = 0.4 leads to complete disinfection regardless of the fluid. For a = 0.5, fluid disinfection is complete for the dilatant fluid only. A value of 0.6 leads to partial disinfection (~90%) for all fluids.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135513155","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}
Mehrdad Kalantar Neyestanaki, Georgiana Dunca, Pontus Jonsson, Michel J. Cervantes
Abstract The flowrate in hydraulic turbines can be measured using the pressure-time method specified by the IEC 60041 standard. This method assumes a one-dimensional (1D) flow and is limited to straight pipes with a uniform cross section and specific restrictions on length (L > 10 m) and velocity (U × L > 50 m2 s−1). However, in low-head hydropower plants, the intake typically has a variable cross section and small length, making it challenging to use this method. This paper presents the development of a methodology that extends the applicability of the pressure-time method for variable cross section by using three-dimensional computational fluid dynamics (3D CFD). A combination of 3D CFD and 1D pressure-time methods is employed iteratively to estimate the kinetic energy correction factor. The obtained time-dependent values are then used in the 1D pressure-time method to calculate the flowrate. The new methodology is applied with experiments performed on a test rig with a reducer. The obtained results illustrate the significantly different kinetic energy correction factor obtained than those obtained using constant or quasi-steady assumptions. The proposed methodology changes the mean deviation compared to the reference flowmeter from −0.83% (underestimation of flowrate) to ±0.1%, increasing the method's accuracy.
摘要水轮机流量的测量可采用IEC 60041标准规定的压力-时间法。该方法假设一维(1D)流动，并且仅限于具有均匀截面和特定长度限制(L >10 m)和速度(U × L >50m2 (s−1)。然而，在低水头水电站中，进水口通常具有变截面和小长度，这使得该方法的使用具有挑战性。本文提出了一种利用三维计算流体力学(3D CFD)扩展变截面压力-时间法适用性的方法。采用三维CFD和一维压力-时间法相结合的方法，迭代估计了动能校正系数。然后将获得的时间相关值用于一维压力-时间方法来计算流量。并在减速器试验台上进行了实验。得到的结果表明，所得到的动能校正系数与使用恒定或准稳态假设得到的校正系数有显著不同。所提出的方法将与参考流量计相比的平均偏差从- 0.83%(流量低估)改变为±0.1%，提高了方法的精度。
{"title":"Extending the Pressure-Time Method to Pipe with Variable Cross-Section with 3D Numerical Simulations","authors":"Mehrdad Kalantar Neyestanaki, Georgiana Dunca, Pontus Jonsson, Michel J. Cervantes","doi":"10.1115/1.4063491","DOIUrl":"https://doi.org/10.1115/1.4063491","url":null,"abstract":"Abstract The flowrate in hydraulic turbines can be measured using the pressure-time method specified by the IEC 60041 standard. This method assumes a one-dimensional (1D) flow and is limited to straight pipes with a uniform cross section and specific restrictions on length (L > 10 m) and velocity (U × L > 50 m2 s−1). However, in low-head hydropower plants, the intake typically has a variable cross section and small length, making it challenging to use this method. This paper presents the development of a methodology that extends the applicability of the pressure-time method for variable cross section by using three-dimensional computational fluid dynamics (3D CFD). A combination of 3D CFD and 1D pressure-time methods is employed iteratively to estimate the kinetic energy correction factor. The obtained time-dependent values are then used in the 1D pressure-time method to calculate the flowrate. The new methodology is applied with experiments performed on a test rig with a reducer. The obtained results illustrate the significantly different kinetic energy correction factor obtained than those obtained using constant or quasi-steady assumptions. The proposed methodology changes the mean deviation compared to the reference flowmeter from −0.83% (underestimation of flowrate) to ±0.1%, increasing the method's accuracy.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135824317","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 blockage ratio (BR) on turbulent flows around square cylinders at moderate Reynolds numbers are investigated using a time-resolved particle image velocimetry. The blockage ratios range from 2.5% to 15% and the Reynolds numbers based on the free-stream velocity and cylinder thickness are 3000, 7500, and 15 000. The flow dynamics are examined in terms of mean flow, Reynolds stresses, frequency spectra, reverse flow area and proper orthogonal decomposition (POD). The results show that the wake characteristics are nearly independent of Reynolds number and blockage ratio. Spectral analyses of the velocity fluctuations demonstrate that the von Kármán shedding frequency is independent of Reynolds number and blockage ratio, however, the Kelvin-Helmholtz frequencies increase with increasing Reynolds number and blockage ratio. The probability density function of the reverse flow area shows unimodal and bimodal distributions for the lower (BR = 5%) and higher (BR = 10%) blockage ratios, respectively, and the mean reverse flow area and its standard deviation decrease with increasing blockage ratio. The results also show that the contributions from the first POD mode pair to the total energy increase with blockage ratio but independent of Reynolds number. The POD mode coefficients show significant cycle-to-cycle variation at lower blockage ratios suggesting that the energetic structures are comparatively less organized at lower blockage ratios. The spectra of the velocity fluctuations, reverse flow area and POD mode coefficients all show dominant peaks at the fundamental shedding frequency.
