Influence of attack angle on the hydrodynamic damping characteristic of a hydrofoil

2021 ◽  
Vol 238 ◽  
pp. 109692
Author(s):  
Yongshun Zeng ◽  
Mindi Zhang ◽  
Yuxin Du ◽  
Zhifeng Yao ◽  
Qin Wu ◽  
...  
Keyword(s):  
Attack Angle ◽  
Hydrodynamic Damping

Evaluation and defense of light commands attacks against voice controllable systems in smart cars

2021 ◽  
pp. 095745652110015
Author(s):  
Zhijian Xu ◽  
Guoming Zhang ◽  
Xiaoyu Ji ◽  
Wenyuan Xu
Keyword(s):  
Laser Beam ◽  
Success Rate ◽  
Incidence Angle ◽  
Attack Angle ◽  
Light Transmittance ◽  
Controllable System ◽  
Lower Light ◽  
Controllable Systems ◽  
Smart Cars ◽  
The Impact

The in-car voice controllable system has become an almost standard feature in smart cars. Prior work shows that the voice controllable system is vulnerable to light commands attack which uses the laser as the medium to inject voice commands. In this article, we first reproduced the light commands attack on acoustic isolated in-car voice controllable system under several scenarios with a lightweight solution. We validate the feasibility of injecting the malicious voice command through a window into the microphone by modulating a laser beam. Then, we tested a variety of mainstream countermeasures such as placing sunscreen film on the glass panel to see whether it can protect the microphone from being attacked. Surprisingly, we find that the lower light transmittance of sunscreen film is the lower the success rate of the attack. Experiment results also show that when the transmittance rate of sun film is 50% which is the darkest sunscreen film that can be applied, the attacking success rate decreased by up to 0.4. We also explore the impact of attack angle by changing the incidence angle of the laser beam and the results demonstrate that light commands is sensitive to attack angle and the successful angle range is ± 15°. Finally, we propose a series of hardware-based protection schemes against light commands attacks.

A new jig-shape optimization method for the high aspect ratio wing

2018 ◽  
Vol 91 (1) ◽  
pp. 124-133
Author(s):  
Zhe Yuan ◽  
Shihui Huo ◽  
Jianting Ren
Keyword(s):  
Aspect Ratio ◽  
Shape Optimization ◽  
High Aspect Ratio ◽  
Optimization Design ◽  
Design Method ◽  
Aircraft Design ◽  
Optimization Method ◽  
Attack Angle ◽  
Structural Deformation ◽  
Content Type

Purpose Computational efficiency is always the major concern in aircraft design. The purpose of this research is to investigate an efficient jig-shape optimization design method. A new jig-shape optimization method is presented in the current study and its application on the high aspect ratio wing is discussed. Design/methodology/approach First, the effects of bending and torsion on aerodynamic distribution were discussed. The effect of bending deformation was equivalent to the change of attack angle through a new equivalent method. The equivalent attack angle showed a linear dependence on the quadratic function of bending. Then, a new jig-shape optimization method taking integrated structural deformation into account was proposed. The method was realized by four substeps: object decomposition, optimization design, inversion and evaluation. Findings After the new jig-shape optimization design, both aerodynamic distribution and structural configuration have satisfactory results. Meanwhile, the method takes both bending and torsion deformation into account. Practical implications The new jig-shape optimization method can be well used for the high aspect ratio wing. Originality/value The new method is an innovation based on the traditional single parameter design method. It is suitable for engineering application.

Development of a Cyclogyro-Based Flying Robot With Variable Attack Angle Mechanisms

2007 ◽  
Vol 12 (5) ◽  
pp. 565-570 ◽  
Author(s):  
Kazuo Tanaka ◽  
Ryohei Suzuki ◽  
Takanori Emaru ◽  
Yoshiyuki Higashi ◽  
Hua O. Wang
Keyword(s):  
Attack Angle ◽  
Flying Robot

scholarly journals Hydrodynamic damping and stiffness prediction in Francis turbine runners using CFD

2016 ◽  
Vol 49 ◽  
pp. 072006 ◽  
Author(s):  
Bernd Nennemann ◽  
Christine Monette ◽  
Joël Chamberland-Lauzon
Keyword(s):  
Francis Turbine ◽  
Hydrodynamic Damping

