The great rain on windshield debate of 2019 (was in interesting discoveries thread)

[rocket23]

nope, screw that^^^^ I'm drinking!

 

[OliverNuther]

ok, but we do agree that rain hitting a windscreen at 30 mph, splatters, making it seem worse than at a stand still.

Yes we do. By the same token put your hand out of the car next time your driving in the rain and compare the impact felt on your hand compared to standing still in the rain. You’re feeling impact velocity, not more rains drops per se.

 

[OliverNuther]

nope, screw that^^^^ I'm drinking!

I’m on board with that also.

 

[rocket23]

Yes we do. By the same token put your hand out of the car next time your driving in the rain and compare the impact felt on your hand compared to standing still in the rain. You’re feeling impact velocity, not more rains drops per se.

I'll take your word for it, with my luck some asshat will come up my right side thinking I;m gonna turn left,lol

 

[Coast GT]

Oh FFS this forum is going nuts. I’m with @OliverNuther on this. The amount of rain that falls or the rate at which it falls has nothing to do with if you are driving or not. If you think it does then you need to stop drinking to coolade and seek help.

The rate at which rain falls is determined by the size of the rain drop, larger drops fall faster than smaller ones. The size of the rain drop is determined by the amount of available water vapor and the intensity of updrafts in a cloud, not whether your Stinger (just to keep a link to the forum)is moving or not.

For those of you in the Republic of Trumpistan that don’t believe, look it up, even NASA explains it in simple terms. I know you probably believe they’re still hiding the aliens and it’s all a made up conspiracy but it’s just basic science.

Regardless what causes it, it’s irrelevant to most of the Aussie Stinger owners on here as most of our country is in severe drought. I’d be happy if more rain was caused when I drive my Stinger, I’d go and help the farmers by driving around the country.

 

[Coast GT]

@rocket23 this one’s for you brother. We are definitely not English.

 

[Jingguily]

Your windshield is a fixed piece of glass measuring x square metres. Rain falls at a concentration of y drops per square metres. The area of your windscreen remains the same irrespective of your speed. So the volume of water hitting it( y drops/sq mtr) remains the same irrespective of your speed. The only way more water can hit your windshield is if more water falls from the sky.

Wrong.

If your car goes faster than the speed of the rain drops (which is not that fast) you will increase the amount of rain drops since you will cover a larger amount of area in relation to the density of rain drops in the air.

EDIT: Added a picture I quickly made to show the simple maths. I wouldn't usually care but some people are just getting straight up disrespectful about such a non-impactful topic .....

 

[OliverNuther]

I don’t know where the disrespectful part comes in. I thought the whole debate was rather genteel. Merlin and I have been the main protagonists here and I don’t feel he has disrespected me and I hope I haven’t disrespected him.

 

[Stinger GT SS]

Im confused, I thought Australia was a Chinese colony.

Really?

 

[StingerGT68]

It's amazing being able to hit the ''ignore' button on this forum.

 

[MerlintheMad]

Republic of Trumpistan

And, like all things in these times, even rainfall gets politicized!

 

[forzanerazzurri]

And, like all things in these times, even rainfall gets politicized!

REEEEESIST!!!!!

 

[rocket23]

back on topic.....if I hear one more,''it's trumps fault''. I'm gonna start sympathizing Hillary supporters!

 

[Ozstung]

I just read this thread in one sitting, boy you guys are entertaining what an effort loved it. No wonder I pay money to be on here.. I remember this "rain" arguement from high school.

 

[rocket23]

Oz , thats alot of reading.....

 

[BlaydeX15]

Woo, math.

To get you on the same wavelength, think of it this way: If you laid a sheet of glass on the ground, it would receive X amount of rainfall from the sky. If you move the sheet left or right along the ground, no matter how fast or where you move it (Assuming rain doesn't slide off), it will not collect any extra rain. If you move it to the left to catch a raindrop, it'll miss an equal raindrop on the right side.

HOWEVER: We can collect more rain by moving it along a different axis. Strap a rocket to it, shoot it directly up into the sky, and it will collect more rain based on it's speed. We're basically accelerating the relative speed of the rain by speeding up the glass.

