Simulation and modal analysis of instability and transition in a steady eccentric stenotic flow.

• Main Author: Moradi Nour, Zeinab
• Format: Others
• Language: English
• Published: KTH, Mekanik 2013
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118945

Direct numerical simulation (DNS) of steady flow, with Re = 750 at inlet, through stenosed pipe has been done to study transition and turbulence of the flow in the post-stenosis area. The pipe has 75% constriction by area reduction and 5% eccentricity of the main pipe diameter at the throat. A sinusoidal Gaussian force is implemented to keep turbulent in the domain. The result shows acceptable agreement with previous study has  been done by Fischer et al. [4]. We simulated the case by NEK5000 which benefits from the spectral element method (SEM) as a higher order accurate method. To have a better understanding of the turbulent flow, we have done the modal decomposition to obtain coherent structures. Among several methods for modal decomposition, we considered Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) for current study. The methods have been implemented in Fortran, accelerated using OpenMP and is potentially settled for computation of large data sets. DMD implementation shows 2.5 speed up. The stuctures correspond to the implementation force are extracted by POD however they have not been recognised by dynamic decomposition.