I want to simulate open-channel flow in ANSYS CFX with a cylinder inside the water, which has a distance from bottom and free surface. I want to simulate free surface waves due to the existence of cylinder. The inlet water is assumed to be laminar. I have done this project by using the method in tutorial 9 of ANSYS CFX but the result is not acceptable. As you can see in the picture, free surface waves appeared between cylinder and inlet, which should be appeared between cylinder and outlet. (Flow direction is from left to right.)