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As offshore wind power expands into deep sea, the precise calculation of steady-state ampacity for high-voltage direct current (HVDC) submarine cable is of critical importance. Existing studies often neglect the influences of ocean currents on the heat transfer in seabed porous media and submarine cable laying conditions, leading to deviation in ampacity assessment. This study established a three-dimensional thermo-electro-hydrodynamic coupled model based on COMSOL multiphysics to systematically investigate the influencing mechanisms of sediment permeability, porosities, and submarine cable laying conditions on the temperature field and ampacity of HVDC XLPE submarine cable under vertical ocean currents. The results show that seawater flow velocity is the decisive factor influencing ampacity. Setting the sediment porosities to 0.4 and the permeability to 103 d, when the flow velocity increases from 2 cm/s to 50 cm/s, the ampacity increases by 35.2%, which is mainly attributed to the significant enhancement of convective heat transfer efficiency in the sediment layer. Setting the sediment permeability to 103 d and the seawater flow velocity to 50 cm/s, when the sediment porosities increases from 0.2 to 0.6, the ampacity increases by 5.6%, which attributes to expanded pore networks enhancing the equivalent thermal conductivity. Sediment permeability and flow velocity exhibit a significant synergistic effect, when the permeability exceeds 102 d, secondary convective heat transfer can be induced in high-speed flow fields. Setting the sediment porosities to 0.4 and seawater flow velocity to 50 cm/s, compared to 102 d of sediment permeability, the flowing fluid can additionally contribute 1.6% of the ampacity gain when the sediment permeability is 103 d. The bipolar system exhibits a significant thermal coupling effect under ocean currents, causing the temperature difference between the two poles to increase with the increase of flow velocity. Setting the sediment porosities to 0.6 and the permeability to 103 d, when the flow velocity is 50 cm/s, the temperature difference between the two poles increases by 1 283.3%, resulting in an ampacity difference up to 136 A. Among the laying parameters, the laying spacing has a greater impact on the ampacity than the laying depth.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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