Experimental and numerical study of cavitating flow around a surface mounted semi-circular cylinder

Experimental and numerical study of cavitating flow around a surface mounted semi-circular cylinder

Ghahramani, Ebrahim (Chalmers University of Technology)
Jahangir, S. (TU Delft Fluid Mechanics)
Neuhauser, Magdalena (ANDRITZ Hydro)
Bourgeois, Sébastien (ANDRITZ Hydro)
Poelma, C. (TU Delft Multi Phase Systems)
Bensow, Rickard E. (Chalmers University of Technology)

2020

In this paper, the cavitating flow around a bluff body is studied both experimentally and numerically. The bluff body has a finite length with semi-circular cross section and is mounted on a surface in the throat of a converging-diverging channel. This set-up creates various 3D flow structures around the body, from cavitation inception to super cavities, at high Reynolds numbers (Re=5.6×10⁴−2.2×10⁵) and low cavitation numbers (σ=0.56−1.69). Earlier studies have shown this flow to be erosive and the erosion pattern varies by changing the flow rate and w/o the cylinder; hence, this study is an attempt to understand different features of the cavitating flow due to the cylinder effect. In the experiments, high-speed imaging is used. Two of the test cases are investigated in more detail through numerical simulations using a homogeneous mixture model. Non-cavitating simulations have also been performed to study the effect of cavitation on the flow field. Based on the observed results, vortex shedding can have different patterns in cavitating flows. While at higher cavitation numbers the vortices are shed in a cyclic pattern, at very low cavitation numbers large fixed cavities are formed in the wake area. For mid-range cavitation numbers a transitional regime is seen in the shedding process. In addition, the vapour structures have a small effect on the flow behaviour for high cavitation numbers, while at lower cavitation numbers they have significant influence on the exerted forces on the bluff body as well as vortical structures and shedding mechanisms. Besides, at very low cavitation numbers, a reverse flow is observed that moves upstream and causes the detachment of the whole cavity from the cylinder. Such a disturbance is not seen in non-cavitating flows.

Bluff body
Cavitation
High speed imaging
Multiphase flow

http://resolver.tudelft.nl/uuid:546582b9-a308-421c-92dc-1041864022a4

https://doi.org/10.1016/j.ijmultiphaseflow.2019.103191

2020-06-23

0301-9322

International Journal of Multiphase Flow, 124

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2020 Ebrahim Ghahramani, S. Jahangir, Magdalena Neuhauser, Sébastien Bourgeois, C. Poelma, Rickard E. Bensow