Tailgating a lorry/semi (modelled in CFD)

[Sven7]

Originally Posted by sendler

That is 1.35 seconds of space. Now you are 60 meters behind the next DRIVER in front of you so there is your 2 seconds. But, these are advanced driving skills and may not be for everyone.

It's not the DRIVER you have to worry about... it's the steel rear bumper. They're not advanced driving skills either- they're hypermiling roulette. Sure, I've done it a few times but you just never know what's going to happen so I now always slow back to a safe distance. You'd be surprised how fast a truck can come up on you when the driver slams on the brakes. Ride your bicycle as fast as possible toward a brick wall and grab the brakes from 10 ft. away. Plenty of room, right?

[sendler]

Originally Posted by Sven7

It's not the DRIVER you have to worry about... it's the steel rear bumper. They're not advanced driving skills either- they're hypermiling roulette. Sure, I've done it a few times but you just never know what's going to happen so I now always slow back to a safe distance. You'd be surprised how fast a truck can come up on you when the driver slams on the brakes. Ride your bicycle as fast as possible toward a brick wall and grab the brakes from 10 ft. away. Plenty of room, right?

10ft? non moving brick wall? sorry. this make no sense. we seem to have hit a nerve here. rational discussion is out the window. if you don't want to draft, don't do it.

[ProDarwin]

Originally Posted by Old Mechanic

You can forget 2 seconds here. 2 seconds will get you passed on the right by another car in the gap you leave, even on the approach lanes at intersections.

Pretty much how it is here too. On 95/66 if traffic is flowing and you drop more than 1 second back, another car fills the gap. Drop back more, another car fills it.

[Sven7]

Originally Posted by sendler

10ft? non moving brick wall? sorry. this make no sense. we seem to have hit a nerve here. rational discussion is out the window. if you don't want to draft, don't do it.

You're both going 60mph, he hits his brakes and slows to 40mph before you slow and hit him at 50mph. It's the same as driving into a wall at 10mph. You don't have the time/space to slow down sufficiently.

[Cd]

Originally Posted by Sven7

You're both going 60mph, he hits his brakes and slows to 40mph before you slow and hit him at 50mph. It's the same as driving into a wall at 10mph. You don't have the time/space to slow down sufficiently.

SolidWorks can render animations, but an animation is typically 30 frames per second.

If a single frame takes two hours to render, you can see how long it would take to render a single second ( In this case, 60 hours per second )

You usually want at least 5 seconds of animation to see what's going on with the airflow.
So right there, we are talking 300 hrs or around two and a half weeks straight.

You can buy time on an online renderfarm and it will speed your renders up from weeks to a single day.

It's especially nerve racking when you have rendered nearly all of the animation and you get a crash at that last second - or that last frame !

[Old Mechanic]

Originally Posted by Sven7

You're both going 60mph, he hits his brakes and slows to 40mph before you slow and hit him at 50mph. It's the same as driving into a wall at 10mph. You don't have the time/space to slow down sufficiently.

This an example or arguing for the sake of argument, which can destroy a forum when it goes unchecked.

When I am in heavy traffic I focus on the distance between vehicles. I don't sti there like a zombie waiting for a brake light. Separation is the key. Maybe you live where traffic is not an issue, but some of us deal with traffic where 3car lengths is the AVERAGE separation of a block of traffic many miles long.

Following your advice for 2 or 3 seconds of separation would create a crawling traffic jam 50 MILES LONG.

It ain't going to happen, no matter how many times you demand some unrealistic change in behaviour. You may be amazed at how well it flows and how few accidents there are. Maybe YOU need to hone your driving skills instead of attacking Sendler for being realistic.

Anyway, if you seriously want to experience what people here face with 45,000 cars crossing the same spot in a road in 86,400 seconds AS A DAILY AVERAGE, then look at the link.

if you veer from the norm, you are punished with tailgaters 6 FEET behind you at 60 MPH and people who will practically take off your parking lights cutting you off.

Traffic Cameras | HamptonRoads.com | PilotOnline.com

In particular look at the bridge tunnel itself.

Then post me more ludicrous advice.

regards
Mech

[sendler]

True. We can send the safety of following distances to the new thread here to get the aerodynamic modeling thread back on topic.
.
Following
.
Copy and paste of the debate leading up to this would be cool.

Originally Posted by Old Mechanic

This an example or arguing for the sake of argument, which can destroy a forum when it goes unchecked.

When I am in heavy traffic I focus on the distance between vehicles. I don't sti there like a zombie waiting for a brake light. Separation is the key. Maybe you live where traffic is not an issue, but some of us deal with traffic where 3car lengths is the AVERAGE separation of a block of traffic many miles long.

Following your advice for 2 or 3 seconds of separation would create a crawling traffic jam 50 MILES LONG.

It ain't going to happen, no matter how many times you demand some unrealistic change in behaviour. You may be amazed at how well it flows and how few accidents there are. Maybe YOU need to hone your driving skills instead of attacking Sendler for being realistic.

Anyway, if you seriously want to experience what people here face with 45,000 cars crossing the same spot in a road in 86,400 seconds AS A DAILY AVERAGE, then look at the link.

if you veer from the norm, you are punished with tailgaters 6 FEET behind you at 60 MPH and people who will practically take off your parking lights cutting you off.

Traffic Cameras | HamptonRoads.com | PilotOnline.com

In particular look at the bridge tunnel itself.

Then post me more ludicrous advice.

regards
Mech

[sendler]

Interesting rendering of air over a motorcycle. Mainly focusing on turbulence? rather than pressure gradients. If it is showing us anything meaningful at all. It looks cool.