My dd is 18 mo and without fail at every meal, deliberately flings good amounts of food on the floor - or more recently at me. She doesn't seem to fling it because she's full or doesn't like it - if i offer her more of the same she'll take it happily, have a few mouthfuls then bam! the rest is on the floor. Her appetite is good and she's not a fussy eater, she'll happily try most things.
She's been able to feed herself finger foods for quite a while and is quite confident with a spoon or fork now, so i don't think it's frustration at not being able to feed herself. I've tried everything i can think of - not reacting, just taking the food away, saying "No!" in my best Mummy-Means-Business voice.......all to no effect. A relative recently said i should "knock that on the head as soon as you can" but they didn't tell me how!
My dd used to do this, she would throw food on the floor, rub it in her hair, up her nose, in her ear etc etc. I put a huge sheet on the floor and tried to ignore her as best i could. I used to play a nursery rhyme cd as a distraction, and eventually she grew out of it, best of luck