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Hello!
I'm coming from a background in electronics engineering so please bear with, I'm building a new 6m~ glider with goals of flying for multiple days, as part of this I'm attempting to wrap my head around aerofoil design and specifically how to chose a foil based off graphs simulated in Flow5 (I'm really just using it as an Xfloil wrapper).

I have settled on two semi custom foils that have the following graphs:

Cl/Cd vs alpha

Cm vs Alpha

Cl vs Xtr top

I'm trying to maximise Cl/Cd vs Alpha to give me the most efficient flight possible but I'm worried I'm sacrificing stability to do this, as you can see aerofoil A in green (its a customised GOE448) has better Cl/Cd but it also has far worse Cm / Alpha, I under stand that Cm is effectively a foils tendency to rotate around its roll axis at a given alpha, the question is.. how much is too much?
given its going to by flown by an autopilot can this just compensate for any amount? or do i still need to be mindful of how much its wanting to roll? if so how much?

another question is Cl vs Xtr top, as I under stand it, Xtr top is effectively where along a foil the flow separates and thus having a higher number is generally better, how do i go about comparing these foils given the results?

the foil shown in green also exabits jagged characteristics at low Reynolds , is this catastrophically bad?

Sorry, I appreciate this is a big question and the answer will almost certainly be "go away and leave this to the professionals" but as engineers you know how problem solving is fun, and this is fun for me :)

Note: the 3 lines are at 100k, 150k and 200k Re

https://preview.redd.it/qrmtk4wkqu3e1.png?width=684&format=png&auto=webp&s=9af7ca4ca1067bff6d53983f7a671fefa7c0904b

Hello folks, these are same length and pitch propellers, sold by RCTimer for RC multicopter . From my googling it says the left is for durability and strength while the right are for stability and smoother flights. Is it true? Another user told me the left has thrust all along the blade, but the right can generate more thrust on the tips and less at the hub. Does anyone know anything about the differences between these 2 designs? Thank you

(The following applies to aviation)

Hey guys. Please ignore the context. I will post it below, however, I'm trying to implement an equation that requires cl_0 (coef. lift subscript-0) and cl_1 (coef. lift subscript-1) in a game engine that doesn't seem to respect the fact that planes even need lift / a coefficient of lift.

Programming language used is called 'lua' but you can ignore it if it helps abstract the concept better ;)

The planes themselves have wings, and the wings measurements / dimensions, however, I'm having a hard time substituting what's needed to get the resultant lift-forces.

Currently, I'm using the thin airfoil theory as a CL approximation, but I feel accuracy wise, this is shooting myself in the foot because the aircraft in the game CAN in fact stall. I wanted a better model if I can find one. Anyways, here's the data I have to work with:

• Many different planes
• Different speeds
• Different stall angles
• Can calculate the angle of attack (difference in the direction the nose is pointing vs the direction of travel) - AKA arctan(w/u) ref
• various points of data on speed and acceleration
• Using sublogic to detect when the plane is in a stall (u is less than 0) or (u is greater than w)
• Can approximate the wing area
• maaaybe can approximate the chordline (but was thinking of referencing something like airfoiltools to get the general shape instead)

Anyways, my question is - what'd be the best way to determine the cl_0 and cl_1? If I need to plot these on a graph programmatically then I don't mind, but I just need some guidance and direction.
Any help is appreciated! Thanks! Regards, me

I'm absolutely frying my brain over this. I'm still in school but every time I try search something a million other random theories come up. I understand why lift works using the Coanda effect with N3L/Bernoulli but it's the effect itself that's frying my brain. I understand that there's a layer where the fluid velocity is practically zero due to the no-slip condition, and then a boundary layer between that and the fast flowing air. But what I'm reading is that this somehow forms a low pressure area which acts like a pull to keep the air flowing faster on top. But I thought it was the effect itself which generated low pressure as a byproduct of the air flowing faster. Isn't this a cyclical argument? I'm so confused. I would be so grateful if anyone could just put this in layman words.

Hi

So basically my question is, how is it that when friction is introduced into a sub-sonic flow in a pipe, we get the result that the flow is accelerated to sonic Mach number rather than decelerate? It feels soo counterintuitive

https://preview.redd.it/dz9hf97wx52e1.png?width=960&format=png&auto=webp&s=cac8f3184a434eb4c5a4e5df319d33061ceee30f

Im not sure if this is the right place to ask, but I have a engineering project and need to know the ideal angle i should launch a toy plane, to ensure maximum distance traveled. How tf do i calculate that?

I'm looking into designing a fixed wing trainer drone and have made my decision on the wing planform, surface area and aspect ratio (of 5). It's a rectangular planform and I require a max wing lift coefficient of 1.0 and a cruise wing lift coefficient of 0.38.

Now how do I go about choosing an airfoil based on the required lift coefficient? How do I calculate what my Cl for the airfoil should be so it can produce the required wing CL for flight? I've cross tested multiple formulae with data from XFLR5 airfoil and wing analysis and never got a satisfactory relationship (was using LLT and viscous mode at Re 200000).

