The vortical structure associated with a streamwise 45 o inclined pulsed jet in a crossflow is in... more The vortical structure associated with a streamwise 45 o inclined pulsed jet in a crossflow is investigated. Using Stereo-PIV data, a vortex detection algorithm and Proper Orthogonal Decomposition (POD), this study exposes the interaction of longitudinal vortices rollup in the jet shear layers and a large spiral rollup known as the counter rotating vortex pair (CVP). The effects of changing the pulse frequency and duty cycle are shown to be an efficient means to control the CVP and the near field flow structure of the jet flow.
This paper conducts a numerical and experimental investigation of a coflow jet airfoil to quantif... more This paper conducts a numerical and experimental investigation of a coflow jet airfoil to quantify lift enhancement, drag reduction, and energy expenditure at a Mach number range from 0.03 to 0.4. The jet momentum coefficient is held constant at 0.08, and the angle of attack varies from 0 to 30 deg. The two-dimensional flow is simulated using a Reynolds-averaged Navier-Stokes solver with a fifth-order-weighted essentially non-oscillatory scheme for the inviscid flux and a fourth-order central differencing for the viscous terms. Turbulence is simulated with the one equation Spalart-Allmaras model. The predicted coflow jet pumping power has an excellent agreement with the experiment. At a constant Mach number, the power coefficient is decreased when the angle of attack is increased from 0 to 15 deg. When the Mach number is increased from 0.03 to 0.3, the suction effect behind the airfoil leading edge is further augmented due to the compressibility effect. This results in an increased maximum lift coefficient and reduced power coefficient at the higher Mach number because of the lower jet-injection pumping pressure required. At Mach 0.4, the lift coefficient is further improved. However as the angle of attack is increased, a λ shock wave interrupts the jet and triggers the boundary layer separation with increased drag and power coefficient. A corrected aerodynamic efficiency that includes the coflow-jet pumping power is introduced. Because of the high lift coefficient and low coflowjet power required, the coflow-jet airfoil in this study achieves a comparable peak aerodynamic efficiency to the baseline airfoil, but the lift coefficient at peak efficiency is substantially increased by 120%. This study indicates that the coflow-jet airfoil is not only able to achieve very high maximum lift coefficient, but also able to improve cruise performance at low angle of attack when the flow is benign.
Wind is an attractive renewable source of energy. Recent innovations in research and design have ... more Wind is an attractive renewable source of energy. Recent innovations in research and design have reduced to a few alternatives with limited impact on residential construction. Cost effective solutions have been found at larger scale, but storage and delivery of energy to the actual location it is used, remain a critical issue. The Integrated Roof Wind Energy System is designed to overcome the current issues of urban and larger scale renewable energy system. The system is built up by an axial array of skewed shaped funnels that make use of the Venturi Effect to accelerate the wind flow. This inventive use of shape and geometry leads to a converging air capturing inlet to create high wind mass flow and velocity toward a vertical-axis wind turbine in the top of the roof for generation of a relatively high amount of energy. The methods used in this overview of studies include an array of tools from analytical modelling, PIV wind tunnel testing, and CFD simulation studies. The results define the main design parameters for an efficient system, and show the potential for the generation of high amounts of renewable energy with a novel and effective system suited for the built environment.
41st AIAA Fluid Dynamics Conference and Exhibit, 2011
This paper uses large eddy simulation (LES) to investigate Co-Flow Jet (CFJ) airfoil flows at hig... more This paper uses large eddy simulation (LES) to investigate Co-Flow Jet (CFJ) airfoil flows at high angle of attack (AOA). The standard Smagorinsky model with Van Driest damping is employed to resolve the subgrid scale stress. The 5th order WENO scheme is used for the reconstruction of the inviscid flux and the 4th order central differencing for the viscous flux. The momentum coefficient(C µ) is chosen as a parameter to control the jet flow of the CFJ airfoil. LES simulations were carried out for the different momentum coefficients. The LES results at 30 o AOA are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The numerically captured qualitative flow structures are very similar to those obtained in experiment. The quantitative prediction of lift and drag agree very well with experiment.
