The Experts below are selected from a list of 42540 Experts worldwide ranked by ideXlab platform
Jen-ping Chen - One of the best experts on this subject based on the ideXlab platform.
-
Wake-Induced Unsteady Flows: Their Impact on Rotor Performance and Wake Rectification
Journal of Turbomachinery, 1996Co-Authors: John J. Adamczyk, M. L. Celestina, Jen-ping ChenAbstract:The impact of wake-induced unsteady flows on blade row Performance and the wake rectification process is examined by means of numerical simulation. The passage of a stator wake through a downstream Rotor is first simulated using a three-dimensional unsteady viscous flow code. The results from this simulation are used to define two steady-state inlet conditions for a three-dimensional viscous flow simulation of a Rotor operating in isolation. The results obtained from these numerical simulations are then compared to those obtained from the unsteady simulation both to quantify the impact of the wake-induced unsteady flow field on Rotor Performance and to identify the flow processes which impact wake rectification. Finally, the results from this comparison study are related to an existing model, which attempts to account for the impact of wake-induced unsteady flows on the Performance of multistage turbomachinery.
-
Wake-Induced Unsteady Flows: Their Impact on Rotor Performance and Wake Rectification
Volume 1: Turbomachinery, 1994Co-Authors: John J. Adamczyk, M. L. Celestina, Jen-ping ChenAbstract:The impact of wake-induced unsteady flows on blade row Performance and the wake rectification process is examined by means of numerical simulation. The passage of a stator wake through a downstream Rotor is first simulated using a three dimensional unsteady viscous flow code. The results from this simulation are used to define two steady state inlet conditions for a three dimensional viscous flow simulation of a Rotor operating in isolation. The results obtained from these numerical simulations are then compared to those obtained from the unsteady simulation both to quantify the impact of the wake-induced unsteady flow field on Rotor Performance and to identify the flow processes which impact wake rectification. Finally, the results from this comparison study are related to an existing model which attempts to account for the impact of wake-induced unsteady flows on the Performance of multistage turbomachinery.Copyright © 1994 by ASME
Hyeonsoo Yeo - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of Trailing-Edge Flap Gap Effects on Rotor Performance Using High-Fidelity Analysis
Journal of Aircraft, 2013Co-Authors: Rohit Jain, Hyeonsoo Yeo, Inderjit ChopraAbstract:Effects of trailing-edge flap gaps on Rotor Performance are investigated using a high-fidelity coupled computational fluid dynamics computational structural dynamics analysis. Both integral flap (the flap is an integral part of the blade such that there are no physical gaps at the flap ends) and discrete flap (the flap is a separate entity with physical gaps in the span and chord directions) are examined on an UH-60A Rotor at high-speed forward-flight conditions. A novel grid deformation scheme based on the Delaunay graph mapping is developed and implemented to allow the computational fluid dynamics modeling of the gaps with minimal distortion of mesh around the flap gap regions. This method offers an alternative to the traditional approach of modeling such configurations using overset meshes. The simulation results show that the effectiveness of the flap is minimally affected with span gaps; the penalty on Rotor Performance is of the order of 1% compared to the integral flap. On the other hand, the chord...
-
Investigation of UH-60A Rotor Performance and Loads at High Advance Ratios
Journal of Aircraft, 2013Co-Authors: Hyeonsoo YeoAbstract:Wind tunnel measurements of the Performance, airloads, and structural loads of a full-scale UH-60A Black Hawk main Rotor operating at high advance ratios (up to 1.0) are compared with calculations obtained using the comprehensive Rotorcraft analysis Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics II to understand physics and quantify this comprehensive code’s accuracy and reliability in the prediction of Rotor Performance and loads at high advance ratios. Detailed comparisons are made on Rotor thrust, control angles, power, and section loads to illustrate and understand unique aeromechanics phenomena in this regime. The analysis correctly predicts the thrust reversal with collective at high advance ratios. Rotor induced plus profile power is also reasonably well predicted with proper modeling of the shank. Airloads and structural loads correlation is fair. A significant underprediction of 2-per-revolution structural loads is observed.
