洞顶余幅对泄洪洞内空气流动特性影响研究

Influence of tunnel top remaining width on air flow characteristics in spillway tunnels

洞顶余幅是影响泄洪洞需气量的一个重要因素,但目前此方面的研究成果还较为匮乏。采用数值模拟的方法研究了不同水流条件下洞顶余幅对泄洪洞洞内空气流场分布、流速变化以及隧洞通风量的影响规律。结果表明:当洞顶余幅大于40%时,空气流速断面分布在降低至零之前,近似于指数变化形式,而当洞顶余幅小于40%时,空气流速接近于线性分布形式;断面空气流速分布形式同时受洞顶余幅条件与水流条件的影响,当水流速度不变时,断面平均流速的峰值位置均出现在洞顶余幅为30%~40%的范围内;洞顶余幅越大,进气口附近的气流漩涡分布范围越广,同时,泄洪洞运行时所需的空气量也越大。

The remaining width at a tunnel top is an important factor affecting the air demand of spillway tunnels,but the research results in this field are still scarce.In this paper,numerical simulation method was used to study the influence of remaining width of tunnel top on distribution of air flow field,changing of flow rate and ventilation volume in spillway tunnel under different flow conditions.The following conclusions were drawn:when the remaining width at the tunnel top was more than 40%,the cross-section distribution of air flow velocity was approximate to the exponential change form before it was reduced to 0.When the remaining width at the tunnel top was less than 40%,the air velocity appeared to be close to the linear distribution form.The distribution form of air velocity in the section was affected by both remaining width condition and flow condition at the tunnel top.When the flow rate remained unchanged,the peak position of the average flow velocity in the section occurred within the remaining width of 30%~40%at the tunnel top.The larger the remaining width at the tunnel top,the wider distribution of air flow vortex near the intake port,also the larger the air volume required for the operation of the spillway tunnel.