耦合升沉运动的七叶侧斜螺旋桨空泡性能研究

为建立有效的预报耦合升沉运动的螺旋桨空泡性能的方法,并基于该方法分析升沉运动对螺旋桨空泡性能的影响,基于RANS方法对耦合升沉运动的七叶侧斜螺旋桨的空泡性能进行了数值模拟,螺旋桨的升沉和旋转运动耦合采用自定义运动方程实现,其中升沉运动简化为简单正弦函数。非定常流场中网格和物理信息的传递采用重叠网格技术实现。将非定常流动中螺旋桨(DTMB 4381)的空泡计算结果与试验结果及现象进行了对比,验证了数值计算模型的准确性。计算中对不同升沉运动周期下的螺旋桨非定常推力及扭矩系数进行了分析,同时对螺旋桨的空泡性能进行了实时监测。计算结果显示,升沉运动使螺旋桨的推力和扭矩系数的非定常特性更加明显,同时导致螺旋桨各叶片上的空泡分布不均匀;升沉运动周期越小,上述现象越明显。同时较小升沉运动周期时,推进系数和空泡面积均为周期性变化,其变化周期均为升沉运动的1/2,螺旋桨空泡面积最小值较无升沉运动时增大约17%,空泡面积最大值则增大约57%。

Numerical Simulation of a Seven-Blade Propeller with Skew on Its Cavitation Performance Coupled with Heave Motion

A numerical simulation of cavitation performance was conducted on a seven blade propeller impacted by coupled heave and rotate motion using RANS method. The coupled motion of propeller was fulfilled using user-defined equations. The heave motion was simplified as a simple sinusoidal function. The overset grid approach was used to transmit physis and mesh information in the unsteady flow field. The validation studies of the DTMB 4381 propeller for unsteady cavitation flow are presented, and the calculation results are in acceptable agreement with the experimental results and observations. In this paper, the unsteady thrust and torque coefficient in different heave motion were analyzed. Also, the cavitation performance of the propeller was recorded in time. The results indicated that the unsteady characteristics of thrust and torque was intensified due to the heave motion and it also leaded to the non-uniform distribution of cavitation on the propeller. A smaller heave period results in a severe unsteady characeeristics and non-uniform distribution. The thrust coefficient and sheet cavitation area change periodically and both the change cycle is one-half of the heave movement as the heave period is small. The minimum area of the propeller cavitation is about 17% higher and the maximum area is about 57% higher than without heave motion. The results obtained from the numerical simulation are expected to sever as a useful theoretical reference for optimization of seven bladed propeller designs.