11.12.2020

# Drag coefficient calculator

By Takazahn

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 parachutes, for this task I want to mainly focus on how each different factor affects the decent speed of the parachute.

So far what I have got are the equation for calculating the drag coefficient, however I am very confused with the equation which can calculate the drag coefficient. The drag coefficient can be calculated with a velocity as one of the variables, as the velocity changes then the drag coefficient would change too right? But the velocity which the parachute is traveling through the medium depends on other factors such as mass am I right?

Thus changing the drag coefficient according to the equation? I am very confused. The drag would be the same for an object not moving, in fact that's how it is calculated in a wind tunnel. Please post the equation and link. Drag coefficients do not contain velocity. As I suspected, plug in units both sides. The drag force and drag coefficient are different things.

What are you trying to calculate? As I suspected, plug in units both dived. The drag force and gray coefficient are giggetent things. What ate youbtrying to calculate? Last edited: Jul 25, This website uses cookies to function and to improve your experience. By continuing to use our site, you agree to our use of cookies. Discussion Closed This discussion was created more than 6 months ago and has been closed.

To start a new discussion with a link back to this one, click here. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' or the latest version listed if standards is not an option.

Send a report to the moderators. Background: simulate the drag coefficient for a truck model I have read the following post www. How do I calculate Area? The area should only be the surface exposed in the Y direction spf. The Discussion Forum supports LaTeX formulae, as long as you follow the syntax mentioned in this thread: www. Thanks Jeff, I have updated my post. Hi Jesse, is the drag force, i.

You can always do an arrow plot of the nx,ny,nz vector if in doubt. Finally, in the formula, is the velocity of the vehicle, i.Calculator Academy. Enter the force of drag, the density of the fluid, velocity, and frontal area of the body. The calculator will display the drag coefficient of this object. The following formula is used to calculate the drag coefficient of an object.

To date, there is no accurate way to calculate it with data. So, in order to calculate the coefficient, a test needs to be set up that allows one to measure the force acting on the object. Using you test setup information, or device, determine the velocity of the fluid moving around the object. This could also be the velocity of the object itself. Calculate or measure the frontal area of the object. This is the area exposed to the force of drag. Calculate the drag coefficient using the information from steps above.

A drag coefficient is a coefficient used to describe how aerodynamic a certain object is. This is done through reducing the drag coefficient. Decrease the frontal area and change the shape to change the coefficient.

### Drag coefficient

Next, measure the velocity and density of the fluid Using you test setup information, or device, determine the velocity of the fluid moving around the object.

Next, measure the frontal area Calculate or measure the frontal area of the object. Calculate Calculate the drag coefficient using the information from steps above. What is a drag coefficient? How can you reduce drag? Like this: Like LoadingThe better, up-to-date ballistics programs let you select either G1 or G7 Ballistic Coefficient BC values when calculating a trajectory. The ballistic coefficient BC of a body is a measure of its ability to overcome air resistance in flight.

Some readers are not quite sure about the difference between G1 and G7 models. What determines how, or which one to use? The simple answer to that is the G1 value normally works better for shorter flat-based bullets, while the G7 value should work better for longer, boat-tailed bullets. G1 vs. The G1 shape looks like a flat-based bullet. The G7 shape is quite different, and better approximates the geometry of a modern long-range bullet.

The G7 standard is more appropriate for long range bullets. The reason the BC for the JLK is less is mostly because the meplat was significantly larger on the particular lot that I tested 0. The following BCs are referenced to the G7 standard, and are constant for all speeds.

When available, these BCs are more appropriate for long range bullets, according to Bryan. XXX number. Share the post "G1 vs. While Bryan Litz published real-world measurements for bullets, of these cover a speed range of at least Mach 0.

Of these, bullets give a better fit to G7, while G1 is better for only 18 bullets. I think that is clear proof that G7 is typically a better drag model for modern bullets than G1. In my opinion the difference is an academic one for the target shooter. It may bring you better on target for the first time, but only if you know all the other variables in the equation for sure. It even changes with the height above ground. Prove it to yourself. On any ballistics program that works with G1 and G7, select some set of atmospheric conditions and enter a load with a MV of 3, fps with a G1 BC of 0. Even at 1, yards the difference in drop is less than half an inch. Try it again with any atmospheric conditions you like and any practical BC.

G7 models. As an example, for a. While all other input variables remain the same, and using a MV of which is the average MV I shoot using I would presume that using a Sierra MK g. Point being that choosing the wrong model to base your calculations on could be a serious miss….

Bryan Litz is an engineer. I know the difference, I started at the bottom and worked my way up.Drag Force Calculation - enter Drag Coefficient. Compute Drag Force, Velocity, or Area. Register to enable "Calculate" button. Introduction Drag force is caused by a fluid such as water or air; or any liquid or gas impinging upon an object.

The drag force is a function of the fluid velocity and density along with the object's reference area and drag coefficient. The drag coefficient may further be a function of the Reynolds number. Reynolds number depends on the fluid density, viscosity, and velocity as well as the object's characteristic length. Drag Force Equation Blevins, and Munson et al. The units below are consistent units for the drag force equation.

