scholarly journals On the Wake Properties of Segmented Trailing Edge Extensions

2018 ◽  
Author(s):  
Sidaard Gunasekaran ◽  
Daniel Curry
Keyword(s):  
Lift Coefficient ◽  
Free Shear Layer ◽  
Structural Vibrations ◽  
Trailing Edge ◽  
Total Drag ◽  
Image Velocimetry ◽  
Effective Angle ◽  
The University ◽  
Naca 0012 ◽  
Low Speed Wind Tunnel

Changes in the amount and the distribution of mean and turbulent quantities in the free shear layer wake of a 2D NACA 0012 airfoil and AR 4 NACA 0012 wing with passive segmented rigid trailing edge (TE) extensions was investigated at the University of Dayton Low Speed Wind Tunnel (UD-LSWT). The TE extensions were intentionally placed at zero degrees with respect to the chord line to study the effects of segmented extensions without changing the effective angle of attack. Force based experiments was used to determine the total lift coefficient variation of hte wing with seven segmented trailing edge extensions distributed across the span. The segmented trailing edge extensions had negligible effect of lift coefficient but showed measurable decrement in sectional and total drag coefficient. Investigation of turbulent quantities (obtained through Particle Image Velocimetry (PIV)) such as Reynolds stress, streamwise and transverse RMS in the wake, reveal a significant decrease in magnitude when compared to the baseline. The decrease in the magnitude of turbulent parameters was supported by the changes in coherent structures obtained through two-point correlations. Apart from the reduction in drag, the lower turbulent wake generated by the extensions has implications in reducing structural vibrations and acoustic tones.

scholarly journals On the Wake Properties of Segmented Trailing Edge Extensions

2018 ◽  
Author(s):  
Sidaard Gunasekaran ◽  
Daniel Curry
Keyword(s):  
Lift Coefficient ◽  
Free Shear Layer ◽  
Structural Vibrations ◽  
Trailing Edge ◽  
Total Drag ◽  
Image Velocimetry ◽  
Effective Angle ◽  
The University ◽  
Naca 0012 ◽  
Low Speed Wind Tunnel

Changes in the amount and the distribution of mean and turbulent quantities in the free shear layer wake of a 2D NACA 0012 airfoil and AR 4 NACA 0012 wing with passive segmented rigid trailing edge (TE) extensions was investigated at the University of Dayton Low Speed Wind Tunnel (UD-LSWT). The TE extensions were intentionally placed at zero degrees with respect to the chord line to study the effects of segmented extensions without changing the effective angle of attack. Force based experiments was used to determine the total lift coefficient variation of hte wing with seven segmented trailing edge extensions distributed across the span. The segmented trailing edge extensions had negligible effect of lift coefficient but showed measurable decrement in sectional and total drag coefficient. Investigation of turbulent quantities (obtained through Particle Image Velocimetry (PIV)) such as Reynolds stress, streamwise and transverse RMS in the wake, reveal a significant decrease in magnitude when compared to the baseline. The decrease in the magnitude of turbulent parameters was supported by the changes in coherent structures obtained through two-point correlations. Apart from the reduction in drag, the lower turbulent wake generated by the extensions has implications in reducing structural vibrations and acoustic tones.

scholarly journals On the Wake Properties of Segmented Trailing Edge Extensions

Aerospace ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 89 ◽  
Author(s):  
Sidaard Gunasekaran ◽  
Daniel Curry
Keyword(s):  
Lift Coefficient ◽  
Free Shear Layer ◽  
Structural Vibrations ◽  
Trailing Edge ◽  
Total Drag ◽  
Image Velocimetry ◽  
Effective Angle ◽  
The University ◽  
Naca 0012 ◽  
Low Speed Wind Tunnel

