Numerical predictions of fluid dynamics and wall erosion characteristics in a circular 90 deg. pipe bend with single and multi mitred joint

Abstract

The present work compares the numerical fluid dynamic and wall erosion characteristics of a single phase fluid flowing through two vertical pipe bend assemblies: sharp (S) and mitred (M). Both the ‘S’ and ‘M’ pipe bend assemblies have circular section with double bends each having a 90° flow turning angle. The ‘S’ bends has a single weld joint and the ‘M’ bends were made of 2 pieces of miter segments, thus having three weld joints. Single phase fluid (water) was made to flow at five Reynolds numbers 1e5 < Re < 10e5 through these pipe bends. Computations were carried out separately on a smooth circular 90° pipe bend with different turbulence models. Grid independency studies were carried out with the chosen turbulence model to optimize the mesh density requirements. The computational results were validated with literature and found to show good agreement. Comparison of flow behaviour in the 90° S and M bends was discussed. Differences in the induced swirl flow at the outlet of these pipe assemblies were reported. Due to abrupt sharp flow turning, higher pressure drop and wall shear stresses were observed in S bend pipe assemblies. The numerical flow visualization results helps in understanding the detailed flow characteristics in the 90-S and 90-M pipe bends.