*Make sure to read the following as I cannot explain my question in one sentence
Winglets are a kind of wingtip device that is installed on an aircraft to reduce drag and improve fuel efficiency. There are two types of practical winglets that have already been installed on real aircraft, the canted winglet and blended winglet.
Winglets work by reducing wingtip vortices while producing an aerodynamic lift vector that points inboard and also slightly forward. The slightly forward component, as many author states, is due to the change in flow direction because of the wingtip vortices at a high angle of attack. With the increase in AoA, the main-wing part increases lift with a high pressure field below, than the winglet part, thus producing another vortex around the transition part of the main-wing and winglet. At higher AoA, the vortex also increases and strikes the leading edge of the specially placed winglet, forming this slightly forward-pointing lift.
My question rises when speaking of canted winglet and blended winglet. For canted winglet, the cant angle cannot be decreased too much, or
A sharp interior angle in this region can interact with the boundary layer flow causing a drag inducing vortex, negating some of the benefit of the winglet.
In the case of a blended winglet, the transition part of the main-wing and the winglet is smoothed. It is being said that this feature decreases the lift and gives a better aerodynamic load. However, this smooth transition, at higher AoA, should also decrease the vortex formed at the transition, as this feature also provides a smooth lift force transition. Is this what they meant by
This feature sacrifices some of the potential induced drag reduction, in return for less viscous drag and less need for tailoring the sections locally.
It seems counter-intuitive that blended winglets reduce more drag than canted winglet, as canted winglet would use up more vortex formed to produce a thrusting lift force. Speaking of this, then, how is blended winglet better?