Changes in the amount and the distribution of mean and turbulent quantities in the free shear layer wake of a 2D National Advisory Committee for Aeronautics (NACA) 0012 airfoil and an AR 4 NACA 0012 wing with passive segmented rigid trailing edge (TE) extensions were investigated at the University of Dayton Low Speed Wind Tunnel (UD-LSWT). The TE extensions were intentionally placed at zero degrees with respect to the chord line to study the effects of segmented extensions without changing the effective angle of attack. Force based experiments were used to determine the total lift coefficient variation of the wing with seven segmented trailing edge extensions distributed across the span. The segmented trailing edge extensions had a negligible effect on the lift coefficient, but showed a measurable decrement in the sectional and total drag coefficient. Investigation of turbulent quantities (obtained through Particle Image Velocimetry (PIV)) such as Reynolds stress, streamwise and transverse root-mean square (RMS) in the wake, reveal a significant decrease in magnitude when compared to the baseline. The decrease in the magnitude of turbulent parameters was supported by the changes in coherent structures obtained through two-point correlations. Apart from the reduction in drag, the lower turbulent wake generated by the extensions has implications in reducing structural vibrations and acoustic tones.

scholarly journals Effect of Piezo-Embedded Inverted Flag in Free Shear Layer Wake

Aerospace ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 33
Author(s):  
Sidaard Gunasekaran ◽  
Grant Ross
Keyword(s):  
Shear Layer ◽  
Oscillation Frequency ◽  
Energy Harvester ◽  
Oscillation Amplitude ◽  
Angle Of Attack ◽  
Lower Surface ◽  
Free Shear Layer ◽  
Polyvinylidene Difluoride ◽  
Image Velocimetry ◽  
Naca 0012

The use of flexible inverted piezo embedded Polyvinylidene Difluoride (PVDF) as a simultaneous energy harvester and as a wake sensor is explored. The oscillation amplitude (characterized by voltage output) and oscillation frequency of the piezo-embedded PDVF was quantified in the wake of a 2D NACA 0012 model and SD7003 model at a Reynolds number of 100,000 and 67,000, respectively. The performance of the sensor was also quantified in the freestream without the presence of the wing. In order to quantify the sensor response to angle of attack and downstream distance, the amplitude and frequency of oscillations were recorded in the wing wake. Increase in angle of attack of the wing resulted in increase in oscillation frequency and amplitude of the PVDF. The results also indicated that the inverted flag configuration performed better in the wake under unsteady conditions when compared to freestream conditions. The results from Particle Image Velocimetry indicated that the wake signature was not affected by the presence of the PVDF in the wake. The root mean square voltage contours in the wake of SD7003 airfoil show remarkable free shear layer wake features such as upper and lower surface stratification and downwash angle which shows the sensitivity of the sensor to the unsteadiness in the wake. The capability of this device to act as a potential energy harvester and as a sensor has serious implications in extending the mission capabilities of small UAVs.

scholarly journals Bifurcating flows of plunging aerofoils at high Strouhal numbers

2012 ◽  
Vol 708 ◽  
pp. 349-376 ◽  
Author(s):  
D. J. Cleaver ◽  
Z. Wang ◽  
I. Gursul
Keyword(s):  
Lift Coefficient ◽  
Strength Parameter ◽  
Asymptotic State ◽  
Trailing Edge ◽  
Vortex Strength ◽  
Starting Position ◽  
Acceleration Rate ◽  
Stall Angle ◽  
Bifurcation Behaviour ◽  
Naca 0012

AbstractForce and particle image velocimetry measurements were conducted on a NACA 0012 aerofoil undergoing small-amplitude high-frequency plunging oscillation at low Reynolds numbers and angles of attack in the range 0–$2{0}^{\ensuremath{\circ} } $. For angles of attack less than or equal to the stall angle, at high Strouhal numbers, significant bifurcations are observed in the time-averaged lift coefficient resulting in two lift-coefficient branches. The upper branch is associated with an upwards deflected jet, and the lower branch is associated with a downwards deflected jet. These branches are stable and highly repeatable, and are achieved by increasing or decreasing the frequency in the experiments. Increasing frequency refers to starting from stationary and increasing the frequency very slowly (while waiting for the flow to reach an asymptotic state after each change in frequency); decreasing frequency refers to impulsively starting at the maximum frequency and decreasing the frequency very slowly. For the latter case, angle of attack, starting position and initial acceleration rate are also parameters in determining which branch is selected. The bifurcation behaviour is closely related to the properties of the trailing-edge vortices. The bifurcation was therefore not observed for very small plunge amplitudes or frequencies due to insufficient trailing-edge vortex strength, nor at larger angles of attack due to greater asymmetry in the strength of the trailing-edge vortices, which creates a preference for a downward deflected jet. Vortex strength and asymmetry parameters are derived from the circulation measurements. It is shown that the most appropriate strength parameter in determining the onset of deflected jets is the circulation normalized by the plunge velocity.

