头形对细长体超空泡生成与外形影响的实验研究

在水洞中对具有非流线形头形的轴对称细长体模型进行了空泡系列实验研究。发现了非流线形头形细长体的空化起始仅决定于空化数，并在一定的空化数下具有稳定的起始位置、脱体角和空化区域；圆锥系列头形(包括圃盘与不同直径系列)细长体可以生成3种稳定的空泡基本形态：局部附体空泡、模型体尾部闭合超空泡和模型体尾部之后闭合超空泡，超空泡的基本外形为椭球体；圆锥系列头形生成的超空泡，在相同空化数下，超空泡的相对长度与长细比均随着锥顶角或直径的增大而增大；在相同的空泡相对长度或长细比下，随着锥顶角或直径的增大，对应的空化数也增大；具有攻角的头形，改变了空泡的脱体角，使超空泡出现了一定程度的不对称性，但并不改变超空泡的基本形态。

Experimental Investigation on the Incipiency and the Shape of Supercavity for Slender Bodies with Different Headforms

A series of experiments were conducted to investigate ventilated cavity physics of slender axisymmetric bodies with nonstreamline headforms in a high-speed water tunnel. Three kinds of conic headforms were designed and over 100 test runs were performed. Based on the experiments of the incipiency, developing progress and the geometric properties of supercavitation for slender axisymmetric bodies with different nonstreamline headforms and different conditions, we draw the following conclusions: (1) The incipiency of the cavity is determined by the cavitation number only, and the location of detachment point, the separating angle and the cavitating area is constant. (2) There are three fundmental kinds of cavity, which are the partial attached cavity, the supercavity closed in the back-end of the body and the supercavity closed behind of the back-end of the body , and the basic cavitating shape is elliptical,as shown in Fig.6. (3)Under the condition of the same cavitation number, the supercavity relative length and the slenderness ratio are enlarged as the conic angle or the diameter of the cone becomes big,as shown in Fig.9. When relative length or the slenderness ratio is the same, cavitation number becomes big as the conic angle or the diameter of the cone becomes big,as shown in Fig.10. (4) When the headform has some angle of attack, the supercavity shape becomes dissymmetry in some degree as the separating angle is varied,as shown in Figs.11 and 12, but the overall shape of supercavity looks still like elliptical.