A novel methodology for the design of diffuser-augmented hydrokinetic rotors

Velocity Augmentation Model for an Empty Concentrator-Diffuser-Augmented Wind Turbine and Optimisation of Geometrical Parameters Using Surface Response Methodology

“…Notably, it is suitable for adverse pressure gradients, insensitive to free-stream turbulence in the far wake region, and eliminates the need for damping functions [72]. The model choice was based on extensive literature recommendations for aerodynamic purposes, especially in shrouded wind turbines [9,11,12,37,40,42,[67][68][69][72][73][74][75][76][77][78].…”

“…To meet this criterion, the height of the first cell within the boundary layer should fall within the viscous sublayer. A recommended guideline is to ensure that the y + value of the mesh on the wall surfaces is approximately 1 [12,68]. This dimensionless wall distance, y + , is given by the following equation:…”

“…where u * stands for the friction velocity, y for the distance between the first node and the wall, and v for the kinematic viscosity [12,77].…”

“…Additionally, shrouded turbines may surpass the Betz limit, signifying peak efficiency and mitigating energy losses related to tip vortices [10][11][12][13]. Shrouded wind turbines offer additional advantages, including noise reduction, reduced risk of blade failure, improved bird safety, and enhanced performance in turbulent environments [14].…”

“…Shrouded wind turbines offer additional advantages, including noise reduction, reduced risk of blade failure, improved bird safety, and enhanced performance in turbulent environments [14]. Despite being promising for built environments and small-scale applications [14], hub flow separation can impact shrouded turbine performance, hindering the shroud's ability to capture mass [12]. The concentrator-diffuser-augmented wind turbine (CDaugWT) consists of a concentrator, a cylindrical section (throat section) housing the wind turbine, and a diffuser with a flange, as shown in Figure 1.…”