Journal article
Unsteady free surface wave-induced separation : Vortical structures and instabilities
Journal of fluids and structures, Vol.25(2), pp.343-363
2009
DOI: 10.1016/j.jfluidstructs.2008.05.002
Abstract
Vortical structures and instability mechanisms of the unsteady free surface wave-induced separation around a surface-piercing NACA0024 foil at a Froude number of 0.37 and a Reynolds number of 1.52×106 are studied using an unsteady Reynolds-averaged Navier–Stokes (URANS) code with a blended k−ε/k−ω turbulence model and a free surface tracking method. At the free surface, the separated flow reattaches to the foil surface resulting in a wall-bounded separation bubble. The mean and instantaneous flow topologies in the separation region are similar to the owl-face pattern. The initial shear-layer instability, the Karman-like instability, and the flapping instability are identified, and their scaling and physical mechanisms are studied. Validation with experimental fluid dynamics (EFD) and comparison with complementary detached-eddy simulation (DES) indicate that URANS resolves part of the organized oscillations due to the large-scale unsteady vortical structures and instabilities, thereby capturing the gross features of the unsteady separation. The URANS solutions show an initial amplitude defect of 30% for the free surface oscillations where the shear layer separates, and the defect progressively increases downstream as URANS rapidly dissipates the rolled up vortices.
Details
- Title: Subtitle
- Unsteady free surface wave-induced separation : Vortical structures and instabilities
- Creators
- M KANDASAMY - Iowa Institute of Hydraulic Research, University of Iowa, Iowa City, IA 52242-1585, United StatesT XING - Iowa Institute of Hydraulic Research, University of Iowa, Iowa City, IA 52242-1585, United StatesF STERN - Iowa Institute of Hydraulic Research, University of Iowa, Iowa City, IA 52242-1585, United States
- Resource Type
- Journal article
- Publication Details
- Journal of fluids and structures, Vol.25(2), pp.343-363
- Publisher
- Elsevier; Kidlington
- DOI
- 10.1016/j.jfluidstructs.2008.05.002
- ISSN
- 0889-9746
- eISSN
- 1095-8622
- Language
- English
- Date published
- 2009
- Academic Unit
- Mechanical Engineering
- Record Identifier
- 9984064598902771
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