OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 3 2025 Results and Discussion Elshafie et al. [43] experimentally studied pulsating turbulent airflow in a heated pipe under constant heat flux, a configuration relevant to modern industrial heat transfer applications. They examined pulsation frequencies ranging from 6.6 to 68 Hz and Reynolds numbers (Re) from 10,000 to 40,000. Their findings demonstrated that the Nusselt number (Nu) was significantly influenced by both Re and frequency (f), particularly in the entrance region, where changes were more pronounced than in the fully developed zone. The downstream position of the oscillator near the pipe exit affected the distribution of local heat transfer (HT). In this study, analogous investigations were conducted for Re = 13,350 to 37,100. Centerline velocity and total pressure increased with increasing Re, while the wall surface temperature decreased. These results are summarized in Table 1, which demonstrates that turbulent kinetic energy (TKE) and vorticity consistently increase with Re. Fig. 6 shows velocity profiles for Re = 37,100 under upstream pulsation, downstream pulsation, and no pulsation (A = 0.2, f = 6.7). The pulsing cases exhibit only slight variations in vorticity and lower velocities compared to the baseline (no pulsation) case. These patterns indicate that while pressure, velocity, TKE, and ω increase with increasing Re, surface temperature decreases. Consequently, h and Nu increase with Re, supporting the validity of the numerical method and exhibiting good agreement with theoretical and experimental findings from Elshafie et al. [43]. Ta b l e 1 Flow properties for various Re values Re Vmean (m/s) Vmax (m/s) Tmax (K) Press. (Pa) TKE ω (s −1) 10,850 7.1313 10.3 329 115 1.15 1.000 13,350 8.7745 12.5 325 160 1.6 1.250 16,800 11.0420 15.6 322 255 2.7 1.600 22,500 14.7885 20.8 320 465 5 2.100 24,650 16.2016 22.6 318 552 6 2.300 31,560 20.7433 28.8 316 925 10 2.800 37,100 24.3846 33 314.2 1.300 15 3.200 a b Fig. 6. Comparison of velocity (V) profiles along the pipe length for Re = 37,100, under steady-state (without pulsations) and pulsating flow conditions (A = 0.2, f = 6.7): a – DN pulsation = downstream pulsation; b – UP pulsation = upstream pulsation
RkJQdWJsaXNoZXIy MTk0ODM1