-
Effects of Torsion Frequencies on Rotor Performance and Structural Loads with Trailing Edge Flap
Smart Materials and Structures, 2012Co-Authors: Rohit Jain, Hyeonsoo YeoAbstract:The effects of variation of blade torsion frequency on Rotor Performance and structural loads are investigated for a 1/rev active flap Rotor and baseline Rotor (no active control). The UH-60A four-bladed articulated main Rotor is studied at a high-speed forward flight condition. The torsion frequencies are varied by modifying the spanwise torsional stiffness of the blade and/or the pitch link stiffness. First, a parametric/optimization study on the flap deployment schedule is carried out using lifting-line comprehensive analysis for the soft, baseline, and stiff Rotor configurations, and then a higher fidelity coupled computational fluid dynamics–computational structural dynamics analysis is carried out for the optimal flap deployment. It is shown that with the soft Rotor there is degradation in Performance—of about 6% with respect to the baseline Rotor in the case where the flaps are not activated, and of about 1% if flap deflections are applied. On the other hand, for the stiff Rotor there is a slight improvement in Performance of about 2.3% when the flaps are not activated, and no appreciable change in the case where active flap deflections are applied. It appears that the peak Performance achievable with using active flaps on a baseline stiffness Rotor cannot be further improved significantly by varying the torsional frequencies. Variation of torsion frequency does not appear to have a significant influence on blade torsion moments and pitch link loads, although the 1/rev flap activation examined has an important role.
-
Investigation of Trailing-edge Flap Gap Effects on Rotor Performance Using CFD/CSD Coupling
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012Co-Authors: Rohit Jain, Hyeonsoo Yeo, Inderjit ChopraAbstract:Effects of trailing-edge flap gaps on Rotor Performance are investigated using a high fidelity, coupled computational fluid dynamics (CFD) – computational structural dynamics (CSD) analysis. Both integral flap (the flap is an integral part of the blade such that there are no physical gaps at the flap ends) and discrete flap (the flap is a separate entity with physical gaps in the spanwise and chordwise directions) are examined on an UH-60A Rotor at high speed forward flight condition. A novel grid deformation scheme based on the Delaunay graph mapping is developed and implemented to allow the CFD modeling of the gaps with minimal distortion of mesh around the flap gap regions. This method offers an alternative to the traditional approach of modeling such configurations using overset meshes. The simulation results show that the effectiveness of the flap is minimally lost with spanwise gaps – the penalty on Rotor Performance is of the order of 1% compared to the integral flap. On the other hand the chordwise gaps significantly degrade the benefits of active flap on Rotor Performance due to the flow penetration between the upper and lower surfaces of the flap.
-
Investigation of Rotor Performance and Loads of a UH-60A Individual Blade Control System
Journal of the American Helicopter Society, 2011Co-Authors: Hyeonsoo Yeo, Ethan A. Romander, Thomas R. NormanAbstract:Wind tunnel measurements of Performance, loads, and vibration of a full-scale UH-60A Black Hawk main Rotor with an individual blade control (IBC) system are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. Measured data show a 5.1% Rotor power reduction (8.6% Rotor lift to effective-drag ratio increase) using 2/rev IBC actuation with 2.0 ◦ amplitude at μ = 0.4. At the optimum IBC phase for Rotor Performance, IBC actuator force (pitch link force) decreased, and neither flap nor chord bending moments changed significantly. CAMRAD II predicts the Rotor power variations with the IBC phase reasonably well at μ = 0.35. However, the correlation degrades at μ = 0.4. Coupled CAMRAD II/OVERFLOW 2 shows excellent correlation with the measured Rotor power variations with the IBC phase at both μ = 0.35 and μ = 0.4. Maximum reduction of IBC actuator force is better predicted with CAMRAD II, but general trends are better captured with the coupled analysis. The correlation of vibratory hub loads is generally poor by both methods, although the coupled analysis somewhat captures general trends.
John J. Adamczyk - One of the best experts on this subject based on the ideXlab platform.
-
Wake-Induced Unsteady Flows: Their Impact on Rotor Performance and Wake Rectification
Journal of Turbomachinery, 1996Co-Authors: John J. Adamczyk, M. L. Celestina, Jen-ping ChenAbstract:The impact of wake-induced unsteady flows on blade row Performance and the wake rectification process is examined by means of numerical simulation. The passage of a stator wake through a downstream Rotor is first simulated using a three-dimensional unsteady viscous flow code. The results from this simulation are used to define two steady-state inlet conditions for a three-dimensional viscous flow simulation of a Rotor operating in isolation. The results obtained from these numerical simulations are then compared to those obtained from the unsteady simulation both to quantify the impact of the wake-induced unsteady flow field on Rotor Performance and to identify the flow processes which impact wake rectification. Finally, the results from this comparison study are related to an existing model, which attempts to account for the impact of wake-induced unsteady flows on the Performance of multistage turbomachinery.