The mean and turbulent flow characteristics of a fully-modulated 45 degree streamwise inclined je... more The mean and turbulent flow characteristics of a fully-modulated 45 degree streamwise inclined jet in crossflow are investigated. Results are obtained using 3D renderings of Stereo-Particle Image Velocimetry (SPIV) data for all three velocity components. The near field flow structure and the interaction with the crossflow are investigated based on ten streamwise slices of data ranging from the jet centerline spanning outward to two jet diameters. The effects of three parameters are studied: the jet Reynolds number, the pulsing frequency and the pulse duty cycle. The mean velocity ratio is defined as the mean jet exit velocity divided by the crossflow velocity, and is kept constant for all cases presented. The duty cycle is varied from 0.5 down to 0.125, such that the mean exit velocity increases in order to maintain the same average mean velocity ratio. The data are further analyzed using a vortex detection algorithm to locate the positions and strength of vortical structures in ver...
Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high an... more Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high angle of attack (AOA). The Smagorinsky model with Van Driest damping is employed to resolve the subgrid-scale stress. The fifth-order weighted essentially non-oscillatory (WENO) scheme is used for reconstruction of the inviscid flux and the fourth-order central differencing for the viscous flux. The LES results at an AOA of 0 deg, 12 deg, 25 deg, and 30 deg with momentum coefficients of Cμ = 0.15 and 0.08 are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The quantitative prediction of lift and drag and qualitative prediction of vortex structures are in good agreement with experiment.
Jets in crossflow are used in a wide range of engineering applications and have been studied for ... more Jets in crossflow are used in a wide range of engineering applications and have been studied for more than 60 years. The transversal penetration and structure of a jet placed in a crossflow is known to be strongly three-dimensional. It is believed that, by using a pulsed jet inclined in the crossflow direction, the momentum transport can be controlled in
Experimental Thermal and Fluid Science, Aug 1, 2007
The flow structure generated by circular and oblate shaped nozzles for an impinging confined 7-by... more The flow structure generated by circular and oblate shaped nozzles for an impinging confined 7-by-7 jet array is investigated. Instantaneous velocity fields, obtained from Digital Particle Image Velocimetry (DPIV) along the crossflow direction are analyzed using Proper Orthogonal Decomposition (POD). Also, a vortex detection algorithm is used to locate and quantify the nature of the instantaneous vortices within the flow. The results show that an oblate shaped nozzle when oriented with its major axis aligned with the exhaust flow has flow characteristics resulting in increased turbulent kinetic energy. This has potential for increased surface transport.
The present study proposes to investigate the flow structure of two 7x7 arrays of impinging jets ... more The present study proposes to investigate the flow structure of two 7x7 arrays of impinging jets with a self-sustained crossflow. A circular and a "cusped" ellipse orifice geometry have been studied. Surface flow visualization and PIV measurements of the entire flow field were used for a Reynolds number ranging from 8,500 to 15,900. The flow visualization of the impinging patterns shows similar results for the different jet orifices geometries. The jets generated cells defined by detachment-reattachment zones with a characteristic "horseshoe" shape around each jet that progressively expand in size with increasing crossflow. PIV measurements in the vicinity of the jet exits reveal a large rotating vortex created by the merging of the crossflow and the jet column return-flow. moves towards the jet column as the crossflow increases in strength. Singular differences in turbulence level are found for the cusped ellipse jet array with its major axis aligned normal or parallel to the crossflow. Evidence of axis switching indicates that lateral transport could be a secondary factor to take into account for surface cooling efficiency.
The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift... more The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift enhancement, drag reduction, and stall margin increase. Digital Particle Image Velocimetry, flow visualization and aerodynamic forces measurements are used to reveal the insight of the CFJ airfoil mixing process.
Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high an... more Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high angle of attack (AOA). The Smagorinsky model with Van Driest damping is employed to resolve the subgrid-scale stress. The fifth-order weighted essentially non-oscillatory (WENO) scheme is used for reconstruction of the inviscid flux and the fourthorder central differencing for the viscous flux. The LES results at an AOA of 0 deg, 12 deg, 25 deg, and 30 deg with momentum coefficients of C l ¼ 0.15 and 0.08 are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The quantitative prediction of lift and drag and qualitative prediction of vortex structures are in good agreement with experiment.
