OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 3 2025 induced turbulence is evidenced by vorticity peaks near the walls. Flow disturbances are evident near the core, and their impact diminishes beyond L = −0.25 m. Fig. 10 compares the velocity contours under upstream and downstream pulsation. In the upstream case, a longer high-velocity region extends toward the pipe exit, indicating a more widespread pressure drop and increased turbulence. Conversely, downstream pulsation localizes the high-velocity region, which may lead to concentrated pressure zones and non-uniform HT. Fig. 11 displays the pressure contours at t = 6 s. The peak pressure is higher downstream (63.21) compared to upstream due to the downstream pulsation, suggesting localized acceleration effects. Fig. 12 displays the turbulent kinetic energy (TKE) contours for upstream pulsation from t = 1 s to 6 s. TKE increases from 0.55 to 0.92 over time, indicating growing turbulence that enhances HT. The persistent and significant symmetry of the distribution promotes uniform HT. Although turbulent kinetic energy (TKE) development initiates and concentrates more rapidly near the boundaries, TKE increases overall, which aligns with the observed higher local heat transfer (HT). The symmetry and rapid increase in turbulence observed with downstream pulsation confirm its effectiveness in enhancing convective HT. Fig. 9. Velocity contour plots for Re = 6,753, heat input Q = 954 W/m², pulsation amplitude A = 0.1, pulsation frequency f = 1 Hz at downstream pulsation
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