| Author |
Message |
DAVE E (Banzaiboxr)
New member
Username: Banzaiboxr
Post Number: 3
Registered: 8-2002
| | Posted on Friday, September 06, 2002 - 12:04 am: | |
Jim,
I will investigate the air flow phenomenon this
weekend on the 405 .Mabey i will see ya.
Dave |
Barry Wolinsky (308gtb)
Member
Username: 308gtb
Post Number: 268
Registered: 2-2002
| | Posted on Thursday, September 05, 2002 - 11:15 pm: | |
Jim,
Once we get a cool day here in New Jersey, I'll check out the "warm air along the fingers in the rain gutter phenomenon."
Barry |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 116
Registered: 6-2002
| | Posted on Thursday, September 05, 2002 - 9:52 pm: | |
Mark - good idea. Similar idea to "tell-tales" on sails. One "sheets" to get the tell-tales all lined up and steady, not with chaotic motion.
Jim S. |
Mark Foley (Sparky)
New member
Username: Sparky
Post Number: 12
Registered: 3-2002
| | Posted on Thursday, September 05, 2002 - 2:53 pm: | |
Back to the original hot air flow thread, it would be easy to visualize the airflow by taping ribbons of very thin paper on the hood and windshield (use blue masking tape so there will not be any adhesive damage). This way you could "see" the airflow.
|
Hans E. Hansen (4re_gt4)
Junior Member
Username: 4re_gt4
Post Number: 152
Registered: 4-2002
| | Posted on Thursday, September 05, 2002 - 12:02 am: | |
Lawrence: Yeah, Yeah, Yeah.!! Few understand this. HP=vel^3. If it takes 80 hp to go 100, it will take 80*8 (that's the change in vel cubed) to go 200 mph. Or 640 hp. Enzo *only* goes 217mph (or so I've heard), but each additional mph at these speeds takes mega hp. |
Lawrence Coppari (Lawrence)
Junior Member
Username: Lawrence
Post Number: 238
Registered: 4-2002
| | Posted on Wednesday, September 04, 2002 - 5:02 pm: | |
Want fast, check out a submarine when it is submerged. None of us knows because it is classified. Above water, it has a big wake. Below, it doesn't.
Much of it has to do with the fact that carriers and subs have nuclear reactors as the power source. They are fast but they have a huge amount of power.
Don't forget, if you want to go twice as fast, you need eight times the power. |
Hans E. Hansen (4re_gt4)
Junior Member
Username: 4re_gt4
Post Number: 151
Registered: 4-2002
| | Posted on Wednesday, September 04, 2002 - 4:36 pm: | |
James: A boat guy who did time in the Navy mentioned that aircraft carriers are amazingly fast, especially for their size. Gave the reason you mentioned: big length/width ratio. |
Lawrence Coppari (Lawrence)
Junior Member
Username: Lawrence
Post Number: 237
Registered: 4-2002
| | Posted on Wednesday, September 04, 2002 - 2:14 pm: | |
Drafting race cars go faster because you have twice the horsepower but less than twice the wake. Any air disturbance (wake) is a waste of energy that is manifested by a reduction in top speed. |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 112
Registered: 6-2002
| | Posted on Wednesday, September 04, 2002 - 12:51 pm: | |
Hans - the needle is the most streamlined shape - it has a high "aspect" ratio. Sailboats try to accomplish the same thing by increasing length while reducing beam. The compromise is stability and wetted surface area. Another interesting example is when two race cars draft. The leading car increases speed!!! This occurs as a result of the effective increase in aspect ratio - the low pressure area behind the lead car is diminished by the presence of the drafting car. Notice the shape of the Bonneville Salt Flats speed record cars. They are long and narrow. So much for the tear drop.
Jim S. |
Hans E. Hansen (4re_gt4)
Junior Member
Username: 4re_gt4
Post Number: 144
Registered: 4-2002
| | Posted on Wednesday, September 04, 2002 - 12:34 am: | |
Hah! Ammunition for arguments with my father who thinks the teardrop reigns supreme. |
Barry Wolinsky (308gtb)
Member
Username: 308gtb
Post Number: 254
Registered: 2-2002
| | Posted on Tuesday, September 03, 2002 - 9:24 pm: | |
Jim,
I appreciate your detailed discussion. As you know, vertical laminar flow ventilation systems are installed in modern operating rooms to help achieve sterile airflow at the table.
Barry |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 109
Registered: 6-2002
| | Posted on Tuesday, September 03, 2002 - 9:00 pm: | |
Barry - you are correct that the flow over the hood of the car and along the rain gutter is laminar. This would be visualized by the classic smoke trails used in wind tunnels as parallel lines. Laminar flow is defined as the smooth, uninterrupted flow of air over the contour of the wings, fuselage, or other parts of an object moving through air. If the smooth flow of air is interrupted over a wing section, turbulence is created which results in a loss of lift and a high degree of drag.
