Written by Ehsan Roohi Golkhatmi   



Two-Phase Flow Simulation Using VOF and LES Turbulent Models


Simulation of cavitating flow on the Clark-Y hydrofoil is studied using computational fluid dynamics (CFD). This simulation is performed by the large Eddy Simulation (LES) model. We applied an incompressible LES modeling approach based on an implicit method for the sub-grid terms. For applying the cavitation model, the flow has been considered as a single fluid, two-phase mixture. A transport equation model for the local volume fraction of vapor is solved whit the LES model and a finite rate mass transfer model is used for the vaporization and condensation processes. The volume of fluid (VOF) method is applied. The results of our simulation are compared with experimental data and the accuracy of this approach has been studied. This simulation is performed using a two phase solver available in the framework of OpenFOAM (open field operation and Manipulation) software package, namely interPhaseChangeFoam.

In Fig. 1 the shape and dynamics of cloud cavitation are shown. Left column is the simulated cavitation and right column is the experimental pictures [1]. Pictures are for different non-dimensional time. It shows that the cavitating flow grows till about the midpoint of the cycle, before the massive vortex shedding appears. Then cavitation become weaker and finally it separates from the wall and disappear in the fluid flow. As Fig. 1 shows, there are good agreement between the current numerical solution with that of experiments. This is due to employing complex turbulence model, i.e., LES, in addition to benefiting from VOF technique in reconstructing the free surface.



Figure 1: shape of cavitation from our simulation and experiment.


The velocity profile in the boundary layer of the airfoil at location x/c=0.2% is illustrated in Fig. 2 from both of simulation and experiment. This time-averaged velocity profile is tracked along the vertical direction from the airfoil wall. Similar to previous results, our simulation is close to experimental data reported for Clark-Y hydrofoil.


Figure 2: Boundary layer velocity profile at x/c =0.2, black line is simulation and dashed line is experiment.



[1] Wang, G., Senocak, I., Shyy, W., Ikohagi, T., and Cao, S., 2001. “Dynamics of Attached Turbulent Cavitating Flows”. Progress in Aerospace Sciences, 37, pp. 551-581.


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