浮体式结构阻力系数试验研究

Experimental Study on Resistance Coefficient of Floating Structure

浮体式结构作为一种适合于沿海地区及内河水利枢纽工程建设的新型生态构筑物,当在平原水利防洪工程中运行时,由于浮体的阻挡,导致水流发生分流产生水头损失,进而影响过流能力。因此,研究浮体式结构阻力系数的变化规律及因素影响机理具有现实意义。本文采用物理模型试验,基于水动力学理论分析,利用量纲分析得到影响浮体式结构阻力系数的影响因素有水位变化系数、浮体结构长度与浮体结构位置比值(长位比)、相对阻水面积及雷诺数。对影响因素与阻力系数进行相关性研究及敏感性分析,结果表明:1)水位变化系数的增加,导致结构背水面的位置出现回流区,水流质点的紊动强度增加,阻力系数增大;2)浮体式结构沿水流长度方向及位置的变化,一定程度上并不会引起水流能量的损失,对浮体结构的阻力系数的影响较小;3)相对阻水面积系数的增大会导致水体过水面积减小,水体质点相互摩擦和碰撞消耗水流能量,引起浮体式结构的阻力系数增大;4)在试验的雷诺数范围内(3.5相对阻水面积>雷诺数>长位比。通过基于最小二乘法的多元线性拟合,比较得到描述浮体式结构阻力系数的计算公式,并采用数理统计对公式进行检验和误差分析,该公式在可靠性及精确度方面能够满足工程需要且形式简单、通用性强,可为相关工程提供理论依据。

Floating structure is a new type of ecological structure suitable for the coastal and inland water conservancy projects.The application of floating structure in plain water conservancy and flood control projects will lead to the diversion of water flow and cause head loss,which will affect the flow capacity.Therefore,it is of practical significance to study and obtain the changing law of the resistance coefficient of the floating structure and the influence mechanisms.The physical model test and dimensional analysis were used to obtain the influencing factors affecting the resistance coefficient of the floating structure,i.e.,the coefficient of water level change,the ratio of the length of the floating structure to the position of the floating structure,the relative water blocking area and the Reynolds number.The sensitivity analysis on influencing factors and resistance coefficient was conducted,and the results show that:1)The increase in the coefficient of water level change results in a recirculation zone at the back surface of the structure,and both the turbulence intensity of the water flow particles and the resistance coefficient increase;2)The change of the floating structures’ length and position will not cause the loss of water flow energy and has little effect on the resistance coefficient;3) The increase in the relative water blocking area coefficient leads to the decrease of the water passing area, and the friction and collision of wa-ter particles consume water flow energy, causing the resistance coefficient to increase. 4) Within the range of the tested Reynolds number (3.5< lg Re<5.0), when the Reynolds number increases, the turbulent and irregular flow field was formed, and the influence of inertial force on the flow field is greater than that of the viscous force, with the resistance coefficient being decreased. 5) The sensitivity of each factor to the resistance coefficient is arranged in the descending order as follows: the coefficient of water level change>the relative water blocking area>Reynolds num-ber>the ratio of length to position. Through the multivariate linear fitting based on the least square method, the calculation formula describing the resistance coefficient of the floating structure was obtained, and the formula was tested and analyzed by mathematical statistics. The formula can meet the engineering needs in terms of reliability and accuracy, and the form is simple and versatile, which can provide a theoretical basis for re-lated projects.