CFD modelling and grid uncertainty analysis of the free-falling water entry of 2D rigid bodies

The open source Computational Fluid Dynamics (CFD) library, OpenFOAM, is utilized to simulate the water impact of two-dimensional wedges and ship bow sections. For the free falling cases, the predicted results are validated against existing experimental data, and the parameter study is performed regarding the number of cells, time step, and width of the water domain applied in the numerical models. Grid uncertainty analysis for the CFD results is performed with a constant Courant-Friedrichs-Lewy number, to assess the consistency and accuracy of the CFD solver in solving the present problem. Three uncertainty estimation methods are compared on the peak slamming forces and pressures: Correction Factor (Cf), Factor of Safety (Fs), and Least-squares Fit (Lf) based approaches. All three of them can provide reliable uncertainty estimation for CFD simulations, as long as the right mesh configuration has been used. The variations of pressure distribution on wedge sections with various deadrise angles and initial entry velocities are analyzed. To examine the capability of the tool to predict the slamming loads for a section with roll motions two cases are simulated: one considering a free roll motion and another with constant roll angles. The predicted slamming loads are compared with the available experimental data and other numerical results.

Automated summary

When using OpenFOAM to simulate water impact, attention should be paid to the impact of parameter settings and uncertainty estimation methods on the results.