Based on the Latin square design of statistics, the thickness of first boundary layer, the turbulence model and the cell number were taken as the three main factors of uncertainty in CFD （computational fluid dynamics...Based on the Latin square design of statistics, the thickness of first boundary layer, the turbulence model and the cell number were taken as the three main factors of uncertainty in CFD （computational fluid dynamics）. Total resistance of hull was calculated and the flow field around the hull was simulated by CFD method. Then, the influence of uncertainty factors on the hull resistance was discussed by regression analysis with trimmed mesh and overset mesh. Through a series of calculation and analysis, the optimal calculation method was put forward, and the relevant parameters of the calculation were determined. Thirdly, the total resistance of different speed was calculated by using these two kinds of grids, which were in good agreement with the experimental results. Finally, according to the ITTC recommended procedures, uncertainty analysis in CFD was carried out with the numerical results of the total resistance by three sets of grids with uniform refinement ratio rG = √2. Then the modified resistance was compared with the experimental result, which improved the accuracy of the resistance prediction.展开更多
Though the turn to the right in Latin America will continue over the short term, the left has not diminished and its resurgence remains possible. The political situation in Latin America has undergone dramatic changes...Though the turn to the right in Latin America will continue over the short term, the left has not diminished and its resurgence remains possible. The political situation in Latin America has undergone dramatic changes since 2015, when an ebbing of the"pink tide"and rise of the right in several countries occurred, coupled with US support to the right.Flexible political strategies and rightists' political pragmatism are occurring as the continent's middle class expands, coupled with US support to the right. Some conditions that promote the right's revival remain operative, but for the new right regimes, addressing economic vitality, the wellbeing of the poor, corruption, and divisions from within are imminent challenges against which a left resurgence has competitive ground.展开更多
文摘Based on the Latin square design of statistics, the thickness of first boundary layer, the turbulence model and the cell number were taken as the three main factors of uncertainty in CFD （computational fluid dynamics）. Total resistance of hull was calculated and the flow field around the hull was simulated by CFD method. Then, the influence of uncertainty factors on the hull resistance was discussed by regression analysis with trimmed mesh and overset mesh. Through a series of calculation and analysis, the optimal calculation method was put forward, and the relevant parameters of the calculation were determined. Thirdly, the total resistance of different speed was calculated by using these two kinds of grids, which were in good agreement with the experimental results. Finally, according to the ITTC recommended procedures, uncertainty analysis in CFD was carried out with the numerical results of the total resistance by three sets of grids with uniform refinement ratio rG = √2. Then the modified resistance was compared with the experimental result, which improved the accuracy of the resistance prediction.
文摘Though the turn to the right in Latin America will continue over the short term, the left has not diminished and its resurgence remains possible. The political situation in Latin America has undergone dramatic changes since 2015, when an ebbing of the"pink tide"and rise of the right in several countries occurred, coupled with US support to the right.Flexible political strategies and rightists' political pragmatism are occurring as the continent's middle class expands, coupled with US support to the right. Some conditions that promote the right's revival remain operative, but for the new right regimes, addressing economic vitality, the wellbeing of the poor, corruption, and divisions from within are imminent challenges against which a left resurgence has competitive ground.
