scholarly journals The Effect of Rigging Angle on Longitudinal Direction Motion of Parafoil-Type Vehicle: Basic Stability Analysis and Wind Tunnel Test

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Takahiro Moriyoshi ◽  
Kazuhiko Yamada ◽  
Hiroyuki Nishida
Keyword(s):  
Stability Analysis ◽  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Longitudinal Direction ◽  
Aerodynamic Characteristics ◽  
Vehicle Stability ◽  
Flexible Wings ◽  
Allowable Range ◽  
Analytical Approaches

The paraglider, a flexible flying vehicle, consists of a parafoil with flexible wings, suspension lines, and a suspended payload. At this time, the suspension lines have several parameters to be designed. Above all, a parameter called Rigging Angle (RA) is sensitive to the aerodynamic characteristics of a paraglider during flight. In this study, the effect of RA is clarified using the two-dimensional stability analysis and a wind tunnel test. The mechanisms about the parafoil-type vehicle stability are clarified through the experimental and analytical approaches as follows. The RA has an allowable range for a stable flight. When the RA is set out of the range, the parafoil cannot fly stably. Furthermore, the behavior of the parafoil wing in the case of lower RA than the allowable range is different from the case of higher RA. The parafoil collapses from the leading edge of the canopy and cannot glide in the case of lower RA.

Wind Tunnel Test of Effect of Sound-Absorbing Material on Lift of Two-Element Airfoil

2013 ◽  
Vol 830 ◽  
pp. 17-23
Author(s):  
Yong Wei Gao ◽  
Qi Liang Zhu ◽  
Long Wang
Keyword(s):  
Wind Tunnel ◽  
High Frequency ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Low Frequency ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Fluctuating Pressure ◽  
Flow Parameters ◽  
Absorbing Material

The flow parameters of fluctuating pressure and fluctuating velocity in the gap can be changed by the porous absorption material on the leading edge of upper surface of the flap of multi-element airfoil (GAW-1),and the aerodynamic characteristics is also altered. Experiment was conducted in the NF-3 wind tunnel. It turns out that porous absorption material has a significant effect on fluctuating velocity (i.e. turbulent kinetic energy), and the lift coefficient drops when fluctuating velocity increases ; but the influence on RMS of fluctuating pressure on upper surface is not obvious; the average speed in gap is reduced. The PSD of fluctuating pressure and fluctuating velocity show that low-frequency signal has a more obvious influence on lift of multi-element airfoils than high-frequency.

scholarly journals Geometrically Nonlinear Aeroelastic Stability Analysis and Wind Tunnel Test Validation of a Very Flexible Wing

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
Changchuan Xie ◽  
Yi Liu ◽  
Chao Yang ◽  
J. E. Cooper
Keyword(s):  
Stability Analysis ◽  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Geometrically Nonlinear ◽  
Analysis Model ◽  
Aeroelastic Stability ◽  
Lattice Method ◽  
Flexible Wings ◽  
Structural Dynamic ◽  
Flutter Boundary

VFAs (very flexible aircraft) have begun to attract significant attention because of their good flight performances and significant application potentials; however, they also bring some challenges to researchers due to their unusual lightweight designs and large elastic deformations. A framework for the geometrically nonlinear aeroelastic stability analysis of very flexible wings is constructed in this paper to illustrate the unique aeroelastic characteristics and convenient use of these designs in engineering analysis. The nonlinear aeroelastic analysis model includes the geometrically nonlinear structure finite elements and steady and unsteady nonplanar aerodynamic computations (i.e., the nonplanar vortex lattice method and nonplanar doublet-lattice method). Fully nonlinear methods are used to analyse static aeroelastic features, and linearized structural dynamic equations are established at the structural nonlinear equilibrium state to estimate the stability of the system through the quasimode of the stressed and deformed structure. The exact flutter boundary is searched via an iterative procedure. A wind tunnel test is conducted to validate this theoretical analysis framework, and reasonable agreement is obtained. Both the analysis and test results indicate that the geometric nonlinearity of very flexible wings presents significantly different aeroelastic characteristics under different load cases with large deformations.

