Mohammad Ahmadi - Dept. of Civil Eng., K. N. Toosi University of Technology, Tehran, Iran
Kourosh Hejazi - Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

The undertow current is a near-bed and sea-level current that compensates for the mass transfer of water to the shore. In this paper, the Lagrangian method of incompressible smoothed particle hydrodynamics has been deployed to simulate the undertow current. To account for the surface roughness a wall function is implemented in the model. The sub-particle scale turbulence has also been included in the model. The capability and accuracy of the new model for free surface simulations, and modeling the undertowcurrent was examined and confirmed.