Why does water splash back onto the hood?

[davidg4781]

I tried searching and couldn't find anything. Hopefully I'm not the only one. But this is the first time I've ever seen something like this.

I noticed this first when I bought the BS. It rained sort of heavily about a week later. When I turned it on, water was splashing/ spitting onto the hood from the front. I thought that was odd went to work.

Then a couple of days ago, it rained again, and I had a puddle growing on my hood as I drove, collecting more water as it moved around. I got to a stop sign and braked a little harder because I wanted it to roll off the front. As soon as it went over the edge it splashed back onto the hood.

Is this coming from the fans maybe?

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[jkeaton]

Does it really matter?

 

[davidg4781]

Does it really matter?

Yes. Kind of why I asked.

Sorry, I thought this was a forum to discuss the Bronco Sport. I don't know why you care why I ask why something happened.

 

[Jmuns]

It’s either aerodynamics or the active grill shutters operating during stopping. I’ve always assumed it’s the shutters.

 

[Dude]

Having both high quality Paint Protection Film (PPF) and a robust high quality ceramic coating professionally applied to your vehicle will minimize (but not totally eliminate) the water splash you described.

 

[Jmuns]

Having both high quality Paint Protection Film (PPF) and a robust high quality ceramic coating professionally applied to your vehicle will minimize (but not totally eliminate) the water splash you described.

I’m assuming you noticed a difference in what he is describing after applying both? I just don’t understand how that would affect water splashing back over the hood from airflow

 

[Dude]

I’m assuming you noticed a difference in what he is describing after applying both? I just don’t understand how that would affect water splashing back over the hood from airflow

Correct. A pretty significant difference. Happened to rain just once before I had those applied and rained a lot afterwards. Could be coincidence but I’ll leave it to the expert scientists to determine if there is a causal relationship.

Also, I am referring to OPs statement: “puddle growing on my hood as I drove, collecting more water as it moved around. I got to a stop sign and braked a little harder because I wanted it to roll off the front. As soon as it went over the edge it splashed back onto the hood.”

That does not happen now (for the most part as I said it’s not totally eliminated).

 

[Sleddog]

My F250 collects some water but it’s a “no worry” situation. Same for my BS. It’s not like the water is going suddenly migrate to the windshield and obscure your vision. It’s in an no air flow spot. And that’s why it accumulates. Once there is enough volume it will run off.

I think it’s more of an annoyance for you than an actual problem. Ignore it and enjoy your BS.

 

[Elegance]

It's definitely the physics of the hood humps and flat front end. I love when it happens. Always gets a chuckle out of me.

The splashback lessened when I installed my bug deflector, if you're looking to stop it from happening.

 

[Mark S.]

Air moving over a surface has a boundary layer. The closer you get to the surface the slower the air moves. In your case, the water on the hood is in the boundary layer, which means the air moving over it is slower than your forward speed. As you brake, you observe Newton's First Law (inertia) in action: the water on the hood wants to continue moving at the same speed it was moving, and its inertia overcomes the relatively slow air movement in the boundary layer and friction of the surface of the hood. Eventually, the water will fall off the front of your hood. When it does it will drop into the slipstream of air moving around your car, thereby exiting the boundary layer. Once free of the boundary layer air, into the full-speed slipstream air, you observe Newton's Third Law (action and reaction). While it may appear the water is being blown backward, it is, in fact, the pressure of air from the slipstream forcing the water to move up and slow down while your car continues forward.

 

[Dude]

Air moving over a surface has a boundary layer….

As I stated earlier, “I’ll leave it to the expert scientists to determine …”

 

[jkeaton]

Yes. Kind of why I asked.

Sorry, I thought this was a forum to discuss the Bronco Sport. I don't know why you care why I ask why something happened.

No need to be sorry.Its aerodynamics or something else.

 

[Dude]

OP asked a valid question and was presented with a scientific (engineering) explanation and at least 2 possible solutions (so far).

And someone else posted on a different thread this eloquent statement: “(I posted) because it’s a forum. A place where we exchange information and perspective.”

I post therefore I am. Lol

 

[Dude]

As I stated earlier, “I’ll leave it to the expert scientists to determine …”

And your explanation explains why PPF and or ceramic coating can have some affect on the water splash phenomenon. Changes the dynamics as does a hood bug deflector.

 

[Hot Rod Mike]

Remove the hood that will stop it.

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