Victor Hidalgo

Implicit large eddy simulation of unsteady cloud cavitation around a plane-convex hydrofoil

The present paper focuses on the erosive cavitation behavior around a plane convex hydrofoil. The Zwart-Gerber-Belamri cavitation model is implemented in a library form to be used with the OpenFOAM. The implicit large eddy simulation (ILES) is app-lied to analyze the three dimensional unsteady cavitating flow around a plane convex hydrofoil. The numerical results in the cases under the hydrodynamic-conditions, which were experimentally tested at the high speed cavitation tunnel of the École Polytechnique Fédérale de Lausanne (EPFL), clearly show the sheet cavitation development, the shedding and the collapse of vapor clouds. It is noted that the cavitation evolutions including the maximum vapor length, the detachment and the oscillation frequency, are captured fairly well. Furthermore, the pressure pulses due to the cavitation development as well as the complex vortex structures are reasonably well predicted. Consequently, it may be concluded that the present numerical method can be used to investigate the unsteady cavitation around hydrofoils with a satisfactory accuracy.

Numerical investigation of unsteady cavitation around a NACA 66 hydrofoil using OpenFOAM

The prediction and control of cavitation damage in pumps, propellers, hydro turbines and fluid machinery in general is necessary during the design stage. The present paper deals with a numerical investigation of unsteady cloud cavitation around a NACA 66 hydrofoil. The current study is focused on understanding the dynamic pressures generated during the cavity collapses as a fundamental characteristic in cavitation erosion. A 2D and 3D unsteady flow simulation has been carried out using OpenFOAM. Then, Paraview and Python programming language have been used to characterize dynamic pressure field. Adapted Large Eddy Simulation (LES) and Zwart cavitation model have been implemented to improve the analysis of cloud motion and to visualize the bubble expansions. Additional results also confirm the correlation between cavity formation and generated pressures.

Experimental study of liquid-solid two phase flow over a step using PIV

The present investigation focuses on the water-sand flow through a rectangular tunnel with a step using the Particle Image Velocimetry (PIV). Two cameras with appropriate optical filters have been used to capture each phase image separately. The optical filters were selected according to the optical properties of the sand and fluorescent tracers. Through data processing the experimental flow field such as the velocity profiles of sand and water had been obtained. In order to compare with the experiment, the steady state two phase flow fields were simulated using RANS method with k-ω SST turbulence model. It is noted that the numerical results matches the experimental results fairly good. Furthermore, the flow rates obtained from experimental and numerical velocity profiles also have a good match with the measurement by flow meter. The flow analysis shows that the water velocity variation induced by the presence of the step in the water-sand flow is equivalent to those cases with low sand concentration. However, the sand velocity in downstream region is 5% greater than the water velocity when the cross section is reduced in 25%.

Bearing fault diagnosis based on ensemble empirical mode decomposition and teager energy operator

In bearing fault diagnosis, impulse periodic signals are associated with the presence of faults. This paper uses ensemble empirical mode decomposition (EEMD) and Teager energy operator (TEO) to emphasize periodic faults, thus improving the identification of frequency characteristic faults. In the paper two validation process are carried out, they involve the analysis of a simulated outer race fault signal, and real bearing vibration signals which includes: inner race, rolling element and outer race faults. The results verify that the proposed model enhances the identification of bearing frequency characteristic faults and its harmonics.

Numerical simulation of cavitation erosion on a NACA0015 hydrofoil based on bubble collapse strength

The prediction of erosion under unsteady cavitation is crucial to prevent damage in hydraulic machinery. The present investigation deals with the numerical simulation of erosive partial cavitation around a NACA0015 hydrofoil. The study presents the calculation of the bubble collapse strength, Sb, based on the bubble potential energy to identify the surface areas with highest risk of damage. The results are obtained with a numerical scheme assuming homogeneous mixture flow, implicit LES and Zwart cavitation model. The 3D unsteady flow simulation has been solved using OpenFOAM. Python language and OpenFOAM calculator (foamCalcEx) have been used to obtain and represent Sb. The obtained results clearly show the instants of erosive bubble collapse and the affected surface areas.