An experimental flow visualization study of the entrance section of channels formed with wavy plates was made. The experiments were conducted in a water channel and a laser illuminated particle tracking was used as the technique of flow visualization. The flow region that were found in the experiments are steady, unsteady and significantly-mixed flows. Instabilities of the flow first appear near the exit of the channel. As the Reynolds number increases, the flows are characterized by the appearance of flow separation and the growth of recirculation region.