The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Horia Hangan - One of the best experts on this subject based on the ideXlab platform.
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distributed forcing flow control in the wake of a Blunt Trailing Edge profiled body using plasma actuators
Physics of Fluids, 2015Co-Authors: Arash Naghiblahouti, Horia Hangan, Philippe LavoieAbstract:A modern flow control technique for reducing the drag associated with the periodic shedding of von Karman vortices in the wake of a Blunt Trailing Edge profiled body is presented. The technique involves distributed forcing of the wake flow using an array of dielectric barrier discharge plasma actuators, with a spanwise spacing matched to the spanwise wavelength of the dominant secondary wake instability. The experiments include measurement of the velocity field in multiple vertical and horizontal planes in the wake using particle image velocimetry, as well as base pressure, at Reynolds numbers of 2000, 3000, and 5000 based on Trailing Edge thickness. The flow control technique causes elongation of the vortex formation region across the span, and significant reduction of the fluctuating and total drag forces, up to a maximum of 94% and 18%, respectively. The effectiveness of the flow control technique is shown to be dependent on the induced momentum coefficient. Proper orthogonal decomposition analysis is ...
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wake instabilities of a Blunt Trailing Edge profiled body at intermediate reynolds numbers
Experiments in Fluids, 2014Co-Authors: Arash Naghiblahouti, Philippe Lavoie, Horia HanganAbstract:Experiments have been conducted to identify and characterize the instabilities in the wake of a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, for a broad range of Reynolds numbers (\(2{,}000\le Re(d)\le 50{,}000\) based on the thickness of the body). These experiments, which include measurements of the wake velocity field using hot-wire anemometry and particle image velocimetry, complement previous studies of the wake flow for the same geometry at lower and higher Reynolds numbers. The spatial characteristics of the primary wake instability (the von Karman vortex street) are found to have relatively little variation in the range of Reynolds numbers investigated, in spite of the transition of the boundary layer upstream of the Trailing Edge from a laminar to a turbulent state. The dominant secondary instability, identified based on the structure of velocity and vorticity fields in the wake extracted using proper orthogonal decomposition, is found to have features similar to the ones described numerically and experimentally by Ryan et al. (J Fluid Mech 538:1–29, 2005), and Naghib-Lahouti et al. (Exp Fluids 52:1547–1566, 2012) at lower Reynolds numbers. The findings suggest that the spatial characteristics of the dominant primary and secondary wake flow instabilities have little dependence on the state of the flow upstream of the separation points, in spite of the distinct change in the normalized vortex shedding frequency upon the transition of the boundary layer.
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Wake instabilities of a Blunt Trailing Edge profiled body at intermediate Reynolds numbers
Experiments in Fluids, 2014Co-Authors: Arash Naghib-lahouti, P. Lavoie, Horia HanganAbstract:Experiments have been conducted to identify and characterize the instabilities in the wake of a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, for a broad range of Reynolds numbers ( $$2{,}000\le Re(d)\le 50{,}000$$ 2 , 000 ≤ R e ( d ) ≤ 50 , 000 based on the thickness of the body). These experiments, which include measurements of the wake velocity field using hot-wire anemometry and particle image velocimetry, complement previous studies of the wake flow for the same geometry at lower and higher Reynolds numbers. The spatial characteristics of the primary wake instability (the von Kármán vortex street) are found to have relatively little variation in the range of Reynolds numbers investigated, in spite of the transition of the boundary layer upstream of the Trailing Edge from a laminar to a turbulent state. The dominant secondary instability, identified based on the structure of velocity and vorticity fields in the wake extracted using proper orthogonal decomposition, is found to have features similar to the ones described numerically and experimentally by Ryan et al. (J Fluid Mech 538:1–29, 2005 ), and Naghib-Lahouti et al. (Exp Fluids 52:1547–1566, 2012 ) at lower Reynolds numbers. The findings suggest that the spatial characteristics of the dominant primary and secondary wake flow instabilities have little dependence on the state of the flow upstream of the separation points, in spite of the distinct change in the normalized vortex shedding frequency upon the transition of the boundary layer.
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Secondary wake instabilities of a Blunt Trailing Edge profiled body as a basis for flow control
Experiments in Fluids, 2012Co-Authors: Arash Naghib-lahouti, Lakshmana Sampat Doddipatla, Horia HanganAbstract:Flow in the wake of a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, has been investigated experimentally, to identify and characterize the secondary instabilities accompanying the von Kármán vortices. The experiments, which involve laser-induced fluorescence for visualization and particle image velocimetry for quantitative measurement of the wake instabilities, cover Reynolds numbers ranging from 250 to 2,150 based on thickness of the body, to include the wake transition regime. The dominant secondary instability appears as spanwise undulations in von Kármán vortices, which evolve into pairs of counter-rotating vortices, with features resembling the instability mechanism predicted by Ryan et al. (J Fluid Mech 538:1–29, 2005 ). Feasibility of a flow control approach based on interaction with the secondary instability using a series of discrete Trailing Edge injectors has also been investigated. The control approach mitigates the adverse effects of vortex shedding in certain conditions, where it is able to amplify the secondary instability effectively.
