FD生成的PMM数据在初步设计阶段进行评估英文文献和中文翻译(13)
The generated model is strictly speaking only applicable for the given approach speed. In case of different approach speeds the model ought to be re-evaluated to find the corresponding coefficients. Test matrix reduction and simulation results based on EFD For standard PMM tests a full standard test program (STP) similar to the programme presented in Table 2 is usually applied. When running just tank tests there has been no significant motivation for minimizing the test programme since the main costs are associated with the initial setup of the model and there has rather been a tendency to utilize the length of the entire towing tank to pick up as many points as possible. This approach is suitable for tank tests, but in connection with numerical model tests where the calculation time is the most expensive “cost”, there is a need to minimize the number of points/calculations. To evaluate a minimum test programme (MTP), a set of simulated manoeuvres based on MTP were compared to similar manoeuvres based on the STP. To establish whether the MTP was acceptable or not a set of criteria or tolerances were defined. If the initially tested MTP did not meet the defined tolerances the number of measuring points was to be increased until the limits were fulfilled.
The predefined acceptable tolerances between STP and MTP are presented in Table 10. In order to meet the criteria a number of iterations were performed increasing the number of data-points in the MTP. Different approaches were tested for example adding points mainly focusing on static points and correspondingly adding points mainly focusing on dynamic points. The final minimum test program comprised the total matrix of dynamic test points from the STP while the static part only contained 58 data points of the total 82 in the STP. In fact the final MTP did not meet all the tolerances, but it was accepted as close enough and robust enough to fulfill the purpose. The criteria values, i.e. differences between final MTP and STP maneuvering parameter, are listed in Table 11. The final minimum test matrix is presented in Table 12. Table 10: Acceptable tolerances between results of MTP and STP simulated manoeuvres, where zz is zigzag, OS is overshoot angle, ITA is initial turning ability and tc is turning circle. 10/10 zz 1st OS [deg] +/- 0.5 10/10 zz 2nd OS [deg] 0.8 ITA [Lpp] 0.02 20/20 zz 1st OS [deg] 0.8 20/20 zz 2nd OS [deg] 0.8 35 tc advance [Lpp] 0.05 35 tc tactical diameter [Lpp] 0.05 35 tc steady drift [deg] 1.0 Table 11: Difference between results of MTP and STP simulated manoeuvres. Port Starboard 10/10 zz 1st OS [deg] -0.7 -0.9 10/10 zz 2nd OS [deg] -1 -1.1 ITA [Lpp] 0.02 0.05 20/20 zz 1st OS [deg] -0.5 -0.9 20/20 zz 2nd OS [deg] -0.6 -0.3 35 tc advance [Lpp] -0.01 0.02 35 tc tactical diameter [Lpp] -0.11 0.02 35 tc steady drift [deg] 0.6 0 As the next step in line towards a full model test matrix of pure numerical model tests the static part of the found MTP was generated using CFD. The purpose was to substitute the static derivative found from the model tests with static derivatives evaluated from numerical model tests. The numerical data was evaluated just as if they have been recorded in the towing tank, i.e. the calculated hydrodynamic forces are faired by the same combination of independent variables as presented in equation 28 to 30. The dynamic coefficients are not reevaluated based on the new static coefficients; to make it simple the static coefficients from the MTP is just replace by the new “CFD” static coefficients. The predicted static hydrodynamic derivatives are presented in Table 13. Simulations were made using both sets of hydrodynamic derivatives presented in Table 11. The main values for 35/-35 degree turning circles and 10/10 and 20/20 starboard and port zigzag manoeuvres are presented in Table 14 and Table 15. The simulation results are plotted in Figure 20 to Figure 23.
摘要本文在演习模拟相结合的基础上，计算和测量流体的输入数据，确保能够执行深水海事组织的标准。基于一套完整的数据降低PMM的测试矩阵，确定10-10标准和20-20锯齿和35转弯模拟。在减少测试矩阵的基础上，为了获得水动力和力矩，所有静态PMM条件都采用RANS方程STAR-CCM+计算。计算静态PMM数据随后被用来更换相应的实测静态PMM数据。在计算，力和力矩之间的比较显示出相当不错的条件，考虑到帐户的数值和实验的不确定性，先提出一个选定的条件，在进行正式的验证和确认。当Y-Force和偏航力矩不变的时候，结果显示X-Force是正确的。对于模拟演习，结果看起来很好，通过比较模拟回转和曲折试验测量得到输入数据，从而发现合理的实验现象。