I do not know if that is an S-duct; the position of the exit looks to be on the chassis, which I think is illegal. The S-duct has always been right between the chassis and the front crash structure/nose cone, which is a loophole in the rules.
It could be experimental for next year. It could also just be aero test devices. This is how your typical S-duct looks when the nose cone is removed:
However, I could also be wrong about this. Force India has a similar set up as Mercedes:
![Image](http://img3.auto-motor-und-sport.de/Force-India-Formel-1-GP-Belgien-Spa-Francorchamps-19-August-2015-fotoshowImage-86fccd2f-889436.jpg)
I think the vanity panel is used here.