Medidor de vazão para rios com grande variação de descargas.

Abstract

The rivers and water courses of the Northeast region of Brazil present peculiar characteristics of generally shallow and wide beings with soft slopes and a regime of wide oscillation of discharges between the periods of droughts and floods. Measurement of the flow of these rivers by means of known spillways or meter channels is deficient because the range of values ​​which is encompassed by these devices is very restricted. In addition to geometric reasons, it is not advisable to use spillways of the type of water dam, in rivers of our region, since it is impossible to create a sufficient hydraulic load in the approach channel, due to the little slope mentioned. On the other hand, by adopting discharge meters designed only for the small flows of the drought period, they will be drowned and will no longer record the important values ​​of the contributions of the short period of time. The accuracy of this test destroys any possibility of using large constructions to measure flow, so that previously calibrated, they can predict the high rates of volume of water drained, since the values ​​taken in these, during the low waters, intolerable errors. "The Flow Rate Meter with Large Variation of Discharges", developed below, proposes to solve the described problems with a theoretical accuracy of around 2%. It has the advantages of encompassing a wide range of discharge values, does not cause large increases in the upstream water level to work, work without large losses of energy and ease of construction. It basically consists of the coupling of a Flat Bottom Venturi Meter Channel for the small flows and a thick V-shaped Sill Meter (New Zealand Meter Channel) which handles the high flood discharge rates. We present the empirical equation obtained by the Dimensional Analysis and the respective calibration curves compiled based on the laboratory data. All measurements, functions, graphs, and conclusions were taken from the tests with a reduced 1/10 scale model of the architected meter. The specific application of this type of Flowmeter for each particular watercourse should be previously studied in a reduced model or by calibration in loco, according to convenience, but the form of the spacial equation and the affectation curves will be the same.