摘要：The influence of the size and the angle of the branch on the onset of gas entrainment is explored in the present study. Since previous studies were performed on small-sized branches and the angles of the branches were specific (0° or −90°), it is difficult to apply them to arbitrary-angled branches. So we conducted a series of experiments in a different direction of −30°, −45°, −60°, and −90° angles with the main pipe of 80-mm diameter and a branch of 31-mm diameter (T-tube). A new correlation is developed and can predict the most experimental data well within the error range of ±20%. And the new correlation can predict the onset of gas entrainment at arbitrary-angled branch and is not constrained by the angle of branches; that is, it has good versatility. We also gained some meaningful conclusions by analyzing experimental data and the entrainment phenomenon: gas is entrained by a vortex flow, and the size of the branch and the angle of the branch have little effect on the form of entrainment at a given hb/d. The critical Froude number (FrL) gradually increases as the angle of the branch changes from −90° to −30°. When this is compared with previous models, it can be found that the correlation of the onset of gas entrainment based on small-sized branches is not suitable for large-scale branches. But we have defined a new critical liquid level (hb*) to successfully expand the scope of application of the correlation.