Same thing if we take that same sheet of glass, and stand it up vertically. In a math world, rain falls perfectly vertically, so no rain will land on the flat side... But if we strap another rocket to it and shoot it across your yard, it will smash into falling rain as it moves, and get wet before crashing into your fence and exploding into a million shards.

So if we look at both of those cases, it is reasonable to assume that there is a middle ground between horizontal and vertical. Something like an angled piece of glass, and moving it in one direction or another would accelerate the rate at which it collides with rain. Where would you find an angled piece of glass that we can accelerate? Hmm...

Let's simplify it. You have a windshield, it is 1.41m x 1.41m, and at a 45 degree angle. 1.41 is a weird number, but it just means that our windshield has a cross section of 1 square meter on both the horizontal and vertical plane. The density of rainfall is one drop per cubic meter, evenly distributed and falling at 1 meter per second.

Sitting still, you will be hit by 1 rain drop per second. Density x rate x area.

Lets pretend you are now moving 10 m/s. 22.4 MPH, 36 km/h. We no longer care about the horizontal plane, we care about the vertical plane. And since the vertical plane is traveling, we add another variable to the equation! Speed. In one second, the vertical plane displaces 10 cubic meters of space, colliding with the 10 rain drops that were once occupying this space. Now, you guys are kinda right, the horizontal plane doesn't change, so from that perspective one rain drop falls on the car... But in that time, the car crashes into 10 rain drops.

Now, that's extremely exaggerated. In real life, rain falls faster than that, so the difference is less pronounced. A real world rain drop reaches terminal velocity at at 10 m/s, so traveling at 10 m/s would only result in a 2x increase in rain contacting the windshield. 1 rain drop falling on the wind shield from the horizontal plane, and your car colliding with one rain drop in it's 10 meters of forward movement.

Since I'm not the owner of a wind tunnel, I can't model how aerodynamics affect rainfall, but we can calculate roughly much extra rain will hit your car based on density, rate, area, and speed. (We're talking spherical cows here, good enough, but the real world is off by a bit)

Density (drops per cubic meter) * Rate (Your speed relative to rain, or the rain's speed relative to you. Same thing... In meters per second) * Area (Square meter cross sectional area of your windshield) = Rate of rain.

Lets say it's a crazy storm. 500 raindrops per cubic meter. It's falling at terminal velocity, 10 m/s, you have the perfect windshield as above, 1 square meter and you're moving at 78.3 MPH (35 meters per second).

Sitting still: you're collecting 500x10x1=5000 raindrops per second on the horizontal plane.

Driving at 78.3 mph: You're collecting 500x35x1= 17,500 raindrops per second on the vertical plane.

The math even works backwards. If we're falling from the sky at the same speed as the rain, we won't get wet at all. Right? 500x0x1=0 Raindrops per second.

Now, it's not perfect. We don't account for steeper windshields, we don't account for your car's slipstream, and we ignore angles and curves in the glass, but it illustrates that movement = more rain collision.

For those that still doubt, consider aerodynamic drag. The faster we move, the more air we displace, and the more power we need to overcome that. In a sufficiently dense rainfall, we would have to start considering hydrodynamic drag. The faster we move, the more water we have to displace, and the more power we need to overcome that! You could technically be in such a heavy rainstorm that your top speed would be significantly reduced, but that effect on your car would be much lower at low speeds, because your car is running into less water.

Now, without being able to calculate the effects of your slipstream or the angle of the Stinger's windshield and the effects of it's curved edges, it's hard to get a good answer, but I would say it's safe to assume that a Stinger traveling at 80 mph is collecting 2-3x as much rain on it's windshield as a stopped one.

 

[rocket23]

No rating....I'd hate to encourage another post on rain and windshields.
..turn on the damn wipers already!! fast for a downpour , slow for rain and intermittent for a spritzing.

 

[BlaydeX15]

No rating....I'd hate to encourage another post on rain and windshields.
..turn on the damn wipers already!! fast for a downpour , slow for rain and intermittent for a spritzing.

Just use RainX, you'll never need Low again. Lol.

 

[rocket23]

are the rain x wipers any good...

 

[MerlintheMad]

Woo, math.

To get you on the same wavelength, think of it this way: If you laid a sheet of glass on the ground, it would receive X amount of rainfall from the sky. If you move the sheet left or right along the ground, no matter how fast or where you move it (Assuming rain doesn't slide off), it will not collect any extra rain. If you move it to the left to catch a raindrop, it'll miss an equal raindrop on the right side.

