Fire Compartment Upper-Layer Temperature Prediction Considering Excess Fuel Gas

In this study, combustion experiments were conducted by changing the fire source conditions and opening conditions for excess fuel gas using a large-scale fire compartment. It was found that the occurrence of external flames depends on the opening factor A √H , surface area of the wall AT, and heat release rate (HRR) QC inside the fire compartment. Moreover, the larger the value of A √H in the experiment, the greater is the temperature rise in the compartment. McCaffrey's proposed temperature prediction model for the upper layer of the fire compartment was also modified and validated.

Assimilation of FY-3D MWHS-2 Radiances with WRF Hybrid-3DVAR System for the Forecast of Heavy Rainfall Evolution Associated with Typhoon Ampil

A detailed investigation about the effects of the Microwave Humidity Sounder-2 (MWHS-2) radiances on board the Fengyun-3D (FY-3D) satellite is combined with developments within the Weather Research and Forecasting Data Assimilation (WRFDA) system and analyses on the evolution of the heavy rainfall associated with Typhoon Ampil during 23–24 July 2018. In the analysis field, the position of Typhoon Ampil is found out to be distinctly affected by the MWHS-2 assimilation. The experiment that assimilates MWHS-2 radiances through hybrid-3DVAR generates the best analysis with large increments around the typhoon, which contributes to the typhoon moving inland to the southwest. In the forecast fields, the MWHS-2 assimilation improves the rainfall in not only the accumulated amount, but also the evolution characteristics. The hybrid-3DVAR experiment reduces the RMSE of the rainfall amount, and enhances the spatial correlation and the fractions skill score of the rainfall evolution to the greatest extent, followed by the 3DVAR MWHS-2 experiment. As for the cause of the rainfall improvements, analyses suggest that it could be closely connected with the characteristics of the circulation structures related to the typhoon evolution. On one hand, the increases of the rainfall amount and intensities in the MWHS-2 assimilation experiments (previously underestimated) correspond to the strengthened typhoon structures with strong anomalies in both the upper-layer temperature and the lower-layer geopotential height. On the other hand, the better rainfall evolution in the hybrid-3DVAR experiment could be explained by its clearer evolution of the structure of typhoon under the effects of an approaching upper trough, and its smallest typhoon track errors around the middle time period.

Variational Estimation of Wave-Affected Parameters in a Two-Equation Turbulence Model

A variational method is used to estimate wave-affected parameters in a two-equation turbulence model with assimilation of temperature data into an ocean boundary layer model. Enhancement of turbulent kinetic energy dissipation due to breaking waves is considered. The Mellor–Yamada level 2.5 turbulence closure scheme (MY2.5) with the two uncertain wave-affected parameters (wave energy factor α and Charnock coefficient β) is selected as the two-equation turbulence model for this study. Two types of experiments are conducted. First, within an identical synthetic experiment framework, the upper-layer temperature “observations” in summer generated by a “truth” model are assimilated into a biased simulation model to investigate if (α, β) can be successfully estimated using the variational method. Second, real temperature profiles from Ocean Weather Station Papa are assimilated into the biased simulation model to obtain the optimal wave-affected parameters. With the optimally estimated parameters, the upper-layer temperature can be well predicted. Furthermore, the horizontal distribution of the wave-affected parameters employed in a high-order turbulence closure scheme can be estimated optimally by using the four-dimensional variational method that assimilates the upper-layer available temperature data into an ocean general circulation model.

Study on Simulation of the Building Fires Using an Advanced New Model

Building fires have been paid significant attention in the nuclear power station’s safety. In order to study the stratification phenomena of the enclosure fires and predict the interface location of upper hot layer filled with smoke and lower cold layer filled with fresh air and upper layer temperature of enclosure fires, an advanced new model is used in this paper, in which one–dimensional differential equations are used to describe the temperature and species distributions of the ambient fluid. And the results of Steckler’s fire experiments are used to compare with the simulation results of five sets of experiment using the new model. The results indicate that this model gives a very good prediction for the location of the interface and the upper layer temperature, especially for the cases with a lower fire heat release rate, even without considering the radiation heat transfer.

Comparison of Measured Transient Ceiling Jet Temperature and Velocity Profiles in the Presence of an Upper Layer With Predictions by LAVENT Computer Fire Model

Development of an upper layer in enclosure fires has a significant effect on the characteristics of the ceiling jet and a direct influence on the placement and performance of fire detection/suppression devices. Detailed transient measurement of ceiling jet velocity and temperature profiles within an upper layer for small-scale fires (2.0 kW and ceiling height of 1 m) are used to analyze the predictions produced by the LAVENT computer fire model. While the model predictions have been compared with large-scale experimental results with fires as large as 33 MW and ceiling height of up to 22m, the large-scale measurements do not have high special resolution and the present work offers a more thorough analysis of the model prediction. Various radiative losses (10–25%) were used to produce predictions that matched the experimental data. Comparison of the small-scale experimental data with the predictions from LAVENT shows that the model, which uses unconfined ceiling jet correlations, does not capture the ceiling jet profile well and over predicts the upper layer temperature during the development of the layer. The peak temperature prediction requires a different radiative loss factor than that which matches the upper layer temperature. In general, the peak temperature measurements are within 10% of the measured value. The velocity is generally over predicted since the retardation of the jet momentum by the upper layer does not seem to be modeled accurately.