The effect of the diameter and spacing of manifold outlets on manifold flow

by Michael Dale Coleman

Institution: Oregon State University
Department: Civil Engineering
Degree: MS
Year: 1965
Keywords: Hydraulics
Record ID: 1587830
Full text PDF: http://hdl.handle.net/1957/48362


A laboratory investigation was undertaken to evaluate the effect of lateral spacing and lateral diameter on the flow characteristics of a three dimensional blowing manifold. The model used in the experimental work was constructed of clear cast acrylic pipe, five inches in diameter. Laterals of two and four inch diameter, yielding diameter ratios of 0.4 and 0.8, respectively, were investigated at spacings of 6.6, 12.0 and 16.2 main conduit diameters (2.75, 5.0 and 6.75 feet). The circular lateral sections were orthogonally connected to the main conduit with a sharp edged connection. The ratio of lateral to conduit flow was adjusted through the use of orifice plates placed at the discharge end of the main conduit. The laterals discharged freely at all times. Pressure taps were placed along the 28 foot experimental section and data were recorded using a calibrated piezometer board. Lateral and conduit flows ranging up to 2.5 cubic feet per second were measured gravimetrically. The effect of lateral spacing and lateral diameter on the flow conditions in the manifold was evaluated using a spacing parameter defined as the ratio between the computed and measured pressure rise across two consecutive laterals (ΔZ/ΔY). The computed pressure rise was determined using an approach outlined by McNown. From graphical presentations of the findings of this study, it is seen that the magnitude of the spacing parameter is a function of the lateral diameter ratio as well as the lateral spacing. The results obtained using a two inch lateral (D[subscript L]/ D = 0.4) agree well with those obtained by Yanes for D[subscript L]/D = 0.5 and indicate that, in most cases, at a spacing exceeding 20 conduit diameters no inter-lateral interference occurs. However, a change in the diameter ratio from 0.4 to 0.8, holding the spacing constant at 16.2 conduit diameters, results in an increase in the magnitude of the spacing parameter (ΔZ/ΔY) from an average value of approximately 1.03 for D[subscript L]/D =0.4 to an average of 1.12 for D[subscript L]/D = 0.8. This increase indicates that for the larger diameter ratios (D[subscript L]/D > 0.5), a spacing exceeding the 15 to 20 conduit diameters predicted by previous investigators is necessary before inter-lateral interference is no longer present.