Explain this
I have a '11 GMC Sierra 2500 gas. I traded a '09 KZ Spree 261RKS loaded weighed in at 5500 lbs. If I held my speed at 60 I could keep my mileage at 9mpg. Anything over 60 and I would drop to mid 8'...
Forum Discussion
Need-A-Vacation,
Yes, what you experienced is factual. As an engineer, frontal aerodynamics is very important as the wind/air resistance and smooth air flow lowers the energy required which increases dramatically as the vehicle/structure's velocity (speed) increases. Actually squares itself! However, that's only part of the equation affecting air/wind energy requirement.
The next highest energy required factor regarding air flow is the suction created at the rear of the vehicle/structure as the parted air displaced by the structure has to refill the space again right behind the moving structure and fill the vacuum that was created by the movement.
This created vacuum sucks backward hard on the moving structure like what occurs in an airplane wing which is sucked up off the ground by the low pressure (vacuum) from the parted air going over the wing shape which pulls the wing upward when trying to refill the vacuum that was created on the top surface of the wing.
The shape and size of the flat rear surface and rounding of the corners on all 4 sides at the rear will make a big difference VS square corners which gives a larger surface in this sucking backward scenario. Rounded corners not only lower the flat surface size but create an easier, faster, and smoother flow for the air to refill the vacuum which lowers the suction forces considerably. Thus, less energy required and less fuel needed. The side and top corners have more to gain than the bottom because air flow is more limited due to it's close distance to the ground surface so it offers the lesser bang for the energy buck but still adds to overall efficiency. Wind tunnel tests have documented the differences over and over for so many decades.
Yes, what you experienced is factual. As an engineer, frontal aerodynamics is very important as the wind/air resistance and smooth air flow lowers the energy required which increases dramatically as the vehicle/structure's velocity (speed) increases. Actually squares itself! However, that's only part of the equation affecting air/wind energy requirement.
The next highest energy required factor regarding air flow is the suction created at the rear of the vehicle/structure as the parted air displaced by the structure has to refill the space again right behind the moving structure and fill the vacuum that was created by the movement.
This created vacuum sucks backward hard on the moving structure like what occurs in an airplane wing which is sucked up off the ground by the low pressure (vacuum) from the parted air going over the wing shape which pulls the wing upward when trying to refill the vacuum that was created on the top surface of the wing.
The shape and size of the flat rear surface and rounding of the corners on all 4 sides at the rear will make a big difference VS square corners which gives a larger surface in this sucking backward scenario. Rounded corners not only lower the flat surface size but create an easier, faster, and smoother flow for the air to refill the vacuum which lowers the suction forces considerably. Thus, less energy required and less fuel needed. The side and top corners have more to gain than the bottom because air flow is more limited due to it's close distance to the ground surface so it offers the lesser bang for the energy buck but still adds to overall efficiency. Wind tunnel tests have documented the differences over and over for so many decades.
