關(guān)于Fluent的升力系數(shù)CL和阻力系數(shù)CD的正確理解

2017-05-18 by:CAE仿真在線來(lái)源:互聯(lián)網(wǎng)

關(guān)于Fluent的升力系數(shù)CL和阻力系數(shù)CD的正確理解,一般初學(xué)的同學(xué)都很容易搞錯(cuò),因?yàn)樵贔luent軟件中存在很多坑,極為容易掉下去。

本文先講講Cd,Cl可以以本文類(lèi)推。

1、公式:

關(guān)于Fluent的升力系數(shù)CL和阻力系數(shù)CD的正確理解fluent分析案例圖片1

Fd是阻力,p是流體密度,u是物體速度,A是參考面積。

A為什么不叫做投影面積呢?這點(diǎn)比較奇怪,原因是:飛機(jī)的升力系數(shù)是計(jì)算機(jī)翼的表面積,而不是投影面積,所以外國(guó)人叫做reference area了。

一般情況下,同一物體隨著速度的升高(對(duì)應(yīng)于雷諾系數(shù)Re增大),Cd呈現(xiàn)降低趨勢(shì)。

2、不同形狀的阻力系數(shù)的基本認(rèn)識(shí)

關(guān)于Fluent的升力系數(shù)CL和阻力系數(shù)CD的正確理解fluent分析案例圖片2

3、試驗(yàn)數(shù)據(jù):

不同物體的升力系數(shù)(試驗(yàn)數(shù)據(jù))
_C_{d系數(shù)}	物體
1.98–2.05	flat plate perpendicular to flow (2D)
1.8–2.0	Eiffel Tower
1.3–1.5	Empire State Building
1.28	flat plate perpendicular to flow (3D) ^[30]
1.2	Usain Bolt^[29]
1.1-1.3	ski jumper^[28]
1.0	coffee filter, face-up^{[unreliable source?]}^[26]
1.0	road bicycle plus cyclist, touring position^[27]
1.0–1.1	skier
1.0–1.3	wires and cables
1.0–1.3	man (upright position)
0.75	a typical model rocket^[25]
0.58	Jeep Wrangler TJ (1997-2005)^[24]
0.48	rough sphere ( $\!\ Re=\!\ 10^{6}$ ), Volkswagen Beetle^[22]^[23]
0.47	smooth sphere ( $\!\ Re=10^{5}$ )
0.37	Ford Transit Custom Mk8 (2013, Turkey)
0.36	Citroen CX (1974-1991, France)
0.35	Maserati Quattroporte V (M139, 2003–2012)
0.33	BMW E30 3 Series (1984-1993, Germany)
0.324	Ford Focus Mk2/2.5 (2004-2011, Europe)
0.31	Maserati Ghibli Sedan (2014) ^[21]
0.3	Saab 92 (1949), Audi 100 C3 (1982)
0.295	bullet (not ogive, at subsonic velocity)
0.29	Mazda3 (2007) ^[20]
0.28	1969 Dodge Charger Daytona and 1970 Plymouth Superbird
0.28	1986 Opel Omega saloon.^[18]
0.28	Mercedes-Benz CLA-Class Type C 117.^[19]
0.27	Nissan GT-R (2007-2010)
0.26	BMW i8
0.26	Nissan GT-R (2011-2014)
0.25	Toyota Prius (3rd Generation)
0.24	Tesla Model S^[16]
0.24	Toyota Prius (4th Generation)^[17]
0.235	Renault Eolab
0.212	Tatra 77A 1935
0.19	General Motors EV1 1996^[15]
0.186-0.189	Volkswagen XL1 2014
0.18	Mercedes-Benz T80 1939
0.15	Schl?rwagen 1939 ^[14]
0.1	smooth sphere ( $\!\ Re=10^{6}$ )
0.076	Milan SL (one of the fastest practical velomobiles) ^[13]
0.075	Pac-car
0.005	turbulent flat plate parallel to the flow ( $\!\ Re>10^{6}$ )
0.001	laminar flat plate parallel to the flow ( $\!\ Re<10^{6}$ )