【作者】 陈森；

【导师】 蔡枫；

【作者基本信息】 福州大学 ， 水利工程（专业学位）， 2018， 硕士

【摘要】 箱式丁坝是视双丁坝及其包围的内部区域为整体的一个单元体,在其上游丁坝上设置缺口,形成上游横向交界面,可在箱体内创造出丰富的水流结构和地形环境,从而改善箱内生境条件以达到生态保护的目的。故具有上游横向交界面的箱式丁坝(即单缺口箱式丁坝)可成为潜在的广泛应用于河流生态治理和恢复的新型水工建筑物。本文将具有上游横向交界面(缺口)的箱式丁坝单元体作为研究对象,主要考虑以缺口长度占丁坝长度的比值(缺占比)、缺口偏离上游丁坝中心的比例(缺偏比)、缺口阻水率三个缺口形态参数作为研究变量,采用数值模拟试验和物理模型试验相结合的方法探讨其对具有上游横向交界面的箱式丁坝(单缺口箱式丁坝)水流结构和水体交换过程的影响规律,并将研究结果模拟应用于工程当中以评价其效果,主要研究成果如下:(1)上游横向交界面(缺口)形成后,箱式丁坝内部存在明显分区,不仅存在相对平静、泥沙易落淤的回溯环流区与涡流区,还具有相对流速较大、泥沙易冲蚀的过缺口水流与绕流;相比常规实体丁坝具有更丰富的水流结构。(2)缺占比越大,回溯环流区和涡流区的平面尺度越小,但流速无明显差异;过缺口水流和绕流水的流速值越小;箱内平均流速、交界面综合交换流速越大;水体交换能力越强。缺占比为0.25时为较优工况配置。(3)缺偏比的增减对过缺口水流和绕流水的流速值、水体交换能力均无较大影响;缺偏比越大,偏转角度越小,涡流区平面尺度愈小,回溯环流区平面尺度愈大。缺占比接近或等于1时为较优工况配置。(4)缺口阻水率小于0.5,过缺口水流偏向主流;缺口阻水率大于0.5,过缺口水流不发生偏转;缺口设置底坎可减小下潜流的流速,从而减轻下潜流对上游丁坝缺口段和坝头的冲刷作用;缺口阻水率为0.4～0.5时为较优工况配置。(5)生态保护型箱式丁坝工程设计中,缺占比不宜大于0.33、缺偏比不宜低于0.4、缺口阻水率不宜大于0.5,并综合考虑水体交换能力适中的工况配置,才能保护回溯环流区尺度并制造局部冲槽为生物提供所需的庇护场所。(6)将较优工况配置应用到闽江南港段,在上游丁坝设置缺口后,其坝头周围流速减小10%,坝头压力得到释放;过缺口水流打破原回溯环流区,使得箱内既有生态栖息静态区域,又有繁衍觅食动态区域。更多还原

【Abstract】 The box groyne with notch is a system which is integrated with the double-groyne and their inner region,and the water flow structure and the water exchange process in the box are controlled by the transverse interface in upstream groyne and the longitudinal interface between the two groyne heads.Setting a notch in upstream groyne enriches the water flow structure and the terrain environment,improving the habitat conditions in the box to achieve the purpose of ecological protection.Therefore,the box groyne with notch can become a potential new hydraulic structure widely used for river ecological rehabilitation and rehabilitation.This paper is based on the national natural science fund project to study the box groyne with upstream transverse interface(notch).The ratio of notch length to groyne length and the ratio that notch offset from the center of the upstream groyne and the notched water resistance rate are main morphological parameters of upstream transverse interface(notches)that are regard as research variables,and using the method of combining physical model experiment and numerical simulation experiment to study the influence of the shape parameters of the notch to the hydraulic characteristic of box groyne with notch.The results of the study will be simulated and applied to the project to evaluate the effect.The main conclusions is following:(1)There is obvious partition inside the box groyne with notch.There is not only a relatively calm backtracking circulation region and eddy current zone where the sediment is easy to silt,but also a notched flow and flow around groyne that it has a relatively large velocity and the sediment is easy to scour.Compared with conventional solid groyne,it has more abundant flow structure.(2)With the increase of the ratio of notch length to groyne length,the plane measure of backtracking circulation region and eddy current region become smaller,but there is no significant difference in flow velocity.As the velocity values of notched flow and flow around groyne become smaller,the average flow velocity in the box and the comprehensive exchange rate of the interface become larger,and water exchange capacity become stronger.There is configuration of optimal working condition when ratio of notch length to groyne length is 0.25.(3)There is no significant influence on the water exchange capacity and the velocity values of notched flow and flow around groyne and deflection mode of notched flow by the increase or decrease of the ratio of notch deviation.The greater the ratio of notch deviation,the smaller the deflection angle,and the smaller the plane scale of eddy current region,and the larger the plane scale of backtracking circulation region.There is configuration of optimal working condition when the proportion of the notch to be close to or equal to 1.(4)The notched flow is biased toward the mainstream when the notched water resistance rate is less than 0.5;the notched flow does not deflect when the notched water resistance rate is greater than 0.5;the notch setting sill can reduce the absolute value of the flow velocity of the downflow near the upstream and downstream groyne,thus reducing the scour effect of downflow.There is configuration of optimal working condition when the notched water resistance rate is 0.4 to 0.5.(5)In the engineering design of ecological protection type box groyne,the ratio of notch length to groyne length should not be greater than 0.33,and the ratio of notch deviation should not be less than 0.4,and the notched water resistance rate should not more than 0.5.At the same time,we should consider the condition that the exchange capacity of water body is moderate,so that it is possible to protect the scale of the back circulation area well and provide the necessary refuge places for the living things.(6)Applying optimal working condition configuration to South Minjiang Port Section.After the notch is set up in the upstream groyne,the velocity of flow around the groyne head decreases by 34%and the pressure of the dam head is released.The notched flow turn to the main stream after it enter the box and flows out of the box body through the longitudinal interface,which breaks the original backtracking circulation area and makes the box have both the static ecological habitat region and the dynamic region of breeding and foraging.更多还原