The vortical structure associated with a streamwise 45 o inclined pulsed jet in a crossflow is in... more The vortical structure associated with a streamwise 45 o inclined pulsed jet in a crossflow is investigated. Using Stereo-PIV data, a vortex detection algorithm and Proper Orthogonal Decomposition (POD), this study exposes the interaction of longitudinal vortices rollup in the jet shear layers and a large spiral rollup known as the counter rotating vortex pair (CVP). The effects of changing the pulse frequency and duty cycle are shown to be an efficient means to control the CVP and the near field flow structure of the jet flow.
This paper conducts a numerical and experimental investigation of a coflow jet airfoil to quantif... more This paper conducts a numerical and experimental investigation of a coflow jet airfoil to quantify lift enhancement, drag reduction, and energy expenditure at a Mach number range from 0.03 to 0.4. The jet momentum coefficient is held constant at 0.08, and the angle of attack varies from 0 to 30 deg. The two-dimensional flow is simulated using a Reynolds-averaged Navier-Stokes solver with a fifth-order-weighted essentially non-oscillatory scheme for the inviscid flux and a fourth-order central differencing for the viscous terms. Turbulence is simulated with the one equation Spalart-Allmaras model. The predicted coflow jet pumping power has an excellent agreement with the experiment. At a constant Mach number, the power coefficient is decreased when the angle of attack is increased from 0 to 15 deg. When the Mach number is increased from 0.03 to 0.3, the suction effect behind the airfoil leading edge is further augmented due to the compressibility effect. This results in an increased maximum lift coefficient and reduced power coefficient at the higher Mach number because of the lower jet-injection pumping pressure required. At Mach 0.4, the lift coefficient is further improved. However as the angle of attack is increased, a λ shock wave interrupts the jet and triggers the boundary layer separation with increased drag and power coefficient. A corrected aerodynamic efficiency that includes the coflow-jet pumping power is introduced. Because of the high lift coefficient and low coflowjet power required, the coflow-jet airfoil in this study achieves a comparable peak aerodynamic efficiency to the baseline airfoil, but the lift coefficient at peak efficiency is substantially increased by 120%. This study indicates that the coflow-jet airfoil is not only able to achieve very high maximum lift coefficient, but also able to improve cruise performance at low angle of attack when the flow is benign.
Wind is an attractive renewable source of energy. Recent innovations in research and design have ... more Wind is an attractive renewable source of energy. Recent innovations in research and design have reduced to a few alternatives with limited impact on residential construction. Cost effective solutions have been found at larger scale, but storage and delivery of energy to the actual location it is used, remain a critical issue. The Integrated Roof Wind Energy System is designed to overcome the current issues of urban and larger scale renewable energy system. The system is built up by an axial array of skewed shaped funnels that make use of the Venturi Effect to accelerate the wind flow. This inventive use of shape and geometry leads to a converging air capturing inlet to create high wind mass flow and velocity toward a vertical-axis wind turbine in the top of the roof for generation of a relatively high amount of energy. The methods used in this overview of studies include an array of tools from analytical modelling, PIV wind tunnel testing, and CFD simulation studies. The results define the main design parameters for an efficient system, and show the potential for the generation of high amounts of renewable energy with a novel and effective system suited for the built environment.
41st AIAA Fluid Dynamics Conference and Exhibit, 2011
This paper uses large eddy simulation (LES) to investigate Co-Flow Jet (CFJ) airfoil flows at hig... more This paper uses large eddy simulation (LES) to investigate Co-Flow Jet (CFJ) airfoil flows at high angle of attack (AOA). The standard Smagorinsky model with Van Driest damping is employed to resolve the subgrid scale stress. The 5th order WENO scheme is used for the reconstruction of the inviscid flux and the 4th order central differencing for the viscous flux. The momentum coefficient(C µ) is chosen as a parameter to control the jet flow of the CFJ airfoil. LES simulations were carried out for the different momentum coefficients. The LES results at 30 o AOA are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The numerically captured qualitative flow structures are very similar to those obtained in experiment. The quantitative prediction of lift and drag agree very well with experiment.