{"title":"Effects Of Blockage Ratio On The Spatiotemporal Dynamics Of Turbulent Flow Separation Around A Square Cylinder At Moderate Reynolds Numbers","authors":"Fati Bio Abdul-Salam, Mark Tachie","doi":"10.1115/1.4063803","DOIUrl":"https://doi.org/10.1115/1.4063803","url":null,"abstract":"Abstract The effects of blockage ratio (BR) on turbulent flows around square cylinders at moderate Reynolds numbers are investigated using a time-resolved particle image velocimetry. The blockage ratios range from 2.5% to 15% and the Reynolds numbers based on the free-stream velocity and cylinder thickness are 3000, 7500, and 15 000. The flow dynamics are examined in terms of mean flow, Reynolds stresses, frequency spectra, reverse flow area and proper orthogonal decomposition (POD). The results show that the wake characteristics are nearly independent of Reynolds number and blockage ratio. Spectral analyses of the velocity fluctuations demonstrate that the von Kármán shedding frequency is independent of Reynolds number and blockage ratio, however, the Kelvin-Helmholtz frequencies increase with increasing Reynolds number and blockage ratio. The probability density function of the reverse flow area shows unimodal and bimodal distributions for the lower (BR = 5%) and higher (BR = 10%) blockage ratios, respectively, and the mean reverse flow area and its standard deviation decrease with increasing blockage ratio. The results also show that the contributions from the first POD mode pair to the total energy increase with blockage ratio but independent of Reynolds number. The POD mode coefficients show significant cycle-to-cycle variation at lower blockage ratios suggesting that the energetic structures are comparatively less organized at lower blockage ratios. The spectra of the velocity fluctuations, reverse flow area and POD mode coefficients all show dominant peaks at the fundamental shedding frequency.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135887993","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}
XiaoYu Wen, Jing Zhu, Botong Li, Limei Cao, Xinhui Si
Abstract The two-dimensional viscoelastic Giesekus flow past a circular cylinder is investigated by the openfoam platform based on the finite volume method. The physical parameters, including Weissenberg number (0.1≤Wi≤10), dimensionless rotation rate (0≤Ro≤2), and mobility factor (0≤α≤0.5), are investigated when Reynolds number is defined as 100. Two cases, i.e., β=0.1 and β=0.9, are considered. The combination effects are discussed using lift coefficients, instantaneous vorticity, time-averaged streamlines, and pressure distribution along the cylinder wall. The results are compared with other numerical computations. Dimensionless rotation rate destroys the symmetry of vertex shedding and suppresses the instability of the viscoelastic fluids. Elastic property facilitates the formation of the closed streamlins around the cylinder surface. These effects are amplified by the introduction of dimensionless rotation rate. However, shear-shinning property has opposite effects on this region. The distribution of polymer stress τxxp and τyyp are given to analyze the effects of viscoelasticity. As the fluids flow presents the shear-shinning property, the values of polymer stresses have an obvious decrease.
