Upstream Flow Control for the Savonius Rotor under Various Operation Conditions

Abstract

Applications of the Savonius rotor have been extended in recent years, necessitating an in-depth investigation on flow characteristics of such a fluid energy converting device. For the wake flow downstream of the Savonius rotor, studies have been reported extensively. Nevertheless, literature specifically devoted to the upstream flow of the Savonius rotor can rarely be found. This review collects and compiles findings from relevant studies to prove the significance of upstream flow patterns to the operation of the Savonius rotor. Then attempts from experimental and numerical aspects to substantiate the important effect of the upstream flow are implemented. Based on practical cases and laboratory works, upstream flow patterns for the Savonius rotor are divided into four types, namely uniform flow, guided flow, rotor wake flow and oscillating flow. Accordingly, conditions under which these upstream flow patterns arise are analyzed respectively. Experimental and numerical results are presented to clarify the influential factors underlying diverse upstream flow patterns. Furthermore, the relationship between the performance of the Savonius and the upstream flow is elucidated, facilitating the development of techniques of controlling the upstream flow. This review provides a systematic reference for the control of the upstream flow for the Savonius rotor, which has the tendency of developing into an independent technical branch.

CFD Validation of Moment Balancing Method on Drag-Dominant Tidal Turbines (DDTTs)

“…It is worth noting that the flow domain for the Savonius turbine was designed with a longer downstream length of 12D (rotor diameter), whereas the Pinwheel turbine had a downstream length of 9D. This design choice was made to ensure the attainment of a fully extended vortex for the Savonius turbine, as its wake decay length is longer than that of the Pinwheel turbine [22][23][24][25][26]. The domains' actual scale was determined through a parametric study that aimed to equalize the blockage ratio of both models.…”

The Biffis Canal Hydrodynamic System Performance Study of Drag-Dominant Tidal Turbine Using Moment Balancing Method

“…The entire channel was 6:1, scaling down from the real channel scale for the convenience of saving meshing memory and parametric study. This design decision was made to ensure the achievement of a fully extended vortex for the Savonius turbine, given that its wake decay length is longer compared to that of the Pinwheel turbine [22][23][24][25][26]. The grid size of the trapezoid-profile tank was gradually refined into a smaller size of 2D × 2D × 4.5H and D × D × 2H cuboid (H is the rotor height), using a gradient mesh refinement approach at 60% and 30% of the grid base size (0.0822 m), respectively.…”

Review of Specific Performance Parameters of Vertical Wind Turbine Rotors Based on the SAVONIUS Type

“…The air circulation velocity was the key parameter in the operation of these devices and must be considered with the upstream, inside, and downstream conditions to obtain optimum performance results. Thus, the numerical studies performed highlight the main flow patterns in the rotor vicinity area meant to establish exactly the working conditions in which this type of rotor must operate [92][93][94][95][96]. A novel model of wind turbine was presented by Doerffer et al with a constructive solution involving twin rotors showing an efficiency of above 20% corresponding to wind velocity [97].…”