Experimental study on flow rate and pressure drop characteristics in T-junction pipes under rolling conditions

Numerous T-junction circular channels are used in the pipeline system of marine dynamic platforms. Unlike terrestrial conditions, the fluid inside the channels experiences additional inertial forces due to rolling motion, leading to complex and variable fluid mixing characteristics within T-junction pipes. The flow and pressure drop characteristics were investigated inside the T-junction pipe under rolling motion conditions, including the average value, the fluctuation value, and the instantaneous value. The working fluid is considered as the de-ionized water. The inlet Reynolds number of the main pipe ranges from 2110 to 25 320, and the flow rate ratio is from 1 to 20. The rolling time and angle are 5-15 s and 0°-15°, respectively. The range of rolling Reynolds number is 0-3520. The results indicate that the influence of the rolling motion on the flow and pressure drop characteristics inside the T-junction pipe depends on the inertial force of the fluid itself. When the inertial force of the fluid itself is large, the influence of the rolling motion on the flow parameters will be weakened. The rolling motion has a greater impact on the branch than on the main pipe. Predictive relationships for flow rates and pressure loss coefficients are established under the stationary and rolling conditions, respectively, with a fitting error of less than 10%. In addition, the boundary that ignores the influence of rolling motion on flow fluctuations and the criteria for identifying fluid backflow are also proposed.