scholarly journals Performance Improvement of Hydrofoil with Biological Characteristics: Tail Fin of a Whale

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1656
Author(s):  
Pan Xiong ◽  
Jianghong Deng ◽  
Xinyuan Chen
Keyword(s):  
Performance Improvement ◽  
Structural Parameters ◽  
Angle Of Attack ◽  
Hydrodynamic Performance ◽  
High Angle ◽  
Ansys Fluent ◽  
Design And Optimization ◽  
Trailing Edge Flap ◽  
Stall Angle ◽  
The Relationship

In order to improve the hydrodynamic performance of hydrofoils, this paper shows excellent hydrodynamic performance according to the flapping motion of fish through the tail fin. The Naca66 hydrofoil is used as the original hydrofoil and the trailing edge flap configuration is added. Ansys-fluent is used to analyze the relationship between the structural parameters (length and angle) of the flap and the hydrodynamic performance of the hydrofoil, the reliability of CFD numerical simulation is verified by PIV experiment. It is found that the hydrofoil, with clockwise rotating short flap, can significantly improve the hydrodynamic performance of a hydrofoil at a small angle of attack; at a high angle of attack, the hydrofoil with counterclockwise flap can increase the critical stall angle and slightly improve the hydrodynamic performance of the hydrofoil. The hydrodynamic performance of hydrofoil with rotatable short flaps reported in this paper can provide valuable information for the design and optimization of this kind of hydrofoil.

The Aerodynamics Investigation of Vortex Trap on Helicopter Blade

2012 ◽  
Vol 225 ◽  
pp. 43-48
Author(s):  
M.F. Yaakub ◽  
A.A. Wahab ◽  
Mohammad Fahmi Abdul Ghafir ◽  
Siti Nur Mariani Mohd Yunos ◽  
Siti Juita Mastura Mohd Salleh ◽  
...  
Keyword(s):  
Lift Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Strong Wind ◽  
High Angle ◽  
Forward Flight ◽  
High Angle Of Attack ◽  
Helicopter Blade ◽  
Stall Angle ◽  
Cfd Analyses

During helicopter forward flight, the retreating blade revolves at high angle of attack compared to advancing blade in order to balance the lift and also to stabilise the helicopter. However, due to the aerodynamics limitations of the retreating blade at forward flight, stall may occur at high angle of attack compared with the advancing blade. This phenomenon is dangerous for pilot when controlling and balancing the helicopter while flying against strong wind. This paper investigates the capabilities of introducing multiple vortex traps on the upper surface of the helicopter airfoil in order to delay the stall angle of retreating helicopter blade. Blade Element Theory (BET) was applied to scrutinize the lift force along the helicopter blade. Computational Fluid Dynamic (CFD) analyses using the Shear-Stress Transport (SST) turbulence model was carried out to investigate the effect of groove on delaying the stall and to predict the separation of flow over the airfoil. Based on the CFD analyses, the optimization of the groove was done by analyzing the numbers and locations of the grooves. Finally, the results from both BET and the CFD analyses were utilised to obtain the lift force achieved by the vortex trap. The study showed that the presence of multiple vortex traps has successfully increased the lift coefficient and most importantly, delaying the stall angle.

High angle-of-attack airfoil performance improvement by internal acoustic excitation

AIAA Journal ◽  
1994 ◽  
Vol 32 (3) ◽  
pp. 655-657 ◽  
Author(s):  
Fei-Bin Hsiao ◽  
Rong-Nan Shyu ◽  
Ray C. Chang
Keyword(s):  
Performance Improvement ◽  
Angle Of Attack ◽  
Acoustic Excitation ◽  
High Angle ◽  
High Angle Of Attack

A quantitative measure of the degree of output controllability for output regulation control systems: Concept, approach, and applications

2021 ◽  
pp. 107754632110201
Author(s):  
Yaping Xia ◽  
Ruiyu Li ◽  
Minghui Yin ◽  
Yun Zou
Keyword(s):  
Structural Parameters ◽  
Quantitative Measure ◽  
Output Regulation ◽  
State Regulation ◽  
Control Effect ◽  
Pendulum System ◽  
Design And Optimization ◽  
Inverted Pendulum System ◽  
State Regulator ◽  
Output Controllability

Currently, many research studies reveal that for state regulator problems, the higher the degree of controllability is, the better the control effect likely is. Note that for the output regulator problems, the control performance is often evaluated by outputs. This article hence generalizes the concept and applications of degree of controllability to the case of output regulator. To this end, a kind of degree of output controllability is presented. Furthermore, simulations on wind turbines and the inverted pendulum system demonstrate that better control effect may be achieved by increasing the degree of output controllability measure. These results imply that similar to the case of degree of controllability for state regulation control, the degree of output controllability measure is likely a feasible candidate index for the design and optimization of the structural parameters of controlled plants in the case of output regulation control.

scholarly journals Leading Edge Blowing to Mimic and Enhance the Serration Effects for Aerofoil

2021 ◽  
Vol 11 (6) ◽  
pp. 2593
Author(s):  
Yasir Al-Okbi ◽  
Tze Pei Chong ◽  
Oksana Stalnov
Keyword(s):  
Boundary Layer ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Shear Instability ◽  
Vortical Flow ◽  
High Angle ◽  
High Angle Of Attack ◽  
Layer Separation ◽  
Aerodynamic Performances

Leading edge serration is now a well-established and effective passive control device for the reduction of turbulence–leading edge interaction noise, and for the suppression of boundary layer separation at high angle of attack. It is envisaged that leading edge blowing could produce the same mechanisms as those produced by a serrated leading edge to enhance the aeroacoustics and aerodynamic performances of aerofoil. Aeroacoustically, injection of mass airflow from the leading edge (against the incoming turbulent flow) can be an effective mechanism to decrease the turbulence intensity, and/or alter the stagnation point. According to classical theory on the aerofoil leading edge noise, there is a potential for the leading edge blowing to reduce the level of turbulence–leading edge interaction noise radiation. Aerodynamically, after the mixing between the injected air and the incoming flow, a shear instability is likely to be triggered owing to the different flow directions. The resulting vortical flow will then propagate along the main flow direction across the aerofoil surface. These vortical flows generated indirectly owing to the leading edge blowing could also be effective to mitigate boundary layer separation at high angle of attack. The objectives of this paper are to validate these hypotheses, and combine the serration and blowing together on the leading edge to harvest further improvement on the aeroacoustics and aerodynamic performances. Results presented in this paper strongly indicate that leading edge blowing, which is an active flow control method, can indeed mimic and even enhance the bio-inspired leading edge serration effectively.

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