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Vanselena
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Hi Does anyone know the drag coefficient of a missile. Would a missile have a lower drag coefficient then a torpedo?
Thanks all
Thanks all
ank_gl said:the drag coefficients of both missile and a torpedo are same,at the end of the day, a torpedo is a missile.
what is different is the drag, due to the different medium of use. a missile is used in air, whereas torpedo shoots in water.
drag = [Cd*density*(velocity^2)*plan area]/2, so the density of the media affects the drag
Vanselena, you only need to know the drag coefficient of the geometry, because the geometry(relative to flow) DEFINES the coefficient of drag & lift. only you need to take different densities for the calculation of drag.
MagikRevolver said:Drag coefficients are based on medium: Cd = D / (.5 * r * V^2 * A)
Basic Algebra, everything in an equation is inter-related.
d and cd are different, but in determining cd, you MUST in the equation supply for the fluid dynamic drag.
ank_gl said:everything can be done analytically wysard. do you know any cfd applications ??
Jeff Reid said:In the same media, the torpedo would be more effiecient, it has a tapered tail, a missle doesnt, but a missle has a rocket engine at the back, elminating the need for a tapered tail (as long as the rocket engine is on).
Tear drop shapes, rounded front, tapered tails, have the lowest drag coefficient.
Think of it as a tear drop that is skinny and has been stretched out. Cambered airfoils are shaped similar to tear drops with a curved tail. It's just a general description, the specifics can vary quite a bit. There are a large number of registered air foil shapes, and these are modified by thickness to chord percentage and the amount of camber.Vanselena said:Is there a particular reason for the tear drop shape? Would it not make more sense to have a missile shape but then taper the back, since the missile shape would have a lower frontal profile then the tear drop?
MagikRevolver said:I'm going to quote N.A.S.A: "The drag coefficient is a number that aerodynamicists use to model all of the complex dependencies of shape, inclination, and flow conditions on aircraft drag. The drag coefficient CD is equal to the drag D divided by the quantity: density r times half the velocity V squared times the reference area A." Flow conditions: Viscosity, Compressibility, Mass.
wysard said:To calculate drag think about the cross sectional area of the missile as compared to the medium it is in. Then factor in the speed. What you get is the mass of media the missile must move out of it's path per unit time to proceed forward. That is 90% of drag. The rest is surface factors that affect laminarity of flow of the media as it is ejected/shifted out of the way and replaced behind the object.
Vanselena said:Is there a particular reason for the tear drop shape?
Vanselena said:I am trying to make this object have the lowest drag coefficient as is possible. The object being a towfish. Is a soft point preferred over a solid point? Where the change occurs from the taper to the cylinder should that be rounded? on the back end where the fins are should I taper that end? Is there an optimal thickness vs length?
Vanselena said:Ultimately I will need to find out the drag coefficient to understand the depth of the towfish at given line leads.
wysard said:OK. I think I get it. brewnog you are saying that Cd is dimensionless ...
ank_gl said:you see it stupid because you are thinking stupidly. since it is determined experimently, it has to be in above said form, or else how ll you find it genius?? had it been an analytical solution, you would have found something similar to the first equation you quoted
errr... stupid
V Mad said:Is that not the definition of coefficient, a dimensionless factor?
Having said that, there may be different Cd applied to different media as their values are obtained experimentally.
I thought that the drag coefficient (as applied to motor vehicle technology) was simply the measured drag of the subject, divided by the measured drag of a rectangular block of the same frontal cross section. Sounds a bit too simplified though doesn't it?
The shape of rockets, missiles etc is not all about minimising drag though, it is about stability (and if guided, response to guidance controls).
pmbasa said:I am just pointing out that the equation used for the coefficient of drag is not helpful unless u have the drag force, but u also need to find the drag force using the coefficient.. it's stupidly circular..
The drag coefficient of a missile is a dimensionless quantity that represents the level of resistance the missile experiences as it moves through the air. It is a measure of the aerodynamic efficiency of the missile.
The drag coefficient of a missile is calculated by dividing the drag force acting on the missile by the product of the dynamic pressure of the air and the reference area of the missile. The reference area is the frontal area of the missile that is perpendicular to the direction of motion.
Several factors can affect the drag coefficient of a missile, including its shape, size, speed, and surface roughness. The angle of attack and air density also play a role in determining the drag coefficient.
The drag coefficient of a missile is an essential parameter in the design and performance of the missile. A lower drag coefficient means the missile experiences less resistance, allowing it to travel faster and farther. It also affects the accuracy and stability of the missile during flight.
Yes, the drag coefficient of a missile can be reduced through various methods, such as improving its aerodynamic shape, using smooth and streamlined surfaces, and reducing its weight. Advanced technologies, such as active flow control and stealth coatings, can also help reduce the drag coefficient of a missile.