HOWEVER: We can collect more rain by moving it along a different axis. Strap a rocket to it, shoot it directly up into the sky, and it will collect more rain based on it's speed. We're basically accelerating the relative speed of the rain by speeding up the glass.

Same thing if we take that same sheet of glass, and stand it up vertically. In a math world, rain falls perfectly vertically, so no rain will land on the flat side... But if we strap another rocket to it and shoot it across your yard, it will smash into falling rain as it moves, and get wet before crashing into your fence and exploding into a million shards.

So if we look at both of those cases, it is reasonable to assume that there is a middle ground between horizontal and vertical. Something like an angled piece of glass, and moving it in one direction or another would accelerate the rate at which it collides with rain. Where would you find an angled piece of glass that we can accelerate? Hmm...

Let's simplify it. You have a windshield, it is 1.41m x 1.41m, and at a 45 degree angle. 1.41 is a weird number, but it just means that our windshield has a cross section of 1 square meter on both the horizontal and vertical plane. The density of rainfall is one drop per cubic meter, evenly distributed and falling at 1 meter per second.

Sitting still, you will be hit by 1 rain drop per second. Density x rate x area.

Lets pretend you are now moving 10 m/s. 22.4 MPH, 36 km/h. We no longer care about the horizontal plane, we care about the vertical plane. And since the vertical plane is traveling, we add another variable to the equation! Speed. In one second, the vertical plane displaces 10 cubic meters of space, colliding with the 10 rain drops that were once occupying this space. Now, you guys are kinda right, the horizontal plane doesn't change, so from that perspective one rain drop falls on the car... But in that time, the car crashes into 10 rain drops.

Now, that's extremely exaggerated. In real life, rain falls faster than that, so the difference is less pronounced. A real world rain drop reaches terminal velocity at at 10 m/s, so traveling at 10 m/s would only result in a 2x increase in rain contacting the windshield. 1 rain drop falling on the wind shield from the horizontal plane, and your car colliding with one rain drop in it's 10 meters of forward movement.

Since I'm not the owner of a wind tunnel, I can't model how aerodynamics affect rainfall, but we can calculate roughly much extra rain will hit your car based on density, rate, area, and speed. (We're talking spherical cows here, good enough, but the real world is off by a bit)

Density (drops per cubic meter) * Rate (Your speed relative to rain, or the rain's speed relative to you. Same thing... In meters per second) * Area (Square meter cross sectional area of your windshield) = Rate of rain.

Lets say it's a crazy storm. 500 raindrops per cubic meter. It's falling at terminal velocity, 10 m/s, you have the perfect windshield as above, 1 square meter and you're moving at 78.3 MPH (35 meters per second).

Sitting still: you're collecting 500x10x1=5000 raindrops per second on the horizontal plane.

Driving at 78.3 mph: You're collecting 500x35x1= 17,500 raindrops per second on the vertical plane.

The math even works backwards. If we're falling from the sky at the same speed as the rain, we won't get wet at all. Right? 500x0x1=0 Raindrops per second.

Now, it's not perfect. We don't account for steeper windshields, we don't account for your car's slipstream, and we ignore angles and curves in the glass, but it illustrates that movement = more rain collision.

For those that still doubt, consider aerodynamic drag. The faster we move, the more air we displace, and the more power we need to overcome that. In a sufficiently dense rainfall, we would have to start considering hydrodynamic drag. The faster we move, the more water we have to displace, and the more power we need to overcome that! You could technically be in such a heavy rainstorm that your top speed would be significantly reduced, but that effect on your car would be much lower at low speeds, because your car is running into less water.

Now, without being able to calculate the effects of your slipstream or the angle of the Stinger's windshield and the effects of it's curved edges, it's hard to get a good answer, but I would say it's safe to assume that a Stinger traveling at 80 mph is collecting 2-3x as much rain on it's windshield as a stopped one.

LOL! You had waaay too much fun composing that. It's what I meant when I said, "Impacting snow is much more intrusive on the windshield than simply standing and watching the flakes coat the glass. Yet there are just as many flakes by your reasoning. You move to meet them. Same with rain drops. You are moving to meet more the faster you go."