Numerical Investigation of Cavitation Characteristics of Chamfered Offsets into-the-Flow
Abstract
Cavitation is initiated when the localized pressure in the flow is reduced to the vapor pressure of the water. Surface irregularities are the main reason for reduction of pressure to vapor pressure when the flow velocity is sufficiently high. Cavitation potential also depends on the shape of the irregularity and the orientation of the irregularity compared to the direction of flow. Cavitation characteristics of chamfered offsets into-the-flow with two different slopes of 1:2 and 1:5 and two different heights of 5 mm and 12 mm are investigated numerically using the realizable k-ε turbulence model and volume of fluid (VOF) technique. A transport equation model for the local volume fraction of vapor was solved and a finite rate mass transfer model was used for simulation of the vaporization and condensation processes. These simulations were performed using a finite volume, two phase solver available in the framework of the OpenFOAM (Open Field Operation and Manipulation) software package. The mass transfer model of Kunz was used and its validation was performed through comparisons between numerical simulations and the available experimental data with good agreement. In addition effects of chamfered offset slope and height on the cloud cavitation thickness and cavitation number of the offset were analyzed. According to the numerical results, increasing the chamfered offset slope and height resulted in formation of a thicker cavitation cloud over the offset, and also more pressure reduction.
Numerical Investigation of Cavitation Characteristics of Chamfered Offsets into-the-Flow
Portland, Oregon
Cavitation is initiated when the localized pressure in the flow is reduced to the vapor pressure of the water. Surface irregularities are the main reason for reduction of pressure to vapor pressure when the flow velocity is sufficiently high. Cavitation potential also depends on the shape of the irregularity and the orientation of the irregularity compared to the direction of flow. Cavitation characteristics of chamfered offsets into-the-flow with two different slopes of 1:2 and 1:5 and two different heights of 5 mm and 12 mm are investigated numerically using the realizable k-ε turbulence model and volume of fluid (VOF) technique. A transport equation model for the local volume fraction of vapor was solved and a finite rate mass transfer model was used for simulation of the vaporization and condensation processes. These simulations were performed using a finite volume, two phase solver available in the framework of the OpenFOAM (Open Field Operation and Manipulation) software package. The mass transfer model of Kunz was used and its validation was performed through comparisons between numerical simulations and the available experimental data with good agreement. In addition effects of chamfered offset slope and height on the cloud cavitation thickness and cavitation number of the offset were analyzed. According to the numerical results, increasing the chamfered offset slope and height resulted in formation of a thicker cavitation cloud over the offset, and also more pressure reduction.