{"title":"Numerical Simulation Of Two-Dimensional Giesekus Flow Past A Rotating Cylinder","authors":"XiaoYu Wen, Jing Zhu, Botong Li, Limei Cao, Xinhui Si","doi":"10.1115/1.4063177","DOIUrl":"https://doi.org/10.1115/1.4063177","url":null,"abstract":"Abstract The two-dimensional viscoelastic Giesekus flow past a circular cylinder is investigated by the openfoam platform based on the finite volume method. The physical parameters, including Weissenberg number (0.1≤Wi≤10), dimensionless rotation rate (0≤Ro≤2), and mobility factor (0≤α≤0.5), are investigated when Reynolds number is defined as 100. Two cases, i.e., β=0.1 and β=0.9, are considered. The combination effects are discussed using lift coefficients, instantaneous vorticity, time-averaged streamlines, and pressure distribution along the cylinder wall. The results are compared with other numerical computations. Dimensionless rotation rate destroys the symmetry of vertex shedding and suppresses the instability of the viscoelastic fluids. Elastic property facilitates the formation of the closed streamlins around the cylinder surface. These effects are amplified by the introduction of dimensionless rotation rate. However, shear-shinning property has opposite effects on this region. The distribution of polymer stress τxxp and τyyp are given to analyze the effects of viscoelasticity. As the fluids flow presents the shear-shinning property, the values of polymer stresses have an obvious decrease.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136057938","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 streamwise aspect ratio and Reynolds number on the separated shear layer and near wake of rectangular cylinders in uniform flow are investigated experimentally using a particle image velocimetry system. Four length-to-height ratios (AR = 1, 2, 3, and 4) were examined at Reynolds numbers (based on freestream velocity and cylinder height) of 3000, 7200, 14,700, and 21,000. The results show that the separated shear layer is either shed directly into the wake region (AR1 and AR2) or reattaches onto the cylinder (AR4), regardless of the Reynolds number. Meanwhile, a transitional regime occurs for AR3 where mean flow reattachment on the cylinder is highly dependent on the Reynolds number. The peak magnitudes of the Reynolds stresses, turbulent kinetic energy, turbulence production, and its transport are highest for AR1 owing to stronger vortex shedding. Aspect ratio and Reynolds number also have significant effects on shear layer transitioning from laminar to turbulence but the transition lengths, when normalized by the corresponding value at Re = 3000, follow a universal power decay law. The wake characteristics, including the recirculation length and wake formation lengths, are independent of Reynolds number for AR1 but decrease with Reynolds number for the longer cylinders, while AR2 shows the largest values. The probability density functions and joint probability density functions are used to examine the effects of Reynolds number on the fluctuating velocities and momentum transport in the shear layer and near-wake region.
{"title":"Reynolds Number Effects On Turbulent Wakes Generated by Rectangular Cylinders with Streamwise Aspect Ratios Between 1 to 4","authors":"Manqi Liu, Sedem Kumahor, Mark Tachie","doi":"10.1115/1.4063434","DOIUrl":"https://doi.org/10.1115/1.4063434","url":null,"abstract":"Abstract The effects of streamwise aspect ratio and Reynolds number on the separated shear layer and near wake of rectangular cylinders in uniform flow are investigated experimentally using a particle image velocimetry system. Four length-to-height ratios (AR = 1, 2, 3, and 4) were examined at Reynolds numbers (based on freestream velocity and cylinder height) of 3000, 7200, 14,700, and 21,000. The results show that the separated shear layer is either shed directly into the wake region (AR1 and AR2) or reattaches onto the cylinder (AR4), regardless of the Reynolds number. Meanwhile, a transitional regime occurs for AR3 where mean flow reattachment on the cylinder is highly dependent on the Reynolds number. The peak magnitudes of the Reynolds stresses, turbulent kinetic energy, turbulence production, and its transport are highest for AR1 owing to stronger vortex shedding. Aspect ratio and Reynolds number also have significant effects on shear layer transitioning from laminar to turbulence but the transition lengths, when normalized by the corresponding value at Re = 3000, follow a universal power decay law. The wake characteristics, including the recirculation length and wake formation lengths, are independent of Reynolds number for AR1 but decrease with Reynolds number for the longer cylinders, while AR2 shows the largest values. The probability density functions and joint probability density functions are used to examine the effects of Reynolds number on the fluctuating velocities and momentum transport in the shear layer and near-wake region.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136057954","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}
Ahmed Alsharief, Xili Duan, Anand Yethiraj, Yuri Muzychka
Abstract This study examines the effects of surface wettability on the drag-reducing performance of three hydrophobic coatings, namely, flouropel coating (FPC-800M), superhydrophobic binary coating (SHBC), and ultra-ever dry (UED)—when applied to curved aluminum surfaces. The wettability and flow characteristics were characterized using three liquids of different viscosities: de-ionized water and silicone oils of 5 and 10 cSt. Static and dynamic contact angles on the surfaces were measured, and the drag reduction was evaluated using a Taylor–Couette flow cell in a rheometer. The static contact angle (SCA) measurements indicated that the coated surfaces were superhydrophobic for water, with a maximum static contact angle of 158 deg, but oleophilic for the 10 cSt silicone oil, with a static contact angle of 13 deg. The rheometer measurements using water showed a maximum drag reduction of 18% for the UED-coated surfaces. Interestingly, the oleophilic surfaces (which have low SCA) showed a maximum drag reduction of 6% and 7% in the silicone oils. The observed drag reduction is due to an increase in the plastron thickness, which is caused by an increase in the Reynolds number and dynamic pressure coupled with a decrease in the static pressure normal to the superhydrophobic wall.
{"title":"Wettability Effects of Curved Superhydrophobic Surfaces On Drag Reduction in Taylor-Couette Flows of Water and Oil","authors":"Ahmed Alsharief, Xili Duan, Anand Yethiraj, Yuri Muzychka","doi":"10.1115/1.4063435","DOIUrl":"https://doi.org/10.1115/1.4063435","url":null,"abstract":"Abstract This study examines the effects of surface wettability on the drag-reducing performance of three hydrophobic coatings, namely, flouropel coating (FPC-800M), superhydrophobic binary coating (SHBC), and ultra-ever dry (UED)—when applied to curved aluminum surfaces. The wettability and flow characteristics were characterized using three liquids of different viscosities: de-ionized water and silicone oils of 5 and 10 cSt. Static and dynamic contact angles on the surfaces were measured, and the drag reduction was evaluated using a Taylor–Couette flow cell in a rheometer. The static contact angle (SCA) measurements indicated that the coated surfaces were superhydrophobic for water, with a maximum static contact angle of 158 deg, but oleophilic for the 10 cSt silicone oil, with a static contact angle of 13 deg. The rheometer measurements using water showed a maximum drag reduction of 18% for the UED-coated surfaces. Interestingly, the oleophilic surfaces (which have low SCA) showed a maximum drag reduction of 6% and 7% in the silicone oils. The observed drag reduction is due to an increase in the plastron thickness, which is caused by an increase in the Reynolds number and dynamic pressure coupled with a decrease in the static pressure normal to the superhydrophobic wall.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135043466","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}
Nuno M. C. Martins, Didia Covas, Caterina Capponi, Silvia Meniconi, Bruno Brunone
Abstract Pipe networks exhibit complex geometries and are equipped with electromechanical devices capable of generating hydraulic transients. Most of these devices are remotely controlled and managed through an integrated system that prioritises network demands. This implies that potential hazardous pressure peaks, that may occur during each operation, may need to be taken into account. Consequently, when multiple operations take place in a short time interval, transient pressure waves, generated in different parts of the network and travelling back and forward, overlap and can be larger than the design maximum pressure. To address this concern, it is essential to evaluate the pressure damping rate of critical maneuvers and to identify a "safe" time interval between maneuvers to prevent the risk of inappropriate pressure waves overlapping. With the aim of analysing the damping rate of closure maneuvers, both numerical and laboratory experiments have been executed for a laminar flow in a reservoir-pipe-valve system. In this context, a three-dimensional Computational Fluid Dynamics, a one-dimensional and global model, the latter based on a sinusoidal function, have been used. Guidelines are then presented for identifying the safe time interval between maneuvers.
