For　the　Rocket-Based　Combined-Cycle　(RBCC)　engine,　the　addition　of　primary　rocket　jets　makes　both　the　flow　field　and　the　shock　train　structure　more　complicated.　In　this　study,　a　three-dimensional　Detached　Eddy　Simulation　(DES)　modeling　was　employed　for　the　numerical　analysis　of　a　full-scale　central-strut　isolator.　The　characteristics　of　shock　train　for　the　flight　Mach　3　were　studied.　As　a　result,　under　the　effect　of　central　high-velocity　central　jets　and　different　back　pressures,　the　structure　of　shock　train　could　be　changed.　At　the　low　back　pressure,　the　expansion　wave　originated　from　the　trailing　edge　of　the　central　strut　still　existed,　and　one　X-type　shock　wave　was　formed　at　downstream.　Then　the　strength　of　the　subsequent　shock　waves　between　the　parallel　jets　and　the　wall　in　shock　train　gradually　decays.　As　the　back　pressure　increased,　the　leading　edge　of　the　shock　train　moved　upstream.　The　shock　train　was　then　transformed　into　two　parts:　one　part　was　the　oblique　shock　wave　generated　in　the　strut　section;　another　was　the　quasi-normal　shock　waves　formed　in　the　mixing　section　within　the　region　between　the　shear　layer　and　the　parallel　jets.　The　origination　of　the　first　shock　wave　could　cause　the　generation　of　the　vortexes　in　the　isolator.　With　the　parallel　jet　addition,　as　the　vortexes　were　transported　downstream,　they　broke　up　into　small　scales　and　in　more　random　orientation　at　the　back　wall　of　the　central-strut.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.