Potential flow Mean Drift Forces
1 Test Description
This benchmark verifies the computation of mean drift forces from potential flow theory in Ashes. The mean drift forces are calculated using hydrodynamic coefficients provided in a .8 WAMIT file format.
The test consists of several load cases with linear waves of varying wave heights, periods, and headings. Each load case is designed to test the mean drift force calculation under different wave conditions and approach angles.
2 Load Cases
The following load cases are simulated to validate the mean drift force calculations:
- Load Case 1: Wave period = 10 s, Wave height = 3 m, Heading = 0°
- Load Case 2: Wave period = 5 s, Wave height = 2 m, Heading = 0°
- Load Case 3: Wave period = 10 s, Wave height = 3 m, Heading = 50°
- Load Case 4: Wave period = 7 s, Wave height = 2 m, Heading = -30°
- Load Case 5: Wave periods = [10 s; 7 s], Wave heights = [3 m; 2 m], Headings = [50°; -30°]
- Load Case 6: Full spectrum with 50 wave components
Load Case 5 represents a combined wave condition with varying parameters, while Load Case 6 tests the mean drift force calculation for a realistic wave spectrum discretized into 50 frequency components.
3 Analytical solution
The mean drift forces computed by Ashes are compared against analytical solutions derived from the hydrodynamic coefficients in the WAMIT .8 file following the equations described in the
Potential flow theory
document.
4 Results
A simulation of 30 seconds is run. For each load case, the relative error between the Ashes simulation results and the analytical solution is calculated. The test is considered passed if the relative error is within 0.1% for all load cases.
The report for this test can be found on the following link: