Fig. 1. Schematic diagram of rod bundle channel domain identification (a) Layout of mixing vanes, (b) Illustration of the ray method, (c) Axial diagram of the rod bundle channel, (d) Structured mesh for modeling, (e) Results of domain identification for vane zone, (f) Results of domain identification for spacer zone

Fig. 2. General momentum source scheme and pressure distribution in the vane zone (a) Illustration of the momentum source in the windward side of vane, (b) Pressure distribution in the vane zone, (c) Body-fitted mesh, (d) Structured mesh, (e) Nearest neighbor interpolation with inverse distance weighting correction

Fig. 3. Flowchart of integrated simulation scheme for detailed porous media and general momentum sources

Fig. 4. Independence validation for body-fitted mesh and modeling scheme

Fig. 5. Partial results of mesh sensitivity analysis

Fig. 6. Validation of simulation results of body-fitted mesh (a) z=17 mm, x=6.3 mm, (b) z=17 mm, x=6.3 mm, (c) z=30 mm, x=6.3 mm, (d) z=90 mm, x=6.3 mm

Fig. 7. Flow contour of detailed porous media simulation spacer zone (a) Body-fitted mesh calculation results at z=-2.5D_h, (b) Detailed porous media calculation results at z=-2.5D_h, (c) Body-fitted mesh calculation results at x=0.5 P, (d) Detailed porous media calculation results at x=0.5 P

Fig. 8. Simulation of mixing vane zone with different schemes (a) Body-fitted mesh calculation results, (b) Calculation results of global momentum source model, (c) Calculation results of local momentum source model

Fig. 9. Comparison of cross-flow at the outlet of mixing vanes with different schemes

Fig. 10. Simulation of axial flow distribution under different schemes at 1 m·s^-1 operating condition (a) z=30 mm, x=-6.3 mm, (b) z=90 mm, x=-6.3 mm

Fig. 11. Simulation results for different schemes at at an average axial flow velocity of 7 m·s^-1 (a) Axial velocity distribution of body-fitted mesh at x = 0.5D_h, (b) Axial velocity distribution of local momentum source model at x = 0.5D_h, (c) Axial velocity distribution of global momentum source model at x = 0.5D_h, (d) Axial velocity distribution of body-fitted mesh at z = 1D_h, (e) Axial velocity distribution of local momentum source model at z = 1D_h, (f) Axial velocity distribution of global momentum source model at z = 1D_h, (g) Lateral flow distribution of body-fitted mesh, (h) Lateral flow distribution of local momentum source model, (i) Lateral flow distribution of global momentum source model

Fig. 12. (a) The left image shows the simulation results of body-fitted mesh, (b) while the right image shows integrated simulation scheme for detailed porous media and general momentum sources

Fig. 13. Diagram of turbulent structure and cross-flow distribution at z=0.5D_h (a) Calculation results of body-fitted mesh, (b) Calculation results of global momentum source model

Fig. 14. Diagram of temperature distributions of body-fitted mesh at z = 1 D_h (a), global momentum source model at z = 1 D_h (b)

Fig. 15. Circumferential nusselt number distribution of central fuel rod

Fig. 16. Axial pressure drop curve in rod bundle channels