Questions tagged [drag]

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1answer
48 views

Does the aerodynamic force qualify as a viscous damping force in the Mechanical Harmonic Oscillator

When reading about a harmonic oscillator, the most common form of damping is proportional to the velocity. $$F_D = c \;\dot{x}$$ Without giving much thought to viscous damping, one example I always ...
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1answer
79 views

Required power to spin fan at certain RPM

I have a flat piece of wood shaped like this: And it is turning around axle. What i would like to know is, if it is rotated e.g. at 1000 RPM, how much power would that take? I know that drag force ...
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1answer
54 views

How do you determine the L/D ratio of F-117 Nighthawk?

I was trying to look for an L/D ratio published everywhere on the web and I can't seem to find it (for a project). Since I couldn't find it, I wanted to try calculating myself. Can't seem to find $C_l$...
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1answer
206 views

How to calculate the viscous damping coefficient given drag force

Force due to drag at low velocities, is equal to some constant times negative velocity $$F_{d}=-c_{1}V$$ The viscous damping coefficient equals decay constant divided by 2 times mass $$\gamma = \...
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1answer
82 views

How to obtain the $dC_d/dC_l^2$ value from the drag polar of an airfoil for Xrotor?

I'm currently trying to do an initial design for a propeller. In order to do this I'm trying to use Xrotor. Xrotor allows the user to enter certain information about both the propeller geometry, ...
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1answer
85 views

RC drone rotor air access

I am attempting to design a "flying saucer." The saucer is an ellipsoidal-ish body with a RC drone inside. I plan to allow for air access to the rotors as shown in the rudimentary diagram below: I am ...
1
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1answer
58 views

How can i calculate drag on an Angled area?

I want to calculate drag force at special angle on a sphere . There are some grooves on the sphere and these groove have a special angle on the sphere. In other words, I want to calculate drag force ...
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1answer
52 views

Coefficient of Drag (Cd) Question

Question: what i thought; see below. we do not know density if i where to use that formula on the image file . and i a m wondering why i was given the Reynolds number . need help.
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2answers
99 views

Could car waste heat be used to lower drag?

If the waste heat was moved to areas of lower pressure such behind the car-green area- Could this reduce the drag from these areas of lower pressure. From what I understand this hot air would ...
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2answers
68 views

Anomaly in viscous force - vs - velocity relationships

It is well known that the viscous force (or drag force) is directionally proportional to the square of the velocity in many cases. For example the torque on motors driving a fan-type load (pump) is ...
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3answers
384 views

Boat Hull Drag in Shallow Water

I paddle several different types of small craft in the ocean and bays near my home. One phenomenon I've observed is beyond my understanding of drag on a narrow displacement hull. When paddling in ...
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1answer
34 views

What are some concepts I can look into to aide in creating a 'compression funnel'(?) without the aide of a motor? [closed]

In short I'm designing a 'Humane fly swatter' for my University application into bachelor of Industrial Design. The idea is to utilise the energy of swatting a fly to capture air through an intake, ...
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3answers
621 views

What is the area when calculating the drag coefficient for a race car wing?

The drag coefficient is given by the following expression $$C_d = \frac{2F_d}{\rho v^2 A}$$ For a race car wing (which is simply an airplane wing upside down to generate downforce), what should we ...
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1answer
1k views

How does the pressurized suspension of the Hyperloop not affect the tube pressure?

So one of the proposed suspension systems that will be used on the hyperloop include the externally pressurized air cushions. These cushions lift (or at least help lift) the capsule and reduce drag ...
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4answers
5k views

How would adding a wind deflector in front of roof-mounted solar panels affect drag on an RV?

I am mounting solar panels on top of a recreational vehicle (RV). To reduce drag, I was planning on building a small ramp in front of the panels to deflect wind before it hits the flat panel and ...
13
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4answers
1k views

Below what Froude number can I neglect wave-making resistance on a vessel?

I want to do some very simplified drag calculations on a vessel. My hope was that calculating the skin-friction resistance would be enough to get a good estimate of the surge resistance. Because wave-...