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宽窄复式河道水流运动特性的试验研究 总被引:2,自引:0,他引:2
在分析水槽试验资料的基础上,首次对宽窄复式河道的滩槽过流能力、断面平均流速、垂线流速及横向分布等水流运动特性进行了研究.研究结果表明,宽窄复式河道的主槽流量随着滩槽宽度比的增大而减小,滩地流量随着滩槽宽度比的增大而增大;水流发生漫滩之后,随着水深的增加,主槽流速先减小后增加,滩地流速不断增加,二者的变化幅度与滩槽宽度比有关;在大部分区域内垂线流速偏离对数分布,主槽一般偏小,滩地偏大;垂线平均流速沿横向分布与一般复式河道相似,但滩槽流速差别减小. 相似文献
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该研究建立了室内水槽概化模型,模拟珠江三角洲典型窄滩复式河道。通过有植被和无植被条件下滩地的水动力特性对比,定性分析滩地有无种树对窄滩复式河道水动力特性的影响。结果表明:受种树影响,种树带进口处水位显著壅高,以此建立经验公式,可用于估算河道种树所引起的上游水位最大壅高量值,从而获得滩地种树对行洪的影响。种树后,水流发生归槽现象,滩地流速、流量沿程减小并最终趋于稳定,主槽流速增大;当滩地水深较大时,受种树带对过水断面的束窄作用,主槽流速在进入种树带后急剧增大,流速的增大有可能引起主槽冲刷增强,加剧河床下切侵蚀。该研究成果不仅能加深对河漫滩水力学的理论认识,同时可为以珠江三角洲为代表的窄滩复式断面河道种树规划设计提供技术依据。 相似文献
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漂浮植被占用了行洪断面面积,增大了河流的阻力,遇到障物后,造成河道严重堵塞。通过室内物理模型试验和数值模拟的方法,研究、分析大面积覆盖水面的漂浮植被对河道泄洪能力、河道水体结构、水流特性的影响。根据紊动强度和雷诺应力沿程变化,从波动幅度上看,植物覆盖区波动幅度较大;对根茎区,无植物覆盖但受影响区紊动强度不大,但较无植物覆盖时的明渠水流有明显增大,植物坝覆盖区及植物坝前缘区变化显著,尤其是植物坝前缘区的紊动强度波动很剧烈。 相似文献
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黄河下游复式河道滩槽分流特征研究 总被引:3,自引:0,他引:3
采用实测资料分析和理论探讨相结合的方法,研究了黄河下游复式河道滩槽分流特征及其主要影响因素。研究结果表明:1986年后,河道萎缩,相同洪水流量下,主槽分流比有所减小,滩地分流比有所增大;1999年后,小浪底水库蓄水拦沙运用,下游河道持续冲刷,主槽过流能力有所恢复,主槽分流比必然有所增大。运用回归分析方法,建立了黄河下游复式河道滩槽分流比与滩槽过水宽度比、过水深度比、过水面积比、流速比、糙率比和主槽宽深比的单因素响应关系和多因素综合关系,在此基础上提出,定量方面,可运用多因素综合关系式依据未来滩槽6项单因素大小对黄河下游复式河道滩槽分流比进行预测;定性方面,在黄河下游滩槽治理过程中,应注意维持主槽一定的平滩流量和较为窄深的断面形态;注意给滩地留出一定的行洪宽度,在必要的行洪宽度内,尽量减少人类活动对滩地的影响,保持滩地畅通的过水通道,保证滩地相应的过洪能力,减轻河道行洪压力,从而达到确保全断面行洪安全的目的。 相似文献
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漫滩水流流速垂线分布规律的研究 总被引:6,自引:0,他引:6
根据顺直河道漫滩水流的运动特点,将复式河道的横断面分为主槽平衡区,滩槽交互区,滩地平衡区及边壁区等4个区,在此基础上,结合水槽试验资料,分析得出漫滩水流各区的流速垂线分布规律,并对现有的对数流速公式进行了修正。 相似文献
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天然河流主槽和滩地间存在复杂的水体交换和混掺。利用大涡数值模拟(LES)研究复式断面明渠浅滩深度和雷诺数对湍流结构的影响,研究结果表明:明渠二次流强度和脉动强度在主槽浅滩深度比为1/2时最大;滩槽交界区二次流对顺流向流速结构有较大影响,并使紊动能发生重分布;复式断面明渠二次流强度和脉动强度随着雷诺数的增加逐渐增大并趋于稳定。 相似文献
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Geng Li Caroline M. Elliott Bruce C. Call Brandon J. Sansom Robert B. Jacobson Binbin Wang 《河流研究与利用》2023,39(9):1857-1874
River turbulence is spatially variable due to interactions between morphology of rivers and physical mechanics of flowing water. Understanding the variation of turbulence in rivers is important for characterizing transport processes of soluble and particulate materials in these systems. We present an exploratory effort to understand ecologically relevant flow patterns using measurements of mean flow and turbulence in a highly engineered river channel around an island in the lower Missouri River. Specifically, the profiles of mean river velocities were investigated to examine the logarithmic relation and associated parameters, including shear velocity and bed roughness. Turbulence intensity and Reynolds shear stress were compared with classic open-channel profiles and previously reported river data in the hydraulics literature. With the capability of pulse-to-pulse coherent Doppler velocity profiling in high spatial resolution, we estimated the profiles of turbulence dissipation rate using resolved one-dimensional velocity spectra. These measurement data allow us to examine the validity of turbulence production-dissipation balance and the classic open-channel profiles of turbulence statistics, including turbulence intensity, Reynolds shear stress, dissipation rate, and eddy viscosity. The field data show a strong variation of turbulence profiles in close vicinity of the river island. In shallow water depths close to the island, turbulence is substantially enhanced in comparison with classic open-channel profiles. Such turbulence enhancement is likely attributed to non-uniformity of the flow structures. 相似文献
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《水科学与水工程》2022,15(3):265-272
