Optimal Design and Numerical Simulation on Fish-Like Flexible Hydrofoil Propeller

Shi

Rev. Int. Contam. Ambie.

et al. 2019

In this paper, a quantifiable method for risk evaluation of water conservancy ina publicprivate partnership (PP) PPP project is presented. Firstly, according to the characteristics of water conservancy PPP project, a risk evaluation index was determined by Delphi method and literature collection method; secondly, the weight of risk evaluation indexes were determined by rank correlation analysis; thirdly, based on grey fuzzy theory, a grey fuzzy comprehensive evaluation model was constructed, and uncertain grey and fuzzy contents were transformed into values that can be accurately measured, which provided a basis for managers to make decisions. Finally, the grey fuzzy comprehensive evaluation model was applied to Fendou Reservoir, a water conservancy PPP project, and it proved to be reasonable and scientific.

Section: Introductionmentioning

confidence: 99%

Risk Evaluation of Water Conservancy in a Public-Private Partnership Project Based on Grey Fuzzy Theory

Shi

Rev. Int. Contam. Ambie.

et al. 2019

“…Liu and Liu (2014) constructed a bionic hydrofoil based on the geometric characteristics of an owl, which effectively improved the lift and drag characteristics of the hydrofoil and revealed the characteristics of the sound source. Xue et al (2016) regarded fish as imitation organisms and designed a fin-peduncle propulsion mechanism in accordance with their shape, which improved the propulsion efficiency of hydrofoil propellers. In the above research report, when obtaining the surface information of an organism, acquiring an accurate bionic physical model through curve-fitting technology is a critical step.…”

Section: Introductionmentioning

confidence: 99%

The Leading-Edge Structure Based on Geometric Bionics Affects the Transient Cavitating Flow and Vortex Evolution of Hydrofoils

Yan

Zhang

Jun-hua³

et al. 2022

Front. Energy Res.

A hydrofoil is a fundamental structure in fluid machinery, and it is widely applied to the fields of propellers, blades of axial flow pumps and underwater machinery. To reveal that the geometric structure of the leading-edge of a hydrofoil is the mechanism that affects the transient cavitating flow, we regard the three fish-type leading-edge structures of mackerel, sturgeon and small yellow croaker as the research objects and use high-precision non-contact 3D scanners to establish three bionic hydrofoils (Mac./Stu./Cro.). We use large eddy simulation to simulate the transient cavitating flow of hydrofoils numerically and compare and analyze their lift–drag characteristics, the transient behavior of unsteady cavitation and the vortex evolution. The numerical simulation results are in good agreement with the experimental results. The warping of leading-edge structure will cause a change in lift–drag characteristics, and the Cro. hydrofoil has a good lift-to-drag ratio. When the leading-edge structure is tilted upward (Cro. hydrofoil), the position of the attached cavity will move forward, which will accelerate the cavitation evolution and improve the velocity fluctuation of the trailing edge. When the leading-edge structure is tilted downward (Stu. hydrofoil), the change in the vortex stretching and dilatation terms will be complex, and the influence area of the vortex will widen.

“…Previously, we observed that the wings/fins of birds/ fish are simply modelled as a rigid foil to discuss bionic propulsion. However, these wings/fins are flexible and it is necessary to discuss the effect of that flexibility on the propulsive characteristics and vortex structure of the foil [23][24][25]. Heathcote and Gursul [26] experimentally measured the thrust and efficiency of a heaving flexible teardrop/flat plate at Reynolds numbers of 9,000 to 27,000.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Effect of Flexibility on the Propulsive Performance of a Heaving Hydrofoil Undergoing Sinusoidal and Non-Sinusoidal Motions

Polish Maritime Research

et al. 2021

Numerical simulations of fluid-structure interaction (FSI) on an elastic foil heaving with constant amplitude in freestream flow are carried out at a low Reynolds number of 20,000. The commercial software STAR-CCM+ is employed to solve the flow field and the large-scale passive deformation of the structure. The results show that introducing a certain degree of flexibility significantly improves the thrust and efficiency of the foil. For each Strouhal number St considered, an optimal flexibility exists for thrust; however, the propulsive efficiency keeps increasing with the increase in flexibility. The visualisation of the vorticity fields elucidates the improvement of the propulsive characteristics by flexibility. Furthermore, the mechanism of thrust generation is discussed by comparing the time-varying thrust coefficient and vortex structure in the wake for both rigid and elastic foils. Finally, in addition to sinusoidal motions, we also consider the effect of non-sinusoidal trajectories defined by flattening parameter S on the propulsive characteristics for both rigid and elastic foils. The non-sinusoidal trajectories defined by S=2 are associated with the maximum thrust, and the highest values of propulsive efficiency are obtained with S=0.5 among the cases considered in this work.