- 主题:[合集] 风阻系数(zz)
合集也Re.
因为我发现好像里面有不少观点跟我的思想相悖。
空气阻力？什么是空气阻力，
参见AE 1(Rwth-Aachen课本），或者汽车理论
空气阻力包括好多好多项的,包括什么诱导阻力，形状阻力，...
而公式F=1/2*density of air*V^2*Area* Cd
其中的Cd叫Trag coefficient,
根据我的空气动力学 知识，
这就不包括那个空气升力（诱导阻力）...
这个公式主要包括的是形状阻力，
Cd主要和Re相关。
而且在低速情况下，一般空气阻力和其他阻力相比，都是可以忽略的，
所以改善Cd，主要是在高速下的性能，也就是动力性了。
如何改变Cd，这就是那个空气动力学了，湍流什么的,
很多都是用CFD软件来模拟流场的.
现在的Cd值，很多是0.3以下的吧，有的能到0.25，标准应该是0.3。
//btw:^_^，球的Cd值是约0.47
【 在 sataco (贞 这周就自控了) 的大作中提到: 】
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: sataco (贞 这周就自控了) 于 (Wed Dec 15 23:03:08 2004) 提到:
: 风阻系数 (Drag Coefficient)
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FROM 134.130.181.*
According to my memory.
The air drag force is mainly determined by two kind of force.
One force is the friction force, which is generated by the friction between air molecule and the surface of the car body.
The Other force is pressure difference force, I call it. It can be easily imagined, the air pressure in front of the car body is greater than the pressure behind. So this difference makes a force. The friction force is very small campared to the pressure force.
By changing the body shape, the steam line around the car body is changed. If we can achieve totally laminar state. According to the aerodynamics , the pressure difference is small. But sometimes impingiment flow is occured, because of irregular shape of the body, such as mirror.
【 在 lofuture (在他乡~抵抗寂寞和孤独) 的大作中提到: 】
: 合集也Re.
: 因为我发现好像里面有不少观点跟我的思想相悖。
: 空气阻力？什么是空气阻力，
: ...................
--
FROM 137.226.140.*
For the equation F=Cd*A*density of air *V^2,
I think this only shows the pressure different force.
According to my study on wind speed measurement in these days,
I think the friction force is not included in that formula.
(This is only my thought)
From the aerodynamic point, the difference of pressure produces
two force: one is the trag force,the other is the lift force.
Changing the shape of the car body, can change the fluid field,
then change the trag force.
The trag coefficient is mainly depending on Renault number.
I don't and can't go into very detail,:)
Maybe I should ask fireleaf about it...
to be continued...
【 在 mika (New World, Take Time) 的大作中提到: 】
: According to my memory.
: The air drag force is mainly determined by two kind of force.
: One force is the friction force, which is generated by the friction between air molecule and the surface of the car body.
: ...................
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FROM 134.130.181.*