Based on the fluid dynamic characteristics of gear pump,a robust design method was proposed to solve the large noise,low volume efficiency in external gear pump caused by high pressure of trapped oil.A type of high pressure gear pump was used as the research object,modeled and simulated by CFD professional software PUMPLINX.The effects on trapped oil pressure by cat eye type unloading groove structure parameters,gear pump speed,load pressure and medium characteristics were analyzed.An approximate model of t...