An Insect Story

Watch a fly, fly. They can't go that fast. Maybe it gets pushed back in by the wind.

Just keep your eyes on the road.

lynlynch:

You state "They can't go that fast".

That's a relative term:

Houseflies travel @ 4 - 10 MPH

Horseflies travel @ 12 - 15 MPH

Dragonflies travel @ 30 - 40 MPH

I couldn't even keep up a housefly's pace for very long...

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Just my $0.02...

When the car moves, the skin of air on its body moves at its speed and the next skin at a lower speed and so on. It is like a fluid flow through the tube (parabilic curve if I remember ?). That's why you get the whoosh of the air when a speeding car passes by.

The fly most often than not, does not cross the inner skin, before it changes it's mind (may be attracted by the need of the meat flesh ?) and tries for another try.

But if rebuffed with fury, may be it will escape with a velocity that will stop it on way side its path, and will try other avenue.

that explains why after a trip to the local rubbish dump, all of the flies I shoo out the window come back. Some even return back into the car from another window

...or maybe I just plain stink

Craziest,

The origin of the Aussie salute.

Jon

This is what I feel:

Fly is like an aircraft. The air craft needs specific speed with respect to the surrounding air. (Remember clogged Pitot tube of Air France plane, which crashed)

When fly is in the car, it flies at a speed with respect to the blocked air in the car, which is moving with the car, at the speed of car.

But when it just goes out of the car, its speed will be with respect to the air outside. At the instance of going out, air velocity outside the car is in reverse direction and of about car speed.

Thus, besides getting pushed back, it starts flying in the air outside and we see it if going back. (In fact we move forward)

Yes but is it like inside the aircraft, going at whatever speed, would it explode because it hit the air to fast. I guess because it couldn't depressurize. Like coming up from the bottom of the water or going down from the air you would have to do it slowly whereas you got throwed out instantly in a wind current.

Meat,

"would it explode because it hit the air to fast?"

Hopefully!

Jon

My stab at your first question: Assume that you had all the windows up when you noticed the fly but as #1 said you are also somehow watching the road. Assume you didn't shoo it out until you (let's make another assumption) lowered the passenger side window using your left hand on the window button while holding your shooing hand on the steering wheel. Assume you were not going fast enough for the fly to get sucked out by a venturi effect. Assume that by the time you put your left hand on the wheel to free up your shooing hand the fly was still not gone. At this point you did the shooing thing (If it was gone why would you ?). Assume you were not going fast enough for a strong inward swirling vortex form. Then the fly might very well have flown off. Possibly into the oncoming velocity stream since we still don't know how fast you were going. Ans to Q 2: I wasn't there. I didn't notice. Maybe.

Hello ML,

Hope you are well?

As I think it was 'Lynlynch' says, it may get 'pushed back into the car by the air pressure surrounding the car when it is at speed. But, if it goes just a tiny bit further, the fly may also get sucked out.

When the care windows are down, have you ever noticed when a fly comes in the front window, only to be sucked out of the back one? With the windows down, this may also create turbulence which the smaller lighter flies cannot overcome?

Interesting question this!

Hello ML,

Hope you are well?

As I think it was 'Lynlynch' says, it may get 'pushed back into the car by the air pressure surrounding the car when it is at speed. But, if it goes just a tiny bit further, the fly may also get sucked out.

When the care windows are down, have you ever noticed when a fly comes in the front window, only to be sucked out of the back one? With the windows down, this may also create turbulence which the smaller lighter flies cannot overcome?

In answer to your question "does the fly fly away or does the wind get it"

I think that would depend on the size of the fly. It maybe that smaller flies may succumb and be 'mangled', while the much larger 'horse fly' might overcome the battering and survive. Of course whether it survives leaving your car only to hit the screen of the car behind will never be known?

I think the faster and so stronger dragon-flies may be able to survive the turbulence pretty well, but, after all that waffle, I am going to do some research!

Hello BB

Long time, we met on some discussions. How are you?

Now, regarding your views:

You say, when windows are down fly comes in the front window. I observe in my car that even if the windows are closed, fly comes on front window (and troubles me).

Of course whether it survives leaving your car only to hit the screen of the car behind will never be known?

I think it survives. The air around the car takes its own path and fly being very light should fly in that air stream, without hitting the car behind.

Hello my friend gsuhas,

How are you?

I am OK mostly!

Thank you for your post.

I understand about the air flows around a vehicle, so does that mean that that flies 'squashed' on a windscreen mostly come from the side, across the screen? Or are perhaps some of the flies who have 'changed their mind' on what direction to take, and as they adjusted their direction they got squashed?

What do you think happens when a fly tries to go out of the open window of a fast moving car? Will it get sucked out or get blown back in? I tend to think there is enough turbulence around the open window that it could get sucked out. But for the same reason is just as likely to get pulled back in?!

that mean that that flies 'squashed' on a windscreen mostly come from the side

Firstly, I have never seen any fly 'squashed' on windscreen of my car. I am sure I am not always on front and all cars are behind me. I am behind some car many times. I have never obseved any dead body of a fly in the garbage which gets collected just below the front wind screen, over the time.

