Application of the One-way Nesting Method to a CFD Model for Investigating the Characteristics of Flows around the Ulleungdo Island

In this study, we investigated the characteristics of the flow around the Ulleungdo Island by applying a nesting method to a computational fluid dynamics (CFD) model. We considered two one-way nested domains. The horizontal (vertical) grids sizes of the outer and inner domain were 60 m (20 m) and 15 m (5 m), respectively. The outer domain covered the entire Ulleungdo Island and the inner domain included the Ulleungdo ASOS. The CFD model simulations were conducted for 5 different inflow wind speeds (5, 10, 15, 20 and 40 m s^-1 at 1000 m above the ground) in the 16 different inflow directions. The results of the outer domain simulations were used as the boundary and initial input data for the inner domain simulations. The results showed that the wind speeds at the Ulleungdo ASOS increased linearly as the inflow wind speed increased in all 16-inflow cases and the wind speeds simulated in the outer domain were slightly larger than those in the inner domain. On the other hand, the wind directions simulated at the Ulleungdo ASOS in the outer domain were similar to those in the inner domain, except for the south-west-souterly and south-westerly cases. Based on the numerical simulations, we established the wind rose at the Ulleungdo ASOS and compared it with the wind rose observed at the Ulleungdo ASOS. The simulated wind rose showed a good agreement with the observed one.