The reliable closure of a conical valve is key to establishing the initial seal of a deep-sea split sediment sampler. The transient characteristics of gap fluid have an important effect on the reliable closure of the conical valve. By using CFD

overlapping mesh and moving mesh methods

a two-dimensional flow model of the gap fluid in the split sediment sampler was established. On this basis

the transient characteristics of axial gap fluid were simulated numerically

and the influence of different closure rates on the flow characteristics between conical surfaces was studied. The simulation results show that at the selected closure rate

the flow in the lower gap of the conical valve is more stable than that in the upper gap and that turbulence forms more easily in the upper gap. With the decrease of the closure rate

the negative work of transient fluid resistance approaches the threshold

and the shear action of the inter-cone fluid becomes weaker. In order to reduce the fluctuation

the paper reduces the negative work done by the resistance and improves the closure efficiency. It is appropriate to choose the closure rate between 0.005 m/s and 0.001 m/s. The study provides important reference for improving the initial seal of the deep-sea split sediment sampler.