Computational Modelling of Flow around Flettner Rotors

Abstract

Abstract for a PhD thesis submitted in January 2019 at the University of Manchester by Sitthichai Ruchayosyothin titled "Computational Modelling of Flow around Flettner Rotors"€ This present study aims to predict the flow past Flettner Rotor. The effective predicted approaches are also explored to provide the most accurate result of flow past both a stationary and rotating cases. The Flettner Rotor comprises of cylinder (curved) and disc (flat) walls; flow always interacts with these surfaces; the curved cylinder surface causes to produce re-circulating flow; the disc associates the increasing of flow speed and producing more propulsion force exerting on the cylinder. The research starts from laminar flow past a rotating cylinder at Re of 200 (Coutanceau and Menard, 1985). The study applies the pure laminar approach (Navier-Stokes Equations) examining 3-D flow. The result shows that the process of wake development is consistent with previous experimental study. The predicted aerodynamic coefficients are a little different with previous 2-D computational study (Mittal and Kumar, 2003) due to 3-D effect. The next test case is to predict turbulent flow past a rotating cylinder at Re of 130,000 (Aoki and Ito, 2001). A number of turbulence modelling are employed which are low-Re k-epsilon and high-Re k-epsilon with a series of eddy viscosity model including linear, quadratic and cubic models. The Reynolds Stresses Equation model (RSM) with different versions (GL: Gibson and Launder (1978) and TCL : Two Component Limit (Craft and Launder, 1996)) are also applied. The standard and analytical wall treatments are in conjunction with those of high-Re k-epsilon approaches to examine the effect of turbulence across fully turbulent region; they require low computational resource. All turbulence models predict the increase and decrease of lift and drag coefficient when spin ratios (alfa : the proportional tangential cylinder to free flow velocity) are larger. However, the predicted results are not effective in the transition flow from laminar to turbulence at spin ratios less than 0.5, the pure laminar approach provides the accurate result in this range. The installation of multiple and end discs on cylinder are predicted at Re of 5,600, 5,800, 12,200 and 48,900 (Thom, 1934; Clayton, 1985). The flow past multiple discs along cylinder is simplified by the flow past disc spacing. Whilst, the flow past a Flettner Rotor is investigated on fully domain size corresponding to real experimental setup at Re of 48,900 (Clayton, 1985). The accurate predicted results are obtained by low-Re k-epsilon and RSM-GL approaches with near wall functions on either disc or cylinder.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Hector Iacovides (Supervisor) & Timothy Craft (Supervisor)