tailieunhanh - Body parameters with application of optimal differential variation method in super cavity model

When a slender body moves very fast through water at sufficient speed the cavity phenomena is happened. In a cavity model the bodys lengths and cavitator diameter are determined by the differential variation optimal method so that the velocity of body is maximum. | Vietnam Journal of Mechanics, VAST, Vol. 38, No. 4 (2016), pp. 267 – 278 DOI: BODY PARAMETERS WITH APPLICATION OF OPTIMAL DIFFERENTIAL VARIATION METHOD IN SUPER CAVITY MODEL 1 Institute Tran Thu Ha1,2,∗ , Nguyen Anh Son3 , Duong Ngoc Hai1 of Mechanics, Vietnam Academy of Science and Technology, Hanoi, Vietnam 2 VNU University of Engineering and Technology, Hanoi, Vietnam 3 National University of Civil Engineering, Hanoi, Vietnam ∗ E-mail: tran thuha1@ Received September 16, 2015 Abstract. When a slender body moves very fast through water at sufficient speed the cavity phenomena is happened. In a cavity model the bodys lengths and cavitator diameter are determined by the differential variation optimal method so that the velocity of body is maximum. Keywords: Super cavity, Runge-Kutta methods, data assimilation. 1. INTRODUCTION In hydrodynamics applications cavitation is the appearance of vapor bubbles and pockets inside homogeneous liquid medium. This phenomenon occurs because the pressure is reduced to the vapor pressure limit. We will study super cavity appearing by the very fast movement of slender body in water that makes uncontrolled gun-launched slender body. Except the body head called by cavitator is directly touching with water, the gas layer can be covered partial or full body depending on the design of body form. The body rotates about its nose. In this paper for simple calculation we choose cavitator formed by the plate disk with diameter (see Fig. 1). The body is consisted of two parts: the cone top and cylinder part with the diameter d. In the super cavity model the following assumptions are (see [1]): - The motion of the projectile is confined to a plane; - The slender body rotates about its nose; - The effect of gravity on the dynamics of this body is negligible; - The motion of the slender body is not influenced by the presence of gas, water vapor or water drops in the cavity; c 2016 Vietnam Academy of Science .