Propulsive Performance And Optimization Of Undulatory Swimming Body

Many aquatic animals have developed its outstanding swimming performance,which contain abundant ?uid mechanical phenomena. The researches on the e?cientswimming of the aquatic animals can not only make us understand the related nat-ural phenomena and its intrinsic law better, but also provide the inspiration for thenew generation of man-made underwater vessels. Waving motion is widely adopted bythe aquatic animals for propulsion. The propulsive performance of several undulatoryswimming bodies are calculated by the panel method based on the in-viscid potentialtheory in this thesis. And the undulatory motion is optimized with the sequentialquadratic programming method. The results and conclusions are as follow:(1) The propulsive performance of the waving plate is calculated by the linearvortex lattice method, and an optimization method for the undulatory motion is de-veloped. In this method, the motion amplitude constraint is added to the optimizationproblem in order to eliminate the singularity, and the sequential quadratic program-ming method is used in order to avoid the saddle point which might be obtained by thetraditional Lagrange multiplier method. With the method, the waving plate motion isoptimized. The results reveal that, the optimum solutions are obtained on the boundaryof the amplitude constraint. The e?ciency is high when frequency is in a small stretchabout the one where the leading edge suction force is a minimum. As wave-numberincreases, the e?ciency in this range increases rapidly, and the corresponding leadingedge suction force decreases which reduce the risk of leading edge stalling. For thesame amplitude constraint, the maximum e?ciency of motion with quadratically vary-ing amplitude where the linear term does not occur (OP02) is close to that with linearlyvarying amplitude (OP01), and either of them is less than the maximum e?ciency ofmotion with quadratically varying amplitude (OP012). As frequency increases, threedimensional e?ects decreases, i.e. the in?uences of aspect ratio on the hydrodynamicquantities decrease.(2) Propulsive performance of two dimensional waving plate with large amplitudemotion is calculated by the nonlinear vortex lattice method based on point vortexelement, and the undulatory motion is optimized by the method above. The resultsreveal that, as amplitude decreases, frequency decrease or wave- number increases,the results of nonlinear vortex lattice method are close to that of linear one, and theoptimum solutions are obtained on the boundary of the amplitude constraint. Whenamplitude and frequency are large, the results are far away from the linear one, andthe optimum solutions are achieved in the interior of the boundary. The maximum efficiency decreases as frequency increase, and increases as wave-number increases.(3) Propulsive performance of two dimensional waving foil calculated by the non-linear vortex lattice method based on constant strength source combined with constantstrength vortex, and the undulatory motion is optimized by the same optimizationmethod. The results show that the optimum solutions are obtained on the boundary ofthe amplitude constraint when frequency or amplitude are small. And they are not onthe boundary when frequency and amplitude are large. These results are qualitativelyconsistent with that of nonlinear waving plate. As frequency increases, the maximume?ciency decreases, the corresponding leading edge suction force increases. And thee?ect of wave-number is adverse.