Flow Mechanism in a 90° Miter-Tee : Part 3-Flow Pattern of Laminar Flow in a Miter-Tee with Chamfering at the Lateral Entrance

The flow pattern of a miter-tee with the branching angle θ_m of 90° and with chamfering at the lateral entrance was studied for laminar flow. The area ratio m was chosen to be equal to 1.0, 1.5 and 2.0 and the magnitude of dimensionless chamfering C was chosen to be equal to 1.0 for each m. Moreover, C was chosen to be equal to 0.5 only 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 obtained results are compared with the cases with sharp edges and rounding at the lateral entrance. The conclusions can be summarized as follows: 1) The Navier-Stokes equations were solved numerically by the finite difference relaxation method when Re_<1h> covering the range between 1 and 200. The influence of such parameter as m, C, Re_<1h> and Q_3^*/Q_1^* on the flow separation caused from the lateral entrance 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 separation occurs at the large value of Re_<1h> when Q_3^*/Q_1^* is 0.5 and Re_<1h> varies and at the small value of Q_3^*/Q_1^* when Re_<1h> is 70 and Q_3^*/Q_1^* varies. The degree of the separation caused from the lateral entrance with chamfering is larger than that with rounding or the sharp edges there. The former is larger than the latter when Re_<1h> is 70 and Q_3^*/Q_1^* is small. Although the separation occurs from the lateral entrance with sharp edges, no separation occurs from the lateral entrance with chamfering and rounding when Re_<1h> is 70 and Q_3^*/Q_1^* is 1.0 or in the neighborhood of 1.0. The mechanism of the flow separation is discussed physically. Besides, 2) the influence of Re_<1h>, Q_3^*/Q_1^*, m and C 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 C when Q_3^*/Q_1^* is 0.5. But it varies with the values of m and C when Re_<1h> is 70 and Q_3^*/Q_1^* is changed. Its degree is larger than that with rounding but smaller than that with tha sharp edges at the lateral entrance. 3) The flow field in the real pipe junction with rectangular cross section was studied experimentally by the flow visualization technique when Re_<1h> covering the range between 5 and 200. The flow is two-dimensional at Re_<1h>≦40 but it is three-dimensional with secondary flow at Re_<1h>≧70. The flow adjacent to the centerline plane is always observed to be two-dimensional. The influence of m, C, Re_<1h> and Q_3^*/Q_1^* on the flow separation caused in the lateral conduit and on the stagnation point was investigated. 4) The results obtained by the numerical analyses and experiments 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.