{"title":"Unified Approach for Damping Rate of Transient Laminar Flow: Experiments, Computational Fluid Dynamics, and One-Dimensional, and Global Models","authors":"Nuno M. C. Martins, Didia Covas, Caterina Capponi, Silvia Meniconi, Bruno Brunone","doi":"10.1115/1.4063697","DOIUrl":"https://doi.org/10.1115/1.4063697","url":null,"abstract":"Abstract Pipe networks exhibit complex geometries and are equipped with electromechanical devices capable of generating hydraulic transients. Most of these devices are remotely controlled and managed through an integrated system that prioritises network demands. This implies that potential hazardous pressure peaks, that may occur during each operation, may need to be taken into account. Consequently, when multiple operations take place in a short time interval, transient pressure waves, generated in different parts of the network and travelling back and forward, overlap and can be larger than the design maximum pressure. To address this concern, it is essential to evaluate the pressure damping rate of critical maneuvers and to identify a \"safe\" time interval between maneuvers to prevent the risk of inappropriate pressure waves overlapping. With the aim of analysing the damping rate of closure maneuvers, both numerical and laboratory experiments have been executed for a laminar flow in a reservoir-pipe-valve system. In this context, a three-dimensional Computational Fluid Dynamics, a one-dimensional and global model, the latter based on a sinusoidal function, have been used. Guidelines are then presented for identifying the safe time interval between maneuvers.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135254763","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}
Youhanna William, S. Kanagalingam, Mohamed H. Mohamed
Abstract The underlying physics ever behind the aerodynamics of an airfoil in Ground Effect (GE) is still not fully resolved. In this work, the aerodynamics for an airfoil in GE is investigated computationally for both transitional and turbulent flow regimes. Large Eddy Simulation (LES) is employed to explore the flow physics around a NACA0012 airfoil in ground vicinity, which is commonly used in wind energy applications. The Angle of Attack (AoA) is fixed at AoA = 10°, while the flight height to chord ratio (h/c) is variable. An analysis is conducted for the aerodynamic forces, i.e., the lift (CL), and the drag (CD). The behavior for the skin fiction drag (CDf) is explored in the light of the flow physics near the ground. In addition, the vortex shedding behavior is estimated at different height (h/c) for the transitional and turbulent flow regimes. At h/c = 0.2, the friction drag (CDf) is improved by 9.6% and 16.3% for the transitional and turbulent flow regimes, respectively. The results show that the frequencies for the vortex shedding decline significantly near the ground. This decline is correlated with the larger vortical structures and vortex developing mechanism.
