In response to the unclear thermal mixing mechanism between hot and cold fluids in the circular T-junctions of marine power platforms and ship power devices,the large eddy simulation method is employed to investigate fluid thermal mixing under high temperature and high pressure conditions.This study examines different branch pipe arrangements with a working pressure of 10 MPa,an inlet fluid temperature difference of 275 K,and a swing Reynolds number of 41 500,all under multi-force field coupling conditions.The proposed mixing coefficient is employed to quantitatively assess the fluid mixing effect within the circular T-junction,while the root mean square temperature is used to evaluate temperature fluctuations at the wall of the circular T-junction,under different branch pipe configurations.The results reveal a temporal and spatial synergistic mechanism between the vortex structure and temperature field in the shear layer and wake region.Notably,the vortex shedding frequency aligns closely with the temperature fluctuation frequency at corresponding positions,with a shedding frequency of 19.3 Hz.The additional inertial force induces periodic changes in both the vortex structure and temperature field within the circular T-junction,accelerating the fluid mixing process.This effect mitigates the thermal stratification phenomenon caused by buoyancy and gravity,resulting in increased temperature fluctuations in the fluid domain,with a characteristic length of approximately 10.2D.Compared to static conditions,mixing coefficients increase by 10.8％,18.3％,and 27.8％for branch pipes arranged vertically upwards,horizontally,and vertically downwards under swing conditions,respectively.The maximum peak of the root mean square temperature for T-junctions arranged vertically downwards under swinging conditions reaches 0.16,approximately double that of stationary conditions.Therefore,when branch pipes are arranged vertically upwards,the thermal mixing effect is optimal,and thermal stratification is minimized,making this arrangement preferable for practical applications.
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