# Research on Replacing Numerical Simulation of Mooring System with Machine Learning Methods
## 2 Data from Numerical Simulation of the CALM System  
### Numerical Simulation in CALM Design  
The CALM (Catenary Anchor Leg Mooring) system, deployed in shallow water, usually consists of a floating buoy, six anchoring lines, and a pair of mooring hawers, as shown in Figure 1. For a normal field environment, the design conditions can be divided into two groups:  
1. [label=(0)]
2. Operation condition: A tanker with full loading and ballast loading is connected to the CALM buoy by mooring hawers.
3. Self condition: CALM buoy stands alone without the tanker connected.  
In each condition, the environmental loads need to be divided into several groups. Despite the actual complex conditions, a simplified method is adopted to deal with the environmental loads. For normal environmental conditions, wind, current, and wave in collinear and non-collinear directions are considered. \"Collinear\" refers to the situation where wind, current, and wave are in the same direction, whereas \"non-collinear\" implies that wind and current have a 30 and 45 degree deviation from the wave, respectively. The direction of the resultant load can either be aligned with one of the anchor legs or between two legs. According to DNV and ABS regulations [21; 22], one mooring line failure situation is analyzed for each governing case in addition to the intact analysis with no mooring line failure. The mooring line numbering scheme is defined in Figure 2. As a result of the symmetrical configuration, mooring line 1 or 2 is assumed to be the failure line. There are, therefore, 10 cases to be assessed if different failing mooring lines and load directions are considered, as shown in Figure 2. Since two operation conditions (full loading and ballast loading) and the self condition need to be investigated, 30 cases need to be simulated for a design assessment. The other design parameters, namely CALM buoy and VLCC (Very Large Crude Carrier), are fixed to simplify the problem.  
In order to verify the feasibility of the mooring design, it is necessary to evaluate the results of buoy offset, anchor line laid length, anchor line tension, and hawser tension from the numerical simulation. According to the ABS regulation [21], the minimum factor of safety against the breakage of each anchor leg component is used, while the DNV regulation [22] employs a utilization factor.  
The input and output parameters of the operation and self condition modules are presented in Figure 3 and summarized as follows. _vw_ means wind speed, _vc_ means flow velocity, _hs_ means wave height, _tp_ means wave spectrum period, _moor_d_ means water depth, \(d\) means anchor chain's diameter, _pta_ means pretension angle, _cable_L_ means length of cable, _cable_stiff_p_ means cable stiff primary coefficient, _cable_stiff_q_ means cable stiff  
Figure 1: Schematic of the CALM system.  
Figure 2: Mooring line numbering scheme and definition of environmental loads’ heading direction (resultant load).  
quadratic coefficient, _cable_br_ means cable strength, CN means working condition, _minlaid_ means minimum left length of cable, _max_hauserC_ means maximal cable force utility factor, _maxchainFC_ means maximum chain force factor, _maxchainFC_DNV_ means maximum chain force factor according to DNV, _maxoffsetC_ means maximum offset of the buoy. _Case No._ is an integer value starting from 0 to 9, totaling 10 cases as mentioned above.  
The numerical simulation in the paper is performed by ANSYS AQWA software (version 11.0). The output parameters obtained through simulation and the input parameters form the dataset for training the machine learning models. To accelerate the calculation, a special program is built on the cloud platform to realize parallel computing.