Hi Fenlander,
The dynamics of unusual sword blade elements have been discussed on the forums many times over the years, and the 'sinuous' (wavy, serpentine) blade is one that is quite interesting. It seems that these blades were more attuned to aesthetics and psychological effect more than practical application.
In actuality, the wavy dynamics of the blade are counterproductive to the thrust for both penetration and especially withdrawal of the blade. In the slashing cut, it seems that the shape counteracts a smooth cut and often interrupts or prevents that action.
These blades are of course well known with the keris, and I would certainly defer to the outstanding knowledge base here on that topic, but it seems these wavy blades examples carry a great deal of traditional and religious oriented symbolism. I am uncertain of the actual combat history concerning these blades, and I hope that will be addressed by keris enthusiasts.
In the case of most other applications, for example in India, these blades tend to carry nagan symbolism, and the swords are typically considered either ceremonial or parade weapons. In European history, swords with these blades are often erroneously termed 'flamberge' but also are considered to be mostly aesthetically employed. I believe much of this may derive from the Biblical allusion to the flaming sword etc.
In China, there were serpentine blades as well, but these also seem to have served as court swords intended to impress, perhaps as 'bearing' type swords, which seems the most likely use for swords of this type as they are held upright and unsheathed while in procession.
In WWI, the German Schmidt-Rubin bayonets that had brutal appearing serrated back edges (actually to serve as pioneer type saws) caused a great deal of consternation among allied forces. They believed these were insidiously employed to cause painful and grievous wounds, and in anger would instantly shoot any German soldier carrying them. In reality, these could hardly penetrate with any effect, and the German soldiers would try to get rid of them lest they be found with them. The psychological effect was clear.
In my opinion wavy or serrated blades are unnecessary and probably impair rather than enhance thier effect. The potential for infection from a wound is also irrelevant, as in combat the objective is to eliminate your opponent and prevent him doing the same to you, which he may well do if after you strike you are waiting for him to be overcome by infection
There were debates throughout the use of the sword whether the cut or the thrust was more effective however, and it was generally held that the thrust was typically much more mortal. This of course overlooking the obvious fatal cuts such as decapitation.
All best regards,
Jim