Review analysis on riblets used in thermal applications and wind turbines

Globally renewable energy sources play a vital role in future energy production. Heat transfer and generation of drag are the two crucial elements in the global energy consumption chain. In this review analysis, we have emphasized how to improve these two areas to extract most of the energy available in nature and to enhance convective internal heat transfer for effective cooling of applications in automobiles, aerospace, electronics, heating, and cooling devices. Heat transfer enhancement achieved in many ways and using riblets is one of the methods of implementing passive techniques. Riblet applications in wind turbines employed with specially created microstructured surfaces and provide a variety of benefits which include a reduction in drag over a wind turbine especially operating at low Reynolds number. The overall drag reduction over a wind turbine depends on height, shape and whether it is fully or partially applied on aerofoil surfaces. Earlier studies proved that optimum drag reduction was achieved by employing riblets with varied geometry along the aerofoil. This analysis discusses the influence of riblets used in wind, hydro and gas turbines, which follows a comparison of heat transfer and aerodynamic effects.