scholarly journals Extended-POD based acoustic analysis of separated aerofoils via simultaneous time-resolved PIV and force measurements

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Douglas William Carter ◽  
Manuel Ferreira ◽  
Bharathram Ganapathisubramani
Keyword(s):  
Acoustic Analysis ◽  
Water Channel ◽  
Force Measurements ◽  
Time Resolved ◽  
Precise Control ◽  
Pressure Fields ◽  
Image Velocimetry ◽  
Torque Transducer ◽  
The University ◽  
Naca 0012

We present a cross-correlation based analysis of the acoustic field generated in the wake of NACA 0012 and NACA 65410 aerofoils at a chord-based Reynolds number Rec = 75000 as obtained from pressure fields reconstructed from a series of planar time-resolved Particle Image Velocimetry (PIV) experiments. The experiments are performed in a water channel facility located at the University of Southampton with an overhead carriage system to allow precise control of the angle of attack α of the aerofoils as well as to mount them to a six-axis force/torque transducer to allow for simultaneous load measurements. Angles of attack in the range 4◦ < α < 17◦ are explored corresponding to a range of conditions from zero flow separation to fully stalled.

scholarly journals A Parametric Study of Trailing Edge Flap Implementation on Three Different Airfoils Through an Artificial Neuronal Network

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 828
Author(s):  
Igor Rodriguez-Eguia ◽  
Iñigo Errasti ◽  
Unai Fernandez-Gamiz ◽  
Jesús María Blanco ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Aerodynamic Coefficients ◽  
Trailing Edge ◽  
High Lift ◽  
Trailing Edge Flaps ◽  
Artificial Neural Network Ann ◽  
Lift And Drag ◽  
Artificial Neuronal Network ◽  
Naca 0012 ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Trailing edge flaps (TEFs) are high-lift devices that generate changes in the lift and drag coefficients of an airfoil. A large number of 2D simulations are performed in this study, in order to measure these changes in aerodynamic coefficients and to analyze them for a given Reynolds number. Three different airfoils, namely NACA 0012, NACA 64(3)-618, and S810, are studied in relation to three combinations of the following parameters: angle of attack, flap angle (deflection), and flaplength. Results are in concordance with the aerodynamic results expected when studying a TEF on an airfoil, showing the effect exerted by the three parameters on both aerodynamic coefficients lift and drag. Depending on whether the airfoil flap is deployed on either the pressure zone or the suction zone, the lift-to-drag ratio, CL/CD, will increase or decrease, respectively. Besides, the use of a larger flap length will increase the higher values and decrease the lower values of the CL/CD ratio. In addition, an artificial neural network (ANN) based prediction model for aerodynamic forces was built through the results obtained from the research.

Maximizing the efficiency of a flexible propulsor using experimental optimization

2015 ◽  
Vol 767 ◽  
pp. 430-448 ◽  
Author(s):  
Daniel B. Quinn ◽  
George V. Lauder ◽  
Alexander J. Smits
Keyword(s):  
Leading Edge ◽  
The Body ◽  
Phase Lag ◽  
Force Measurements ◽  
Experimental Optimization ◽  
Image Velocimetry ◽  
Flexible Panel ◽  
Gradient Based ◽  
Power Scale ◽  
Effective Angle

AbstractExperimental gradient-based optimization is used to maximize the propulsive efficiency of a heaving and pitching flexible panel. Optimum and near-optimum conditions are studied via direct force measurements and particle image velocimetry (PIV). The net thrust and power scale predictably with the frequency and amplitude of the leading edge, but the efficiency shows a complex multimodal response. Optimum pitch and heave motions are found to produce nearly twice the efficiencies of optimum heave-only motions. Efficiency is globally optimized when (i) the Strouhal number is within an optimal range that varies weakly with amplitude and boundary conditions; (ii) the panel is actuated at a resonant frequency of the fluid–panel system; (iii) heave amplitude is tuned such that trailing-edge amplitude is maximized while the flow along the body remains attached; and (iv) the maximum pitch angle and phase lag are chosen so that the effective angle of attack is minimized. The multi-dimensionality and multi-modality of the efficiency response demonstrate that experimental optimization is well-suited for the design of flexible underwater propulsors.

