Quote:
Originally Posted by winkosmosis
I've heard that the trucks with the engine in the long nose are more aerodynamic, and I assumed that's why... because it forms a step for the air, roughly approximating a more aerodynamic shape.
Similarly, you'd expect a teardrop made from Lego blocks to be more aerodynamic than a box made of Lego blocks, even though both present the same surface area perpendicular to flow.
|
Uh-Uh.
It's literally better for the air to form it's own bubble in front of the flat nose of the CoE truck, because there is more skin friction and shape induced drag for the same surface area on the extended nose trucks.
When the airflow "hits" the cab nose at highway speed, there becomes a bubble effect on the CoE trucks that displaces air further ahead of the cab due to air spoiling at the nose, creating it's own "teardrop-ish" shape.
The extended nose design could have something in it's favor if it were actually shaped to divert airflow from the smaller nose up over the cab and around the widest points without having to make contact with them, though.
Watching the teardrop shape, we understand that nose extensions are only necessary to an extent ahead of the primary body, and the angles at which they direct flow can be very steep compared to tail angles.
I'm trying to find a virtual image of the bubble that forms in front of a CoE in a wind tunnel, but I'm not having any luck.
Also, I found this post here:
Quote:
Originally Posted by aerohead
From NASA/Freightliner research,it has been determined that a conventional tractor has no inherent advantage over a COE tractor.Both can be effectively streamlined.Presently,the lowest drag rig is a COE design.
|