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Old 12-18-2018, 06:46 PM   #41 (permalink)
MPG...what?
 
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ive had the same thing happen with our cars.

Id post the pictures but i cannot find them at the moment. I even compared them to the "ideal" tear drop car shape and they were nearly spot on.

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Old 12-18-2018, 07:22 PM   #42 (permalink)
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The windshield/cowl transition is a problem area insofar as there is high pressure there--which the snow physically manipulates by being blown into that area and accumulating until the pressure differential is less than the force required to blow it away. Toyota has hit on another way to mitigate this. Here's the 2018 Camry's hood:



The 2018 Sienna:



And 2018 Prius:



That scallop at the back of the hood induces low pressure behind it. Take a look at a CFD pressure distribution map of the 2012 Prius:



That line of green at the scallop edge is lower pressure than the yellow across the rest of the hood, and the pressure at the cowl behind it isn't any higher than across the hood. It looks stupid, but it's apparently effective enough to use on multiple models.
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Old 12-18-2018, 09:20 PM   #43 (permalink)
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Quote:
Originally Posted by Vman455 View Post
The windshield/cowl transition is a problem area insofar as there is high pressure there--which the snow physically manipulates by being blown into that area and accumulating until the pressure differential is less than the force required to blow it away. Toyota has hit on another way to mitigate this.
Snow would be blown AWAY from a high pressure zone; it would be drawn and settle into a LOW pressure zone.
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Old 12-19-2018, 07:05 PM   #44 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Snow would be blown AWAY from a high pressure zone; it would be drawn and settle into a LOW pressure zone.
That might be true if there was no windshield behind it. Don't take my word for it, here's Hucho:


Hucho, W.H., ed. Aerodynamics of Road Vehicles, 4th Ed. (Warrendale, PA: Society of Automotive Engineers, Inc., 1998), 162.


Hucho, W.H., ed. Aerodynamics of Road Vehicles, 4th Ed. (Warrendale, PA: Society of Automotive Engineers, Inc., 1998), 195.

T. Yomi Obidi, physics professor at City Colleges of Chicago:


Obidi, T.Y. Theory and Applications of Aerodynamics for Ground Vehicles (Warrendale, PA: SAE International, 2014), 81.

CFD images of various production and non-production cars:









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Old 12-20-2018, 04:22 AM   #45 (permalink)
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Interesting perspectives on this issue and the attempt to find the right words for these phenomena is mind expanding (for me).

Snow settles where the air velocity is low enough, otherwise it gets blown off the surface and will not settle.

Low air velocity = High Pressure

High air velocity = Low pressure

In short, the snow flakes falling on various automotive shapes in it's final form represents the equalization of air pressure zones and air velocities.

Going back to some old schoolbook rules as reference.

Equilibrium Rule
https://physics.tutorvista.com/motio...rium-rule.html
Quote:
Definition

Equilibrium of a body is defined as the state when all the forces and actions acting on the body nullify each other resulting in a stable, balanced and unchanging position. It is the stage when the body is either in a state of rest or moving with a constant velocity
Normally I would think of the term "equilibrium" under the context of Newton's laws of motion, but there are different conditions or applications of the concept such as this snowfall issue that challenge my perception.

https://physics.tutorvista.com/motio...rium-rule.html
Quote:
Types of Equilibrium

There are mainly three types of equilibrium:
How all these rules come into our understanding of aerodynamics is pretty fascinating if you ask me. Sometimes it's too easy to get enamored with the forms and forget the forces.

Newton's laws of motion
https://www.grc.nasa.gov/www/k-12/airplane/newton.html
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Old 12-20-2018, 05:32 PM   #46 (permalink)
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Frank Lee is going to love those 4500+k pics... if he's still on dial-up.
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Old 01-11-2019, 03:37 PM   #47 (permalink)
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Not exactly the same but on topic of nature's template displayed, I noticed these patterns in the mud spray on my work truck. This is never driven above about 35 mph but look at those pretty little templates trailing the rivet heads. Also the trailing part of the feul door and the separation on the too radiused curve on the back. Part of this must be the effect of the rivets cleaning the heavy dirt out of the air but I thought it looked cool and reminded me of the teardrop template.
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Old 01-11-2019, 06:59 PM   #48 (permalink)
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Also thinking about the above pic, you can't see but the whole back is very dirty from road spray swirling around behind the square back except on that corner radius. Why is there a clean "pocket" over those edges?
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Old 01-11-2019, 07:55 PM   #49 (permalink)
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Also thinking about the above pic, you can't see but the whole back is very dirty from road spray swirling around behind the square back except on that corner radius. Why is there a clean "pocket" over those edges?
That's probably an area where the flow has separated but before wake eddies have formed, so no dirt is deposited on the body as air moves past and none is carried back there by recirculation.
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Old 02-03-2019, 10:12 AM   #50 (permalink)
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