The effect of local scour on the hydrodynamic force upon a submarine pipeline under unidirectional flow has been numerically investigated. The flow field around the pipeline is obtained using the Navier–Stokes equations with the SST k-ω turbulence model, and the sediment transport model, considering suspended load and bed load, is accounted for. Firstly, the influences of the Reynolds number (1 × 10⁴ ≤ Re ≤ 1 × 10⁵) and Shields number (1.2 ≤ θ/θ_cr ≤ 2.5) on the scour below the pipeline are analyzed; then, the effect of local scour on the hydrodynamic force upon the pipeline is examined by comparing with the condition that the pipeline is put on the flat seabed. It is found that the presence of local scour leads to a significant effect on the hydrodynamic force acting on the pipeline. Additionally, the Reynolds number affects the hydrodynamic force significantly, while the Shields number has a relatively low effect. The reduction coefficient (λ) is adopted to quantify the influence of the local scour around the pipeline on the hydrodynamic force. According to the reduction coefficient, the presence of local scour increases the drag coefficient by about 10% when the Reynolds number is 1 × 10⁴, while it decreases the drag coefficient significantly when the Reynolds number is larger than 2 × 10⁴, and the reduction coefficient trends towards a constant value with the increase in the Reynolds number.

A 2D numerical model for viscous flow is established in OpenFOAM version 10 to analyze the hydrodynamic response of submarine power cables for offshore wind turbines under combined wave–current conditions. It focuses on analyzing the effect of the cable suspension ratio e/D and the current-to-wave velocity ratio U_c/U_m on the Morison coefficient of the suspended cable. The results indicate that for the cable suspension ratio e/D of less than 0.5, the strength of the dependence of both the drag coefficient C_d and inertia coefficient C_M on the cable suspension ratio e/D is significantly influenced by the current-wave-ratio U_c/U_m, while this dependence becomes less pronounced for e/D greater than 0.5. And the inertia force coefficient C_M decreases monotonically with the current-to-wave velocity ratio U_c/U_m, while the drag force coefficient C_d demonstrates a more complex, non-monotonic relationship with it. Based on the simulation results in this paper, a quantitative relationship between C_d, C_M, and the key governing parameters is established using a two-layer feedforward neural network model, providing a method for predicting wave–current forces on subsea suspended cables.