Answer Happy

Theory The theoretical discharge for: • The rectangular notch is given by: Q = ²√2gbH² (1) Ignoring head losses and considering head loss coefficient Ca due mainly to the contraction of the flow area downstream of the notch, the actual discharge Q is considerably less and may be expressed as: Q=C₁√ √2g bH² (2)
Where. b: Breadth of the rectangular notch H= Height of flow over notch 0 = Angle of vee notch Generally, all constants are collected in m: Q = mH" Can take log of both sides: log(Q) = log(m) + n log(H) H 十四 (a) Figure 2 - (a) Triangular weir, (b) Rectangular weir GERE Water Flow (5) (6)
Procedure 1. Set up the equipment as shown in Figure 1. 2. Admit water to channel until water discharges over the weir plate. 3. Close flow control valve and allow water level to stabilize. 4. Set Vernier Height Gauge to a datum reading using the top of the hook. 5. Position the gauge about half way between the weir plate and the stilling baffle. 6. Admit water to the channel, adjust flow control valve to obtain heads, H, increasing in steps of about 1 cm. 7. For each flow rate, stabilize conditions, measure and record H. 8. Take readings of volume and time using the volumetric tank to determine the flow rate. 9. Find Cd and n for each case directly from the reading, and using log-log plot. Raw Data, Results and Sample Calculations • Rectangular weir: b = 30 mm Volume Head of of Q (m³/s) Log (Q) Log (H) Water, H (m) Cd Cd Experimental Theoretical % Error Water, (L) 5 0.0643 5 0.0596 0.054 0.0435 0.038 Reading No. 1 2 3 4 5 5 55 Time, T (sec) 4.9 5.5 6.1 8.9 10.6
Plot and Calculations: • Plot of Log (Q) vs. Log (H) for Rectangular Weir and determine the slope and Intercept of the plot. Plot Q vs H5/2 and use it find Cd. • . Plot a graph of Q (y-axis) against H³/2(x-axis) for the rectangular weir • Use a linear function to plot the best fit and express the relationship between Q and H" and in the form of: Q = mH",in which the exponent value n is 1.5 for the rectangular weir and 2.5 for the triangular weir. • Calculate the coefficients of discharge Cd (theoretical method) using equations: Ca = √√Ca=; is 29 tano/2 Record C values calculated from the theoretical method in the Result Tables. . Compare the experimental results to the theory by calculating the percentage of error.