Shape optimization and experimental research of near space airship

2018 ◽  
Vol 233 (10) ◽  
pp. 3589-3602
Author(s):  
Dongli Ma ◽  
Guanxiong Li ◽  
Muqing Yang ◽  
Shaoqi Wang ◽  
Liang Zhang
Keyword(s):  
Wind Tunnel ◽  
Shape Optimization ◽  
Drag Coefficient ◽  
Force Measurement ◽  
Wind Tunnel Test ◽  
Volume Ratio ◽  
Aerodynamic Characteristics ◽  
Near Space ◽  
Transition Position ◽  
Favorable Pressure Gradient

Shape optimization has important effects on drag reduction of the near-space airship. This paper uses the Bezier curve to parameterize the hull of the airship. Based on multiple island genetic algorithms, the optimization platform combined with different programs is established, and a kind of low drag hull is obtained by optimization. Force measurement and flow observation wind tunnel test are used to research the aerodynamic characteristics of the ellipsoid hull and the optimized hull. Results show that, optimization mainly increases the volume ratio and the favorable pressure gradient region of the hull, therefore the surface area is reduced and transition position of the hull can be delayed. Compared with the LOTTE shape, transition position of the optimized shape moved backward by 13.78%, and the volume drag coefficient is reduced by 11.1%. It is known from the wind tunnel test that compared with the ellipsoid hull, transition position of the optimized shape moves backward obviously. Under the condition that the volume Reynolds number is 2.97 × 106, compared with the ellipsoid hull, volume drag coefficient of the optimized shape can reduce by 39.0%.

Study on the Aerodynamic Characteristics and Galloping Instability of Conductors Covered with Sector-Shaped Ice by a Wind Tunnel Test

2020 ◽  
Vol 20 (06) ◽  
pp. 2040016
Author(s):  
Jia-Xiang Li ◽  
Jian Sun ◽  
Ye Ma ◽  
Shu-Hong Wang ◽  
Xing Fu
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Ice Thickness ◽  
Shape Parameters ◽  
Aerodynamic Coefficient ◽  
Wind Tunnel Tests ◽  
And Control

Conductors with sector-shaped ice are susceptible to galloping. To prevent and control galloping, it is necessary to study the conductor aerodynamic characteristics. Wind tunnel tests were performed to study the influence of two shape parameters (ice thickness and ice angle) of a conductor with sector-shaped ice on the aerodynamic characteristics considering the roughness of the surface. In addition, the unstable areas for galloping are discussed according to Den Hartog theory and Nigol theory. The results show that with increasing ice thickness, the aerodynamic coefficient curves fluctuate more strongly, and galloping tends to occur; with increasing ice angle, the unstable area becomes larger according to Nigol theory, and the increasing drag coefficient will suppress the unstable areas according to Den Hartog theory. With the increasing two shape parameters, the most affected ranges of the aerodynamic coefficient curves are 150–180∘.

Research on the Aerodynamic Characteristics of Ellipse Wing Sail

2011 ◽  
Vol 347-353 ◽  
pp. 2249-2254
Author(s):  
Yi Huai Hu ◽  
Xiang Ming Zeng ◽  
Song Yue Li
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Aerodynamic Characteristic ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
The Novel ◽  
Better Than

A kind of novel airfoil sail is proposed in this paper based on the research of traditional arc wing sails. The aerodynamic characteristic- the lift coefficient and drag coefficient is numerically calculated with FLUENT 6.0 and the results are verified by wind tunnel test. It is proved that the aerodynamic characteristic of the novel sail is much better than the arc wing sail.

11701 Study on Deformable Wind Tunnel Model to Obtain Adequate Aerodynamic Characteristics by Experimental Shape-Optimization

2008 ◽  
Vol 2008.14 (0) ◽  
pp. 83-84
Author(s):  
Yoshihiro NAKAMURA ◽  
Futoshi NAGAMINE ◽  
Mitsuru IKEDA ◽  
Takeshi MITSUMOJI ◽  
Masahiro SUZUKI
Keyword(s):  
Wind Tunnel ◽  
Shape Optimization ◽  
Aerodynamic Characteristics ◽  
Wind Tunnel Model ◽  
Tunnel Model

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.

Comparative Analysis on Aerostatic Coefficients of Bridge Deck Based on Wind Tunnel Test

2010 ◽  
Vol 29-32 ◽  
pp. 377-382
Author(s):  
Fu You Xu ◽  
Bin Bin Li ◽  
Cai Liang Huang ◽  
Zhe Zhang
Keyword(s):  
Comparative Analysis ◽  
Wind Tunnel ◽  
Working Conditions ◽  
Turbulence Intensity ◽  
Flow Separation ◽  
Bridge Deck ◽  
Force Measurement ◽  
Wind Tunnel Test ◽  
Microscopic Mechanism ◽  
Comprehensive Study

A comprehensive study of force measurement test in wind tunnel is conducted for the streamlined deck model of Dalian Cross-sea Bridge scheme. The factors, including stacking load in erection, vehicles arrangement, central slot and so on, are analyzed in terms of the influence of the three-component coefficient in the way of microscopic mechanism. The stall angles under different working conditions are also investigated. The results show that stacking loads and vehicle arrangement barely have any impact on the three-component coefficient, which can be neglected approximately; lift and pitching coefficients decrease for the slotted deck, and the slot width has little influence on the aerostatic coefficients; bridge railing, stacking loads and vehicles change the flow separation and re-attachment around the deck, increasing the turbulence intensity, leading to the fluctuation of stall angles.

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.

scholarly journals Aerodynamic Characteristics Over Fine-Grained Gravel Surfaces in a Wind Tunnel

2021 ◽  
Vol 9 ◽  
Author(s):  
Jiaqi Liu ◽  
Reiji Kimura ◽  
Jing Wu
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Lower Layer ◽  
Aerodynamic Characteristics ◽  
Gobi Desert ◽  
Near Surface ◽  
Fine Grained ◽  
Wind Speeds ◽  
Speed Fluctuations

Gravels can protect soil from wind erosion, however, there is little known about the effects of fine-grained gravel on aerodynamic characteristics of the near-surface airflow. Drag coefficient, wind-speed gradient, and turbulent transfer coefficient over different coverages of gravel surfaces were investigated in a compact boundary-layer wind tunnel. The drag coefficient of the fine-grained gravel surface reached the maximum value at 15% coverage and then tended to stabilize at gravel coverage 20% and greater. At a height of 4 cm, near-surface airflow on gravel surfaces can be divided clearly into upper and lower sublayers, defined as the inertial and roughness sublayers, respectively. The coefficient of variation of wind speed over gravel surfaces in the roughness sublayer was 8.6 times that in the inertial sublayer, indicating a greater effect of gravel coverage on wind-speed fluctuations in the lower layer. At a height of 4 cm, wind-speed fluctuations under the observed wind speeds were independent of changes in gravel coverage. In addition, an energy-exchange region, where sand particles can absorb more energy from the surrounding airflow, was found between the roughness and inertial sublayers, enhancing the erosional state of wind-blown sand. This finding can be applied to evaluate the aerodynamic stability of the gravel surface in the Gobi Desert and provide a theoretical basis for elucidation of the vertical distributions of wind-blown sand flux.

Sign in / Sign up

Export Citation Format

Share Document