Abstract
This paper describes the preparation of the experimental setup and the results of the CFD analysis for the investigation of the unsteady cavitating flow around a prismatic NACA 2412 hydrofoil at different flow conditions. The experimental research is carried out in the cavitation water tunnel located in the Centre of Hydraulic Research in Lutin. The tunnel is integrated into the closed horizontal loop of the hydraulic test rig. The transparent test section provides a full view of the flow around the hydrofoil. The hydrofoil incidence angle is fully adjustable. Two variants of hydrofoil of the same geometry have been designed. One variant is equipped with pressure tap holes for the measurement of the static pressure, and the other variant is covered with a grid of five PVDF films, fully integrated in the hydrofoil. The PVDF films enable to measure the impact forces exerted on the hydrofoil surface by the collapsing cavitation structures. The high-frequency pressure oscillations downstream of the hydrofoil trailing edge are measured using the PVDF hydrophone. The cavitating flow is visualized using two simultaneously operating high-speed cameras providing the top and side views of the flow. A preliminary CFD analysis using the ANSYS CFX package helped to determine the flow regimes for the experimental study. The obtained CFD results agree well with the preliminary measurements.
Highlights
Unsteady cavitation phenomena represent a serious problem for hydrodynamic machines operated at a wide range of flow rates
Coherent collapses of large unsteady vapour structures result in significant erosion of the material in hydraulic machines due to cavitation and can severely shorten machine useful life, disrupt machine operation and efficiency as a result of altered geometry, and even cause catastrophic structural failures leading to high maintenance costs
The interaction between the separated flow and cavitation results in periodic pressure oscillations with high amplitudes leading to significant forces acting on the blades
Summary
Unsteady cavitation phenomena represent a serious problem for hydrodynamic machines operated at a wide range of flow rates. Coherent collapses of large unsteady vapour structures result in significant erosion of the material in hydraulic machines due to cavitation and can severely shorten machine useful life, disrupt machine operation and efficiency as a result of altered geometry, and even cause catastrophic structural failures leading to high maintenance costs. In order to study the interaction and the consequent cavitation instabilities, an experimental setup with a simplified geometry (prismatic NACA 2412 hydrofoil) has been prepared in the cavitation facility in the Centre of Hydraulic Research in Lutín. Advanced turbulence models including SASSST and Reynolds-stress models have been tested to capture the highly unsteady phenomena on the hydrofoil
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