河床沉积物非均质性影响下的潜流交换数值模拟
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摘要
为了揭示河床沉积物非均质性对潜流交换的影响,构建了沙波地形作用下的地表水-地下水耦合模型,通过生成不同的渗透系数随机场,讨论了不同地表水动力过程和河床沉积物非均质性对潜流交换通量、交换空间及平均停留时间的影响规律。结果表明,所构建的地表水-地下水耦合模型能够准确刻画水沙界面附近流场,模型具有良好的适用性;均质或非均质河床沉积物情景下,水沙界面上的平均交换通量、停留时间与雷诺数之间均呈现幂函数关系,潜流交换深度则在地表水进入完全紊流之后趋于稳定。结果还表明,较强的河床沉积物非均质性能够有效增强水沙界面上潜流交换通量和空间交换频率,但会制约潜流交换空间并缩短水流在潜流带中的停留时间。
The hyporheic exchange plays a crucial role in maintaining fluvial ecological processes. In order to examine the influence of streambed heterogeneity on the hyporheic exchange,a surface water-groundwater coupling model is constructed for solving flow interactions over a sand dune. By generating different permeability random fields,the influences of hydrodynamic processes and streambed heterogeneity on the hyporheic exchange flux,exchange space and mean residence time are addressed. The results showed that the coupling model has good performance and it can accurately depict the flow fields near the sediment-water interface. Under homogeneous or heterogeneous scenarios,the mean exchange flux and bulk residence time via Reynolds number are representing power law relationships,and the mean exchanged depth tends to be stable after the surface flow transitions into highly turbulent conditions. Results further shown that higher heterogeneity can effectively enhance the hyporheic exchange flux and spatial exchange frequency along the sediment-water interface. However,it will restrict the exchange volume and shorten the mean residence time of flow in the hyporheic zone.
The hyporheic exchange plays a crucial role in maintaining fluvial ecological processes. In order to examine the influence of streambed heterogeneity on the hyporheic exchange,a surface water-groundwater coupling model is constructed for solving flow interactions over a sand dune. By generating different permeability random fields,the influences of hydrodynamic processes and streambed heterogeneity on the hyporheic exchange flux,exchange space and mean residence time are addressed. The results showed that the coupling model has good performance and it can accurately depict the flow fields near the sediment-water interface. Under homogeneous or heterogeneous scenarios,the mean exchange flux and bulk residence time via Reynolds number are representing power law relationships,and the mean exchanged depth tends to be stable after the surface flow transitions into highly turbulent conditions. Results further shown that higher heterogeneity can effectively enhance the hyporheic exchange flux and spatial exchange frequency along the sediment-water interface. However,it will restrict the exchange volume and shorten the mean residence time of flow in the hyporheic zone.
引文
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[11] CHEN X,CARDENAS M B,CHEN L.Hyporheic exchange driven by three-dimensional sandy bed forms:sensitivity to and prediction from bed form geometry [J].Water Resources Research,2018,54(6):4131- 4149.
[12] TOMPSON A F B,ABABOU R,GELHAR L W.Implementation of the three-dimensional turning bands random field generator [J].Water Resources Research,1989,25(10):2227-2243.
[13] GELHAR L W.Stochastic subsurface hydrology from theory to applications[J].Water Resources Research,1986,22(9s):135-145.
[14] KLINGBEIL R,KLEINEIDAM S,ASPRION U,et al.Relating lithofacies to hydrofacies:outcrop-based hydrogeological characterisation of Quaternary gravel deposits [J].Sedimentary Geology,1999,129(3/4):299-310.
[15] CHEN X,CARDENAS M B,CHEN L.Three-dimensional versus two-dimensional bed form-induced hyporheic exchange[J].Water Resources Research,2015,51(4):2923-2936.
[16] JANSSEN F,CARDENAS M B,SAWYER A H,et al.A comparative experimental and multiphysics computational fluid dynamics study of coupled surface- subsurface flow in bed forms[J].Water Resources Research,2012,48(8):W08514.
[2] CARDENAS M B,WILSON J L,ZLOTNIK V A.Impact of heterogeneity,bed forms,and stream curvature on subchannel hyporheic exchange [J].Water Resources Research,2004,40(8):474- 480.
[3] SAWYER A H,CARDENAS M B.Hyporheic flow and residence time distributions in heterogeneous cross-bedded sediment [J].Water Resources Research,2009,45(8):W08406.
[4] PRYSHLAK T T,SAWYER A H,STONEDAHL S H,et al.Multiscale hyporheic exchange through strongly heterogeneous sediments [J].Water Resources Research,2015,51(11):9127- 9140.
[5] SALEHIN M,PACKMAN A I,PARADIS M.Hyporheic exchange with heterogeneous streambeds:laboratory experiments and modeling [J].Water Resources Research,2004,40(11):309-316.
[6] RYAN R J,BOUFADEL M C.Influence of streambed hydraulic conductivity on solute exchange with the hyporheic zone [J].Environmental Geology,2006,51(2):203-210.
[7] GOMEZ-VELEZ J D,KRAUSE S,WILSON J L.Effect of low-permeability layers on spatial patterns of hyporheic exchange and groundwater upwelling [J].Water Resources Research,2014,50(6):5196-5215.
[8] BLOIS G,BEST J L,SAMBROOK SMITH G H,et al.Effect of bed permeability and hyporheic flow on turbulent flow over bed forms [J].Geophysical Research Letters,2015,41(18):6435- 6442.
[9] 陈孝兵,赵坚,李英玉,等.床面形态驱动下潜流交换试验 [J].水科学进展,2014,25(6):835-841.(CHEN X B,ZHAO J,LI Y Y,et al.Experimental study of bedform-drived hyporheic exchange [J].Advances in Water Science,2014,25(6):835-841.(in Chinese))
[10] 鲁程鹏,束龙仓,陈洵洪.河床地形影响潜流交换作用的数值分析 [J].水科学进展,2012,23(6):789-795.(LU C P,SHU L C,CHEN X H.Numerical analysis of riverbed topography influencing hyporheic exchange [J].Advances in Water Science,2012,23(6):789-795.(in Chinese))
[11] CHEN X,CARDENAS M B,CHEN L.Hyporheic exchange driven by three-dimensional sandy bed forms:sensitivity to and prediction from bed form geometry [J].Water Resources Research,2018,54(6):4131- 4149.
[12] TOMPSON A F B,ABABOU R,GELHAR L W.Implementation of the three-dimensional turning bands random field generator [J].Water Resources Research,1989,25(10):2227-2243.
[13] GELHAR L W.Stochastic subsurface hydrology from theory to applications[J].Water Resources Research,1986,22(9s):135-145.
[14] KLINGBEIL R,KLEINEIDAM S,ASPRION U,et al.Relating lithofacies to hydrofacies:outcrop-based hydrogeological characterisation of Quaternary gravel deposits [J].Sedimentary Geology,1999,129(3/4):299-310.
[15] CHEN X,CARDENAS M B,CHEN L.Three-dimensional versus two-dimensional bed form-induced hyporheic exchange[J].Water Resources Research,2015,51(4):2923-2936.
[16] JANSSEN F,CARDENAS M B,SAWYER A H,et al.A comparative experimental and multiphysics computational fluid dynamics study of coupled surface- subsurface flow in bed forms[J].Water Resources Research,2012,48(8):W08514.