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Mahyar Kazemian，硕士
2023-01-16

VE0308 | 欧洲规范 圆柱形状

项目介绍

在欧洲规范 EN 1991-1-4{%32 中引用了 [1]]]、ASCE/SEI 7-16 和 NBC 2015 等规范中规定了风荷载参数，例如风压系数 (Cp )基本形状。 The important point is how to calculate wind load parameters faster and more accurately rather than working on time-consuming as well as sometimes complicated formulas in standards.

One of the important points in the CFD simulation is to find accurate and compatible configurations regarding input data such as turbulence models, wind velocity profile, turbulence intensity, boundary layer condition, order of discretization, and so on, which are not mentioned in Eurocode. In the current example for cylinder shape, we recommend compatible settings regarding the Eurocode standard. As can be seen in EN 1991-1-4, there are complicated formulas to obtain the Cp value related to different Reynolds numbers.

Analytical Solution

The dimension of the cylinder as shown in Figure 1 is designed for Reynolds number (Re= 2*106) based on the Equation 7.15 (EN 1991-1-4), where b is the diameter, ν is the kinematic viscosity of the air (ν=15*10-6 m2/s), v(ze) is the peak wind velocity:

Re=b⋅v(ze)ν=1⋅301.5⋅10-5=2⋅106
雷诺值
气缸尺寸（单位：米）
气缸尺寸（单位：米）

Here are the assumptions and recommended settings (Table 1), which present better agreement with Cp and force coefficient value with Eurocode example :

风速 V 30 m/s
Reynolds Number (Equation 7.15, EN 1991-1-4) Re 2*106 -
高度 l 1 m
直径 D 1 m
Position of the Minimum Pressure/Flow Separation (Table 7.12, EN 1991-1-4) αmin/αA 80/120 度
Value of the Minimum Pressure Coefficient (Table 7.12, EN 1991-1-4) Cp0,min -1.9 -
Base Pressure Coefficient (Table 7.12, EN 1991-1-4) Cp0,h -0.7 -
The Solidity Ratio (Equation 7.28, EN 1991-1-4) φ 1 -
The Effective Slenderness (Table 7.16, EN 1991-1-4) λ 1 -
End-effect Factor (Figure 7.36 - Equation 7.17, EN 1991-1-4) ψλ - ψλa 0.6-(0.6-1) -
Force Coefficient (Figure 7.28, EN 1991-1-4) Cf,0 0.55 -
Air Density ρ 1.25 kg/m3
Turbulence Model Steady RANS k-ω SST - -
Kinematic Viscosity (Equation 7.15, EN 1991-1-4) ν 1.5*10-5 m2/s
Scheme Order 第二 - -
Residual Target Value 10-5 - -
Residual Type 压强 - -
Minimum Number of Iterations 800 - -
Boundry Layer NL 10 -
Type of Wall Function Enhanced / Blended - -
Turbulence Intensity (Best Fit) i 7.5%-15% -

结果

Finally, the Cp contour for 7.5% turbulence intensity (Figure 2) and the diagram for various turbulence intensities are plotted in Figure 3, in which I=7.5% is shown better agreement in predicting the average wind pressure coefficient. For another criterion (Force coefficient Cf,0 in Table 2) which can be obtained regarding Figure 7.28 in EN 1991-1-4, the value of 15% is closer to Eurocode example.

I=7.5% 时圆柱体的 Cp 等值线
I=7.5% 时圆柱体的 Cp 等值线
RWIND 2中不同湍流强度的Cp值与欧洲规范的比较
RWIND 2中不同湍流强度的Cp值与欧洲规范的比较
Turbulence Intensity (%) Fd (N) ρ (kg/m3) u (m/s) A (m2) Cf,0
1.00 253 1.25 30 1 0.45
5.00 226 1.25 30 1 0.40
7.50 253 1.25 30 1 0.46
10.00 257 1.25 30 1 0.46
15.00 303 1.25 30 1 0.54
20.00 328 1.25 30 1 0.58
25.00 361 1.25 30 1 0.64
欧洲规范 - - - - 0.55

Also, the cylinder model with recommended settings is available to download here:

《欧洲规范》圆柱验算示例
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《欧洲规范》圆柱验算示例
参考
  1. 欧洲标准化委员会。 (2005)。 EN 1991-1-4 欧洲规范 1： 结构作用 - 第 1-4 部分： 一般作用-风荷载作用。
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