## 4 Validation of Equivalent Field Source Model  
### Simulation Validation of the Equivalent Model  
To validate the accuracy of the equivalent model, the detailed model is employed to directly calculate the electromagnetic field in free space. The results are then compared with those obtained from the equivalent model. For the electric field analysis, a plane located 500 mm from the front of the axial flow fan within the computational domain is selected. As illustrated in Figure 11, Figure 11a,b depict the electric field distributions at a frequency of 100 MHz, calculated by the detailed model and the equivalent model, respectively.  
It is observed that when the axial flow fan is in operation in free space, it serves as a radiation source, emitting electromagnetic radiation interference externally. Additionally, the results from both computational models depicting the variation in electric field intensity with frequency at a distance of 1 m from the fan are shown in Figure 12.  
The Feature Selective Validation (FSV) technique is a method utilized for validating computational electromagnetics and predictive electromagnetic compatibility data evaluations. In this paper, the FSV technique is applied to evaluate the variance between the computational results of the detailed model and the equivalent model. The FSV technique can evaluate the \"quality\" of the association between two sets of data according to specific criteria, mainly focusing on the total amplitude difference measure (ADMtot), the total feature difference measure (FDMtot), and the total global difference measure (GDMtot). These  
Figure 10: Computational domain of the equivalent model.  
variances are presented as numerical values and are described using natural language as six levels depending on the range of the data: excellent (0-0.1), very good (0.1-0.2), good (0.2-0.4), fair (0.4-0.8), poor (0.8-1.6), and very poor (>1.6).  
The evaluation results of FSV in Figure 10 are shown in Table 1. The proportion of \"good\" or higher in ADM reaches 89.33%, the proportion of \"good\" or higher in FDM reaches 75.86%, and the proportion of \"good\" or higher in GDM reaches 67.26%. The FSV evaluation results indicate that the results derived from the equivalent model show greater consistency in comparison to the electric field results obtained from the detailed model.  
Table 2 lists the grid and computation time comparison of the two models. The detailed model requires a total of 4,572,216 grids for calculations within the domain. In contrast, when utilizing the equivalent field source model, the number of grids is reduced by 60.3% due to the smaller calculation domain. In the secondary calculations, due to the replacement of the detailed model with the equivalent model, the size of the radiation source changes. This change increases the minimum grid size within the computational domain from 0.198 mm to 9.769 mm and significantly reduces the total number of grids. Consequently, there is a noteworthy 74.0% decrease in computational time, highlighting  
\begin{table}
\begin{tabular}{c c c} \hline \hline \(\mathbf{ADM_{tot}}\) & \(\mathbf{FDM_{tot}}\) & \(\mathbf{GDM_{tot}}\) \\ \hline
0.1801/very good & 0.3002/good & 0.384/good \\ \hline \hline \end{tabular}
\end{table}
Table 1: FSV evaluation results of the two computational models.  
Figure 11: Electric field distribution for two models. (**a**) Calculated by detailed model; (**b**) calculated by equivalent model.  
Figure 12: Comparison of electric field intensity at the monitoring point.  
the substantial enhancement in computational efficiency achieved through the use of an equivalent model compared to a detailed model across the entire domain.