# What is Drag coefficient: Definition and 90 Discussions

In fluid dynamics, the drag coefficient (commonly denoted as:

c

d

{\displaystyle c_{d}}
,

c

x

{\displaystyle c_{x}}
or

c

w

{\displaystyle c_{w}}
) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area.The drag coefficient of any object comprises the effects of the two basic contributors to fluid dynamic drag: skin friction and form drag. The drag coefficient of a lifting airfoil or hydrofoil also includes the effects of lift-induced drag. The drag coefficient of a complete structure such as an aircraft also includes the effects of interference drag.

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1. ### I Drag Coefficient of a 'flexible' object (e.g. a piece of paper)

Hi all and thanks for your time. I'm a little new to this site and was unsure what the prefix to this post should be, so I put it under 'intermediate'. Imagine having a piece of paper glued to the palm of your hand. You swing your hand down and the edges of the paper bend backwards because of...
2. ### Induced drag relation with speed

Hi everyone. I was wondering if you guys could explain me why I saw people say that: Induced drag changes for a factor of 1/V2 Induced drag coefficient for a factor of 1/V4 If I don't make any mistakes, Drag = 1/2 rho * S * V² * Cd. Manipulating the formula I find, 1/Cd = 1/2 rho * S * V² *...
3. ### I Fluid dynamics: drag coefficient and pressure at the stagnation point.

Hi, In my textbook the author say that the drag coefficient is the drag force divided by the pressure at the stagnation point time the area perpendicular to the stream. ##c_d = \frac{2F_d}{\rho v^2 A}## To get the pressure at the stagnation point I'm using Bernoulli for an incompressible fluid...
4. ### I Effect of vent ratio on the drag coefficient of round parachutes

For my 12th grade school project, I'm planning to research on the effect of vent ratio on the drag coefficient of round parachutes. My idea was to make small model parachutes and drop them from a height, and derive the drag coefficient after certain assumptions. But I also thought it'd be...
5. ### Find dissipative function for the non-linear force f=-bv^n

For a nonconservative force, What would be the dissipative function for a force f=-bvⁿ in Lagrangian (Where v is the velocity) [#qoute for a nonconservative force f=-bv The dissipative function is D=-(1/2)bv² ] Since ##f=\frac{\partial D}{\partial \dot x}## so the dissipative function should...
6. ### Potential and Kinetic energy equations including drag coefficient

1. Golf ball initial potential energy uncertainty (110-5kg 0.01 m 0.01m/s2)= 110-9J4.31210-5=4.31210-14j 2. Golf ball initial potential energy calculation (4.4 x10-4kg 9.8 m/s2 0.609 m)= 4.31210-54.31210-14j 3.Golf ball final potential energy uncertainty ( 110-5kg 0.0 m0.01 m/s2)= 0.0 J 4...
7. ### Effect of Surface Area on the Drag Coefficient of a Parachute

Summary:: Does the surface area of a parachute affect its drag coefficient? If so, how? I have been trying to figure out the effect of surface area on the drag coefficient of a parachute. I have designed a lab in which parachutes of different surface areas are dropped and the terminal velocity...
8. ### Help with drag coefficient calculated from ballistic coefficient

I want to make a video game about snipers and I would like it to have proper bullet physics, not something very accurate, but with "credible" bullet physics. So I need to implement a simple trajectory solver. I thought of taking into account just the gravity and turbulent air drag. The...
9. ### Is there a way to calculate the Drag coefficient from any given object?

Hi guys, for my final high school project I want to create a simulation in Unity (A game engine) in which you should be able to make an airplane fly with extremely accurate physics. In the regular formula for Drag is: Fd = 1/2 * ρ * v^2 * Cd * A. I can get all these things except the Drag...
10. ### Special Relativity Math Thing (Fresnel's Drag Coefficient)

I am wondering if there is a typo in my textbook. Please see the attachment. The textbook says "...keeping only the lowest term in x = v/c." I am wondering if it should be "x = v/(nc)," as I circled in blue on the left side. It is a binomial expansion of the denominator. Shouldn't x be v/(nc)...
11. ### A Predicting how far an object will fly

Hi, I have an experimental setup where we are taking certain different types of metals of varying shapes and sizes, weighing them, taking approximate measurements, and then blowing it off of a table of a fixed height with an Air Nozzle. The data taken down in experiment is the PSI at which the...
12. ### Can You Simplify Calculating Drag Coefficient for an Inverted Cone?