Exploration on application of dredging thermal protection in the leading edge of the wing

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040105
Author(s):  
Xiao-Jun Zhu ◽  
Feng Li
Keyword(s):  
High Temperature ◽  
Wind Tunnel ◽  
Heat Pipe ◽  
Thermal Protection ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Temperature Zone ◽  
Temperature Heat ◽  
Thermal Protection Structure ◽  
High Temperature Heat Pipe

Aiming at the severe aerodynamic heating problem in the leading edge of the hypersonic vehicle, in order to ensure the sharp shape of the leading edge of the wing, a dredging thermal protection structure is proposed, and the built-in high-temperature heat pipe structure is used to provide thermal protection for the leading edge of the wing. By means of numerical simulation and arc wind tunnel test, the dredging thermal protection structure of the leading edge of the wing is analyzed, and the thermal protection effect of the built-in high-temperature heat pipe is obtained. The numerical results show that under certain thermal conditions, the temperature at the leading edge of the wing decreases by 304 K, and the minimum temperature of the tail increases by 130 K. The heat flow is dredged from the high-temperature zone to the low-temperature zone, and the thermal load of the leading edge of the wing is weakened. The same result can be obtained by the arc wind tunnel test, which verifies the accuracy of the numerical method and the feasibility of the dredging thermal protection structure with high-temperature heat pipe embedded in the leading edge of the wing.

scholarly journals Wind Tunnel Test of the S814 Thick Root Airfoil

1996 ◽  
Vol 118 (4) ◽  
pp. 217-221 ◽  
Author(s):  
D. M. Somers ◽  
J. L. Tangler
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Rotor Blades ◽  
Roughness Effects ◽  
Root Region ◽  
University Of Technology ◽  
Thick Airfoil

The objective of this wind-tunnel test was to verify the predictions of the Eppler Airfoil Design and Analysis Code for a very thick airfoil having a high maximum lift coefficient designed to be largely insensitive to leading-edge roughness effects. The 24 percent thick S814 airfoil was designed with these characteristics to accommodate aerodynamic and structural considerations for the root region of a wind-turbine blade. In addition, the airfoil’s maximum lift-to-drag ratio was designed to occur at a high lift coefficient. To accomplish the objective, a two-dimensional wind tunnel test of the S814 thick root airfoil was conducted in January 1994 in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. Data were obtained with transition free and transition fixed for Reynolds numbers of 0.7, 1.0, 1.5, 2.0, and 3.0 × 106. For the design Reynolds number of 1.5 × 106, the maximum lift coefficient with transition free is 1.32, which satisfies the design specification. However, this value is significantly lower than the predicted maximum lift coefficient of almost 1.6. With transition fixed at the leading edge, the maximum lift coefficient is 1.22. The small difference in maximum lift coefficient between the transition-free and transition-fixed conditions demonstrates the airfoil’s minimal sensitivity to roughness effects. The S814 root airfoil was designed to complement existing NREL low maximum-lift-coefficient tip-region airfoils for rotor blades 10 to 15 meters in length.

Experimental Studies on Aerodynamic Characteristics of Pantograph System According to the Pantograph Cover Configurations for High Speed Train

2011 ◽  
Author(s):  
Yeongbin Lee ◽  
Minho Kwak ◽  
Kyu Hong Kim ◽  
Dong-Ho Lee
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Force ◽  
Experimental Studies ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Experimental Models ◽  
High Speed Train ◽  
Drag And Lift

