Opposing flow junctions are considered as important elements in thermal and hydraulic equipment. This study numerically investigates the effects of angles and junction radii on coherent flow structures at opposing flow junctions with subcritical conditions. Hence, the three-dimensional unsteady Reynolds-averaged Navier–Stokes equations are solved with the k–ε turbulence model on a non-staggered grid using the indirect addressing treatment. After the verification of the numerical model, several numerical simulations are conducted for angles 35°, 40°, 45°, 50°, 60°, 70°, 80°, and 90° with different upstream Froude numbers and junction radii. The streamwise-oriented vortical cells only elongate into the branch channel of the opposing flow junction with angle 90°. By decreasing the angle between the main channel and confluent tributary, these cells decay in the main channel width, and one of the separation zones is gradually eliminated, as that does not form in the opposing flow junctions with angle 40°. The enhancement of junction radii decreases the dimensions of the separation and stagnation zones. Numerical simulation results of a curved-edge opposing flow junction with angle 80° indicate that any of the streamwise-oriented vortical cells in the main channel and separations zones in the branch channel are not formed. In such a condition, three vortical cells formed along the branch without decay, two cells are located near the side wall, and another cell is near the free surface.

中文翻译：

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不同角度和连接半径的对流流道混合过程

在热力和液压设备中，对流连接被认为是重要的元素。这项研究数值研究了角度和结点半径对具有亚临界条件的相对流结点处相干流结构的影响。因此，三维不稳定雷诺平均Navier-Stokes方程求解与ķ - ε使用间接寻址处理的非交错网格上的湍流模型。在验证了数值模型之后，针对具有不同的上游弗洛德数和结半径的角度35°，40°，45°，50°，60°，70°，80°和90°进行了一些数值模拟。沿流向的涡流室仅以90°角延伸到相对的流动连接的分支通道中。通过减小主通道和汇合支流之间的角度，这些单元将在主通道宽度上衰减，并且逐渐消除了一个分离区域，因为分离区域不会在相对的40°角的流路中形成。接合半径的增加减小了分离区和停滞区的尺寸。角度为80°的弯边相对流结的数值模拟结果表明，在主通道中未形成任何流向涡旋单元，在分支通道中未形成分离区。在这种情况下，沿着分支形成的三个涡旋细胞没有衰减，两个细胞位于侧壁附近，另一个细胞位于自由表面附近。