Summary: Hello, I have a task to calculate the air drag coeficient experimentally. I have a cone which I had dropped from height of 1.5 m and measured the time. Then I derived the equation of of velocity and acceleration but they are very complicated. Is there any simpler method? a=g-k/m*V^2
13. ### Engineering Need to find L/D ratio for F117

I was trying to look for an L/D ratio published everywhere on the web and I can't seem to find it for our project. Since I couldn't find it, I wanted to try calculating myself. Can't seem to find $$C_l$$ or $$C_d$$ though without some sort of paywall on research papers. So L/D would just be...
14. ### Ridiculously low drag coefficient from OpenFOAM CFD

(New thread following up to a conversation in another thread). I'm using SimFlow 3.1 with OpenFOAM 5 on Linux to try to evaluate the drag coefficient of a water rocket body, constructed from a 2-liter Coke bottle with a conical nose, traveling through air at 77 m/s. This should be a simple...
15. ### How to estimate a constant drag coefficient of a boat?

Hi there, I have modeled with MAXSURF a few variations of a prehistoric logboat in order to test a few theories. Now, I am trying to look at resistance-performance over a range of speed. To do so, I need to include a constant drag coefficient without knowing the drag force and velocity (both...
16. ### How can I plot the drag coefficient vs x-coordinate using Fluent 6.3.26

hello i want to plot the drag coefficient vs x-coordinate using fluent 6.3.26 best regard
17. ### List of drag coefficient for basic shapes has no angles

When I type "drag coefficient" in Google, and view some of the images, the standard list of geometrical shapes come into view, such as this one: https://upload.wikimedia.org/wikipedia/commons/thumb/3/37/14ilf1l.svg/220px-14ilf1l.svg.png If we take the cone for example, there is a drag...
18. ### How do I find the terminal speed of a body in water?

Homework Statement A baseball has a terminal speed of 42 m/s in air (ρ = 1.2 kg/m^3). What would be its terminal speed in water (ρ = 1.0 x 10^3 kg/m^3)? A) 0.05 m/s B) 1.5 m/s C) 18 m/s D) 42 m/s E) 1200 m/s Homework Equations D=½Cρ*Av^2 where the magnitude of the drag force (D), relative...
19. ### I Fizeau's Exp: TRANSFORMING VELOCITIES to Explain

In 1851 Fizeau made a famous experiment which corroborated de Fresnel's drag coefficient of the luminiferous ether. In the experiment two light beams traveled through a tube of moving water (at 7cm per second), one moving against the water flow (let's called it beam A), and one for the water...
20. ### When should the drag coefficient of a rocket peak?

Hi, When considering the drag coefficient of a rocket in transonic/supersonic flight, I always expected the drag coefficient to peak at exactly Mach 1 due to the abrupt increase in pressure that occurs when breaking the sound barrier. However, I have been looking at several websites and...
21. ### What does FL represent in the drag coefficient equation?

So I did a project about a year ago and I can't remember one of the things I wrote in this equation. The equation apparently I got it from NASA's website. https://www.grc.nasa.gov/www/k-12/airplane/dragco.html This is my equation CD = FL/ (0.5 * Air viscosity * V^2 * Area) = 0.4These are the...
22. ### Calculating Drag Coefficient from Wind Tunnel Data

Homework Statement Using a wind tunnel to measure force and velocity at different drive %, we obtained some data for drag. We used one dimpled sphere and one smooth sphere. There are a couple of questions I am stuck on. "The force you have measured is known as the drag force and can be...
23. ### Terminal Velocity: Solve Physics IA Problem

Hello, I am finishing my IB internal assessment in physics. I have thrown four balls (with different masses, 400,450,475,500 grams) from a height, which is approximately 23 meters. My teacher told me to set up a graph which showed mass vs. vt^2. He said that the inverse of M=...
24. ### Constant Ratio of Drag coefficient and terminal velocity

Guys,, please check my own way to get Drag coefficient and Terminal Velocity by given Drag force,.. okay,, lets for example: we know drag force is Fd= Cd*pf*v^2*A/2,, ill give little example (Cd=.02)*(pf=1027kg/m^3)*(v^2=.0025m/s)*(A=24m)/2 =( Fd .6162N) so drag force is .6162N,, okay..according...
25. ### How to calculate Drag Coefficient?