-
Wake-Induced Unsteady Flows: Their Impact on Rotor Performance and Wake Rectification
Volume 1: Turbomachinery, 1994Co-Authors: John J. Adamczyk, M. L. Celestina, Jen-ping ChenAbstract:The impact of wake-induced unsteady flows on blade row Performance and the wake rectification process is examined by means of numerical simulation. The passage of a stator wake through a downstream Rotor is first simulated using a three dimensional unsteady viscous flow code. The results from this simulation are used to define two steady state inlet conditions for a three dimensional viscous flow simulation of a Rotor operating in isolation. The results obtained from these numerical simulations are then compared to those obtained from the unsteady simulation both to quantify the impact of the wake-induced unsteady flow field on Rotor Performance and to identify the flow processes which impact wake rectification. Finally, the results from this comparison study are related to an existing model which attempts to account for the impact of wake-induced unsteady flows on the Performance of multistage turbomachinery.Copyright © 1994 by ASME
J. L. Tangler - One of the best experts on this subject based on the ideXlab platform.
-
Nebulous Art of Using Wind-Tunnel Airfoil Data for Predicting Rotor Performance: Preprint
2002Co-Authors: J. L. TanglerAbstract:The objective of this study was threefold: to evaluate different two-dimensional S809 airfoil data sets in the prediction of Rotor Performance; to compare blade-element momentum Rotor predicted results to lifting-surface, prescribed-wake results; and to compare the NASA Ames combined experiment Rotor measured data with the two different Performance prediction methods. The S809 airfoil data sets evaluated included those from Delft University of Technology, Ohio State University, and Colorado State University. The Performance prediction comparison with NASA Ames data documents shortcomings of these Performance prediction methods and recommends the use of the lifting-surface, prescribed-wake method over blade-element momentum theory for future analytical improvements.
-
The Nebulous Art of Using Wind-Tunnel Airfoil Data for Predicting Rotor Performance
ASME 2002 Wind Energy Symposium, 2002Co-Authors: J. L. TanglerAbstract:The objective of this study was threefold: to evaluate different two-dimensional S809 airfoil data sets in the prediction of Rotor Performance; to compare blade-element momentum Rotor predicted results to lifting-surface, prescribed-wake results; and to compare the NASA Ames combined experiment Rotor measured data with the two different Performance prediction methods. The S809 airfoil data sets evaluated included those from Delft University of Technology, Ohio State University, and Colorado State University. The Performance prediction comparison with NASA Ames data documents shortcomings of these Performance prediction methods and recommends the use of the lifting-surface, prescribed-wake method over blade-element momentum theory for future analytical improvements.Copyright © 2002 by ASME
-
The nebulous art of using wind tunnel aerofoil data for predicting Rotor Performance
Wind Energy, 2002Co-Authors: J. L. TanglerAbstract:The objective of this study was threefold: to evaluate different two-dimensional S809 aerofoil data sets in the prediction of Rotor Performance; to compare blade element momentum Rotor predicted results with lifting surface, prescribed wake results; and to compare the NASA Ames combined experiment Rotor measured data with the two different Performance prediction methods. The S809 aerofoil data sets evaluated included those from Delft University of Technology, Ohio State University and Colorado State University. Substantial differences in prediction Performance resulted from the different two-dimensional aerofoil data sets. Predicted Performance comparison with NASA Ames data documents shortcomings of these methods and recommends the use of the lifting surface, prescribed wake method over blade element momentum theory for future analytical improvements. Copyright © 2002 John Wiley & Sons, Ltd.