In this study, the aerodynamic characteristics of pantograph system according to the pantograph cover configurations for high speed train were investigated by wind tunnel test. Wind tunnel tests were conducted in the velocity range of 20∼70m/s with scaled experimental pantograph models. The experimental models were 1/4 scaled simplified pantograph system which consists of a double upper arm and a single lower arm with a square cylinder shaped panhead. The experimental model of the pantograph cover is also 1/4 scaled and were made as 4 different configurations. It is laid on the ground plate which modeled on the real roof shape of the Korean high speed train. Using a load cell, the aerodynamic force such as a lift and a drag which were acting on pantograph system were measured and the aerodynamic effects according to the various configurations of pantograph covers were investigated. In addition, the total pressure distributions of the wake regions behind the panhead of the pantograph system were measured to investigate the variations of flow pattern. From the experimental test results, we checked that the flow patterns and the aerodynamic characteristics around the pantograph systems are varied as the pantograph cover configurations. In addition, it is also found that pantograph cover induced to decrease the aerodynamic drag and lift forces. Finally, we proposed the aerodynamic improvement of pantograph cover and pantograph system for high speed train.

scholarly journals Aerodynamic study of a suspension bridge deck by CFD simulations, wind tunnel tests and full-scale observations

2021 ◽  
Vol 1201 (1) ◽  
pp. 012007
Author(s):  
I. Kusano ◽  
E. Cheynet ◽  
J. B. Jakobsen ◽  
J. Snæbjörnsson
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Suspension Bridge ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Wide Range

Abstract Assessing the aerodynamic characteristics of long-span bridges is fundamental for their design. Depending on the terrain complexity and local wind conditions, episodes of large angles of attack (AoA) of 15° may be observed. However, such large AoAs ( above 10°) are often overlooked in the design process. This paper studies the aerodynamics properties of a flow around a single-box girder for a wide range of AoAs, from –20° to 20°, using numerical simulations. The simulations are based on a 2D unsteady Reynolds-averaged Navier–Stokes (URANS) approach using the k − ω SST turbulence model with a Reynolds number of 1.6 × 105. Numerically obtained aerodynamic static coefficients were compared to wind tunnel test data. The CFD results were generally in good agreement with the wind tunnel tests, especially for small AoAs and positive AoAs. More discrepancies were observed for large negative AoA, likely due to the limitation of modelling 3D railings with 2D simulations. The simulated velocity deficit downstream of the deck was consistent with the one measured in full-scale using short-range Doppler wind lidar instruments. Finally, the Strouhal number from the CFD simulations were in agreement with the value obtained from the full-scale data.

An experimental parametric study on planar sheared wings tip devices for low-to-moderate aspect ratio wings

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lourelay Moreira dos Santos ◽  
Guilherme Ferreira Gomes ◽  
Rogerio F. Coimbra
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Parametric Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Sweep Angle ◽  
Wind Tunnel Tests ◽  
Content Type ◽  
Wing Tips ◽  
Wing Tip

Purpose The purpose of this study is to investigate the aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips. Design/methodology/approach In this work, wind tunnel tests were made to study the influence in aerodynamic characteristics over a typical low-to-moderate-aspect-ratio wing of a general aviation aircraft, equipped with sheared – swept and tapered planar – wing tips. An experimental parametric study of different wing tips was tested. Variations in its leading and trailing edge sweep angle as well as variations in wing tip taper ratio were considered. Sheared wing tips modify the flow pattern in the outboard region of the wing producing a vortex flow at the wing tip leading edge, enhancing lift at high angles of attack. Findings The induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some wing tip models present complex geometries and many of them present benefits in particular flight conditions. Results have demonstrated that sweeping the wing tip leading edge between 60 and 65 degrees offers an increment in wing aerodynamic efficiency, especially at high lift conditions. However, results have demonstrated that moderate wing tip taper ratio (0.50) has better aerodynamic benefits than highly tapered wing tips (from 0.25 to 0.15), even with little less wing tip leading edge sweep angle (from 57 to 62 degrees). The moderate wing tip taper ratio (0.50) offers more wing area and wing span than the wings with highly tapered wing tips, for the same aspect ratio wing. Originality/value Although many studies have been reported on the aerodynamics of wing tips, most of them presented complex non-planar geometries and were developed for cruise flight in high subsonic regime (low lift coefficient). In this work, an exploration and parametric study through wind tunnel tests were made, to evaluate the influence in aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips (wing tips highly swept and tapered).

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