Abstract
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.
Highlights
Cavitation is a typical vapor-liquid flow, and mass transmission is determined using the bypass pressure and the local vaporisation pressure of the fluid
The results showed that the cavitation of the hydrofoil with a large amplitude is mainly confined to the area behind a convex groove, whereas the hydrofoil with a flat leading-edge and small amplitude shows flaky cavitation in the whole span direction
The cavity of the hydrofoil is mainly concentrated at its trailing edge, and the influence range of cavitation is the smallest
Summary
Cavitation is a typical vapor-liquid flow, and mass transmission is determined using the bypass pressure and the local vaporisation pressure of the fluid. The fluid bypassing a hydrofoil will generate lift In accordance with this principle, hydrofoils are widely used in the field of hydraulic machinery. The fluid flow state will inevitably be changed by the difference in physical properties, such as density and viscosity, between air and water and other liquid fluids, thereby affecting the cavitation performance of hydraulic machinery. Changing the structure of the leading-edge of a hydrofoil and developing a new type of aerofoil suitable for hydraulic machinery are important. A large number of fishes are living in oceans and Bionic Hydrofoil freshwater lakes. These fishes have excellent hydraulic properties and provide basic materials for changing the structure of the leading-edge of a hydrofoil
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