As I have looked through the internet and did my research I have found some information on how to calculate the drag coefficient, however none of what I have search for matches what I need. Currently I am doing a physics assignment for grade 12 and I am investigating the physics behind...
26. ### How does Turbulence Intensity affect drag and flow separation?

Just to the point.. How Turbulence Intensity affect a drag? As far as I know if there is decrease in Turbulence Intensity, the coefficient of drag will decrease to, but I don't know why the reason behind that. Also, the relationship with flow separation too. I hope someone can help me with...
27. ### Automotive Car mileage after reducing Drag Coefficient in half

I was wondering what would be the car mileage, if we reduce the current Drag coefficient from 0.30 to 0.15? Or to 0.10?
28. ### Coefficient of Drag on a model rocket

Hello everyone, I am predicting the altitude of a model rocket based on some testing I did where I found the impulse of a little single stage model rocket motor. I am wondering how to incorporate drag into my calculations to make it more accurate. I know D=Cd*rho*v^2*A and I can definitely find...
29. ### What is the needed flow rate of the impeller with this info?

Hi everyone! As an experiment I am trying to calculate building my own PWC similar to a jetski assuming it is for sea level use. I really appreciate all detailed answers as I want to understand. The impeller will be installed under rear of craft, engine is mounted on top. Given Information...
30. ### Drag Coefficient of a trapezoidal bar

I have a peculiar problem of calculating a trapezoidal bar (used as sacrifical anode) in offshore substructures. Can anyone advise me how to calculate the Cd value of such a section. Flow is along the length of the bar.
31. ### What Causes a Negative Drag Coefficient in Projectile Trajectory?

Hi, I am working on a video capture project in which i am videoing the projectile of a ball that is being thrown in the air and trying to fit it to a curve for the expected trajectory of a projectile with quadratic drag.I am running into the issue that in order for my expected trajectory to fit...
32. ### Drag, terminal velocity, and force.

Homework Statement Coal miners often find mice in deep mines but rarely find rats; let’s see if we can figure out why. A mouse is roughly 5 cm long by 2 cm wide and has a mass of 30 g; a rat is roughly 20 cm long by 5 cm wide and has a mass of 500 g. Assume that both have a drag coefficient CD...
33. ### Is Drag Coefficient Constant for same shape, different size?

I've read that drag coefficient depends on the shape of the object but I am confused as to what shape means. Does it mean geometric shape or is area included in that? Say I have one sphere of radius r and keep fluid velocity, density, and viscosity constant and find its drag coefficient. Would...
34. ### How Does Linear Drag Affect a Baseball's Trajectory?

Homework Statement A baseball is hit at a height of 3 ft off thte ground. It leaves the bat with an initial speed of 165ft/sec, at an angle of 10 degrees from the horizontal. The linear drag coefficient is k=0.38; gravitational acceleration is 32 ft/sec^2 Homework Equations [/B] Find a vector...
35. ### Calculating drag coefficient for complex shape

Me and a friend at school are doing an honors project for a Computer Science class. We're trying to find the aerodynamic drag coefficient of complicated 3D Shapes entirely virtual. We started out the project with a specific physics engine in mind. It turned out this engine "Bullet Physics"...
36. ### How can I determine the drag coefficient of a cardboard propeller?