Effects of Attack Angle and Relative Thickness of Novel Wing-Shaped Turbulators on Turbulent Hydrothermal Performance in a Two-Pass Square Channel

2021 ◽  
pp. 1-7
Author(s):  
Tong-Miin Liou ◽  
Chieh Chu Chen ◽  
Chun-Sheng Wang
Keyword(s):  
Nusselt Number ◽  
Fused Deposition Modeling ◽  
Transverse Velocity ◽  
Attack Angle ◽  
Ir Camera ◽  
Pressure Drops ◽  
Square Channel ◽  
Fused Deposition ◽  
Flow Parameters ◽  
Number Ratio

Abstract This work aims to combine the effects of the near wall and core flow disturbance by proposing novel wing-shaped turbulators. The new turbulators are fabricated with the fused deposition modeling (3D printing) technology. To explore their effects on detailed flow fields, local temperature distributions, and pressure drops in a two-pass square channel, Particle Image Velocimetry (PIV), Infrared Thermography (IR camera), and pressure transducer measurements are performed. The turbulator pitch, clearance, and truncation gap ratio based on the channel hydraulic diameter of 45.5 mm are respectively fixed at 0.7, 0.25 and 0.06. Varied parameters include turbulator attack angle (α = 10°, 15°, 20°, and 30°), maximum thickness to chord line ratio (t/C = 0.08, 0.13, 0.16, 0.20, and 0.23), and bulk Reynolds number (Re = 5,000-20,000). From the experimental results and flow parameters analyzed, the dimensionless spanwise-averaged mean transverse velocity and cross-sectionally averaged vorticity magnitude are identified to be the most relevant ones to spanwise-averaged local Nusselt number ratio in the first and second pass. Among all examined cases and previous data with Fanning friction factor ratio (f¯/fo) less than 50, the case with α = 20° and t/C = 0.20 attains the highest thermal performance factor and overall Nusselt number ratio (Nu¯/Nuo) up to 1.68 and 5.36, respectively. Furthermore, empirical correlations of Nu¯/Nuo and f¯/fo versus α, t/C, and Re are proposed.

Effects of Attack Angle and Relative Thickness of Novel Wing-Shaped Turbulators on Turbulent Hydrothermal Performance in a Two-Pass Square Channel

2020 ◽  
Author(s):  
Tong-Miin Liou ◽  
Chieh-Chu Chen ◽  
Chun-Sheng Wang
Keyword(s):  
Nusselt Number ◽  
Fused Deposition Modeling ◽  
Transverse Velocity ◽  
Attack Angle ◽  
Ir Camera ◽  
Pressure Drops ◽  
Square Channel ◽  
Fused Deposition ◽  
Flow Parameters ◽  
Number Ratio

Abstract This work aims to combine the effects of the near wall and core flow disturbance by proposing novel wing-shaped tabulators. The new tabulators are fabricated with the fused deposition modeling (3D printing) technology. To explore their effects on detailed flow fields, local temperature distributions, and pressure drops in a two-pass square channel, Particle Image Velocimetry (PIV), Infrared Thermography (IR camera), and pressure transducer measurements are performed. The tabulator pitch, clearance, and truncation gap ratio based on the channel hydraulic diameter of 45.5 mm are respectively fixed at 0.7, 0.25 and 0.06. Varied parameters include tabulator attack angle (α = 10°, 15°, 20°, and 30°), maximum thickness to chord line ratio (t/C = 0.08, 0.13, 0.16, 0.20, and 0.23), and bulk Reynolds number (Re = 5,000–20,000). From the experimental results and flow parameters analyzed, the dimensionless spanwise-averaged mean transverse velocity and cross-sectionally averaged vorticity magnitude are identified to be the most relevant ones to spanwise-averaged local Nusselt number ratio in the first and second pass. Among all examined cases and previous data with Fanning friction factor ratio (f¯/fo) less than 50, the case with α = 20° and t/C = 0.20 attains the highest thermal performance factor and overall Nusselt number ratio (Nu¯/Nuo) up to 1.68 and 5.36, respectively. Furthermore, empirical correlations of Nu¯/Nuo and f¯/fo versus α, t/C, and Re are proposed.

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