Compound open channel flows appear in most natural rivers are of great importance in river management and flood control. In this study, large eddy simulations were carried out to simulate the compound open channel flows with four different depth ratios (hr = 0.10, 0.25, 0.50, and 0.75). The main flow velocity, secondary flow, Reynolds stress, and bed shear stress were obtained from numerical simulations. The depth-averaged streamwise momentum equation was used to quantify the lateral momentum exchange between the main channel and floodplain. The instantaneous coherent structures were presented by the Q criterion method. The impact of hr on flow structure and turbulence characteristics was analyzed. The results showed that with the increase of hr, the high velocity area in the main channel shifted to the floodplain, and the dip phenomenon became more obvious; the Reynolds stress largely contributed to the lateral momentum exchange within the flows near the side walls of floodplain; and the vortex structures were found to significantly increase in the floodplain region. 相似文献
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利用室内变坡水槽,模拟了复式河道滩地3种植物对漫滩水流的干扰作用,并借助声学多普勒测速仪(ADV)施测了不同垂线、不同测点的瞬时流速,计算了不同条件下的河道糙率。基于水动力及植物柔性变形分析,建立了淹没状态下的植物河道糙率计算的基本关系,反映出糙率值不仅与水流动力条件有关,还与植物类型、淹没高度、布置及其自身力学性能有关,同时,利用试验资料及理论分析成果,进一步获取了植物河道的附加糙率值,借此分析与评价河道植物对水流阻力的影响程度。 相似文献
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Turbulent flow in natural river channels drives geophysical processes and exerts a fundamental influence on aquatic biota. An extensive range of turbulence properties have previously been synthesized into four categories or “dimensions” with ecological relevance: intensity, periodicity, orientation and scale (IPOS). We apply this framework across three rivers with differing morphologies in order to assess the statistical coherence of the four IPOS categories within turbulence field data and their utility in discriminating between fundamental units of river habitat. Intensity, periodicity-scale and orientation were identified as the key gradients in the turbulence data set using multivariate analysis. These gradients all revealed statistically significant differences between rivers and/or geomorphic units. The intensity gradient accounted for the highest variance and most pronounced inter-reach differences, but the periodicity-scale and orientation gradients were also useful in distinguishing between certain combinations of rivers and/or geomorphic units. Different turbulence gradients, or combinations of gradients, were important in characterizing differences between rivers and geomorphic units (riffes, pools, steps). The gradients provided improved prediction of geomorphic units compared to standard hydraulic variables (mean velocity, depth), although the extent of improvement in prediction varied between river morphologies. The analysis reveals the statistical coherence of the four categories or “dimensions” of turbulence in multivariate space, connects the ecologically defined IPOS categories of turbulence properties with river types and fundamental units of river habitat (geomorphic units). Turbulence signatures of natural channel morphology are expressed across all four dimensions of turbulence, providing clear evidence that these four dimensions should be routinely considered in ecohydraulics and hydromorphology research to facilitate a full understanding hydraulic habitat. 相似文献
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复式河槽综合糙率计算方法比较与分析 总被引:7,自引:0,他引:7
综合糙率是复式河槽水力计算的一个重要参数。本文系统地总结了推求综合糙率的各种典型方法,包括Pavlovskij方法.Einstein-Banks方法,Lotter方法,Krishnamurthy-Christertsen方法以及Dracos-Hardegger方法。运用277组复式河槽水槽实验资料和野外实测资料,验证了上述各种方法的有效性。通过比较和分析,发现这些方法都不适用于估算复式河槽综合糙率。本文对这些方法产生误差的原因进行了分析,并指出产生误差的原因在于前四种方法忽略了滩槽动量交换;后一种方法虽然考虑了动量交换,但该方法并不普遍适用。本文对现有资料的分析,提出了一个滩槽糙率相同情况下的复式河槽综合糙率关系式。 相似文献
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淤滩与刷槽之间没有必然的联系 总被引:1,自引:0,他引:1
实测资料与动床摸型试验均表明,在洪水过程中淤滩与刷槽虽然同时发生,但它们之间并没有必然的联系。在多沙河流上洪水漫滩必然会造成滩地淤积,并在滩唇形成自然堤,阻断滩槽水流交换;主槽的冲刷发生在涨水期,在落水期不管含沙量大小,河床均处于淤积状态。漫滩后的清水在滩地上流动缓慢,远远小于主槽水流的运动速度,因此漫滩水往往在落水期才能汇入主槽,且只能起到减少主槽淤积的作用,无法改变由于洪水的非恒定性形成的落水期河床必然淤积的状态。实测资料表明,含沙量100~200 kg/m3的不漫滩洪水在涨水期仍可造成主槽的强烈冲刷。 相似文献
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复式断面河流洪水的水流特性 总被引:9,自引:0,他引:9
本文描述了复式断面河流洪水的水流特性,并用流体力学的基本理论加以论证。在各国学者对复式断面洪水研究成果的基础上,建立了亲的能量耗散的理论模型。 相似文献