静气动弹性影响下带小翼汽车尾翼的设计与优化

Design and optimization of a car empennage with winglet under effect of static aeroelasticity

翼尖小翼能利用机翼翼尖产生的三维绕流为机翼提供额外的升力和前进的推力,其独特的作用机理同样适合用在汽车尾翼上。由于汽车的尾部流场与航空器有较大差别,使传统的航空器翼型很难满足汽车用翼尖小翼的设计需求,同时翼尖小翼的附加会使尾翼翼面因额外的弹性变形而产生新的气动载荷分布,这就需要对车用翼尖小翼进行设计和优化。首先,利用准均匀B样条曲线来拟合翼型,再对拟合的翼型进行小翼的三维参数化建模,最后,使用双向流固耦合的分析方法来考虑静气动弹性对附加了小翼的汽车尾翼的实际影响,并在三维流场中通过数值仿真的手段对小翼翼型及其形状参数进行优化设计。最优样本进行了风洞试验验证和比较,结果说明仿真具有较高的模拟精度,同时风洞试验与数值仿真的结果表明:翼尖小翼通过优化设计能为安装有普通尾翼的汽车带来额外下压力的同时减小其气动阻力;相较于刚性翼,考虑静气动弹性的新型尾翼,其最优解集有使汽车模型的升力系数增加而阻力系数减小的趋势。

A winglet can use the three-dimensional flow,generated by the wingtip,to provide the wing with additional lift and forward thrust. Its unique mechanism of action is also suitable for the application to a car empennage. However,because the wake of a vehicle has many differences with an aircraft,traditional airfoils of an aircraft are difficult to satisfy the design requirements of a winglet that is installed on the car empennage. Meanwhile,adding a winglet will create new aerodynamic load distribution due to the additional elastic deformation. Therefore,the design and optimization of a car-use winglet is needed.Firstly,quasi-uniform B-spline curve was applied to fit the airfoil,then the fitting airfoil was employed in building the three-dimensional model of the winglet. After that, the Bi-directional fluid-structure interaction was used to add the actual influence of static aeroelasticity on the car empennage with the winglet. Finally,the airfoil shape and shape parameters of the winglet were optimized with the threedimensional numerical simulations. Wind tunnel tests were performed to validate and compare the results of numerical optimization,showing that the numerical simulations have high fidelity. The results of wind tunnel tests and numerical simulations indicate that,through design and optimization,a winglet can reduce drag and produce additional downforce for a vehicle with an ordinary car empennage. Compared with a rigid winglet,the optimal solution set of the new car empennage,under the influence of static aeroelasticity,have the trend to increase the lift coefficient and reduce the drag coefficient of the car model.