Regarding sucking or getting blown out, when some high velocity of flowing fluid (air) is there on a surface, air from inside will get sucked. But, if it is absolutely true, the whole air from the car inside should get sucked out. This never happens. Means, at some place air is getting sucked out because of high velocity flow outside the open window. But at some other point air must be getting sucked inside the car, because of little vacuume being created. The motion of fly across the window will depend up on in which of the two zone as above it is.

Take care

(and not get disturbed while driving... when some fly troubles you on front wind screen)

I regularly go on a round trip of 900 Km (560 Miles), plus or minus 80Km (50 Miles) and have to stop halfway to clean the dead flies off my screen. Perhaps the flies where you are have more sense? But this has always happened when I drive, but especially in the summer.

From a mundane question this is pretty interesting is it not gsuhas?

Take care my friend.............

Surely BB my friend

I also drive quite extensively. I drove 40000 kms in last year and half. Many of these drives were through good jungles. But no dead flies here in India. Very interesting. A good research subject for insect researchers.

I have a sport pickup truck. In the early '90's, it was considered by some to be fuel efficient to replace the tailgate with a net/open-fence structure. Less turbulence was the thinking. An article in Sport Truck described that scenario in a wind tunnel versus 3 other scenarios: solid tailgate up with bed open, solid tailgate up with bed covered at top rails, and solid tailgate up with rearmost half of bed covered at top rails. The most aerodynamic was the last. The worst was no tailgate.

Hi Westseed1,

Well that is a surprise. I would have thought the fully covered bed would have been the most efficient. Take care.

Wind tunnels are as empirical as you can get.

Ok, so in addition to input from my wind tunnel friends, I did my own test.

Driving my pickup down the highway at 100 kph

with loose leaves in the front of the bed and serious bulk material in the back.

Those leaves tumbled a lot but they never took a run out of the bed !

Hi Westseed1,

I like your idea on using the leaves in the back of your truck! It just takes that extra bit of ingenuity to make the difference between a success and perhaps failure?

Well done you!

That is how it is with my Crossfire with the top down. hardly any turbulance even at insect killing speeds.

Jon

Nice looker that Crossfire.

Educate us auto nut bars as to how the name might relate to the

engine.

Weatseed1,

The name Crossfire comes as a reference to the distinctive character lines that run from front to rear through the body sides. They create a surface that is upward facing as it passes over the rear fender, but they cross mid-way through the door to form a downward facing surface as they reach the front fender. Also, since it shares elements from Chrysler and Daimler-Benz, the name is a reference to their collaboration.

The standard transmission is a 6-speed manual, and a 5-speed automatic is optional. Base Crossfires, originally sold beginning in the 2004 model year, are equipped with a 3.2 L, 18-valve, SOHC V6 engine which produces 215 hp and 229 ft·lb of torque.
The Mercedes SLK was the platform from which the Crossfire is built. Since the 2005 model year, the SLK has been built on a platform with SLR-style looks. The Crossfire remains the only car based on the older chassis.
The last model year built was 2008. I got one of those.

SOHC, 18 valves = cam has 18 lobes !! Where did Daimler-Chrysler find the room to put the cam shaft bearings. I need to do some homework. This is serious.

Westseed1,

Mercedes engine thats been around for a while.

Jon

Hello sail4evr,

GA to you Sir, for a good explanation. Really interesting subject actually.

Sounds plausible, except...

...except that the fly's preference (if we may call it that) always seems to be to remain inside (to not even cross or allow itself to be forced into approaching the window opening of) the vehicle cabin...and this in spite of velocity of vehicle (and slipstream past window). This seems to suggest:

1. A preference for the typically-cooler temp inside the cabin?
2. An attempt to evade the swatter, but without "awareness" (i.e., without sensing) that the non-open/fixed glass(es) are anything other than open (that is to say, outdoor [out-of-cabin]) space? (For a fly to flee [as opposed to diverting from path of] pursuer (pursuing hand/object) always runs the greater risk of being overtaken [and swallowed]).
3. An effect of having compound eyes...(see also 2., above).
4. 2., 3., and 4. . and 5.
5. And effect of there being no sky overhead (only a surrounding, horizontal circle of sky) within the confines of the vehicle cabin.

ZooloJest.

Meatlogger,

In the old days cars had wing windows that provided suction when you got up to speed. Dust, smoke, ashes, flies and whatever would be drawn out of the car. You could see it happen without turning your head too far from view of the road ahead.

You could flip it around to force air into the car too.

Now I open the window a little and crank up the blower for the positive pressure effect.

I noticed wasps cleaning the bugs out of the radiator and windshield (windscreen for my Brit cousins) so I didn't had such a tough cleaning job.

Jon