It’s even possible that the boat adds basically no additional drag, and it’s even remotely possible that it decreases drag. Mythbusters proved that a flatbed pickup truck actually gets worse mileage when driving with the rear door down instead of up, even though it seems like driving with it up would create a big wall that would constantly smash into the air.
Aerodynamics isn’t nearly as intuitive as people assume.
There’s like a 90% chance you’re right, but aerodynamics gets especially messy with stuff like this that has a more or less flat wall at the back. A significant portion of the drag comes from the turbulence behind the vehicle, rather than cutting (more “plowing” in this case) through the air in front. When you change the geometry of the back, you change that drag.
So, if I were to bet, I would bet that turning the boat around would help. But I wouldn’t bet my life on it. Some wacky interaction with the geometry of the rear could somehow cause it to get worse.
Depending on how heavy simulations you want, it’s surprising how light hardware you can get away with in OpenFOAM. I used it for some university courses on a 2012 MacBook Pro (dual booted with Ubuntu) around 2021, and I could run 2D, two-phase simulations just fine.
Of course, if you want to run 3D stuff with large shear forces or turbulence and high time resolution you’re gonna have to grab a veeeery big coffee while you wait. However, the ability to stop and restart the simulation is really nice, and lets you see what’s been simulated so far.
I’m not so sure it is. If the leading surface was completely bluff, the length of roof were shorter than the protruding boat and it was moving very fast then yeah, maybe.
In reality, the nose of the RV plus the length of roof surface along with non-Mach speeds will virtually guarantee the bulk of the airflow will remain coupled to that roof until a radical change in geometry such as the boat.
It’s even possible that the boat adds basically no additional drag, and it’s even remotely possible that it decreases drag. Mythbusters proved that a flatbed pickup truck actually gets worse mileage when driving with the rear door down instead of up, even though it seems like driving with it up would create a big wall that would constantly smash into the air.
Aerodynamics isn’t nearly as intuitive as people assume.
Okay but there’s no way the flow separates from that roof enough to clear the boat
I would guess the same, but for a wacky shape like that rv it’s pretty hard to say
Okay but if they would just at the very least, turn that boat around 180°, I’m pretty sure the aerodynamics would improve.
There’s like a 90% chance you’re right, but aerodynamics gets especially messy with stuff like this that has a more or less flat wall at the back. A significant portion of the drag comes from the turbulence behind the vehicle, rather than cutting (more “plowing” in this case) through the air in front. When you change the geometry of the back, you change that drag.
So, if I were to bet, I would bet that turning the boat around would help. But I wouldn’t bet my life on it. Some wacky interaction with the geometry of the rear could somehow cause it to get worse.
You’re going to make me learn OpenFOAM aren’t you
Do it! It’s great fun to play around with!
Ive worked with Ansys Fluent in university but really fucking love CFD and could probably use the practice regardless.
Ah…right…old laptop and AI-driven component shortages… Someday I’ll have a shitload of compute, just you all wait!
Depending on how heavy simulations you want, it’s surprising how light hardware you can get away with in OpenFOAM. I used it for some university courses on a 2012 MacBook Pro (dual booted with Ubuntu) around 2021, and I could run 2D, two-phase simulations just fine.
Of course, if you want to run 3D stuff with large shear forces or turbulence and high time resolution you’re gonna have to grab a veeeery big coffee while you wait. However, the ability to stop and restart the simulation is really nice, and lets you see what’s been simulated so far.
I’m not so sure it is. If the leading surface was completely bluff, the length of roof were shorter than the protruding boat and it was moving very fast then yeah, maybe.
In reality, the nose of the RV plus the length of roof surface along with non-Mach speeds will virtually guarantee the bulk of the airflow will remain coupled to that roof until a radical change in geometry such as the boat.
I loved Mythbusters. It was a much happier time. Evil was not quite out in the open as it is today.
I watched that episode and they didn’t prove shit. Those tests were terrible. That shit was about as scientific as The Big Bang Theory.
It was 100% correct.
Here’s the white paper using CFD. big words.
Relevant XKCD