CFD-based investigation of turbulent flow behavior in 90-deg pipe bends

Abstract

This work investigated the influence of bend curvature on the parameters of turbulent flow through a 90° pipe bend using the numerical CFD method, implemented in ANSYS Fluent. The numerical predictions were validated to be in good agreement with existing experimental measurements. The turbulence of the secondary motion was found to be generally stronger at the outer end of the pipe bend, with the most adverse effect recorded at about 45° along the bend. It was also observed that the RMS velocity is larger near the wall, especially at the outer wall region, and it is highest at 45° due to an increase in the circulation of dean vortices, indicating a turbulence generation. In addition, the RMS velocity increases downstream due to an additional mean strain resulting from the creation of secondary flow as the flow travels through the bend. Furthermore, larger static pressure and turbulent viscosity were observed at the outer wall due to the flow deceleration and swirling. Therefore, it can be established that the bend curvature affects the stability of the flow field inside a pipe bend.