The mean and turbulent flow characteristics of a fully-modulated 45 degree streamwise inclined je... more The mean and turbulent flow characteristics of a fully-modulated 45 degree streamwise inclined jet in crossflow are investigated. Results are obtained using 3D renderings of Stereo-Particle Image Velocimetry (SPIV) data for all three velocity components. The near field flow structure and the interaction with the crossflow are investigated based on ten streamwise slices of data ranging from the jet centerline spanning outward to two jet diameters. The effects of three parameters are studied: the jet Reynolds number, the pulsing frequency and the pulse duty cycle. The mean velocity ratio is defined as the mean jet exit velocity divided by the crossflow velocity, and is kept constant for all cases presented. The duty cycle is varied from 0.5 down to 0.125, such that the mean exit velocity increases in order to maintain the same average mean velocity ratio. The data are further analyzed using a vortex detection algorithm to locate the positions and strength of vortical structures in ver...
Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high an... more Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high angle of attack (AOA). The Smagorinsky model with Van Driest damping is employed to resolve the subgrid-scale stress. The fifth-order weighted essentially non-oscillatory (WENO) scheme is used for reconstruction of the inviscid flux and the fourth-order central differencing for the viscous flux. The LES results at an AOA of 0 deg, 12 deg, 25 deg, and 30 deg with momentum coefficients of Cμ = 0.15 and 0.08 are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The quantitative prediction of lift and drag and qualitative prediction of vortex structures are in good agreement with experiment.
Jets in crossflow are used in a wide range of engineering applications and have been studied for ... more Jets in crossflow are used in a wide range of engineering applications and have been studied for more than 60 years. The transversal penetration and structure of a jet placed in a crossflow is known to be strongly three-dimensional. It is believed that, by using a pulsed jet inclined in the crossflow direction, the momentum transport can be controlled in
Experimental Thermal and Fluid Science, Aug 1, 2007
The flow structure generated by circular and oblate shaped nozzles for an impinging confined 7-by... more The flow structure generated by circular and oblate shaped nozzles for an impinging confined 7-by-7 jet array is investigated. Instantaneous velocity fields, obtained from Digital Particle Image Velocimetry (DPIV) along the crossflow direction are analyzed using Proper Orthogonal Decomposition (POD). Also, a vortex detection algorithm is used to locate and quantify the nature of the instantaneous vortices within the flow. The results show that an oblate shaped nozzle when oriented with its major axis aligned with the exhaust flow has flow characteristics resulting in increased turbulent kinetic energy. This has potential for increased surface transport.
The present study proposes to investigate the flow structure of two 7x7 arrays of impinging jets ... more The present study proposes to investigate the flow structure of two 7x7 arrays of impinging jets with a self-sustained crossflow. A circular and a "cusped" ellipse orifice geometry have been studied. Surface flow visualization and PIV measurements of the entire flow field were used for a Reynolds number ranging from 8,500 to 15,900. The flow visualization of the impinging patterns shows similar results for the different jet orifices geometries. The jets generated cells defined by detachment-reattachment zones with a characteristic "horseshoe" shape around each jet that progressively expand in size with increasing crossflow. PIV measurements in the vicinity of the jet exits reveal a large rotating vortex created by the merging of the crossflow and the jet column return-flow. moves towards the jet column as the crossflow increases in strength. Singular differences in turbulence level are found for the cusped ellipse jet array with its major axis aligned normal or parallel to the crossflow. Evidence of axis switching indicates that lateral transport could be a secondary factor to take into account for surface cooling efficiency.
The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift... more The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift enhancement, drag reduction, and stall margin increase. Digital Particle Image Velocimetry, flow visualization and aerodynamic forces measurements are used to reveal the insight of the CFJ airfoil mixing process.
Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high an... more Large eddy simulation (LES) is conducted to investigate coflow jet (CFJ) airfoil flows at high angle of attack (AOA). The Smagorinsky model with Van Driest damping is employed to resolve the subgrid-scale stress. The fifth-order weighted essentially non-oscillatory (WENO) scheme is used for reconstruction of the inviscid flux and the fourthorder central differencing for the viscous flux. The LES results at an AOA of 0 deg, 12 deg, 25 deg, and 30 deg with momentum coefficients of C l ¼ 0.15 and 0.08 are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The quantitative prediction of lift and drag and qualitative prediction of vortex structures are in good agreement with experiment.
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Papers by Bertrand Dano