A Model of Discharge Coefficient in Tertiary Box Combined with Overflow and Orifice

This research investigates the effectiveness of tertiary boxes in irrigation systems by optimizing structural functions, combining overflow and orifice mechanisms to achieve more accurate water distribution. Designs incorporating overflow and orifice can achieve more balanced water allocation under various flow conditions. The discharge coefficient (C_d) is measured due to variations in orifice number and diameter, and in the sharp-crested weir width. The results show that the discharge coefficient (C_d) changes with variations in the width of the sharp-crested weir, indicating an accumulation or fluctuation along the weir width, diameter of orifice, and number of orifices. The optimal configuration between the discharge coefficient and the sharp-crested weir for sharp-crested weir widths of 0.33 m and 0.42 m was found, using 3 orifices, each with a diameter of 4 cm. The discharge coefficient over the sharp-crested weir for the width of 0.33 m uses the formula, C_d = 0.7384 (h₁/p)-0.094 for Channel-1 and C_d = 0.3294 × (h₁/p)-0.296, for Channel-2 and 3. The discharge coefficient on orifice uses the formula, C_d = 0.482 × (h₁/d)-0.0709, for Channel-1 and C_d = 0.3765 × (h₁/d) × 0.1751, for Channel-2 and 3. However, the discharge coefficient over the sharp-crested weir for the width of 0.42 m uses the formula, C_d = 0.8215 × (h₁/p)-0.058, for Channel-1 and C_d = 0.3202 × (h₁/p)-0.286, for Channel-2 and 3, the discharge coefficient on orifice uses the formula, C_d = 0.3469 × (h₁/d) × 0.2651, for Channel-1 and C_d = 0.177 × (h₁/d) × 0.614 for Channel-2 and 3.