# Questions tagged [drag]

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### 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-...
7k 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 ...
• 133
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 ...
1k 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 ...
• 143
75 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 ...
• 22.6k
1 vote
287 views

### Is the drag coefficient/velocity of of a vehicle based on frontal area?

Does the frontal area of a vehicle determine the velocity/drag coefficient of a car? A Ferrari 458 has a Cd of 0.33 while a Corvette C6 has a Cd of 0.29. Does this mean the Corvette will have less ...
1 vote
78 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 ...
1 vote
592 views

### Does more downforce affect the acceleration and top speed?

How can downforce make a race car faster, apart from being faster around corners? I just recently learned that downforce can help a car accelerate from 0-60 mph faster. Usually, I thought drag didn't ...
1 vote
118 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 ...
1 vote
53 views

### Does the terminal velocity of a sphere in free drop increase with increasing diameter?

I was trying today to calculate the terminal velocity of a hailstones with increasing diameter and mass. I was trying to figure out if larger hailstones will have a higher impact velocity or lower. I ...
• 22.6k
1 vote
87 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 ...
• 11
1 vote
92 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 ...
• 899
1 vote
474 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 ...
• 228
36 views

### Is there a way to simulate the drag effect created by acceleration while in a stationary object?

There was a video of a train that had tvs in the windows so it appeared the rider was moving across the landscape. If the train was stationary the passenger would not believe the ride was real because ...
98 views

### How long does it take and how far does it travel a sphere in free fall before reaching a percentage of the terminal velocity?

Assume a sphere (hail) that is free dropping in air. At some the sphere will reach close to the terminal velocity. The question is: how long $t_p$ in seconds does it take before a percentage $p$ of ...
• 22.6k
106 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 ...
37 views

### Drag coefficient of a complex object made using simple objects (with known drag coefficient) in small Re?

Let say you have an object made of simple objects (figA1). You know the drag coefficients of simpler objects (here spheres and rods, figB1). Is there a way to estimating the drag coefficients of the ...
147 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, ...
59 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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19 views

### Analytical / Experimental calculation of pressure loss for simple crossflow of air across a simple cylinder

I need a way to find pressure loss of air flowing across a single tube for both laminar and turbulent flows. I have referred to several sources (Y. Cengel Heat and Mass Transfer and Fluid Dynamics ...