Approximate Expressions of Drain Hydrographs and Designing Drain Pipes

Studies on the hydroponics system of flooding and circulating solution in growing vats (IV)

Abstract

In this paper approximate, equations on the drain hydrographs of the growing vat have been expressed so that the mathematics following can be handled easily, and a rational design for drain pipes from the relations between elapsed time and discharge have been prepared by considering, the flow in the drain pipe to be a quasi-uniform in a circular channel.
The results obtained are summarized as follows:
(1) The approximate expressions of the hydrograph on outflow from an overflow type spillway in the vat are given, and the corrections to be made when supply time and liquid surface area in the vat differ are also given.
(2) The design procedure that gives hydraulically the most efficient cross-sectional area (diameter d=1.066 h_max) for the maximum discharge in each section between lateral inflows for, the drain pipe flow expressed as a quasi-uniform flow of the circular channel are shown.The changing flow in the pipe can be made known by this procedure.
(3) The flow of the drain pipe using the above most efficient standardized pipes, whose d is gradually increased the more downstream, it is nearly results in the depth h for the maximum velocity, or h=0.813 d.This is a desirable design judging from the function and freeboard of the drain pipe.
(4) The material cost (as a PVC pipe) of this composite drain pipe is 30-37% cheaper than that of the existing simple drain pipe.And a standard-length of 4 m is better for the section length of the composite pipe (equal to the distance between separations in vats).
(5) The most efficient cross-sectional area of the drain pipe can be determined more safely and easily by using only the maximum inflow (discharge) from the vat.