Effects of Reynolds number on energy extraction performance of a two dimensional undulatory flexible body

2017 ◽  
Vol 142 ◽  
pp. 185-193 ◽  
Author(s):  
Fang Ji ◽  
Diangui Huang
Keyword(s):  
Reynolds Number ◽  
Flexible Body ◽  
Two Dimensional ◽  
Energy Extraction ◽  
Extraction Performance

Numerical Investigation Into the Effects of Motion Parameters on Energy Extraction of the Parallel Foils

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Y. L. Wang ◽  
W. Jiang ◽  
Y. H. Xie
Keyword(s):  
Laminar Flow ◽  
Two Dimensional ◽  
Energy Extraction ◽  
Flow Simulations ◽  
Reduced Frequency ◽  
Wide Range ◽  
Extraction Performance ◽  
Motion Parameters ◽  
Parallel Configuration ◽  
Working Parameters

Due to the deficiency of the research on parallel foils, the parallel configuration of foils is concerned and the effects of motion parameters on energy extraction are systematically discussed in the present study. The foils undergo combined plunging and pitching motions. The effects of motion parameters (pitching amplitude, plunging amplitude, reduced frequency, and spacing between foils) in wide range are investigated at Re = 1100 through two-dimensional (2D) unsteady laminar flow simulations. The features of power output and efficiency changing with these motion parameters as well as the evolution of the vortex fields are gained. The principle that how motion parameters affecting energy extraction performance is studied. The extraction performance of parallel foils and single foil is compared at the optimal working parameters of the single foil. Numerical results indicate the optimal extraction performance of the parallel foils is superior to that of the single foil. CPm improves by 6.87% relatively. Therefore, it reveals that the parallel foils can perform the better extraction characteristics than the single foil by controlling parameters.

Energy extraction performance of a flapping wing with active elastic airbag deformation at the leading edge

2021 ◽  
Vol 228 ◽  
pp. 108901
Author(s):  
Xiao-Dong Bai ◽  
Ji-Sheng Zhang ◽  
Jin-Hai Zheng ◽  
Yong Wang
Keyword(s):  
Leading Edge ◽  
Flapping Wing ◽  
Energy Extraction ◽  
Extraction Performance

scholarly journals Energy Extraction Performance of Tandem Ground-effect Hydrofoils

2021 ◽  
Vol 809 (1) ◽  
pp. 012001
Author(s):  
Hao Yang ◽  
Guanghua He ◽  
Weijie Mo ◽  
Wei Wang
Keyword(s):  
Ground Effect ◽  
Energy Extraction ◽  
Extraction Performance

Investigation of slip/no-slip surface for two-dimensional large tilting pad thrust bearing

2017 ◽  
Vol 69 (6) ◽  
pp. 995-1004 ◽  
Author(s):  
Zhixiang Song ◽  
Fei Guo ◽  
Ying Liu ◽  
Songtao Hu ◽  
Xiangfeng Liu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Slip Surface ◽  
Load Capacity ◽  
Slip Condition ◽  
Optimized Design ◽  
Two Dimensional ◽  
Boundary Slip ◽  
Content Type ◽  
Tilting Pad ◽  
Turbulence Effect

Purpose This paper aims to present the slip/no-slip design in two-dimensional water-lubricated tilting pad thrust bearings (TPTBs) considering the turbulence effect and shifting of pressure centers. Design/methodology/approach A numerical model is established to analyze the slip condition and the effect of turbulence according to a Reynolds number defined in terms of the slip condition. Simulations are carried out for eccentrically and centrally pivoted bearings and the influence of different slip parameters is discussed. Findings A considerable enhancement in load capacity, as well as a reduction in friction, can be achieved by heterogeneous slip/no-slip surface designs for lubricated sliding contacts, especially for near parallel pad configurations. The optimized design largely depends on the pivot position. The load capacity increases by 174 per cent for eccentrically pivoted bearings and 159 per cent for centrally pivoted bearings for a suitable design. When slip zone locates at the middle of the radial direction or close to the inner edge, the performance of the TPTB is better. Research limitations/implications The simplification of slip effect on the turbulence (definition of Reynolds number) can only describe the trend of the increasing turbulence due to slip condition. The accurate turbulence expression considering the boundary slip needs further explorations. Originality/value The shifting of pressure center due to the slip/no-slip design for TPTBs is investigated in this study. The turbulence effect and influence of slip parameters is discussed for large water-lubricated bearings.