I'd like to know how to work out the drag coefficient of a sheet of cardboard. I know the formula, but to get it you need the drag force which in turn needs the drag coefficient. For reference, the cardboard is about 3mm thick and is roughly 60cm by 20cm. It has a 100g weight attached to the...
37. ### 3d Shape with lowest drag coefficient subsonic ground level

Hello, What shape has the lowest drag coefficient at ground level and at subsonic speeds (0-150kph) with the following dimensions? Width 60cm (at 45%) Height 120cm (at 45%) Length 220cm These dimensions will fit my motorcycle (not too narrow and not too long). I am thinking it would be a...
38. ### Physics Problem with Lifting Force and Drag Coefficient

Homework Statement Flying aircraft X is designed in 2014. The current model has a top speed of 812 m/s, a mass of 72,000 kg when fully loaded, and a maximum thrust to weight ratio of 0.44. Calculate the lifting force and the drag coefficient for the Quinjet when it is flying level at top speed...
39. ### Coefficient of drag and surface smoothness

So i am working on a program that models the movement of a rocket through different planets. and i sm starting to get teach my self fluid dynamics. As i was reading a presentation by NASA about the forces that act on a rocket they got into shape effects on drag, i noticed from their equation Cd...
40. ### Modeling a car slowing down from speed

Hello! I'm trying to model a car slowing down from speed with the forces of drag and friction and gravity from the road slope.. The model, which models the resistive forces is as follows.. [ Ffriction + Fdrag + Fslope ] / m = -a (deceleration) where: Friction force Ffriction = A...
41. ### Creating a Numerical Model for a falling Ball

Homework Statement A ball was dropped through a known vertical distance with the time of drop also recorded. The aim of the task is to create a numerical model in excel in order to approximate the drag coefficient. Homework Equations This is my method. 1. FBD for the ball falling. (assume...
42. ### What Are Lift and Drag Coefficients?

Can someone please explain the lift coefficient and drag coefficient in simple terms? Thanks.
43. ### Drag Coefficient and Reynolds Number Related to free fall

Homework Statement Hi, I am doing a theoretical investigation which will be compared to an experimental I'll do later. I am trying to calculate how much time will it take an object to fall a heigh H. the object is a 5x5x5 cm cube. I have the Reynolds number as this Re=3546*Velocity; and I...
44. ### Accumulated drag coefficient over an automotive

Hello everyone, I have a question regarding the accumulated drag curve shown in the figure below for the CFD simulation of external flow over an automobile. (It is written Vehicle Cd in the figure) It can be seen in several regions that the accumulated drag curve is dropping (ie., having a...
45. ### Accumulated drag coefficient for an automobile

Hello everyone, I have a question regarding the accumulated drag curve shown in the figure below for the CFD simulation of external flow over an automobile. (It is written Vehicle Cd in the figure) It can be seen in several regions that the accumulated drag curve is dropping (ie., having a...
46. ### Drag Coefficient: Does Cd Vary in Different Mediums?

Hi Is the drag coefficient for a particular object the same in different mediums? Say we have Cd = 1 in air for one object, is Cd the same for this object in water?
47. ### [Aerodynamics] Why does the drag coefficient increase after turbulence

As you can see, around Reynolds number of 5 105 the transition occurs for a smooth sphere. However, why is it that after this transition that the drag coefficient increases at turbulence?
48. ### Drag coefficient of an airplane control surface

Hello, I was reading somewhere about how to control Rudders in RC planes. The basic equation here is the drag equation: F=0.5*ρ*v^2*C*A (take ρ=1Kg/m3) where v is the velocity, C is the Drag coefficient of the control surface (Rudder in this case) and A is the area. I am wondering if we have...
49. ### Reynolds number and drag coefficient of a cylinder

Lately, I have conducted an experiment where I dragged various circular cylinders through water in order to find the resistance, and hopefully also the drag coefficient. It seems to me that this coefficient is dependent on what is called the Reynolds number. Using some sources, I can easily find...
50. ### How To Calculate Drag Coefficient?

We know that the drag force on an object is defined as: FD = ρ*v2*CD*A/2 , where ρ is the density of the fluid the object is traveling in, v is the velocity of the object, CD is the drag coefficient of the object and A is the surface area of the object. Rearranging the formula to find drag...