Study of three types of wave leading edge on the performance of industrial turbine blade cascade Hamed Ghandi Department of Aerospace Engineering, Faculty of Engineering, Science and Research Branch, Islamic Azad University, Isfahan, Iran Reza Aghaei Togh Department of Aerospace Engineering, Faculty of Engineering, Science and Research Branch, Islamic Azad University, Isfahan, Iran, and Abolghasem Mesgarpoor Tousi Aerospace Engineering Faculty, Amirkabir University of Technology, Tehran, Iran Abstract Purpose – The blade profile and its geometrical features play an important role in the separation of the boundary layer on the blade. Modifying the blade geometry, which might lead to the delay or elimination of the flow separation, can be considered as a passive flow control methodology. This study aims to find a novel and inexpensive way to reduce loss with appropriate modifications on the leading edge of the turbine blade. Design/methodology/approach – Three types of wave leading edges were designed with different wavelengths and amplitudes. The selected numbers for the wave characteristics were based on the best results of previous studies. Models with appropriate and independent meshing have been simulated and studied by a commercial software. The distribution of the loss at different planes and mid-plane velocity vectors were shown. The mass flow average of loss at different incidence angles was calculated for the reference blade and modified ones for the sake of comparison. Findings – The results show that in all three types of modified blades compared to the reference blade, the elimination of flow separation is observed and therefore the reduction of loss at the critical incidence angle of I = –15°. As the amplitude of the wave increased, the amount of loss growing up, while the increase in wavelength caused the loss to decrease. Originality/value – The results of the present numerical analysis were validated by the laboratory results of the reference blade. The experimental study of modified blades can be used to quantify numerical solutions. Keywords Loss, Industrial turbine, Cascade, Wave leading edge Paper type Research paper Introduction Industrial turbines as rotators experience reduced efficiency and therefore low power due to separation and the resulting expansion of secondary flows. This reduction in power will cause poor consumer performance and increases overall loss. To reduce losses and improve turbine performance, it is necessary to somehow control the flow separation, i.e. to delay or stop it. Separation control methods, including vortex generator by external power methods such as blower, jet, or plasma, are known as an active control. Cheap and convenient methods called passive control, which involves changes in geometry to reduce loss by delay or removal of separation (Lin et al., 1991; Aghaei Togh and Tousi, 2015; Lei et al., 2011; Aghaei-Togh and Tousi, 2018). Gomez and Niehuis (2012) studied the effect of vortex jet air generator on the high- pressure turbine blade performance. Experiments have been performed in a cascade located in a high-speed wind tunnel with a range of Reynolds number 390,000–800,000. The results show that when vortex generator is turned on, it can reduce the loss by vorticity formation upstream of the separation point caused, reducing the size of the separation bubbles. Huang et al. (2006) investigated the influence of plasma actuator at two different locations (0.4, 0.675 chord) on the turbine blade surface as an active control method to reduce the length of flow separation. The force created by the electric field prevents fluid separation by absorbing the ionized fluid to the surface of the blade and directs it downward. The use of protuberance in aerofoils has been around since 1995, with observations of humpback whale motions. Despite its high weight, the huge whales have good maneuverability. The protuberance includes sinusoidal, cosine or oscillating changes on the surfaces of the blades or wings. Johari et al. (2007) carried out an experimental study of the effect of protrusion on the aerofoil profile (NACA-021–634) in the water tunnel. Experiments were performed on different The current issue and full text archive of this journal is available on Emerald Insight at: https://www.emerald.com/insight/1748-8842.htm Aircraft Engineering and Aerospace Technology © Emerald Publishing Limited [ISSN 1748-8842] [DOI 10.1108/AEAT-06-2020-0115] Received 12 June 2020 Revised 13 September 2020 Accepted 1 October 2020