moonpool is a vertical well in floating barge, frequently found in drilling ships and in diving support vessel. In this thesis, numerical simulation of two-dimensional flow in moonpool situated in moving vessel is carried out using the commercial software FLUENT. The focus of the simulation is to understand drag generation mechanics of moonpool flow. The ratio of water height to width of moonpool (L/D) is set to 1, the range of Reynolds number based on width of moonpool $Re_D$ is from 10,000 to 50,000. The corresponding Froude number range is from 0.101 to 0.505.
To examine the effect of free surface motion at the drag, simulations are carried out by employing two different boundary conditions at the free surface : the symmetry condition and the moving free surface condition. The unsteady drag characteristics are analyzed from the simulated data.
We find that the unsteadiness of the drag is mainly caused by the two agents : one is the unsteady shear layer impingement on the bottom portion of the moonpool wall and the other is the free surface motion. As the Froude number increases, the free surface motion starts to dominate the drag fluctuation.