-
Measured and predicted Rotor Performance for the SERI advanced wind turbine blades
1992Co-Authors: J. L. Tangler, B. Smith, Neil Kelley, D. JagerAbstract:Measured and predicted Rotor Performance for the SERI advanced wind turbine blades were compared to assess the accuracy of predictions and to identify the sources of error affecting both predictions and measurements. An awareness of these sources of error contributes to improved prediction and measurement methods that will ultimately benefit future Rotor design efforts. Propeller/vane anemometers were found to underestimate the wind speed in turbulent environments such as the San Gorgonio Pass wind farm area. Using sonic or cup anemometers, good agreement was achieved between predicted and measured power output for wind speeds up to 8 m/sec. At higher wind speeds an optimistic predicted power output and the occurrence of peak power at wind speeds lower than measurements resulted from the omission of turbulence and yaw error. In addition, accurate two-dimensional (2-D) airfoil data prior to stall and a post stall airfoil data synthesization method that reflects three-dimensional (3-D) effects were found to be essential for accurate Performance prediction. 11 refs.
Rohit Jain - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of Trailing-Edge Flap Gap Effects on Rotor Performance Using High-Fidelity Analysis
Journal of Aircraft, 2013Co-Authors: Rohit Jain, Hyeonsoo Yeo, Inderjit ChopraAbstract:Effects of trailing-edge flap gaps on Rotor Performance are investigated using a high-fidelity coupled computational fluid dynamics computational structural dynamics analysis. Both integral flap (the flap is an integral part of the blade such that there are no physical gaps at the flap ends) and discrete flap (the flap is a separate entity with physical gaps in the span and chord directions) are examined on an UH-60A Rotor at high-speed forward-flight conditions. A novel grid deformation scheme based on the Delaunay graph mapping is developed and implemented to allow the computational fluid dynamics modeling of the gaps with minimal distortion of mesh around the flap gap regions. This method offers an alternative to the traditional approach of modeling such configurations using overset meshes. The simulation results show that the effectiveness of the flap is minimally affected with span gaps; the penalty on Rotor Performance is of the order of 1% compared to the integral flap. On the other hand, the chord...
-
Effects of Torsion Frequencies on Rotor Performance and Structural Loads with Trailing Edge Flap
Smart Materials and Structures, 2012Co-Authors: Rohit Jain, Hyeonsoo YeoAbstract:The effects of variation of blade torsion frequency on Rotor Performance and structural loads are investigated for a 1/rev active flap Rotor and baseline Rotor (no active control). The UH-60A four-bladed articulated main Rotor is studied at a high-speed forward flight condition. The torsion frequencies are varied by modifying the spanwise torsional stiffness of the blade and/or the pitch link stiffness. First, a parametric/optimization study on the flap deployment schedule is carried out using lifting-line comprehensive analysis for the soft, baseline, and stiff Rotor configurations, and then a higher fidelity coupled computational fluid dynamics–computational structural dynamics analysis is carried out for the optimal flap deployment. It is shown that with the soft Rotor there is degradation in Performance—of about 6% with respect to the baseline Rotor in the case where the flaps are not activated, and of about 1% if flap deflections are applied. On the other hand, for the stiff Rotor there is a slight improvement in Performance of about 2.3% when the flaps are not activated, and no appreciable change in the case where active flap deflections are applied. It appears that the peak Performance achievable with using active flaps on a baseline stiffness Rotor cannot be further improved significantly by varying the torsional frequencies. Variation of torsion frequency does not appear to have a significant influence on blade torsion moments and pitch link loads, although the 1/rev flap activation examined has an important role.
-
Investigation of Trailing-edge Flap Gap Effects on Rotor Performance Using CFD/CSD Coupling
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012Co-Authors: Rohit Jain, Hyeonsoo Yeo, Inderjit ChopraAbstract:Effects of trailing-edge flap gaps on Rotor Performance are investigated using a high fidelity, coupled computational fluid dynamics (CFD) – computational structural dynamics (CSD) analysis. Both integral flap (the flap is an integral part of the blade such that there are no physical gaps at the flap ends) and discrete flap (the flap is a separate entity with physical gaps in the spanwise and chordwise directions) are examined on an UH-60A Rotor at high speed forward flight condition. A novel grid deformation scheme based on the Delaunay graph mapping is developed and implemented to allow the CFD modeling of the gaps with minimal distortion of mesh around the flap gap regions. This method offers an alternative to the traditional approach of modeling such configurations using overset meshes. The simulation results show that the effectiveness of the flap is minimally lost with spanwise gaps – the penalty on Rotor Performance is of the order of 1% compared to the integral flap. On the other hand the chordwise gaps significantly degrade the benefits of active flap on Rotor Performance due to the flow penetration between the upper and lower surfaces of the flap.
