arXiv subjects

Ebrahim Kadivar

Publications and source records attributed to Ebrahim Kadivar.

3 recordsLinked to original sources

arXiv2018

Boundary layer instability control in the unsteady cloud cavitating flow

In this article, we propose a passive boundary layer control method to control the vortex structure of the cavity on the suction side and wake region of the CAV2003 benchmark hydrofoil. This method may be used in different applications such as marine, turbomachinery and hydraulic machinery. First, we used a hybrid URANS model for turbulence to simulate the 3D unsteady cloud cavitating flow and validated it based on experimental data. We performed the numerical simulations using open source code OpenFOAM and an Euler-Euler cavitation model. Second, we studied the effect of passive boundary layer control method on vortex structure on the suction side of the hydrofoil and in wake region. We showed that this control method may influence the boundary layer structure on the hydrofoil surface and also near the trailing edge. Using this technique the pressure distribution and the fluctuating part of the velocity field on the hydrofoil surface were modified over the chord length. This method induced a stabilization of the boundary layer and delay its separation. Therefore a significant reduction in cavitation-induced vibration may be expected.

physics.flu-dyn↗

arXiv2018

Effect of Cavitating-bubble Generators on the Dynamics of Unsteady Cloud Cavitation

The present paper is devoted to the 3D numerical study of unsteady cloud cavitation around the CAV2003 benchmark hydrofoil using a passive cavitation controller method called cavitation-bubble generator (CGs). We investigate this passive controller on the hydrofoil surface to affect the whole processes of vaporization, bubble generation and bubble implosion. Firstly we simulate the unsteady cavitating flow around the hydrofoil without CGs using a Partially- averaged Navier Stokes (PANS) method. The turbulence approach is coupled with a mass transfer model which implements to an open source finite-volume package. Then we tested different sizes and angles of CGs on the hydrofoil surface. The results of an appropriate design of the CGs shows a significant decrease of the maximum length of the attached cavity and a large decrease of wall-pressure fluctuation intensity on the hydrofoil surface.

physics.flu-dyn↗

arXiv2018

Investigation of cloud cavitation passive control method for hydrofoils using Cavitating-bubble Generators (CGs)

In this article, we propose a passive method to control unsteady cloud cavitation on hydrofoils using cavitation-bubble generator (CGs). This method may be used in many engineering applications, in particular in marine and turbomachinery. First, we used a Partially-averaged Navier Stokes (PANS) model for turbulence to simulate the unsteady cavitating flow and validated it based on experimental data. This model was coupled with a mass transfer model and implemented to the open source software package OpenFOAM. Second, the effect of a proper design of CGs on qualitative parameters such as cavitation structure and the shape of cavity were studied. The effect of CGs on the destructive effects of cavitation such as vibration, turbulent velocity fluctuations and high- pressure amplitude were analyzed. Our results showed that a proper design of CGs may reduce the amplitude of the force fluctuations on the hydrofoil substantially. Further on, the local boundary layer around the hydrofoil surface was altered and the turbulent velocity fluctuation was reduced significantly using this technique.

physics.flu-dyn↗