Effects of Heat Transfer During Peristaltic Transport in Nonuniform Channel With Permeable Walls

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Siddharth Shankar Bhatt ◽  
Amit Medhavi ◽  
R. S. Gupta ◽  
U. P. Singh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Incompressible Fluid ◽  
Friction Force ◽  
Viscous Incompressible Fluid ◽  
Peristaltic Transport ◽  
Two Dimensional ◽  
Peristaltic Motion ◽  
Long Wavelength ◽  
Permeable Walls

In the present investigation, problem of heat transfer has been studied during peristaltic motion of a viscous incompressible fluid for two-dimensional nonuniform channel with permeable walls under long wavelength and low Reynolds number approximation. Expressions for pressure, friction force, and temperature are obtained. The effects of different parameters on pressure, friction force, and temperature have been discussed through graphs.

scholarly journals Active vorticity control in a shear flow using a flapping foil

1994 ◽  
Vol 274 ◽  
pp. 1-21 ◽  
Author(s):  
R. Gopalkrishnan ◽  
M. S. Triantafyllou ◽  
G. S. Triantafyllou ◽  
D. Barrett
Keyword(s):  
Reynolds Number ◽  
Vortex Formation ◽  
Interaction Patterns ◽  
Energy Extraction ◽  
Stable Pattern ◽  
Torque Measurements ◽  
Reverse Circulation ◽  
Visualization Experiments ◽  
Oscillating Foil ◽  
The Impact

It is shown experimentally that free shear flows can be substantially altered through direct control of the large coherent vortices present in the flow.First, flow-visualization experiments are conducted in Kalliroscope fluid at Reynolds number 550. A foil is placed in the wake of a D-section cylinder, sufficiently far behind the cylinder so that it does not interfere with the vortex formation process. The foil performs a heaving and pitching oscillation at a frequency close to the Strouhal frequency of the cylinder, while cylinder and foil also move forward at constant speed. By varying the phase of the foil oscillation, three basic interaction modes are identified. (i) Formation of a street of pairs of counter-rotating vortices, each pair consisting of one vortex from the initial street of the cylinder and one vortex shed by the foil. The width of the wake is then substantially increased. (ii) Formation of a street of vortices with reduced or even reverse circulation compared to that of oncoming cylinder vortices, through repositioning of cylinder vortices by the foil and interaction with vorticity of the opposite sign shed from the trailing edge of the foil. (iii) Formation of a street of vortices with circulation increased through merging of cylinder vortices with vortices of the same sign shed by the foil. In modes (ii) and (iii) considerable repositioning of the cylinder vortices takes place immediately behind the foil, resulting in a regular or reverse Kármán street. The formation of these three interaction patterns is achieved only for specific parametric values; for different values of the parameters no dominant stable pattern emerges.Subsequently, the experiments are repeated in a different facility at larger scale, resulting in Reynolds number 20000, in order to obtain force and torque measurements. The purpose of the second set of experiments is to assess the impact of flow control on the efficiency of the oscillating foil, and hence investigate the possibility of energy extraction. It is found that the efficiency of the foil depends strongly on the phase difference between the oscillation of the foil and the arrival of cylinder vortices. Peaks in foil efficiency are associated with the formation of a street of weakened vortices and energy extraction by the foil from the vortices of the vortex street.

Bifurcation Characteristics of Flows in Rectangular Sudden Expansion Channels

2005 ◽  
Author(s):  
Francine Battaglia ◽  
George Papadopoulos
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Critical Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Expansion Ratio ◽  
Sudden Expansion ◽  
Two Dimensional ◽  
Effective Expansion ◽  
Three Dimensional Simulations

The effect of three-dimensionality on low Reynolds number flows past a symmetric sudden expansion in a channel was investigated. The geometric expansion ratio of in the current study was 2:1 and the aspect ratio was 6:1. Both experimental velocity measurements and two- and three-dimensional simulations for the flow along the centerplane of the rectangular duct are presented for Reynolds numbers in the range of 150 to 600. Comparison of the two-dimensional simulations with the experiments revealed that the simulations fail to capture completely the total expansion effect on the flow, which couples both geometric and hydrodynamic effects. To properly do so requires the definition of an effective expansion ratio, which is the ratio of the downstream and upstream hydraulic diameters and is therefore a function of both the expansion and aspect ratios. When the two-dimensional geometry was consistent with the effective expansion ratio, the new results agreed well with the three-dimensional simulations and the experiments. Furthermore, in the range of Reynolds numbers investigated, the laminar flow through the expansion underwent a symmetry-breaking bifurcation. The critical Reynolds number evaluated from the experiments and the simulations was compared to other values reported in the literature. Overall, side-wall proximity was found to enhance flow stability, helping to sustain laminar flow symmetry to higher Reynolds numbers in comparison to nominally two-dimensional double-expansion geometries. Lastly, and most importantly, when the logarithm of the critical Reynolds number from all these studies was plotted against the reciprocal of the effective expansion ratio, a linear trend emerged that uniquely captured the bifurcation dynamics of all symmetric double-sided planar expansions.

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