How will rain affect a discs flight??

mhammy

We're having an argument on how much rain will reduce the distance of a thrown disc. We have a "professional" disc golfer here who says that it would decrease his distance by less than 1 percent. The rest of us aren't buying it. So, assuming that there is no head or tail wind present and no outside friction sources other than the normal friction produced by the atmosphere, how much decrease in distance would one encounter while throwing a disc in the rain. Assume that it's a normal rain shower and not a torrential down pour, whatever normal is.

DaveC426913

Seems to me 1% isn't unreasonable. By volume, what is the ratio of water versus air in its flight? Surely less than 1%. By mass, what is the ratio of disc to accumulated rain? Surely less than 1%.

There are certainly many other factors to consider, I'm just ballparking orders of magnitude.

AlephZero

Water vapor is less dense than air (molecular weight of water = 18 compared with 28 for nitrogen and 32 for oxygen) so the aerodynamic lift and drag will both be reduced by the increased humidity that accompanies the rain. Which of those factors "wins" in terms of changing the range will depend how much the disk "flies" as it is thrown.

Any water droplets that remain on the disk will tend to mess up the aerodynamics, increase the drag and reduce the lift, but I guess they won't stay there for long because of the forward velocity and/or spin of the disk. @DaveC, this is not caused by the added mass of the water droplets, but the change in surface shape of the disk affecting the boundary layer of the air flow.

I don't know now to estimate the effect of these things on the range, though.

DaveC426913

Hey, golf balls and some designs for airplane wings actually incorporate rows of bumps or divots in order to control the boundary layer and flow separation.

laurent711

I don't know now to estimate the effect of these things on the range, though.

AlephZero

Yes, but the key word in that sentence is "design", not a random arrangement of random sized bumps.

AlephZero

Your image isn't displaying for me (in Internet Explorer) - but "now" was a typo for "how".

DaveC426913

I know. I was really reachin'...