Flow Mechanism in a 90° Miter-Tee : Part 2-Flow Pattern of Laminar Flow in a Miter-Tee with Roundness at the Lateral Entrance

The flow pattern of a miter-tee with the branching angle of 90° and with roundness at the lateral entrance was studied for laminar flow. The areal ratio m was chosen to be equal to 1.0, 1.5 and 2.0 and the dimensionless roundness R was chosen to be equal to 1.0 for each m. Moreover, R was chosen to be equal to 0.5 for m of 1.0. The Reynolds number Re_<1h> was taken to be less than or equal to 200. The ratio of lateral discharge to total discharge Q_3^*/Q_1^* was changed from 0.0 to 1.0 at 0.1 intervals. The conclusions can be summarized as follows: 1) To investigate the flow mechanism in a miter-tee of the laminar flow, the Navier-Stokes equations were solved numerically by the finite difference relaxation method when Re_<1h> covered a range between 1 and 200. The influence of such parameter as m, R, Re_<1h> and Q_3^*/Q_1^* on the flow separation caused in the lateral conduit and the stagnation point was investigated. The effect of the flow dividing in the lateral conduit is larger than that in the main conduit. Its degree in the lateral conduit grows when the separation occurs. Generally, the degree of the separation caused in the lateral conduit with roundness at the lateral entrance is smaller than that without roundness there when Q_3^*/Q_1^* is 0.5 and Re_<1h> is greater than or equal to 70. But the former is larger than the latter when Re_<1h> is 70 and Q_3^*/Q_1^* is small. The mechanism of the flow separation is discussed physically. Moreover, 2) the influence of Re_<1h>, Q_3^*/Q_1^*, m and R on the stagnation point is studied. The stagnation point is located on the lateral wall of the middle point of the main conduit independent of Re_<1h>, m and R when Q_3^*/Q_1^* is 0.5. But the stagnation point varies with the values of m and R when Re_<1h> is 70 and Q_3^*/Q_1^* is changed. 3) The flow field in the real pipe junction with rectangular cross section was studied experimentally by the flow visualization technique when Re_<1h> covered a range between 5 and 200. The flow is two-dimensional at Re_<1h>≦40 but three-dimensional with secondary flow at Re_<1h>≧70. The flow adjacent to the center-line plane is always observed to be two-dimensional. The influence of m, R, Re_<1h> and Q_3^*/Q_1^* on the flow separation caused in the lateral conduit and the stagnation point was investigated. 4) The results obtained by the numerical analysis and experiment coincide fairly well. Both results coincide quantitatively well when Re_<1h> is small or when Re_<1h> is large but Q_3^*/Q_1^* is small.