*2.3. Model Validation*

In this paper, data from the Burro eight-spill test [27], which was conducted in 1980, was used as the basis of the validation analysis. In the test, LNG was released onto the water surface of a round pond, with 25 gas concentration monitors placed at different heights in the downwind. In addition, the water pond had an average diameter of 58 m, with an average water level about 1.5 m below the surrounding ground level. Based on the Burro series tests, the reliability of the multiphase model was evaluated by comparing the numerical results with the experimental results based on the diffusion range and concentration change of methane.

Figures 3 and 4 show the contour distribution of methane volume fraction after LNG spill 80 s on the *x* = 57 m and *y* = 1 m planes, respectively. In Figures 3a,b and 4a,b, the distribution areas of methane with different volume fractions on the horizontal and vertical planes are basically consistent with the experimental data. Figures 3c and 4c show the comparison of the coverage areas of dispersion clouds with different volume concentrations. There is a very good quantitative agreement between the simulation results and the experimental data. Besides, Table 1 shows that the comparison between the calculated and experimental values of maximum volume fraction of methane at different distances in downwind direction. It shows that the calculated maximum volume fraction of methane is lower than that of the experiment; however, in the area away from the leakage source, the calculated maximum volume fraction of methane is higher than that of the experiment. The reason is that the coupled heat transfer between the ground and the LNG vapor cloud is assumed to be constant in the simulation; in fact, the heat produced by ground heat transfer and solar radiation is variable. The error analysis method of the heavy gas diffusion model proposed by Emark et al. [28] is used to analyze the deviation between the simulation result and the test value. The method includes relative deviation (FB), geometric mean deviation (MG), geometric mean-variance (VG), relative mean square error (MRSE), relative mean square error (FAC2) and normalized mean square error (NMSE), which can be used to judge the validity of the numerical model. The deviation between numerical simulation and experimental values is shown in Table 2. It can be seen that all the deviations were within the allowable range of the evaluation parameters. Therefore, the multiphase model is suitable for the study of LNG leakage and diffusion.

**Figure 3.** Comparison of experimental and simulated values of methane volume concentration at a vertical height of 1 m. (**a**) Burro eight-test measured value. (**b**) Fluent simulation results. (**c**) Comparison of test and simulation.

**Figure 4.** Comparison between experimental and simulated values of methane volume concentration at 57 m in downwind direction. (**a**) Burro-eight test measured value. (**b**) Fluent simulation results. (**c**) Comparison of test and simulation.

**Table 1.** Experimental and simulated values of maximum volume fraction of methane at different distances in downwind direction.


**Table 2.** The error comparison of simulation results.

