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Abstract

Outdoor wind is one of the important driving forces of fire smoke movement in high-rise buildings. This paper investigates the smoke spread velocity along a corridor induced by an adjacent compartment fire with outdoor wind. Based on momentum and mass conservation laws, a theoretical model predicting the smoke spread velocity was developed. Reduced-scale experiments were performed for model validation. Correlations for smoke spread velocity in the corridor under the effect of outdoor wind were proposed. It is found that the initial velocity can be very well predicted according to the stratification stability of smoke with the criterion of Fr. Moreover, the velocity profiles along the corridor decay exponentially.

4. Results and discussion

4.1. The determination of undetermined parameters To make the research results applicable to actual working conditions, the experimental results were firstly scaled up according to the Froude modelling. Therefore, the parameters and results used in this section were all full-scale values. In order to determine which one is dominant, outdoor wind effect or thermal buoyancy effect, Fr of the 35 tests were calculated according to Eq. (10) and shown in Table 2. The vertical temperature profiles at 0.9 m from the doorway in the corridor of tests 28–31 are shown in Fig. 4(a)–(d). It can be seen that when the outdoor wind velocity reaches 3.46 m/s, the corresponding Fr increases from 1.96 to 3.56 and the stratification denoted by temperature becomes disorder. Similar outcomes always showed in other heat release rates: vertical temperature profiles lose stable stratification when Fr rises above 3.2 with increasing outdoor air velocity. Thus, when Fr < 3.2, it can be considered that the smoke enters the corridor stratified and the velocity decay should comply with Eq. (13) while the initial velocity of smoke at the door can be calculated using Eq. (24). When Fr > 3.2, smoke entering the corridor completely mixed with the air and the velocity decay should comply with Eq. (17) while the initial velocity of smoke at the door can be calculated by Eq. (27). In Table 1, it can be seen that the velocity of test 1, 2, 6, 7, 8, 12, 13, 14, 20, 21, 22, 28, 29 and 30 could be determined by Eqs. (13) and (24) while other tests could be determined by Eqs. (17) and (27).