Experimental investigation of boiling two-phase flow instability of nitrogen in a vertical tube

Boiling flow instability of nitrogen in a vertical tube is experimentally investigated in the present study. The experiments reveal that pressure has a significant effect on the characteristics of the heat flux-mass flux type boiling flow instability. First, the pressure has strong effects on both the developing time and the fluctuation amplitude. Especially increasing pressure leads to decrease the fluctuating amplitude of mass flux. Then, the mass flux evolving curves under different pressures feature out a shape like a leaf. The characteristics of the heat flux-mass flux type boiling flow instability under lower pressure are very complicated, however, with increasing pressure, this type of instability is gradually suppressed.     

黄河河相关系一个突出的特点及其机理初探

通过分析实测资料,得到黄河中游吴堡站、下游柳园口站及高村以下所有河段均存在"在同一流量下,过水面积接近相等"的现象,这是黄河河相关系中一个非常重要的特点,但其物理意义目前尚不清晰。引入"在输沙平衡状态下河床相对稳定,其相对可动性最小"的假定,结合水流连续方程、运动方程和输沙平衡方程,通过求解河相要素,得到以悬移质造床为主时水深—河宽比率关系式,进而从理论角度初步解释了上述河相特征的内在机理。该河相关系特征并非表现在黄河所有河段中,而只能存在于以悬移质运动为主、同时悬沙沉降处于过渡状态的河段中。     

引江济淮工程安徽段生态岸坡防护结构形式综述*

运河工程沿线渠道开挖将产生大面积的人工创面，采用生态岸坡防护工程对创面修复有积极作用。以引江济淮工程安徽段岸坡防护工程为研究对象，基于设计资料和现场调研梳理了引江济淮工程安徽段生态岸坡防护结构使用情况。结果表明：引江济淮工程生态结构选型主要受地质条件及特征水位影响，土质岸坡常水位以上采用30%孔隙率的混凝土预制块体结构，枯水位局部河段试验性采用带有鱼巢功能的水下矩阵块体结构。膨胀土区域采用大框格预制块体结构及柔性水位保持毯材料，孔隙率分别为79%和95%，使用区域均位于最高洪水位以上。