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권순범(Soon-Bum Kwon),김인구(In- Goo Kim),안형준(Hyung-Joon A hn),이동원(Dong-Won Lee),백승철(Seung-Cheol Back),김경호(Kyung-Ho Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
When u safety valve equipped in a nuclear power plant opens in un instant by an accident, a moving shock wave propagates downstream the valve, inducing a complicated unsteady flow field. The moving shock wave may exert severe load to the structure. So, to reduce the load acting on the wall of POSRV a gradual opening of POSRV is adopted in general. In theses connections, a numerical work is performed to investigate the effect of valve opening time on the unsteady flow fields downstream of the valve. Compressible, two-dimensional Navier-Stokes equations arc used with the finite volume method. The obtained results show that sharp pressure rise through moving shock for the case 0 r instant opening is attenuated by employing the gradual opening of valve. It is turned that the flows for the two cases of gradual valve opening time show the similar to that of highly under-cxpaJl(.Ied one in jet structure having expansion and compression waves and Mach stem. Also, comparing with the results for the two cases of opening time, the shorter the valve opening is, the pressure gradient at the downstream of the valve becomes softly.