Abstract: The hole bottom flow field is the key flow field of reverse circulation sample, and it is formed with inner nozzle, end nozzle and center channel.To improve the reverse circulation pumping performance and enhance the effect of the reverse circulation, the diameter parameter of the intersection and spiral nozzle is researched.Using computational fluid dynamics（CFD) software, the pressure field and velocity field generated within the nozzle were simulated.In order to compare the import and export mass flow, the suction coefficient is introduced.The effect of nozzle diameter on the reverse circulation was discussed.The results show that intersection nozzle flow field is influenced greatly by the nozzle diameter parameter, and the spiral nozzle flow field is influenced little by the nozzle diameter parameter.Under the condition of the same diameter, the pressure change range of the intersection nozzle is higher than the spiral nozzle.With the diameter increasing, suction capacity of intersection and spiral nozzle increases, but the intersection nozzle suction capacity within the nozzle diameter change is with a large range.

Key words: CFD, Reverse circulation, Flow field, Inner nozzle, Diameter