References Blevins, Robert D. Applied Fluid Dynamics Handbook. Krieger Publishing Co. Munson, Bruce R. Young, and Theodore H. Fundamentals of Fluid Mechanics. John Wiley and Sons, Inc. All rights reserved. Please contact us for consulting or questions about drag force. Drag Force Calculation with built-in drag coefficient values. Select fluid:. Tree C values from Munson et al. Flag C values from Munson et al.This is a powerful and flexible program, but the usual rule applies - garbage in, garbage out.

Required data Bullet diameter Bullet length Nose length Meplat diameter Drive-band diameter Base diameter Boat-tail angle degrees Boat-tail length If the bullet has a secant nose. Secant radius calibres If no secant radius is entered, a tangent radius will be assumed and calculated automatically. Dimensional units inches millimetres. Jacketed lead core, soft point or FMJ bullets Jacketed lead core, hollow point bullets Jacketed steel core military type bullets 9. Soft lead, unjacketed bullets Cast linotype, unjacketed bullets Bronze or brass, used for 'solid' bullets 8.

However, this is not an infallible rule and inspection of a spark-shadowgraph is the best way to determine this parameter. What this program does Using the entered dimensions of your bullet of interest, the program produces an image of the bullet so you can check that the shape is correct. A curve of Drag Coefficient against Mach number is generated.

Also computed is the G1 and G7 Ballistic Coefficients for a range of Mach numbers, and the barrel twists required for a Stability Factor 1. If requested, the program will go on to calculate a table of bullet drops, wind drifts, terminal velocities and terminal energies every 50 yards up to yards, and also for a custom range at any distance using the computed drag curve.

Using the program Try to fill in as many of the bullet dimensions as possible, even if the value is zero, as in the boat-tail length for flat based bullets. If you miss out some dimensions, the program will try to make intelligent decisions about what those dimensions are, but it is best to be clear about the bullet dimensions in the first place.

## Drag Coefficient Calculator

However, too much information can lead to conflicts! They are resolved in this way. Any entered value of base diameter will take precedence over that calculated from a boat-tail angle and boat-tail length. If a bullet weight is entered for the first calculation, the bullet density will be estimated from this weight and the calculated bullet volume.

In any subsequent re-calculations, the bullet weight will be estimated from the volume determined from the new bullet dimensions and the bullet density carried through from the previous calculation. The only way to change the weight of the bullet without changing any other dimensions is to change the bullet density which tacitly changes the bullet construction.

When a trajectory is required, values entered for the local atmospheric pressure anything other than Hg will take precedence over local pressures estimated from the barometric pressure and the altitude.

Drive-bands are standard for large calibre artillery shells, and are often used on small calibre 'solid' bullets made of bronze or some other metal that will not easily engrave into the barrel rifling. If your bullet of interest does not have a drive-band, enter a diameter the same as the bullet diameter. The nose angle the angle between a line from the nose-body junction to the nose-meplat junction - or the nose point if there is no meplat - and the bullet axis must not more than 45 degrees.

If the bullet nose is shorter than this, the program may have difficulties in drawing the bullet. For example, a hemispherical nose will have a 45 degree nose angle no meplat in this case.

Physics Fluid Flow (7 of 7) Bernoulli's Equation

If you want to describe a shorter nose, ensure the meplat diameter is increased correspondingly. However, note the warnings about short noses below! Limitations The results of this program are considered valid for Mach numbers between 0. The original "McDrag" program see "History" below on which this program is based, was tested against the actual experimental data for a large range of projectiles of differing shapes. For nose lengths shorter than one calibre, the calculated contribution of drag from the bullet head will probably be too high for transonic and supersonic speeds.

Boat-tail lengths longer than 1. Likewise, the base diameter should not be less than 0. This does not mean that the results will not be useful if these limits are stretched, but warnings will be given to indicate that the accuracies quoted above will probably not be valid.Drag Force Calculation with built-in Drag Coefficients. Register to enable "Calculate" button.

Introduction The drag force on an object is produced by the velocity of a liquid or gas approaching the object. Drag force is dependent upon the drag coefficient of the object and the geometry of the object. For some objects, the drag coefficient is independent of the object's dimensions.

However, for other shapes of objects, the drag coefficient is dependent on the dimensions and may be additionally dependent on the Reynolds number. Our calculation has drag coefficients for a solid hemisphere, hollow hemisphere, solid cone, ellipsoid, annular disk, solid cylinder, solid cube, and solid square rod.

Equations The drag force equation used for the calculation on this page is Blevins, and Munson et al. The drag coefficients C used in our calculation are from Blevins Drag coefficients for the solid hemisphere, hollow hemisphere, and cube are independent of dimensions or Reynolds number. The drag coefficient for the solid cone, ellipsoid, thin annular disk, solid cylinder, and solid square rod have drag coefficients that are functions of the shape's dimensions. Blevins provides tables of the drag coefficient versus dimensions. LMNO Engineering has fit equations to the Blevins tabular data with the resulting drag coefficient shown in the calculation above. Notation Our calculation allows a variety of units with all of the conversions completed internally. The units shown below are SI international system of units. Messages given by calculation Messages indicating input values are out of the acceptable ranges.

Warning messages. References Blevins, Robert D. Applied Fluid Dynamics Handbook. Krieger Publishing Co. Munson, Bruce R. Young, and Theodore H. Fundamentals of Fluid Mechanics. John Wiley and Sons, Inc.