Moving Reference Frame (MRF): Airflow on a Dimpled Rotating Cylinder

Description

This project simulates airflow over a dimpled rotating cylinder using ANSYS Fluent software. A cylindrical object is placed inside a rectangular channel. The airflow enters the channel at a horizontal velocity of 0.45 m/s and collides with the cylindrical body.

The cylinder rotates about its central axis at an angular velocity of 20 radians per second (rad/s), so a moving wall must be defined. For this reason, the fluid simulation domain is divided into two parts: the rotating region, which contains the cylinder rotating at a constant angular velocity, and the surrounding fluid region, which is the interior of the rectangular channel outside the cylinder.

The cylinder wall features dimples whose protruding side faces the inside of the cylinder and whose recessed side faces the outside. The aim of the study is to investigate the pressure distribution and the rotational phenomena around the rotating cylindrical wall, since the presence of dimples on the cylinder surface influences the behavior of the fluid.

The geometry of the present model is three-dimensional and is designed using SOLIDWORKS software. The meshing is performed with ANSYS Meshing software. The mesh type is unstructured, and the number of elements is equal to 1,064,903.

Dimpled Methodology

A cylindrical wall is created in the form of an interface, that is, a common surface shared between two regions that allows the fluid to flow across its boundary. Around this wall, a dedicated flow region in the shape of a hollow cylinder is defined to represent the rotating cylinder. The Frame Motion (MRF) method is then used to simulate this inner cylindrical region, which rotates at the same angular velocity as the main cylinder.

Dimpled Conclusion

At the end of the solution process, contours of pressure, velocity, and turbulent kinetic energy are obtained. Using the MRF method, the cylinder can be assumed stationary while the surrounding airflow is treated as rotating at the same rotational speed of 20 rad/s around the central axis of the cylinder. The contours clearly show the velocity and pressure distributions within the domain.