Improving power-extraction efficiency of a flapping plate: From passive deformation to active control

2014 ◽  
Vol 51 ◽  
pp. 384-392 ◽  
Author(s):  
Fang-Bao Tian ◽  
John Young ◽  
Joseph C.S. Lai
Author(s):  
D Dinesh Kumar ◽  
Challa Babu ◽  
K Jyotheeswara Reddy ◽  
K Kumar ◽  
N K Kumar

Author(s):  
Yadong Li ◽  
Guoqing Zhou ◽  
Jie Wu

The power extraction performance of a fully-active flapping foil with synthetic jet is numerically investigated in this work. An elliptic airfoil with ratio of 8, which is placed in a two-dimensional laminar flow, is adopted to extract power from the flow. The foil implements the imposed translational and rotational motions synchronously. A pair of synthetic jets with the same frequency and strength is integrated into the upper and lower surfaces of flapping foil. As a result, the flow field around the foil could be affected by the synthetic jets greatly. At the Reynolds number of 1000 and the pitching axis location of half chord, the effects of the jet strength, the inclined angle between the jet direction and the chord line, as well as the phase angle between the synthetic jets and the flapping motion on the power extraction performance are systematically investigated. Compared with the traditional flapping foil, it is demonstrated that the enhancement of power extraction efficiency can be achieved with the help of synthetic jets. Based on the numerical analysis, it is indicated that the jet flow on the foil surfaces alters the vortex-shedding process and modifies the pressure distribution on the foil surface. As a result, the overall power extraction of the flapping foil can be benefitted.


2021 ◽  
pp. 80-84
Author(s):  
N.P. Gadetski ◽  
V.G. Korenev ◽  
A.N. Lebedenko ◽  
I.I. Magda ◽  
O.G. Melezhik ◽  
...  

The relativistic magnetrons operating at millimeter wavelengths demonstrate problems with microwave power extraction, both in the radial and in axial direction. The preferred axial extraction concept can be implemented ei-ther as ‘diffractional output’ or via introduction of additional resonant elements into the output waveguide. In this paper several solutions for axial-directed extraction are discussed, including circular ring ‘antennas’ at the end of the anode-cathode space, and resonance-length rods at the faces of the anode-block cavities. These have allowed increasing the power extraction efficiency by a factor of 101 to 102.


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