Turbulent flow over a fully-developed wavy channel is investigated by the nonlinear $textsc{k}$-$varepsilon$-f$_{u}$ model of Park et al.$^{(1)}$ The Reynolds number is fixed at Re$_{b}$ = 6760 through all wave amplitudes and the wave configuration is varied in the range of 0$leq$a/λ$leq$0.15 and 0.25$leq$λ/H$leq$4.0. The predicted results for wavy channel are validated by comparing with the DNS data of Maa$eta$ and Schumann$^{(2)}$ The model performance Is shown to be generally satisfactory. As the wave amplitude increases, it is found that the form drag grows linearly and the friction drag is overwhelmed by the form drag. In order to verify these characteristics, a large eddy simulation is performed for four cases. The dynamic model of Germane et al.$^{(3)}$ is adopted. Finally, the effects of wavy amplitude on separated shear layer are scrutinized.