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active flow control for reduction of fluctuating aerodynamic forces of a Blunt Trailing Edge profiled body
International Journal of Heat and Fluid Flow, 2010Co-Authors: Arash Naghiblahouti, Horia HanganAbstract:Abstract Vortex shedding in the wake of two-dimensional bluff bodies is usually accompanied by three dimensional instabilities. These instabilities result in streamwise and vertical vorticity components which occur at a certain spanwise wavelength. The spanwise wavelength of the instabilities ( λ Z ) depends on several parameters, including profile geometry and Reynolds number. The objective of the present work is to study the three dimensional wake instabilities for a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, and to manipulate these instabilities to control the aerodynamic forces. Results of numerical simulations of flow around the body at Re( d ) = 400, 600, and 1000, as well as planar Laser Induced Fluorescence (LIF) flow visualizations at Re( d ) = 600 and 1000 are analyzed to determine the wake vorticity structure and λ Z . Based on the findings of these analyses, an active flow control mechanism for attenuation of the fluctuating aerodynamic forces on the body is proposed. The flow control mechanism is comprised of a series of Trailing Edge injection ports distributed across the span, with a spacing equal to λ Z . Injection of a secondary flow leads to amplification of the three dimensional instabilities and disorganization of the von Karman vortex street. Numerical simulations indicate that the flow control mechanism can attenuate the fluctuating aerodynamic forces at lower Reynolds numbers (Re( d ) = 400 and 600) where λ Z is constant in time. However, the control mechanism loses its effectiveness at Re( d ) = 1000, due to the temporal variations of λ Z .
Zhengyin Ye - One of the best experts on this subject based on the ideXlab platform.
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flow control over the Blunt Trailing Edge of wind turbine airfoils using circulation control
Energies, 2018Co-Authors: Heyong Xu, Chenliang Qiao, Qingli Dong, Zhengyin YeAbstract:A new partial circulation control (PCC) method is implemented on the Blunt Trailing Edge DU97-Flatback airfoil, and compared with the traditional full circulation control (FCC) based on numerical analysis. When the Coanda jet is deactivated, PCC has an attractive advantage over FCC, since the design of PCC doesn’t degrade aerodynamic characteristics of the baseline flatback section, in contrast to FCC, which is important in practical use in case of failure of the circulation control system. When the Coanda jet is activated, PCC also outperforms FCC in several respects. PCC can produce much higher lift coefficients than FCC over the entire range of angles of attack as well as the entire range of jet momentum coefficients under investigation, but with slightly higher drag coefficients. The flow field of PCC is less complex than that of FCC, indicating less energy dissipation in the main flow and hence less power expenditure for the Coanda jet. The aerodynamic figure of merit (AFM) and control efficiency for circulation control are defined, and results show that PCC has much higher AFM and control efficiency than FCC. It is demonstrated that PCC outperforms FCC in terms of effectiveness, efficiency and reliability for flow control in the Blunt Trailing Edge wind turbine application.
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active circulation control on the Blunt Trailing Edge wind turbine airfoil
AIAA Journal, 2017Co-Authors: Heyong Xu, Chenliang Qiao, Huiqiang Yang, Zhengyin YeAbstract:Active circulation control on a thick Blunt Trailing Edge wind turbine airfoil is proposed and numerically investigated by solving Reynolds-averaged Navier–Stokes equations along with Spalart–Allma...
Philippe Lavoie - One of the best experts on this subject based on the ideXlab platform.
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spatiotemporal analysis of fluctuating base pressure and velocity in a Blunt Trailing Edge wake
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Heather A Clark, Philippe LavoieAbstract:Three-dimensional instabilities in the wake of a Blunt Trailing Edge profiled body are examined through experimental measurements of velocity and the spanwise distribution of fluctuating surface pressure on the model rear face near separation. Spatial and temporal variability of the vortex shedding behaviour result in low-frequency modulation of the pressure signals. The time-dependent amplitude is characterized using the wavelet transform, while subsequent correlation analysis and reduced-order modelling provide quantitative evidence of the dominant influence of large-scale instabilities. The cross-correlation of the wake velocity and the surface pressure are examined in the framework of the Extended Proper Orthogonal Decomposition, through which reduced-order models of the measured variables are related to construct an empirical estimator of velocity. Implications of the observed modal correlations and the statistical signature of large-scale spatial variations are discussed in relation to the estimation of multi-scale wake phenomena.