Any tips? Also can I just use the data from my wing analysis? I get CL and CD of the wing at different AOA but I'm concerned about their accuracy. Thanks for your time.

Heyyy, I don't understand why characteristic mach number is not always 1, I mean its match number at sonic condition, that is when flow speed is equal to that of speed of sound in that point. Somebody please explain me where I am making a wrong interpretation.

Thanks very much for answering

Question about vortex’s, Venturi effect for performance car application.

When designing aero for ground effect, I was trying to understand why vortexes from splitters/fins cause air to stick to a surface better.

Is it due to the added angular momentum meaning for a given air volume it has more “energy” resisting the higher pressure air in the area around the car?

is it because with spinning air, a smaller percentage of the area touches the car meaning for a given volume so the force of the car “pulling” on the air is less than if air was traveling flat over the car?

Or does it have to do with the air speed being faster due to it covering more distance in the spiral and lowering the pressure?

Also could creating vortexes that flow right at the side skirts make it harder for air to rush into the lower pressure area under the car, improving downforce?

Hi everyone,

I’m currently working on designing a fixed-wing UAV and am in need of a detailed blueprint or design plan that matches (or is close to) the following dimensions:

• Wingspan: 109.6 cm
• Fuselage Length: 70 cm
• Other Dimensions: Currently unsure but open to suggestions based on typical proportional designs.

The UAV will primarily be used for competetions and I’d like a design that balances stability, efficiency, and ease of construction.

If anyone has open-source plans, personal designs they’d be willing to share, or can point me toward resources where I could find such blueprints, I’d greatly appreciate it.

I’m also open to suggestions regarding:

• Ideal airfoil profiles for this wingspan.
• Material recommendations for lightweight and durable construction.
• Electronics and power system integration for optimal performance.

Feel free to ask if you need more details or context about the project!

Thanks in advance for your help! 😊

Hello everybody :)

I am currently doing research for a project regarding Aircraft Design in university and trying to find a relation for estimating the zero lift angle of attack for a wing. I found something in DATCOM but it is only really applicable for Wings with NACA airfoils. I have an E210 (13,64%) Profile, so there is my Problem. I tried to find something in Raymer too but didn’t find anything usable. I would be happy and thankful if someone here has any idea.

I've been invited to take the test for aerodynamic surface design graduate (aston martin), which is about 55 minutes long. Has anyone recently attempted the test? If so, what kind of questions should I expect?

The Kutta law states Lift Force=ρVΓ, we can use dimensional analysis here and see that the dimensions of the lift is [MLT-2] but the dimensions of ρVΓ is [ML-3][LT-1][L2T-1]=[MT-2] which is not equal to the dimensions of force so am i missing smth about the equation itself or is there some crazy hidden detail that im not picking up?

I feel like I should be able to figure this out but my brain is maxed out for other reasons. If I put a box fan at the top of the stairs blowing into the hallway, would that create a slight positive pressure in the bedrooms (and help reduce drafts from the windows)? I want to help move warm air to the rooms from the first floor fireplace anyways but wondering about this added benefit... Thanks!

When flow seperates behind an object there is low pressure and drag increase. How is an aerfoil stalling and the flow detatching on the suction side creating higher pressure than attached air? In our lecture lift was shown as integral over ∆c_p whith the formula for c_p=(p-p_inf)/q_inf=1-(V/V_inf)^2

q_inf=(1/2)rhoV_inf Shouldn't the speed be higher due to the back flow? What am I missing?

Everywhere I look for an answer it just says Lift decreases when stalling but not why in detail. Would very much appreciate an explanation because I have been trying to get an answer for two days.

Hello friends.

I'm new into aerodynamics world and I'm searching for my first software for fixed-wings drone aerodynamic simulations. During my researches, OpenFOAM seemed to be a good tool, but I've heard some cons due to it's suposed complexities to operate and slow learning curve.

OpenFOAM is capable of this task (simulate aerodynamics for fixed-wing drones)? Can I calculate forces on it (like lift and drag)?

I'm kinda lost because, as I said, I'm completely new in this field. Thanks in advance for all the kind answers :)

Hi guys, right now I am doing my masters in aerodynamics, I am considering specializing in Supersonics for my career. So I would like to know how vast the job opportunities are in this field.

Thanks a lot for answering!

Why do rear wings on cars not have fins like diffusers do, why does the diffuser need them and the rear wing doesn’t?

I've been working on this question for a little while concerning a novel I'm working on. I've managed to use my high-school-level knowledge of math to figure out the force needed to lift a heavy weight of approximately three hundred pounds, but I'm afraid that's where my ability to work things out meets its match.

I have no idea how to make heads or tails of the math required to calculate engine size and speed, as well as every other variable that might be necessary.

I apologize if this is the wrong place to ask, but I would appreciate help with this topic.

Hello all I am working on a new rear deck lid for my track car, the vehicle must be run with windows down. Would holes in the trunk around the license plate area let air out and reduce drag? Or would it cause issues? Any advice or insight would be appreciated. Thanks!