But if you just want to simulate ropes, there's a few models out there from academics going "let's try and model this difficult system more accurately". Take a look at stuff like imc-der [0] and ridgerunner [1].
[0] https://github.com/QuantuMope/imc-der
[1] https://jasoncantarella.com/wordpress/software/ridgerunner/
If knots are what's interest you more, then maybe you can have a look at the self-collision avoidance of "Repulsive Curves" http://www.cs.cmu.edu/~kmcrane/Projects/RepulsiveCurves/
There is some research into the topology of DNA (especially circular DNA, like plasmids which is a knot) that considers things like writhe and twist. Not sure it would adapt too well to macroscopic systems though.
There is also the excellent KnotPlot for actually drawing the knots. I bought a licence once on a whim, but rarely use it :)
That does raise an interesting question- can proteins spontaneously fold into knots? The answer is yes although I was discouraged when I originally asked this question in grad school.