Effects of nose bluntness, angle of attack, and oscillation amplitude on hypersonic unsteady aerodynamics of slender cones

AIAA Journal ◽  
1971 ◽  
Vol 9 (2) ◽  
pp. 297-304 ◽  
Author(s):  
LARS ERIC ERICSSON
Keyword(s):  
Oscillation Amplitude ◽  
Angle Of Attack ◽  
Unsteady Aerodynamics

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.

A Harmonic Balance Approach for Modeling Three-Dimensional Nonlinear Unsteady Aerodynamics and Aeroelasticity

2002 ◽  
Author(s):  
Jeffrey P. Thomas ◽  
Earl H. Dowell ◽  
Kenneth C. Hall
Keyword(s):  
Limit Cycle ◽  
Harmonic Balance ◽  
Structural Model ◽  
Oscillation Amplitude ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Finite Amplitude ◽  
Limit Cycle Oscillation ◽  
Unsteady Aerodynamic ◽  
Cycle Oscillation

Presented is a frequency domain harmonic balance (HB) technique for modeling nonlinear unsteady aerodynamics of three-dimensional transonic inviscid flows about wing configurations. The method can be used to model efficiently nonlinear unsteady aerodynamic forces due to finite amplitude motions of a prescribed unsteady oscillation frequency. When combined with a suitable structural model, aeroelastic (fluid-structure), analyses may be performed at a greatly reduced cost relative to time marching methods to determine the limit cycle oscillations (LCO) that may arise. As a demonstration of the method, nonlinear unsteady aerodynamic response and limit cycle oscillation trends are presented for the AGARD 445.6 wing configuration. Computational results based on the inviscid flow model indicate that the AGARD 445.6 wing configuration exhibits only mildly nonlinear unsteady aerodynamic effects for relatively large amplitude motions. Furthermore, and most likely a consequence of the observed mild nonlinear aerodynamic behavior, the aeroelastic limit cycle oscillation amplitude is predicted to increase rapidly for reduced velocities beyond the flutter boundary. This is consistent with results from other time-domain calculations. Although not a configuration that exhibits strong LCO characteristics, the AGARD 445.6 wing nonetheless serves as an excellent example for demonstrating the HB/LCO solution procedure.

Unsteady aerodynamic characteristics of a morphing wing

2018 ◽  
Vol 91 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Jinwu Xiang ◽  
Kai Liu ◽  
Daochun Li ◽  
Chunxiao Cheng ◽  
Enlai Sha
Keyword(s):  
Lift Coefficient ◽  
Angle Of Attack ◽  
Large Angle ◽  
Unsteady Aerodynamics ◽  
Aerodynamic Characteristics ◽  
Static Case ◽  
Morphing Wing ◽  
Trailing Edge ◽  
Content Type ◽  
Unsteady Aerodynamic

Purpose The purpose of this paper is to investigate the unsteady aerodynamic characteristics in the deflection process of a morphing wing with flexible trailing edge, which is based on time-accurate solutions. The dynamic effect of deflection process on the aerodynamics of morphing wing was studied. Design/methodology/approach The computational fluid dynamic method and dynamic mesh combined with user-defined functions were used to simulate the continuous morphing of the flexible trailing edge. The steady aerodynamic characteristics of the morphing deflection and the conventional deflection were studied first. Then, the unsteady aerodynamic characteristics of the morphing wing were investigated as the trailing edge deflects at different rates. Findings The numerical results show that the transient lift coefficient in the deflection process is higher than that of the static case one in large angle of attack. The larger the deflection frequency is, the higher the transient lift coefficient will become. However, the situations are contrary in a small angle of attack. The periodic morphing of the trailing edge with small amplitude and high frequency can increase the lift coefficient after the stall angle. Practical implications The investigation can afford accurate aerodynamic information for the design of aircraft with the morphing wing technology, which has significant advantages in aerodynamic efficiency and control performance. Originality/value The dynamic effects of the deflection process of the morphing trailing edge on aerodynamics were studied. Furthermore, time-accurate solutions can fully explore the unsteady aerodynamics and pressure distribution of the morphing wing.

Effect of Angle of Attack and Mach Number on Slender-Wing Unsteady Aerodynamics

1978 ◽  
Vol 15 (6) ◽  
pp. 358-365 ◽  
Author(s):  
Lars E. Ericsson ◽  
J. Peter Reding
Keyword(s):  
Mach Number ◽  
Angle Of Attack ◽  
Unsteady Aerodynamics ◽  
Slender Wing

Validation of the AeroDyn Subroutines Using NREL Unsteady Aerodynamics Experiment Data

2002 ◽  
Author(s):  
David J. Laino ◽  
A. Craig Hansen ◽  
Jeff E. Minnema
Keyword(s):  
Wind Tunnel ◽  
Test Data ◽  
Complex Dynamics ◽  
Angle Of Attack ◽  
Unsteady Aerodynamics ◽  
Hysteresis Loops ◽  
Structural Vibration ◽  
Detailed Knowledge ◽  
Vibration Modes ◽  
Wind Tunnel Tests

Completion of the full-scale wind tunnel tests of the NREL Unsteady Aerodynamics Experiment (UAE) Phase VI allowed validation of the AeroDyn wind tuxbine aerodynamics software to commence. Detailed knowledge of the inflow to the UAE was the bane of prior attempts to accomplish any in-depth validation in the past. The wind tunnel tests permitted unprecedented control and measurement of inflow to the UAE rotor. The data collected from these UAE tests are currently under investigation as part of an effort to better understand wind turbine rotor aerodynamics in order to improve aero-elastic modeling techniques. Preliminary results from this study using the AeroDyn subroutines are presented, pointing to several avenues toward improvement. Test data indicate that rotational effects cause more static stall delay over a larger portion of the blades than predicted by current methods. Despite the relatively stiff properties of the UAE, vibration modes appear to influence the aerodynamic forces and system loads. AeroDyn adequately predicts dynamic stall hysteresis loops when appropriate steady, 2-D airfoil tables are used. Problems encountered include uncertainties in converting measured inflow angle to angle of attack for the UAE phase VI. Future work is proposed to address this angle of attack problem and to analyze a slightly more complex dynamics model that incorporates some of the structural vibration modes evident in the test data.

scholarly journals Effects of angle of attack on unsteady aerodynamics force of bicycle helmet

2019 ◽  
Vol 2019 (0) ◽  
pp. IS-29
Author(s):  
Takumi Ogino ◽  
Akiyoshi Iida ◽  
Hirotsugu Ota ◽  
Mitsuhiro Sugita
Keyword(s):  
Angle Of Attack ◽  
Unsteady Aerodynamics ◽  
Bicycle Helmet
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