As shown in Figure 5, empirical curves are used to simulate experimental data using IBM SPSS 22 software (Allen et al. 2014). Equations (10) and (11) are valid for 0.05 ≤ H_t′/P′ < ∼0.75–0.8, and the coefficients of A, B, C, and D are tabulated in Table 3. After applying Equation (10) for compound labyrinth weir and Equation (11) for compound linear weir, the data display a well-behaved nature when the C_dc (α°) curves have been generalised to H_t′/P′ = 1.0, as shown in Figure 5 with dashed lines. Equations (10) and (11) were selected instead of polynomial formulas because the data have a good correlation representation (R² ≥ 0.98). In addition, extrapolation performance remains well-behaved up to H_t′/P′ ≤ 2.0. Equations (10) and (11) reflect a good choice for the designer in the case of using compound labyrinth weirs with different sidewall angles: