Quote:
Originally Posted by scarabchuck
Did you check the link out ? That particular car holds quite a few open road race wins (silver state classic is one of them) , a closed course record and one a zero200zero event. It performs quite well at 200...
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Drag increases with
speed (
v). I hope that this is self-evident. An object that is stationary with respect to the fluid will certainly not experience any drag force. Start moving and a resistive force will arise. Get moving faster and surely the resistive force will be greater. The hard part of this relationship lies in the detailed way speed affects drag. Are the two quantities directly proportional? Does drag increase as the square of speed? The square root of speed? The cube of speed … ? According to our model, it should be the first of these. Drag should be proportional to the square of speed.
R ∝
v[SIZE=2]2[/SIZE] But for some situations this is not quite correct. As I said before, drag is a complex phenomena. It is cannot always be written with simple mathematical formulas. My first guess would always be that drag is proportional to the square of speed, but I would not be surprised if, over some range of values, it was found to be directly proportional, or proportional to the 3/2 power, or even that drag and speed were related by some polynomial. Welcome to the world of empirical modeling -- where relationships are determined by actual physical experiments rather than an ideology of pure theory. Which brings us to our last factor …
Drag is influenced by other factors including shape, texture, viscosity (which results in viscous drag or skin friction), compressibility, lift (which causes induced drag), boundary layer separation, and so on. These factors can be dealt with separately in a more complete theory of drag (how tedious in one sense, but how necessary in another) or they can be piled into one monolithic fudge factor (oh yes, please) called the coefficient of drag (
Cd).
Drag increases with
speed (
v). I hope that this is self-evident. An object that is stationary with respect to the fluid will certainly not experience any drag force. Start moving and a resistive force will arise. Get moving faster and surely the resistive force will be greater. The hard part of this relationship lies in the detailed way speed affects drag. Are the two quantities directly proportional? Does drag increase as the square of speed? The square root of speed? The cube of speed … ? According to our model, it should be the first of these. Drag should be proportional to the square of speed.
R ∝
v[SIZE=2]2[/SIZE] But for some situations this is not quite correct. As I said before, drag is a complex phenomena. It is cannot always be written with simple mathematical formulas. My first guess would always be that drag is proportional to the square of speed, but I would not be surprised if, over some range of values, it was found to be directly proportional, or proportional to the 3/2 power, or even that drag and speed were related by some polynomial. Welcome to the world of empirical modeling -- where relationships are determined by actual physical experiments rather than an ideology of pure theory. Which brings us to our last factor …
Drag is influenced by other factors including shape, texture, viscosity (which results in viscous drag or skin friction), compressibility, lift (which causes induced drag), boundary layer separation, and so on. These factors can be dealt with separately in a more complete theory of drag (how tedious in one sense, but how necessary in another) or they can be piled into one monolithic fudge factor (oh yes, please) called the coefficient of drag (
Cd).