Fig. 1. Structural diagram of CRUD

Fig. 2. Diagram of oscillatory condition

Fig. 3. Node diagram of primary loop

Fig. 4. Diagram of rod bundle meshing

Fig. 5. Principal diagram of coupling scheme

Fig. 6. Axial velocity distribution of rod channel cross-section at z=0.4 m, z=0.55 m, and z=0.75 m at t = nT

Fig. 7. Axial velocity distribution of rod channel cross-section at z=0.4 m, z=0.55 m, and z=0.75 m at t=(n+0.5)T

Fig. 8. Distribution of secondary flow in cross section at typical moments (a) T=nT, (b) T=(n+0.25)T, (c) T=(n+0.5)T, (d) T=(n+0.75)T

Fig. 9. Dynamic fluctuation of temperature of local points on the circumferential wall during oscillation period