{"title":"Ground Effect Investigation On the Aerodynamic Airfoil Behavior Using Large Eddy Simulation","authors":"Youhanna William, S. Kanagalingam, Mohamed H. Mohamed","doi":"10.1115/1.4063696","DOIUrl":"https://doi.org/10.1115/1.4063696","url":null,"abstract":"Abstract The underlying physics ever behind the aerodynamics of an airfoil in Ground Effect (GE) is still not fully resolved. In this work, the aerodynamics for an airfoil in GE is investigated computationally for both transitional and turbulent flow regimes. Large Eddy Simulation (LES) is employed to explore the flow physics around a NACA0012 airfoil in ground vicinity, which is commonly used in wind energy applications. The Angle of Attack (AoA) is fixed at AoA = 10°, while the flight height to chord ratio (h/c) is variable. An analysis is conducted for the aerodynamic forces, i.e., the lift (CL), and the drag (CD). The behavior for the skin fiction drag (CDf) is explored in the light of the flow physics near the ground. In addition, the vortex shedding behavior is estimated at different height (h/c) for the transitional and turbulent flow regimes. At h/c = 0.2, the friction drag (CDf) is improved by 9.6% and 16.3% for the transitional and turbulent flow regimes, respectively. The results show that the frequencies for the vortex shedding decline significantly near the ground. This decline is correlated with the larger vortical structures and vortex developing mechanism.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135254786","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 Bayesian estimation is applied to the analysis of backflow vortex instabilities in typical 3- and 4-bladed liquid propellant rocket engine inducers. The flow in the impeller eye is modeled as a set of equally intense and evenly spaced 2D axial vortices, located at the same radial distance from the axis and rotating at a fraction of the impeller speed. The circle theorem is used to predict the flow pressure in terms of the vortex number, intensity, rotational speed, and radial position. The theoretical spectra so obtained are frequency broadened to mimic the dispersion of the experimental results and parametrically fitted to the measured data by maximum likelihood estimation with equal and independent Gaussian errors. The method is applied to three inducers, tested in water at room temperature and different operating conditions. It successfully characterizes backflow instabilities using the signals of a single pressure transducer flush-mounted in the impeller eye, effectively bypassing the aliasing limitations and the data acquisition/reduction complexities of traditional multiple-sensor cross-correlation methods. The identification returns the estimates of the model parameters and their standard deviations, providing the information necessary for assessing the accuracy and statistical significance of the results. The flowrate is found to be the major factor affecting the backflow vortex instability, which, on the other hand, is rather insensitive to the occurrence of cavitation. The results are consistent with the data reported in the literature, as well as with those generated by the auxiliary models specifically developed for initializing the maximum likelihood searches and supporting the identification procedure.
{"title":"Maximum Likelihood Identification of Backflow Vortex Instability in Rocket Engine Inducers","authors":"Stefano Guidolotti, Luca d'Agostino","doi":"10.1115/1.4063695","DOIUrl":"https://doi.org/10.1115/1.4063695","url":null,"abstract":"Abstract Bayesian estimation is applied to the analysis of backflow vortex instabilities in typical 3- and 4-bladed liquid propellant rocket engine inducers. The flow in the impeller eye is modeled as a set of equally intense and evenly spaced 2D axial vortices, located at the same radial distance from the axis and rotating at a fraction of the impeller speed. The circle theorem is used to predict the flow pressure in terms of the vortex number, intensity, rotational speed, and radial position. The theoretical spectra so obtained are frequency broadened to mimic the dispersion of the experimental results and parametrically fitted to the measured data by maximum likelihood estimation with equal and independent Gaussian errors. The method is applied to three inducers, tested in water at room temperature and different operating conditions. It successfully characterizes backflow instabilities using the signals of a single pressure transducer flush-mounted in the impeller eye, effectively bypassing the aliasing limitations and the data acquisition/reduction complexities of traditional multiple-sensor cross-correlation methods. The identification returns the estimates of the model parameters and their standard deviations, providing the information necessary for assessing the accuracy and statistical significance of the results. The flowrate is found to be the major factor affecting the backflow vortex instability, which, on the other hand, is rather insensitive to the occurrence of cavitation. The results are consistent with the data reported in the literature, as well as with those generated by the auxiliary models specifically developed for initializing the maximum likelihood searches and supporting the identification procedure.","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135351991","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}
{"title":"Discussion on “Suction and Injection Impacts on Casson Nanofluid With Gyrotactic Micro-organisms Over a Moving Wedge” (Jabeen, K., Mushtaq, M., Akram Muntazir, R. M., 2022, ASME J. Fluids Eng., 144(1), p. 011204)","authors":"Asterios Pantokratoras","doi":"10.1115/1.4063460","DOIUrl":"https://doi.org/10.1115/1.4063460","url":null,"abstract":"","PeriodicalId":54833,"journal":{"name":"Journal of Fluids Engineering-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135689452","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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