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隧道在进行通风设计时,需考虑到摩擦阻力对于空气流动的影响,其中衬砌的壁面粗糙度是决定通风摩阻大小的一个重要因素。为了研究隧道洞壁粗糙度对通风摩阻系数的影响,采用Fluent软件建立模型,通过改变隧道壁面粗糙单元的高度、间距以及断面直径等控制因素来研究通风摩阻的变化。结果表明:当气流掠过壁面且流速很小时,壁面附近的流线基本与壁面粗糙单元的外轮廓相平行,而当流速超过一定值时,靠近壁面的流线会与壁面产生一定程度的流动脱离、回流;在初始风速一定的前提下,壁面粗糙度越大,壁面的摩阻损失系数越大,壁面粗糙度越小,粗糙单元对流体流动所起到的阻碍作用越小。结合大部分公路隧道的实际情况进行归纳并提出了隧道壁面摩阻损失系数参照表,可直接依照隧道的实际参数选取摩阻损失系数值,对隧道通风设计具有一定的参考价值。
Tunnel ventilation design, the need to take into account the frictional resistance on the air flow, in which the wall lining roughness is to determine the size of the ventilation friction is an important factor. In order to study the influence of the tunnel wall roughness on the ventilation friction coefficient, the Fluent software was used to establish the model. The changes of the ventilation friction resistance were studied by changing the height, spacing and section diameter of the roughness elements in the tunnel wall. The results show that when the air flow passes the wall and the flow velocity is small, the flow line near the wall is basically parallel to the outer contour of the wall roughness unit. When the flow velocity exceeds a certain value, the flow line near the wall will produce a certain degree of flow with the wall Off and backflow. Under the premise of a certain initial wind speed, the larger the wall roughness, the larger the coefficient of friction loss of the wall and the smaller the roughness of the wall, the smaller the effect of the roughness unit on fluid flow. Combining with the actual situation of most of the tunnels, the reference table of the friction loss coefficient of the tunnel wall is proposed and the coefficient of friction loss can be selected directly according to the actual parameters of the tunnel, which is of certain reference value to the tunnel ventilation design.