# Tag Info

26

For regular paper weight and size A6, roughly a card postal size one can tear from the middle vertically the top half and bend the two flaps 90 degrees in opposite directions like a helicopter's blades and fold the bottom half on itself like a narrow rod to make it act like balast. This will be a primitive gyro- copter and will descend in a slow controled ...

17

I really love this game idea! I think a flat piece of paper falling face-down is probably the least aerodynamic thing you could possibly drop if it maintained its shape and orientation, but naturally the paper bends and changes angle (edge-down) as it descends, tending towards the path of least resistance. Therefore, my thought is that your goal should be to ...

15

Most helicopters of modern manufacture are dynamically unstable while hovering- they require constant, "hands-on" control inputs from the pilot to keep things in balance. This task is very demanding and requires a lot of practice to master. Hiller helicopters (which have been out of production for many years) were one of the rare examples of ...

9

It all depends on the level of efficiency you seek. A train, given its size, has a ridiculously small cross section. This small frontal area footprint is being 'pushed' by the inertia of hundreds of tonnes of metal. All high speed train have aerodynamic noses, but some will tend to be pedantic about how many thousandths of a percent efficiency they can ...

8

What a fun challenge! We had a good time trying out various designs :) I did eventually come up with a helicopter-style design that falls about 50% slower quite consistently. Build instructions: Cut diagonally along the red line. Fold one half in the opposite direction. Fold up the edges along green lines to add rigidity. Put a single staple through the ...

6

In general, most airfoils only approximately display the $2\pi$ lift slope as predicted by thin airfoil theory. That is because airfoils are not actually infinitely thin in practice, and will deviate from thin airfoil theory by a small amount. $a_0$ is left in the above equation so one can predict the elliptical finite wing lift slope (effects of aspect ...

6

There are propellers with different aerofoil sections. For example, the propeller attached to the Rolls Royce engine kept in my graduate college had symmetric aerofoil sections roughly about 25 % and smoothly varying to bottom flat airfoil sections at the rest. The aerofoil profile selections are based on the performance requirement, structural rigidity, ...

6

Knowing the derivation is important because it usually tells you what initial assumptions were made in the derivation and what the limits of applicability of the resulting equation are. Understanding both of these things is an essential skill all engineers must master.

6

Should I, as an engineer-in-training hoping to complete research, focus on trying to understand equations to my satisfaction, or should I instead just become well acquainted the equations, their use cases, and their general behavior? Engineers apply equations to predict behavior. The critical requirement is to know the constraints of the equation. The ...

6

Extrapolating from the Gyrocopter idea for A4 paper size, I arrived at following conclusions: Bending (i.e. not creasing a fold) part of the helicopter blade along its length provides ample structural stability at the cost of some air resistance. The result however has a nice wing profile. Structural stability is most important at the blades' root, so you ...

5

According to the wiki, these are called Stockbridge dampers. The design is tuned for a specific length and one might also expect a specific mass/material. The weights are mounted on flexible arms, typically a length of stiff cable, which allow the assembly to absorb energy that might otherwise be imparted to the longer power lines, or more accurately, that ...

5

The factors that affect a car's top speed - IMHO - can be grouped to the power train factors : engine power gear box and differential ratios size of the wheel and to the losses: overall aerodynamic coefficient of drag friction related loses (e.g. wheel resistance), (however for the top speed it has a negligible effect). Usually regarding the losses the ...

4

There are two major benefits to dimensional analysis (non-dimensional coefficients) according to Frank M. White, Fluid Mechanics, 2nd Ed. My answer is heavily paraphrased from this source. They allow scientists/engineers to reduce the number of experiments required to explore a given phenomenon. They provide scaling laws allowing experiments to be performed ...

4

There are far too many factors involved to definitively state that a table fan cools more than a ceiling fan or vice versa. For starters, there are different styles of both. It also depends highly on what you consider "cools better". For example, if you were to come inside and are sweaty, and are looking to cool down quickly, standing in front of a small ...

4

What you seek is called 3D photogrammetry and is a relatively exciting segment of 3D modeling. You can use those terms to search with your favorite search engine and be overwhelmed with options. I found a link to a summary performed a bit more than a year ago, which might be more useful to you. https://pfalkingham.wordpress.com/2016/09/14/trying-all-the-...

4

The problem you cite in the question is a pretty standard homework problem in a graduate fluid mechanics course (it might be also an undergraduate course but less likely). Therefore, I would be reluctant to provide the solution. What is important to remember when dealing with this problem is that it is crucial to attend the lecture at which the subject was ...

4

A plane relies on aerodynamic lift to stay airborn. This is much more efficient than using raw vertical thrust like a rocket does. The downside is that planes always need to be moving perpendicular to the direction of gravity. Pretty much all planes except for fighter jets do not have enough thrust to take off vertically. For traveling from point A to B on ...

4

probably not, here is why. the coanda effect describes how a moving mass of air entrains nearby air and sets it in motion. So if we start with an extremely fast-moving but small jet of air, with it we can urge a much larger mass of air into motion. However, energy conservation dictates that the kinetic energy of the large mass of air set into motion be less ...

4

As the air moves from the center out it accelerates in a pattern similar to a hurricane. the velocity vector angle changes to reduce the rotational whirlpool and angular momentum component of the airflow but add to its pressure and centripetal momentum. The blade angle of attack to airstream follows air velocity vector more or less under 14 degrees to give ...

4

It is important to realize any airborne device will go in the direction of the sum of all force vectors (including gravity). We have our centrifugal impeller drawing air in from the bottom. The device will be pulled down. The air flow out the sides will create low pressure, pulling the device down. The device will have a better chance flying if it is ...

3

There are two speeds that the pilot is concerned about. First is airspeed, and the second is ground speed. Ground speed (speed of the aircraft relative to the ground) can and is checked by GPS. This speed tells the pilot how long the flight will be and if they are staying on track with their fuel calculations for the flight, crucial, but less critical ...

3

The qualitative behaviour of a physical system often depends on the relative size of two (or more) different effects. For example, in fluid flow, turbulence tends to develop when the force to accelerate the fluid (i.e. its inertia) is big compared with the viscous forces in the flow. In the opposite situation where the inertia forces are small relative to ...

3

This is a simple math question. Multiply your x and y coordinates by the scaling factor you want. Say your chord length is 100mm. To make it 150mm, multiply all your values by 1.5. If you have a picture of an airfoil, just scale the image by 150%.

3

As a Naval Architect, this is a question that I am often asked. The centre of effort is very close to the geometric centre of the spade as you know. Is there a fixed skeg or keel immediately in front of the rudder? That affects the hydrodynamics significantly because the hydrofoil would then have an effective length that is the skeg width (aligned with ...

3

As the diagram shows you may be able to use a standoff arm to maintain separation between the payload and the guide line. However friction between the standoff and the guide line may cause the two to tangle or jam. Given no knowledge of the payload layout or size. You could run the guide line down the center line of the paracute, not sure if it would be ...

3

I would argue that "tempered water" was the unfortunate result of a marketing department not doing their homework. Typically in plumbing design, I come across "tempered water" on emergency fixtures (emergency eyewash or emergency showers) or for things like the mixing valves on showers. OSHA has requirements for tempered water delivered ...

3

A curved elbow will be considerably better than square elbow, because it reduces turbulence. The exact mathematical shape of the curve is not really important; usually a circular radius is chosen because it is easier to fabricate. It is important to keep the cross sectional area the same as the air moves through the turn; two circular arcs that share the ...

3

There's a lot more to it than just minimum drag shape. At 200 kph, you want it to be aerodynamically stable as well. If the pipe is supporting the fairing, and you want to limit the load on the pipe, then the pipe has to be forward of the center of resistance of the fairing. The shape will depend on temperature, altitude, humidity, the size of the pipe, ...

3

The two main considerations concerning wind power generation is the speed of the air and the duration of wind (air flow). The more of both, the better. Trying to harness wind flow within a building will be difficult because the air flow will most likely be low (slow speeds) and the duration of flow may also be short, except on very windy days. Even a wind ...

3

No - the sphere would likely stick to one wall, or bounce between them. A sphere is not a very aerodynamic shape, having both a relatively blunt front, and sudden cut off at the back. This causes a lot of turbulence, such as the familiar vortex shedding shown here: This shows how the air flows around a fixed sphere in free space - in your hose, the vortex ...

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