Flow Visualization: Aerodynamics of Truck vs. Nascar

[talleyho12]

why dont you use solid particles like glitter or something?

[yournamehere484]

I'm not the most versed in fluid mechanics, but I see a couple of issues. One is flow is not laminar as it approaches the vehicle, there is no streamline, and it looks like a burst point occurs prior to the vehicle. Second I doubt Reynold's number was matched, for a geometrically similar object you need to match the Reynolds number by manipulation of the fluid or the scale of the object. Thus even if the flow were to be initially laminar, you still don't have a very accurate visualization.

[anthonystuart69]

i believe it's called a stock car...amazing how many people think that "nascar" is a type of car

[ISCLChannel1011]

@anthonystuart69 i agree

[warbird133]

The water in your experiment was way too turbulent! Your die injected through the honeycomb dissipated much too quickly. This will not allow you to get good flow vis at any point in the channel. That's why you couldn't see good buildup and shedding of eddy structures and vortices downstream of the separation points. Plus, the car was too large for the channel and wall boundary layer effects also prevented good data. Good attempt though.

[greggybone]

should put an air brake on the back of truck as well if you're going to compare them at all

[michelmuffdiver]

Crazy eyes!!!!!!

[jimemarsden]

It seems as though there is a lot of drag around the back windshield of the nascar car...

[sjh7132]

It's not drag if that chunk of air just moves with the car. It didn't seem to be swirling all that fast.

[Fesar123]

well made experiment. Just one thing....U should use a darker color than red. Red shapes with white background isn't a good choice for human eyes. Blue or black are better colors, they can give more details of the flow...but anyway. Awesome video. 10/10* =)

[Sybbus]

What I love about this experiment that even though it's a very crude example of flow property testing, you can still see the bare basics of each shape. Did anyone see the fluid twisting as it went over the trailing edge of the cabin on the ute and over the tray? Brilliant!

[carpentermatt78]

very entertaining

[jgregorio62]

Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object.

What you show in the video is fluid dynamics.

[DeBroeze]

Not quite true. Aerodynamics is a part of fluid dynamic sciences. Aerodynamics also concerns flows over e.g. airfoils, not only cars. This video is meant as aerodynamics, however its not quite correct, since the flow is already turbulent before passing the car (as mentioned earlier). Still, this video can be regarded as 'aero dynamics', and thus (also) fluid dynamics

[fearsomepirate]

Air is a fluid. Aerodynamics is particularly concerned with the interaction of air with objects, such as cars and trucks. Since air at the velocities and conditions associated with cars is often turbulent and not moving fast enough for compressibility to matter, such a simple experiment can in fact reveal useful information as long as the Reynolds number is reasonable.

[bunchofdicks]

air is not a fluid, air is a mixture of gases

[fearsomepirate]

Both liquids and gases are fluids. Look at the definition of a fluid in any standard fluid mechanics textbook, like Kundu & Cohen.

[masteropie001]

That was shit.

[wololo10]

WHATS THE REYNOLDS?

[DeBroeze]

Reynolds is some guy who 'invented' a dimensionless number which says something about the type of flow. The Reynolds-number, defined as Re = (velocity * characteristic diameter) / viscosity, is above approx. 2400 turbulent for internal flows, whereas its turbulent for external flows when its approx. above 500000.

[ulkgb]

how you do it??... i wanna try!!!

[delavar2000]

i think this video says nothing.

the colored flow is turbulent before the Car.

[vinay1mfh]

? could you explain please

[CrazyVanders]

The flow is already turbulent before, so there is no laminar flow passing through the car. So you can not see what part of the car makes it turbulent

[fearsomepirate]

Transition to turbulence isn't the only relevant thing in aerodynamics. Boundary layer and wake profiles are quite important, and this experiment gives a reasonable visualization of the two.

[weallfollowmanutd]

Not much different to a truck then!

[bsara1729]

informative