The paper presents Unsteady Reynolds Average Navier Stokes (U-RANS) simulations for 3D flow past a full-scale rotating cylinder, known as Flettner Rotor (FR). The U-RANS simulations are performed using the commercially available flow simulation software CD-Adapco STAR CCM+. A preliminary 2D study was conducted to set-up a numerical model using a moving mesh technique; this analysis was directed to define suitable domain shape and dimension, time-step and grid-resolution. The further 3D simulations were performed to evaluate in deep the influence of some of the main parameters on the effectiveness of the rotors; in particular the Spin Ratio, i.e. the ratio of circumferential-cylindervelocity- to-free stream-velocity (SR) and the effect of the endplates (EP) also called Thom disk. The functioning characteristic of the device has been predicted by lift and drag coefficients for various rotation rates. The selected dimensions of the cylinder and the chosen range of design parameters are similar to those of a real installation on board, therefore the Rn obtained (1.3 - 5.0 E+06) are quite close to the real values and significantly higher than the ones used by other authors in literature. The high-Rn simulations presented here were onerous in terms of computing time but they have proven to be very helpful to evaluate the reliability of numerical studies of large- and small-scale models. Data obtained ware compared with experimental trends found in the literature. The final task of the research is the assessment of FR concept as an effective naval propeller, therefore the downstream flow field has been closely studied in order to obtain simple and reliable indications on the effective positioning of multiple cylinders on the ship. This study is based on several visualizations of the rotating cylinder wake and takes into account the trailing vortices extinction distance. Consistently with the point of evaluating the necessity and the feasibility of high Rn simulations, a cost-andbenefit analysis has been enabled showing the computational times of the simulations and numbers of CPUs used.
Preliminary Analysis for Marine Application of Flettner Rotors / De Marco, A; Mancini, S; Pensa, C.. - 1:(2014), pp. 249-260. ( INT-NAM 2014 Istanbul 23/10/2014-24/10/2014) [10.13140/2.1.4921.3765].
Preliminary Analysis for Marine Application of Flettner Rotors
De Marco A;Mancini S;Pensa C.
2014
Abstract
The paper presents Unsteady Reynolds Average Navier Stokes (U-RANS) simulations for 3D flow past a full-scale rotating cylinder, known as Flettner Rotor (FR). The U-RANS simulations are performed using the commercially available flow simulation software CD-Adapco STAR CCM+. A preliminary 2D study was conducted to set-up a numerical model using a moving mesh technique; this analysis was directed to define suitable domain shape and dimension, time-step and grid-resolution. The further 3D simulations were performed to evaluate in deep the influence of some of the main parameters on the effectiveness of the rotors; in particular the Spin Ratio, i.e. the ratio of circumferential-cylindervelocity- to-free stream-velocity (SR) and the effect of the endplates (EP) also called Thom disk. The functioning characteristic of the device has been predicted by lift and drag coefficients for various rotation rates. The selected dimensions of the cylinder and the chosen range of design parameters are similar to those of a real installation on board, therefore the Rn obtained (1.3 - 5.0 E+06) are quite close to the real values and significantly higher than the ones used by other authors in literature. The high-Rn simulations presented here were onerous in terms of computing time but they have proven to be very helpful to evaluate the reliability of numerical studies of large- and small-scale models. Data obtained ware compared with experimental trends found in the literature. The final task of the research is the assessment of FR concept as an effective naval propeller, therefore the downstream flow field has been closely studied in order to obtain simple and reliable indications on the effective positioning of multiple cylinders on the ship. This study is based on several visualizations of the rotating cylinder wake and takes into account the trailing vortices extinction distance. Consistently with the point of evaluating the necessity and the feasibility of high Rn simulations, a cost-andbenefit analysis has been enabled showing the computational times of the simulations and numbers of CPUs used.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