Experimental investigation on the momentumless wake using trailing edge blowing

2008 ◽  
Vol 222 (8) ◽  
pp. 1477-1486 ◽  
Author(s):  
Y Wu ◽  
X Zhu ◽  
Z Du
Keyword(s):  
Three Dimensional ◽  
Velocity Profiles ◽  
Axial Fan ◽  
Trailing Edge ◽  
Mean Velocity ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Velocity Spectra ◽  
Momentumless Wake ◽  
Wake Characteristics

A developed plate stator model with and without trailing edge blowing (TEB) is studied using experimental methods. Wake characteristics of flow over the stator in the three-dimensional wake regimes are studied using hot-wire anemometry (HWA) and particle image velocimetry (PIV) techniques. First, the mean velocity profiles have been measured in the wake of the stator using HWA. Four wake characteristics have been obtained through momentum thickness judgments: pure wake, weak wake, momentumless wake, and jet. These velocity profiles show some differences in momentum deficit for the four cases. Then, the velocity spectra of the pure wake and momentumless wake obtained through the HWA measurements showed that TEB can eliminate the shedding vortex of the stator. Characteristic length scales based on the wake turbulent intensity profiles showed that the momentumless wake can reduce the wake width and depth. PIV measurement is carried out to measure the flow field of the four wakes. Finally, the application of TEB approaching momentumless wake status is used on an industrial ventilation low-pressure axial fan to assess noise reduction. The results show that TEB can make the outlet of the stator uniform, reduce velocity fluctuation, destroy the vorticity structure downstream of the stator, and reduce interaction noise level of the stator and rotor.

scholarly journals Numerical Simulation and Hydrodynamic Performance Predicting of 2 Two-Dimensional Hydrofoils in Tandem Configuration

2021 ◽  
Vol 9 (5) ◽  
pp. 462
Author(s):  
Yuchen Shang ◽  
Juan J. Horrillo
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Resource Constraints ◽  
Lift Coefficient ◽  
Parametric Method ◽  
Experimental Results ◽  
Hydrodynamic Performance ◽  
Tandem Configuration ◽  
Artificial Neural Network Ann ◽  
Naca 0012

In this study we investigated the performance of NACA 0012 hydrofoils aligned in tandem using parametric method and Neural Networks. We use the 2D viscous numerical model (STAR-CCM+) to simulate the hydrofoil system. To validate the numerical model, we modeled a single NACA 0012 configuration and compared it to experimental results. Results are found in concordance with the published experimental results. Then two NACA 0012 hydrofoils in tandem configuration were studied in relation to 788 combinations of the following parameters: spacing between two hydrofoils, angle of attack (AOA) of upstream hydrofoil and AOA of downstream hydrofoil. The effects exerted by these three parameters on the hydrodynamic coefficients Lift coefficient (CL), Drag Coefficient (CD) and Lift-Drag Ratio (LDR), are consistent with the behavior of the system. To establish a control system for the hydrofoil craft, a timely analysis of the hydrodynamic system is needed due to the computational resource constraints, analysis of a large combination and time consuming of the three parameters established. To provide a broader and faster way to predict the hydrodynamic performance of two hydrofoils in tandem configuration, an optimal artificial neural network (ANN) was trained using the large combination of three parameters generated from the numerical simulations. Regression analysis of the output of ANN was performed, and the results are consistent with numerical simulation with a correlation coefficient greater than 99.99%. The optimized spacing of 6.6c are suggested where the system has the lowest CD while obtaining the highest CL and LDR. The formula of the ANN was then presented, providing a reliable predicting method of hydrofoils in tandem configuration.

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