That we can feel a high concentration of heat implies laminar flow, for if turbulence were present, the hot air would be mixed with ambient air and we would not perceive a concentrated "river" of hot air along the rain gutter.
Laminar flow reduces drag. But at a cost. Behind a streamlined object is a low pressure area. If the object is too streamlined, then a low pressure area will form behind the object with consequent reduction in velocity. This is the principle used when "dimples" are added to the surface of golf balls. A smooth golf ball would create less turbulence, but lower pressure behind it. The dimples lead to surface turbulence and a "breakup" of the low pressure area behind the ball.
By the way, the tear drop (raindrop) is not the most efficient (streamlined) shape. A drop of water is most energy efficient when spherical. Surface tension, pulling symmetrically, would create a sphere. Air flow across the falling droplet would stretch it to look like a needle (high aspect ratio - length to width - the most streamlined shape). The tear drop is a stalemate, the balance between wind shear on the surface and surface tension.
Please forgive my rambling.
Jim S. |
Barry Wolinsky (308gtb)
Member
Username: 308gtb
Post Number: 251
Registered: 2-2002
| | Posted on Tuesday, September 03, 2002 - 7:40 pm: | |
I think the technical term for this type of airflow is "laminar flow."
Barry |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3108
Registered: 2-2001
| | Posted on Tuesday, September 03, 2002 - 7:31 pm: | |
Thanks James, |
Hans E. Hansen (4re_gt4)
Junior Member
Username: 4re_gt4
Post Number: 140
Registered: 4-2002
| | Posted on Tuesday, September 03, 2002 - 1:05 am: | |
My 'GT4 has exactly the same hot airflow characteristics. It's kinda fun to try to trace the precise hot airflow by moving my hand all over the windshield and roof area. |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 106
Registered: 6-2002
| | Posted on Monday, September 02, 2002 - 11:02 pm: | |
Magoo, you are right. In the scheme of things, noticing a lot of hot air is relatively low on everyone's interest meter. That the hot air comes from this observer is even less important. No offense taken, in fact, I appreciate your comments on all threads. Keep them coming.
Jim S. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3105
Registered: 2-2001
| | Posted on Monday, September 02, 2002 - 10:16 pm: | |
James, You and me both. Sorry for the doubting Thomas comment. |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 105
Registered: 6-2002
| | Posted on Monday, September 02, 2002 - 3:21 pm: | |
Thanks - I knew it was the normal radiator flow getting caught in the streamlining of air over the car, but I never would have guessed that this many F-drivers would have noticed. Hard to one-up you guys. Quite an experienced gathering on this FerrariChat.
Jim S. |
David Feinberg (Fastradio2)
Junior Member
Username: Fastradio2
Post Number: 147
Registered: 4-2002
| | Posted on Monday, September 02, 2002 - 2:59 pm: | |
Jim...
My BB has the same hot air characteristics, as the radiator air output is on the front bonnet. It makes for more enjoyable Fall and early Winter driving with the windows down...
David
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Lawrence Coppari (Lawrence)
Junior Member
Username: Lawrence
Post Number: 232
Registered: 4-2002
| | Posted on Monday, September 02, 2002 - 2:15 pm: | |
My 328 does it. Hot air comes through the slots and over the hood and up the windshield. As my car is open, you can feel it if you put your hand out the top just above the windshield.
Hot air has to exit somewhere. If you look into the loovers, you can see the back of the radiator. When the car is sitting still and the fans come on you can also feel it but not as much because it comes out and is directed upward. It does not get caught up in the airflow over the front of the car.
You are just feeling what you are paying for and not getting - energy loss. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3100
Registered: 2-2001
| | Posted on Monday, September 02, 2002 - 1:42 pm: | |
Man, Now that's a good one. I'm just thankful mine is running ok. Nothing malicious intended here but.....Whatever. |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 104
Registered: 6-2002
| | Posted on Monday, September 02, 2002 - 11:49 am: | |
I noticed a very interesting phenomenon. While driving the Boxer, I rested my hand on the open window and placed my fingers on the rain gutter above the window. I felt very warm air running under my fingers across the palm of my hand. If I moved my hand slightly away from the car, I did not feel the hot air. As I moved my hand forward and aft, I could trace the hot air flowing from the front of the windshield, along the rain gutter, towards the aft end of the car. I suspect (and seek other's opinion) that the radiator air flow spreads across the front of the car, and then "migrates" towards the sides as it flows over the car. I am likely feeling radiator air flow channeled along the rain gutter.
I am interested to see if anyone else feels this hot air flow. I suspect that the boxer is the only car with radiator air flow exiting above the front hood.
Jim S. |