静止环境中有阻力圆盘浮力射流特性的研究——(I)数学模型及计算方法的验证

建立静止环境中有阻力圆盘浮力射流的RNG湍流模型,考虑浮力对射流的影响,采用混合有限分析数值格式来离散求解数学模型,结合有效的试验资料进行模型和计算方法的检验,预报给出了阻力盘对圆形浮力射流轴线浓度的影响范围;提出轴线浓度校正系数的概念,从而清晰直观地证实了阻力盘具有提高射流近区稀释度的作用;确立了H/D为影响轴线浓度的重要参数,且H/D=10为阻力盘是否提高近区稀释度的判别标准;数值模拟发现,当H/D<1时,正常绕流发生的弗劳德数F0的范围会很快缩小,容易出现非正常绕流;并且盘离射流孔口较近时,射流容易被反射,离孔口较远时,绕流容易出现分叉。并就如何控制射流流态和提高稀释度提出了两点建议。

Research on the behavior of obstructed round buoyant vertical jets in static ambient, 1,verification of mathematical model and numerical method

The RNG turbulence model considering the buoyancy effect is used to establish a mathematical model of obstructed round buoyant vertical jets in static ambient. The hybrid finite analytic method with stagged grid is used to solve this model. With the concept of concentration correction factor, the effect of the disc to improve the near field dilution of buoyant jet is confirmed. Meanwhile, the H/D, H is vertical distance of disc from jet exit section and D is disc diameter, primarily affects the concentration distribution behind the disc. It is found that the range of Froude number, in which normal round flowing occur, decreases quickly while H/D<1. When the plate is near the port, jet can be easily reverberated by the plate, and when the plate is far from the port, the round flow after the plate will bifurcate out of the range of Froude number. The two steps to control flow pattern and improve dilution on the axial near the plate are proposed also.