Publication

Hydrofoil Roughness Effects on von Kármán Vortex Shedding

François Avellan, Mohamed Farhat, Philippe Ausoni
2007
Conference paper

Abstract

The shedding process of the von Kármán vortices is shown to be highly related to the state of the boundary layer over the entire hydrofoil: The selected hydrofoil has a laminar-turbulent boundary layer transition at mid-chord for an incidence angle of 0° and tested Reynolds number range. With the help of a distributed roughness, the transition to turbulence is triggered at leading edge. The vortex shedding frequency and the vortex-induced vibration are compared For the two roughness configurations. Cavitation is used as a mean of visualization of the wake flow: Since vortex-induced vibration and high speed visualization are synchronized, the hydrofoil vibration level is considered versus the vortex span-wise organization. The occurrence of the 3D structures of shed vortices and the modulation of the vortex-induced vibration signals are investigated.

Official source

https://infoscience.epfl.ch/record/113749?ln=en

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Ontological neighbourhood

Physics

Mechanics: Fluid mechanics

Related concepts (20)

Boundary layer

In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condition (zero velocity at the wall). The flow velocity then monotonically increases above the surface until it returns to the bulk flow velocity. The thin layer consisting of fluid whose velocity has not yet returned to the bulk flow velocity is called the velocity boundary layer.

Boundary layer thickness

This page describes some of the parameters used to characterize the thickness and shape of boundary layers formed by fluid flowing along a solid surface. The defining characteristic of boundary layer flow is that at the solid walls, the fluid's velocity is reduced to zero. The boundary layer refers to the thin transition layer between the wall and the bulk fluid flow. The boundary layer concept was originally developed by Ludwig Prandtl and is broadly classified into two types, bounded and unbounded.

Laminar flow

In fluid dynamics, laminar flow (ˈlæmənər) is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids. In laminar flow, the motion of the particles of the fluid is very orderly with particles close to a solid surface moving in straight lines parallel to that surface.

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