I discovered Cy Twombly at the tate last weekend this is his series Bacchus (2005) that is on show at the tate. Have to say I was impressed...!
The explanations given below are better than anything I could say, I'd just say that you really have to go and see these for yourself to experience them - when you get into the room you're surrounded by them - they're really something you experience, not just look at. They just look like twirly blood streaks here. You only get the violence and the movement by standing in the middle of them!
And to be honest I don't think it's as straight forwardly bloody violence as it looks here, there's quite a lot of energy, life and light in it all.