输水渠道潜冰运动规律的物理模型与数值模拟研究

发布时间：2018-02-13 07:29

本文关键词： 潜冰启动物理模型数值模型临界条件压差分布　出处：《天津大学》2014年硕士论文　论文类型：学位论文

【摘要】：高纬度地区的输水渠道在冬季输水过程中，会形成冰塞、冰坝等冰情现象。这将显著的减小输水流量、抬高水位，而冰塞体的溃决会造成下游更严重的灾害。下潜至冰盖底面的冰凌称为潜冰。由于冰凌下潜和停滞是冰塞形成和发展的基础，在研究冰凌下潜临界条件的基础上，本文进一步研究潜冰运动规律，，特别是停滞与启动的临界条件，对冰害的防治具有重要意义。本文采用物理模型与数值模拟相结合的方法进行研究，按照重力相似准则，开展了不同水流条件和冰凌尺度的潜冰运动物理模型试验；建立了三维数值模型，分析潜冰的水动力特性，并获得了潜冰停滞与启动临界条件。具体研究内容与成果概括如下：（1）选择密度接近天然冰密度的聚乙烯作为冰盖和潜冰的模型材料。对模型试验的相似准则进行了研究，按照重力相似准则对潜冰的运动状态进行了物理模型试验。通过改变冰盖下水流速度V、水深h及潜冰的形状（厚度t，长度l，宽度b）等因素，证实了潜冰的纵向启动流速大于横向启动流速。潜冰运动规律研究的关键为研究纵向状态潜冰的临界条件——停滞与启动。试验获得了潜冰临界状态的影响因素：随着相对形状t/l，相对水深t/h及相对宽度b/B的增加，潜冰的临界冰厚Froude数Ft相应减小。对不同工况下试验数据进行回归分析，得到更为准确的潜冰滑动启动临界条件的形式。（2）为进一步分析潜冰的临界状态，采用数值模拟研究潜冰底面水压力的计算方法。结合Realizable-紊流模型，及壁面函数对潜冰底面的文丘里效应和前缘效应进行了精准的模拟。以Larsen的物理模型试验为原型建立数值模型，获得冰盖下流速V沿水深h的分布情况。将数值模型输出结果与试验数据进行对比，证实模拟结果的有效性。通过分析文丘里效应和前缘效应的影响因素：冰盖下水流流速V，相对水深t/h和相对宽度b/B，得到了非全宽潜冰的文丘里效应和前缘效应的修正计算公式。在此基础上进行积分，获得了潜冰底面水压力的估算公式。（3）基于对水压力、拖曳力、剪切力、有效浮力及摩擦力的研究，分析潜冰的受力平衡，获得了潜冰停滞与启动临界条件的计算公式。通过对比该计算公式与试验数据，验证了计算公式的准确性。
[Abstract]:In the course of winter water conveyance in high latitudes, ice jams, ice dams and other ice conditions will be formed. This will significantly reduce the flow of water and raise the water level. And the collapse of the ice plug can cause a more serious disaster downstream. The ice that submerges to the bottom of the ice sheet is called ice diving. Because the ice drop and stagnation are the basis for the formation and development of the ice slug, on the basis of studying the critical conditions for ice ice diving, In this paper, it is of great significance to study the law of submersible ice movement, especially the critical condition of stagnation and start-up, for the prevention and cure of ice damage. In this paper, the method of combining physical model with numerical simulation is used to study, according to the principle of gravity similarity, the physical model tests of subsurface ice motion with different flow conditions and ice scale are carried out, and the three-dimensional numerical model is established. The hydrodynamic characteristics of submersible ice are analyzed, and the critical conditions of ice stagnation and start-up are obtained. The specific research contents and results are summarized as follows:. 1) Polyethylene with density close to natural ice density was selected as model material for ice sheet and latent ice. The similarity criterion of model test was studied. According to the gravity similarity criterion, the physical model tests on the motion state of submerged ice have been carried out. By changing the velocity of flow under the ice cap, water depth h and the shape (thickness t, length l, width b) of the submerged ice, and so on, some factors, such as thickness t, length l, width b, are changed. It is proved that the longitudinal start-up velocity is higher than the transverse starting velocity. The key to the study of the law of submersible ice motion is to study the critical condition of the longitudinal state of submerged ice-stagnation and startup. The factors affecting the critical state of submersible ice are obtained by experiments. With the relative shape of t / L, the relative depth of water t / h and the relative width of b / r / B, The critical ice thickness Froude number (Ft) of submersible ice decreases correspondingly. Regression analysis is carried out on the test data under different operating conditions to obtain a more accurate form of critical conditions for submersible ice sliding starting. (2) in order to further analyze the critical state of submerged ice, a numerical simulation method is used to study the water pressure at the bottom of the submerged ice. The Venturi effect and the leading edge effect on the underlying surface of the submerged ice are simulated accurately with the wall function. The numerical model is established based on Larsen's physical model test. The distribution of velocity V along the water depth h under the ice cap is obtained. The numerical model output results are compared with the experimental data. By analyzing the influencing factors of Venturi effect and leading edge effect, such as velocity of flow under ice cap, relative depth t / h and relative width b / B, the Venturi effect and leading edge effect of incomplete wide diving ice are obtained. Revise the calculation formula. On this basis, the integral, A formula for estimating the water pressure at the bottom of subsurface ice is obtained. Based on the study of water pressure, towing force, shear force, effective buoyancy force and friction force, the stress balance of submersible ice is analyzed, and the formula for calculating the critical condition of stagnation and start-up of submersible ice is obtained. The accuracy of the formula is verified.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV672;TV133

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