感潮河段交汇区水流特性数值模拟 --以宁波三江口为例

河流交汇为城市的发展提供了便利,对区域防洪、航运及河道演变影响重大。针对感潮河段交汇区域特有的非恒定往复流条件,以宁波三江口为例,运用Delft-3D建立二维水动力数学模型。基于实测水文和地形资料,引入四种评估参数对模型进行了率定与验证。重点分析了洪、枯两季涨、落急时刻,交汇区流速分布及水面形态等水流特性。结果表明:涨潮时,交汇区流场可类比分叉水流;落潮时,则为交汇水流;交汇区顶点及左支入汇侧下游存在两个低流速区,并可形成分离区;汇流区流速整体呈落潮大于涨潮的趋势,洪、枯季间最大流速相近。此外,涨、落急时刻典型特征断面水面呈单一横比降,且落急时刻比降明显大于涨急时刻;落急时,交汇口水面呈混合层附近高,两侧低的"马鞍形"分布。

Numerical simulation of flow characteristics in a tidal river confluence - A case study of Sanjiangkou in Ningbo City

Riv er confluence pr ovides convenience fo r the dev elopment of cities and has sig nificant inf luence on the reg ioncs flo od co nt rol, inland nav igat ion, and fluv ial pr ocesses. Aiming at the unidir ect ional flow s in a tidal river co nfluence ( Sanjiangkou, Ning bo city ) , w e established a two2dimensio nal hydro dy nam ic mathematical model using Delft23D. Based o n the measured hy dr olog ical and t opog raphic data, we applied four commo nly used parameters to calibr ate and validate the model r esults, focu2 sing on such flow characteristics as the tidal curr ent fields, velo city distribut ion and horizo nta l wat er lev el chang es at the max imum flood and ebb tides in w et and dry seasons. The results show ed that the f low f ield in the confluence area is analo go us to the distribut ary flow during t he flood tide, and is the co nfluence f low during the ebb t ide. There are tw o low2v elo city r eg io ns in the co nfluence vertex and the dow nstr eam of the left branch co nfluence area and they can form a separation reg ion. T he confluence flow v elocity during the ebb t ide is g enera lly lar ger than that during the flo od tide. The max imum f low velo cities in t he w et and dr y seasons ar e close. In additio n, the w ater surface of the thr ee ty pical cr oss2sections show s a sing le tr ansverse slo pe during the maximum floo d and ebb t ides. the w ater surface slo pe at the max imum ebb tide is g reater than that at the max imum f loo d tide. At the max imum ebb tide, the w ater surface of the confluence area is hig h near the mix ed layer and low at its tw o sides, show ing a " saddle shape" .