掺气分流墩设施水力特性的试验研究

Experimental research on the hydraulic characteristics of aerated flow spilitting piers

掺气分流墩设施是设在陡坡急流中的大型分流墩.该分流墩将贴壁急流转变成为充分扩散、四面临空、剧烈紊动、充分掺气的水流.水舌在空中碰撞、混掺、碎烈、水滴化,大大增加了水流与空气的接触面.水流进入消力池时,入池单宽流量减小;消力池水流流态受下游水深控制,可以分为四种流态.该设施的最优收缩比范围为0.5～0.7.墩头脉动壁压满足重力相似,优势频率不满足重力相似且 fr=1,墩头脉动壁压优势频率在 0.1～0.388Hz 之间,远小于墩头自振频率.掺气分流墩属超空化体型,不会发生空蚀破坏.掺气分流墩设施的水舌掺气核心区长度仅为普通二元水舌核心区长度的 1/5～1/2,最小平均含水率仅为普通二元水舌的 14%,当 S/h＞20时,βsm逐渐趋于0.1,已为水滴化状态.消力池掺气充分.当λ=0.5 时,消力池底板压强系数减少了约30%.与普通二元水舌消力池比较,水跃长度可缩短1/3,跃后水深可降低1/5,消能率提高了(6～16)%.

The dissipator with an aerated flow splitting pier is a big flow splitting pier which is established on the abrupt slope. It can change the super flow into a flow that is sufficiently diffused, cutely turbulent and sufficiently aerated in all directions. Since the water jet though this pier collides, blends, disintegrates and falls in drops in the air, the interface surface between the flow and the air is significantly increased and the specific discharge decreases when the flow drops into the plunge pool. The flow condition in the plunge pool is controlled by the water depth downstream and can be classified into 4 kinds. The optimized contractibility ratio of the aerated flow splitting pier is changed within the scope of around 0.5~0.7. The fluctuating wall pressure of the pier head meets gravitational similitude law but the majority frequency f_(r) is unfit for the law as f_(r) is approaching 1 according to the experimental data. The majority frequency of fluctuating wall pressure of the pier head is around 0.1~0.388Hz which is far more less than the intrinsic frequency of the pier head. The body shape of the aerated flow splitting piers is super-cavitated so that no cavitating damage could occur. The length of the core of the aerated water jet through the aerated flow splitting pier is only 1/5~1/2 of that of 2-d aerated water jet. The ratio of the minimum containing water is only 14 percentage of 2-d aerated water jet. On the condition that s/h is greater than 20, β_(sm) gradually inclines to 0.1, and the flow is sufficient to aerate and drip in air and so is the flow in the plunge pool. The pressure coefficient at the bottom of the plunge pool is decreased by about 30 percentage at λ=0.5. Compared with 2-d water jump, the length of the stilling basin is decreased by about 1/3, and the water depth downstream is by about 1/5 and the efficient of the energy-dissipation is increased by 6~16 percentage.