Potential Hydrodynamic Performance Enhancement of Hydrokinetic Turbine with Hydrophobic Coatings

2021 ◽  
Vol 35 (6) ◽  
pp. 924-932
Long Chen ◽  
Kai-Wern Ng
2021 ◽  
Vol 930 ◽  
Dong Zhang ◽  
Qiao-Gao Huang ◽  
Guang Pan ◽  
Li-Ming Yang ◽  
Wei-Xi Huang

The effects of chordwise deformation and the half-amplitude asymmetry on the hydrodynamic performance and vortex dynamics of batoid fish have been numerically investigated, in which the two parameters were represented by the wavenumber ( $W$ ) and the ratio of the half-amplitude above the longitudinal axis to that below ( $HAR$ ). Fin kinematics were prescribed based on biological data. Simulations were conducted using the immersed boundary method. It was found that moderate chordwise deformation enhances the thrust, saves the power and increases the efficiency. A large $HAR$ can also increase thrust performance. By using the derivative-moment transformation theory at several subdomains to capture the local vortical structures and a force decomposition, it was shown that, at high Strouhal numbers ( $St$ ), the tip vortex is the main source of thrust, whereas the leading-edge vortex (LEV) and trailing-edge vortex weaken the thrust generation. However, at lower $St$ , the LEV would enhance the thrust. The least deformation ( $W=0$ ) leads to the largest effective angle of attack, and thus the strongest vortices. However, moderate deformation ( $W=0.4$ ) has an optimal balance between the performance enhancement and the opposite effect of different local structures. The performance enhancement of $HAR$ was also due to the increase of the vortical contributions. This work provides a new insight into the role of vortices and the force enhancement mechanism in aquatic swimming.

M. Nachtane ◽  
M. Tarfaoui ◽  
A. El Moumen ◽  
D. Saifaoui ◽  
H. Benyahia

Marine energy is gaining more and more interest in recent years and, in comparison to fossil energy, is very attractive due to predictable energy output, renewable and sustainable, the Horizontal Axis Hydrokinetic Turbine (HAHT) is one of the most innovative energy systems that allow transforms the kinetic energy into electricity. This work presents a new series of hydrofoil sections, named here NTSXX20, and was designed to work at different turbine functioning requirement. These hydrofoils have excellent hydrodynamic characteristics at the operating Reynolds number. The design of the turbine has been done utilising XFLR5 code and QBlade which is a Blade-Element Momentum solver with a blade design feature. Tidal current turbine has been able to capture about 50% from TSR range of 5 to 9 with maximum CPower of 51 % at TSR=6,5.   The hydrodynamics performance for the CFD cases was presented and was employed to explain the complete response of the turbine.

2020 ◽  
Vol 18 (1) ◽  
pp. 51-65 ◽  
Mabrouk Mosbahi ◽  
Sana Elgasri ◽  
Mariem Lajnef ◽  
Bouzid Mosbahi ◽  
Zied Driss

VT Gopinathan ◽  
J Bruce Ralphin Rose

Bioinspired aerodynamics is an emerging subject in the design of advanced flight vehicles with superior performance and minimum fuel consumption. In the present review article, a comprehensive evaluation is focused on previous studies and investigations toward the performance enhancement of aerodynamic surfaces with leading-edge (LE) tubercles. The implementation of tubercles has been biologically imitated from humpback whale (HW) flippers. Particularly, aerodynamicists are much interested in this bioinspired technology because of the exclusive maneuvering and flow control potential of HW flippers. LE protuberances are considered as a passive flow control method to improve the aerodynamic performance in various applications like aviation, marine, and wind energy. The aerodynamic and hydrodynamic performance variations caused by specific tubercles amplitude and wavelength are also compared through numerical and wind tunnel testing. The prospective utilization of tubercles on boundary layer flow control is measured with regard to conventional and swept-back wing designs. Flow control mechanisms of tubercles are outlined with several interesting facts in addition to the outcomes of various bioinspired aerodynamic investigations in the recent years.

Yong Ma ◽  
Yuanyao Zhu ◽  
Aiming Zhang ◽  
Chao Hu ◽  
Sen Liu ◽  

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