基于CFD的空心高墩防风超高模板优化研究

Optimization on Windbreak Ultra-High Formwork for Hollow High Piers Based on CFD

根据兰新铁路第二双线(新疆段)在风区进行高墩施工时的防风要求,提出在常规模板上再加高一段模板的高墩超高模板防风方法。运用大型商用软件FLUENT,采用计算流体动力学方法 (CFD),对不同来流方向条件下、内外模板不同加高组合方案空心高墩防风超高模板的三维绕流场进行数值模拟计算,依据施工人员安全、混凝土养护和施工综合效率3个方面的折减后综合等效风速比评价防风效果,进行空心高墩防风超高模板优化研究。结果表明:由于迎风侧超高模板的阻挡作用,来流在空心墩内部形成回流,气流沿背风侧顺时针流向迎风侧,空心墩内部迎风侧风速较背风侧小,墩内迎风侧可用于施工人员的临时避风;防风超高模板采用外模板超高1.5m、内模板不超高的方案为最优,其折减后综合等效风速比为0.2。

Considering the windbreak requirement for high pier construction of the second double-line pro- ject （Xinjiang part） on Lanzhou-Xinjiang Railway, the windbreak method with ultra-high formwork is presented, that is, an extra formwork section is installed above the normal formwork. With large commer- cial software FLUENT and by means of Computational Fluid Dynamics （CFD） method, the 3D ambient flow fields of the windbreak ultra-high formworks for hollow high piers with integrated schemes of differ- ent height of internal and external formworks are analyzed in different incoming flow directions. The wind- break effect of the ultra-high formwork for high piers is evaluated so as to optimize the windbreak ultra- high formworks for hollow high piers based on the reduced comprehensive equivalent wind speed rate for construction personnel safety, concrete curing and construction overall efficiency. Results show that wind recirculation is formed by the incoming flow inside the hollow pier due to the blocking effect of the ultra- high formwork along windward side. The air flows clockwise from leeward side to windward side. The wind speed of windward side is slower than that of leeward side in hollow pier, and windward side in hol- low pier can be the temporary shelter from wind for construction personnel. The optimal scheme with the reduced comprehensive equivalent wind speed rate 0. 2 is that only external formwork is 1.5 m higher than concrete surface while the height of internal formwork is normal.