CALIBRATION OF FLOW MEASUREMENT USING ORIFICE PLATES

Investigation was carried out to study the characteristic of flow over four model of orifice measuring structure in a concrete lined rectangular open channel in the irrigation laboratory of the department of agricultural and bio-resource engineering Ahmadu Bello university Zaria Kaduna. The four physical orifice mode (with a pipe at angle 60, 45 degree and without pipe at theoutlet andwith zeropipeweredesignedwith steel metal plate) usedfor thestudy, thedischarge from thewater pumped machinethrough theopen channel wasdetermineusing direct method and used to determine the coefficient of discharge (C d ) for each of the measuring structure. The C d obtains for the orifice structure with pipe at angle 60, 45, and with no pipe at the outlet and with zero pipeswas found to be 0.99, 0.085, 2.755 and 1.122 respectively. The mathematical function for the head discharge for the orifice with pipe at angle 60, 45, and with no pipe at the outlet and with zero pipes were found to be;