Horseshoe vortex is formed at the junction of an object immersed in fluid-flow and endwall as a result of three-dimensional boundary layer separation. When a boundary layer flow (either laminar or turbulent) encounters any obstacle projecting from the surface, some distance upstream of the obstacle the boundary layer separates as a result of the adverse pressure gradient, and rolls up to form three-dimensional complex vortices. Generally horseshoe vortex is observed near the endwall region and also forms near the tip endwall clearances. The passage flow is characterized by boundary layer effects, secondary flows generated by the pressure gradients, leading edge horseshoe vortex formation. The vortices form the characteristics of horseshoe shaped vortex, with legs of the vortices extending to downstream, on both sides of the blade. The numerical study was carried out for two turbine blades, considering the effect with and without endwall tip clearances from 0 to 5% of span of the airfoil. The flow without tip clearance (c = 0 mm), will have maximum influence of the horseshoe vortex structure formation, because of strong pressure gradient observed near to the region to the blade leading edge. This affects the secondary flows in the endwall region, which implies more losses. And for the flow with higher clearances (c = 5 mm), it is observed that the horseshoe vortex formation in the leading edge of the blade is very weak, because of reduced adverse pressure gradient. The numerical simulation has been carried out for two turbine blades to study HSV structure and the interference effects on the blade flow characteristics. Additionally, the passage flow between the two turbine blades with and without endwall clearance effect is studied. Results of the numerical simulation of horseshoe vortex formation and effect of endwall clearances on the structures are presented. The velocity and static pressure are plotted and studied. © Springer India 2017.