Underwater Configuration and Safe Operating Domain of a Deep-Sea Mining Vehicle–Flexible Hose System Considering Structural and Two-Phase Flow Constraints

Flexible hoses connecting seabed mining vehicles to relay stations must remain suspended, limit vehicle loads, satisfy bending constraints, and maintain stable slurry transport. This study combines a lumped mass hose model, time domain vehicle motion analysis, and sequential structural-to-flow coupling with CFD–DEM to determine the safe operating domain of a 220 m single-arch hose. Thirteen buoyancy layouts were screened using seabed clearance, effective tension, curvature, and vehicle loads. Among the tested layouts, a buoyancy section extending from the vehicle end to 0.6L provided the best compromise. During outward travel, turning-induced peaks governed structural safety; after path optimization, the peak longitudinal and lateral hose loads were 17.78 and 22.38 kN, respectively, and the minimum bending radius remained above 2 m. At a reference slurry velocity of 5 m/s and solid volume fraction of 10%, a 40 m vehicle–relay spacing produced strong particle slip and concentration rebound near the lower bend, whereas 197 m promoted particle accumulation and a thicker moving bed. Integrating structural and conveying constraints yielded a recommended horizontal spacing of 80–160 m. Scaled pool tests and a published vertical pipe benchmark supported the numerical approach. The resulting domain provides a practical basis for path boundary design under the assumptions adopted here.