The water-lubricated tilting pad thrust bearings (WTTBs) of the reactor coolant main pump and high-power RDT operate at a large linear velocity, heavy load, and low viscosity. On the basis of the performance prediction of WTTBs in the mixing flow pattern, a hypothesis of the regional flow pattern is proposed. To compare the lubrication performance under four kinds of flow pattern modes, a thermo-elasto-hydrodynamic lubrication model of the WTTB considering the flow pattern is established, and a partition iteration algorithm for the mixing flow pattern is provided. Moreover, a method for controlling the flow pattern by changing the pad surface morphology is proposed. A simulation is used to indicate that the bearing performance under the mixing flow pattern calculated by the regional flow pattern mode is between that of the laminar and turbulent flows. The regional mixing flow pattern mode can automatically retrogress to the single flow pattern mode by changing the operation conditions. Both the circumferential bulge and radial concave pad surfaces are beneficial for increasing the turbulent area and thereby improving the load-carrying capacity of the WTTB.