天然挺水植物明渠三维紊流特性研究

以天然挺水植物茭草、芦苇、水葱及模拟植物PVC管为试验材料并种植于大结构混凝土明渠中,研究其在流量及种植密度相同条件下明渠中水流的三维时均流速、脉动强度及雷诺切应力的分布特点。结果表明,明渠水流流速垂线更符合抛物线分布;天然挺水植物之间、天然挺水植物与PVC管间的时均流速分布相差较大,难以用一种分布模式描述;含挺水植物水流紊流特性表现出明显的各向异性;紊动强度与植物的生长形态及柔韧性密切相关;除水葱外,芦苇、茭草及PVC管的雷诺切应力-ρu′zu′x基本接近;相比天然挺水植物PVC管对水流切应力-ρu′yu′z影响最为显著;切应力-ρu′xu′y垂线分布于相对水深0.5处出现极值,总体呈ε形状。

Study of Three-dimensional Turbulent Characteristics in Open Channel with Natural Emerged Plant

In the concrete flume,taking the planted Zizania latifolia,reed,Scirpus tabernaemontani and PVC tube as the test materials,under the same conditions of discharge and planting density,the distribution characteristics of three-dimensional time average velocity,fluctuating intensity and Reynolds shear stress are analyzed in open channel flow.Test results show that the vertical velocity in open channel flow is more consistent with parabolic distribution;there exists obvious difference of those natural emerged plants including the PVC tube;the plant’s velocities are not accord with same law;the anisotropy of turbulent characteristics of natural emerged plant flow is obvious;fluctuating intensity have closely related with the plant’s growth style and flexibility;Reynold shear stress(-ρu′zu′x) of Zizania latifolia,reed and PVC tube display similar rule except Scirpus tabernaemontani;comparison of natural emerged plant,the influence of PVC tube on the shear stress of flow(-ρu′yu′z) is more significant;the extreme point of vertical shear stress(-ρu′xu′y) appears in the position of 50% depth and it has ε-style distribution as a whole.