A fundamental principle of aeronautical engineering has been overturned
121–130 of 143 posts
Re: A fundamental principle of aeronautical engineering has been overturned
#122Re: A fundamental principle of aeronautical engineering has been overturned
#123[deleted]
Re: A fundamental principle of aeronautical engineering has been overturned
#124Any competitive sailor or foil-racer knows that the underwater surface has the least friction and best laminar flow when sanded with fine-grid sandpaper, around 1000 to 1500 grid. It always surprised me that this was not true in air and airplane wings were supposedly best when glossy. So now it turns out that this is indeed not true, and airfoils also benefit from micro-roughness for lowest friction. Now the surprisi…
> It always surprised me that this was not true in air and airplane wings were supposedly best when glossy.
I was an AE major and I don’t recall ever learning that airplane wings were best when perfectly smooth, even as a simplification in undergraduate courses. We were taught that drag is reduced by maintaining an attached laminar flow.
Airplane wings are glossy because they’re metal (or CFRP) and painted for durability and corrosion and UV resistance.
Re: A fundamental principle of aeronautical engineering has been overturned
#125Earlier quoted context omitted.
Water is fairly viscous, and when you try to pull through too fast you completely change regime due to cavitation. In comparison, from my days studying aerodynamics for RC soaring, air has a wider range of "viscosities" (represented by the Reynolds number) depending on the scale of your aeroplane and the speeds you intend to go through the atmosphere. The aerodynamic ideal or what count as useful tricks (winglets, di…
Asking as a complete neophyte - how does this reconcile with modern war planes being inherently unstable as far they flight dynamics go, without their enormous thrust capabilities? I’m just curious, I know nothing about the subject, but it seems that the solution we came up with is thrust, baby.
Unstable fighters gives them much more maneuverability at the cost of “not returning to straight and level flight” that normal planes have.
It’s not directly related to how the wind goes over the wings.
Re: A fundamental principle of aeronautical engineering has been overturned
#126Earlier quoted context omitted.
At least a decade. I remember people could smoke on planes. On some airlines seat backs and bathrooms had cigarette ashtrays in them. Smoking was phased out between 1988 and 2000, with most airlines being smoke free in the mid-1990s. But the ashtrays persisted well into the 2000s. Two reasons: they needed to refresh the cabins, which is on a longer maintenance cycle done every few years, and before that, they needed…
> For ashtrays being removed . I don't think it's safe to generalize from this to a functional aspect of the plane. Removing the ashtrays serves no purpose, so there's no cost to letting it wait for a decade or two. Improving the aerodynamics does serve a purpose and might be done faster.
At least one total loss was caused by a waste fire in the lavatory from a cigarette-the ashtrays are mandatory safety equipment and the FAA won’t let you fly without them operable.
Re: A fundamental principle of aeronautical engineering has been overturned
#127Earlier quoted context omitted.
Water is fairly viscous, and when you try to pull through too fast you completely change regime due to cavitation. In comparison, from my days studying aerodynamics for RC soaring, air has a wider range of "viscosities" (represented by the Reynolds number) depending on the scale of your aeroplane and the speeds you intend to go through the atmosphere. The aerodynamic ideal or what count as useful tricks (winglets, di…
Asking as a complete neophyte - how does this reconcile with modern war planes being inherently unstable as far they flight dynamics go, without their enormous thrust capabilities? I’m just curious, I know nothing about the subject, but it seems that the solution we came up with is thrust, baby.
A key difference is that war planes occasionally want to be able to rapidly change their trajectories.
With sufficient thrust you can fly around in a cube.
Re: A fundamental principle of aeronautical engineering has been overturned
#128Earlier quoted context omitted.
Asking as a complete neophyte - how does this reconcile with modern war planes being inherently unstable as far they flight dynamics go, without their enormous thrust capabilities? I’m just curious, I know nothing about the subject, but it seems that the solution we came up with is thrust, baby.
A key difference is that war planes occasionally want to be able to rapidly change their trajectories. With sufficient thrust you can fly around in a cube.
Would you a have a link that would show case something like that? It feels like only a T-1000 would be able to make any rapid coherent decisions under such load. Thank you.
Re: A fundamental principle of aeronautical engineering has been overturned
#129Earlier quoted context omitted.
The core tenant of the paper is that roughness reduces drag IN the transition zone. A very small region of the total flow. Thats the region between laminar and turbulent flow. Laminar flow is typically 5x less drag than turbulent, and will be encountered about a Reynolds number of 500K-1M (ratio of inertial flow to viscous flow). Surfboards will have a Reynolds number of 10^7 which is entirely turbulent. A Cessna air…
> Surfboards will have a Reynolds number of 10^7 which is entirely turbulent. A fin, foil or daggerboard below the board/boat is operating well within the range of Reynolds' numbers where laminar flow is relevant.
The vertical stabilizing surface of these elements is really insignificant to the entire surface of a board. Combining drag coefficients is done with the wetted surface area.
In truth there's some contamination from the upstream flow. Stabilizing elements are behind the center of pressure, so they will see the most "diry flow"
Re: A fundamental principle of aeronautical engineering has been overturned
#130It's almost certainly my adblocker playing poorly with their "subscribe to read" stuff, but I had to lol at the failure mode. When I load the page, I get the splash image/headline, and below it: > Subscribe to listen [9 minutes] > Aerodynamic drag is a major “barrier” in high-speed airplanes, automobiles, and bullet trains. This is because a design with less aerodynamic drag allows the aircraft to move at higher spee…
I got "you've read your last free article", and I thought "No I haven't, there's no article for me to even read". Then I closed the tab.