The present study is primarily to pursue the analysis on the experimental results of the preceding study (Part I)¹⁾ for the motion and thermal behaviours of the relatively shallow flow of fire products along the ceiling in the full scale corridor.
In so far as y -profiles of the velocity and temperature concerned, approximately the same patterns were obtained among their normalized form (V/V max, T/T max or θ/θ max) respectively, when the flow was fully developed. On the other hand, in so far as the optical smoke density C_S and gas concentration C_G , their y -profiles were tailed as compared to those of the velocity and the temperature especially far from the fire source.
The y -averaged velocity V_av and temperature T_av decreased exponentially along the corridor and the modes of their changes were expressed as followings on the basis of the reduced-time on time parameter τ ;
ln (V_av/V₀) = −K_V · x/δ_V ,     (1)
ln (T_av/T_av0) = −K_T · x/δ_V ,     (2)
where V_av0 and T_av0 was the average velocity and temperature at x = 0 and t = τ (t : time) respectively. δ_V was the observed flow thickness and were retained to be equal until the flow front reached to the opposite end of the corridor. K_V and K_T were the reduced time (τ) dependent attenuation coefficient for the velocity and temperature. The value of ratio K_V /K_T was found to be conserved as equal to 1/2.
In the initial stage of burning, y -averaged gas concentration C_avG decreased exponentially along the corridor. However, as the stratification of the flow was developed, C_G became constant excluding the front part of the flow where the exponential decrease were still recognized and therefore illustrated terrace along the corridor.
The distribution of the averaged smoke density C_avS along the corridor showed a different pattern. The obvious accumulation of the smoke at and around the x = 35 m was observed 8 min when the flow front reached to the opposite closed end of the corridor.
The mean radius and the number of the smoke particles was found to be comparatively small, so its contribution to Δρ/ρ in estimating ∂ρ/∂y could be neglected. Therefore the hydrodynamic stability of the flow could be discussed in terms of the Richardson number on the basis of the temperature and were estimated from the y -temperature and y -velocity profile.
The effective diffusion coefficient for momentum (Km ) and for heat (Kh ) were also discussed with Richardson number (Ri_T ) on the hydrodynamic stability of the flow. Km and Kh were reduced vs.
Ri_T from ca. 2.8 × 10^-4 to 1.0 × 10^-4 (m²/sec) for Km and from 4 × 10^-4 to 0.2 × 10^-4 (m²/sec) for Kh respectively regarding the increase of Ri_T from ca. 0.5 to 1.2.
The contribution of smoke particles on the stability of the flow was also discussed regarding the particle size and concentration of the smoke (D_VSav = 0.5μ , N = 2.4 × 10¹²/m³) in the present flow was obtained by unpolarized He-Ne laser.