An LES study of secondary motion and wall shear stresses in a pipe bend

• Published in: Physics of fluids (1994) Vol. 33; no. 11
• Main Authors: Apte, Sourabh V., Karra, Shashank K., Doğan, Ömer N.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.11.2021
• Subjects: Fluid dynamics; Fluid flow; High Reynolds number; Isothermal flow; Large eddy simulation; Physics; Pipe bends; Power spectral density; Proper Orthogonal Decomposition; Reynolds number; Secondary flow; Shear stress; Switching; Wall shear stresses
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/5.0065338

Large-eddy simulations (LES) of a single-phase, turbulent flow in a 90 ° pipe bend are performed at three Reynolds numbers (5300, 27 000, and 45 000) to investigate the correlation between secondary flow motion and wall shear stresses, which is suspected to be a potential mechanism responsible for material erosion. The isothermal flows are validated against available experimental and numerical data first. The snapshot proper orthogonal decomposition (POD) is applied for the medium and high Reynolds number flows to identify the secondary flow motions and the oscillation of the Dean vortices that are found to cause swirl-switching. Distinguished frequencies of the POD time coefficients at Strouhal numbers of 0.25 and 0.28 are identified for Reynolds numbers at 27 000 and 45 000, respectively. Moreover, shear stress on the pipe wall and the associated power spectral density are obtained and shown to have the same oscillating frequency as the swirl-switching.