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distributed forcing flow control in the wake of a Blunt Trailing Edge profiled body using plasma actuators
Physics of Fluids, 2015Co-Authors: Arash Naghiblahouti, Horia Hangan, Philippe LavoieAbstract:A modern flow control technique for reducing the drag associated with the periodic shedding of von Karman vortices in the wake of a Blunt Trailing Edge profiled body is presented. The technique involves distributed forcing of the wake flow using an array of dielectric barrier discharge plasma actuators, with a spanwise spacing matched to the spanwise wavelength of the dominant secondary wake instability. The experiments include measurement of the velocity field in multiple vertical and horizontal planes in the wake using particle image velocimetry, as well as base pressure, at Reynolds numbers of 2000, 3000, and 5000 based on Trailing Edge thickness. The flow control technique causes elongation of the vortex formation region across the span, and significant reduction of the fluctuating and total drag forces, up to a maximum of 94% and 18%, respectively. The effectiveness of the flow control technique is shown to be dependent on the induced momentum coefficient. Proper orthogonal decomposition analysis is ...
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wake instabilities of a Blunt Trailing Edge profiled body at intermediate reynolds numbers
Experiments in Fluids, 2014Co-Authors: Arash Naghiblahouti, Philippe Lavoie, Horia HanganAbstract:Experiments have been conducted to identify and characterize the instabilities in the wake of a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, for a broad range of Reynolds numbers (\(2{,}000\le Re(d)\le 50{,}000\) based on the thickness of the body). These experiments, which include measurements of the wake velocity field using hot-wire anemometry and particle image velocimetry, complement previous studies of the wake flow for the same geometry at lower and higher Reynolds numbers. The spatial characteristics of the primary wake instability (the von Karman vortex street) are found to have relatively little variation in the range of Reynolds numbers investigated, in spite of the transition of the boundary layer upstream of the Trailing Edge from a laminar to a turbulent state. The dominant secondary instability, identified based on the structure of velocity and vorticity fields in the wake extracted using proper orthogonal decomposition, is found to have features similar to the ones described numerically and experimentally by Ryan et al. (J Fluid Mech 538:1–29, 2005), and Naghib-Lahouti et al. (Exp Fluids 52:1547–1566, 2012) at lower Reynolds numbers. The findings suggest that the spatial characteristics of the dominant primary and secondary wake flow instabilities have little dependence on the state of the flow upstream of the separation points, in spite of the distinct change in the normalized vortex shedding frequency upon the transition of the boundary layer.
Heyong Xu - One of the best experts on this subject based on the ideXlab platform.
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flow control over the Blunt Trailing Edge of wind turbine airfoils using circulation control
Energies, 2018Co-Authors: Heyong Xu, Chenliang Qiao, Qingli Dong, Zhengyin YeAbstract:A new partial circulation control (PCC) method is implemented on the Blunt Trailing Edge DU97-Flatback airfoil, and compared with the traditional full circulation control (FCC) based on numerical analysis. When the Coanda jet is deactivated, PCC has an attractive advantage over FCC, since the design of PCC doesn’t degrade aerodynamic characteristics of the baseline flatback section, in contrast to FCC, which is important in practical use in case of failure of the circulation control system. When the Coanda jet is activated, PCC also outperforms FCC in several respects. PCC can produce much higher lift coefficients than FCC over the entire range of angles of attack as well as the entire range of jet momentum coefficients under investigation, but with slightly higher drag coefficients. The flow field of PCC is less complex than that of FCC, indicating less energy dissipation in the main flow and hence less power expenditure for the Coanda jet. The aerodynamic figure of merit (AFM) and control efficiency for circulation control are defined, and results show that PCC has much higher AFM and control efficiency than FCC. It is demonstrated that PCC outperforms FCC in terms of effectiveness, efficiency and reliability for flow control in the Blunt Trailing Edge wind turbine application.
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active circulation control on the Blunt Trailing Edge wind turbine airfoil
AIAA Journal, 2017Co-Authors: Heyong Xu, Chenliang Qiao, Huiqiang Yang, Zhengyin YeAbstract:Active circulation control on a thick Blunt Trailing Edge wind turbine airfoil is proposed and numerically investigated by solving Reynolds-averaged Navier–Stokes equations along with Spalart–Allma...
Arash Naghiblahouti - One of the best experts on this subject based on the ideXlab platform.
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distributed forcing flow control in the wake of a Blunt Trailing Edge profiled body using plasma actuators
Physics of Fluids, 2015Co-Authors: Arash Naghiblahouti, Horia Hangan, Philippe LavoieAbstract:A modern flow control technique for reducing the drag associated with the periodic shedding of von Karman vortices in the wake of a Blunt Trailing Edge profiled body is presented. The technique involves distributed forcing of the wake flow using an array of dielectric barrier discharge plasma actuators, with a spanwise spacing matched to the spanwise wavelength of the dominant secondary wake instability. The experiments include measurement of the velocity field in multiple vertical and horizontal planes in the wake using particle image velocimetry, as well as base pressure, at Reynolds numbers of 2000, 3000, and 5000 based on Trailing Edge thickness. The flow control technique causes elongation of the vortex formation region across the span, and significant reduction of the fluctuating and total drag forces, up to a maximum of 94% and 18%, respectively. The effectiveness of the flow control technique is shown to be dependent on the induced momentum coefficient. Proper orthogonal decomposition analysis is ...
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wake instabilities of a Blunt Trailing Edge profiled body at intermediate reynolds numbers
Experiments in Fluids, 2014Co-Authors: Arash Naghiblahouti, Philippe Lavoie, Horia HanganAbstract:Experiments have been conducted to identify and characterize the instabilities in the wake of a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, for a broad range of Reynolds numbers (\(2{,}000\le Re(d)\le 50{,}000\) based on the thickness of the body). These experiments, which include measurements of the wake velocity field using hot-wire anemometry and particle image velocimetry, complement previous studies of the wake flow for the same geometry at lower and higher Reynolds numbers. The spatial characteristics of the primary wake instability (the von Karman vortex street) are found to have relatively little variation in the range of Reynolds numbers investigated, in spite of the transition of the boundary layer upstream of the Trailing Edge from a laminar to a turbulent state. The dominant secondary instability, identified based on the structure of velocity and vorticity fields in the wake extracted using proper orthogonal decomposition, is found to have features similar to the ones described numerically and experimentally by Ryan et al. (J Fluid Mech 538:1–29, 2005), and Naghib-Lahouti et al. (Exp Fluids 52:1547–1566, 2012) at lower Reynolds numbers. The findings suggest that the spatial characteristics of the dominant primary and secondary wake flow instabilities have little dependence on the state of the flow upstream of the separation points, in spite of the distinct change in the normalized vortex shedding frequency upon the transition of the boundary layer.
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active flow control for reduction of fluctuating aerodynamic forces of a Blunt Trailing Edge profiled body
International Journal of Heat and Fluid Flow, 2010Co-Authors: Arash Naghiblahouti, Horia HanganAbstract:Abstract Vortex shedding in the wake of two-dimensional bluff bodies is usually accompanied by three dimensional instabilities. These instabilities result in streamwise and vertical vorticity components which occur at a certain spanwise wavelength. The spanwise wavelength of the instabilities ( λ Z ) depends on several parameters, including profile geometry and Reynolds number. The objective of the present work is to study the three dimensional wake instabilities for a Blunt Trailing Edge profiled body, comprised of an elliptical leading Edge and a rectangular Trailing Edge, and to manipulate these instabilities to control the aerodynamic forces. Results of numerical simulations of flow around the body at Re( d ) = 400, 600, and 1000, as well as planar Laser Induced Fluorescence (LIF) flow visualizations at Re( d ) = 600 and 1000 are analyzed to determine the wake vorticity structure and λ Z . Based on the findings of these analyses, an active flow control mechanism for attenuation of the fluctuating aerodynamic forces on the body is proposed. The flow control mechanism is comprised of a series of Trailing Edge injection ports distributed across the span, with a spacing equal to λ Z . Injection of a secondary flow leads to amplification of the three dimensional instabilities and disorganization of the von Karman vortex street. Numerical simulations indicate that the flow control mechanism can attenuate the fluctuating aerodynamic forces at lower Reynolds numbers (Re( d ) = 400 and 600) where λ Z is constant in time. However, the control mechanism loses its effectiveness at Re( d ) = 1000, due to the temporal variations of λ Z .
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the near wake structure of a Blunt Trailing Edge profiled body part 2 plif and piv measurements
40th Fluid Dynamics Conference and Exhibit, 2010Co-Authors: Lakshmana Sampat Doddipatla, Kamran Siddiqui, Arash Naghiblahouti, Horia HanganAbstract:Wake flows behind two dimensional bodies are mainly dominated by two coherent structures, namely the Karman-Benard vortices and the streamwise vortices, also referred to as rolls and ribs respectively. The three dimensional wake instabilities lead to distinct instability modes (mode-A, mode-B and mode-C or mode S) depending on the flow Reynolds number and geometric shape. The present investigation explores the mechanism in which the flow transitions to three dimensionality in the near wake of a profiled leading Edge and Blunt Trailing Edge body. A combination of Planar Laser Induced Fluorescence visualizations and Particle Image Velcoimetry measurements are conducted for Reynolds numbers ranging from 250 to 2300. The results indicate that three instability modes (mode-A, mode-B and mode-C) appear in the wake transition to three dimensionality, and their order of appearance does not occur through the traditional route as observed in circular cylinder flows. It is found that mode-C instability with a spanwise spacing of 2.4D (D being the Trailing Edge thickness) dominates the near wake development.
