A Study on the Wake Vortex Encounter and Movement Interference Characteristics of Projectiles Successively Launched Underwater

doi:10.12382/bgxb.2022.0616

Abstract

Abstract:

In order to study the wake vortex interference and trajectory characteristics of projectiles launched successively underwater at different launching time intervals, based on the Realizable k-ε turbulence model and energy equation, volume of fluid (VOF) and overlapping grid technology were adopted. Firstly, verification of numerical method and validation of grid independence were presented. The numerical simulation results were in good agreement with the experimental results. Then the numerical simulation method of projectiles launched successively underwater was established. Based on these, the pressure distribution on the side facing the inflow as well as on the backside, trajectory and pitch attitude, particularly the evolution mechanism of vortex in wake flow were studied. The results showed that hairpin vortex-like flow structure was found, multiple hairpin vortex-like flow structures usually exist in a combined form in the flow field region at the tail of the vehicle. The jet event occurred along the inner side of the vortex leg, and the sweep event occurred outside the vortex leg. Meantime, along the inside of the vortex, a low-speed band with a certain streamwise scale was formed. Under the transverse-flow effect, when the surface of the secondary projectile passed through the low-speed strip region of the vortex in the wake, the pressure distribution characteristics of the flow facing side and its opposite side were greatly improved, the stability of trajectory and pitch attitude was increased.

Key words: secondary projectile, successive launch underwater, hairpin vortex packet, time intervals, transverse-flow speed

CLC Number:

TJ301

SHI Yao, REN Jinyi, GAO Shan, PAN Guang, QUAN Xiaobo. A Study on the Wake Vortex Encounter and Movement Interference Characteristics of Projectiles Successively Launched Underwater[J]. Acta Armamentarii, 2023, 44(10): 3195-3203.

Figures/Tables 18

Fig.1 Geometry and boundary conditions

Table 1 Controlled variable value

Eu	σ	Fr	d/l	h/l	H/l
4.79	5.63	3.67	0.125	0.0375	8.0

Fig.2 Meshing details

Fig.3 Schematic diagram of the experimental setup

Table 2 Variation of stagnation inlet pressure with time

时间/s	0	0.0001	0.0400	0.0760
绝对压力/Pa	101325	101325	293312	101325

Fig.4 Comparison of simulation result(left) and experimental result(right)

Fig.5 Process of vehicle attitude extraction

Fig.6 Comparison of ballistic curves

Fig.7 Comparison of deflection angles

Fig.8 Evolution of the wake vortexstructure and surface velocity vector

Fig.9 Evolution of the wake vortex structure of the vehicle at different launch sequences (U=0.25, Z2=1)

Fig.10 Evolution of the wake vortex structure of the vehicle at different launch sequences (U=0.25, Z2=2)

Fig.11 Comparison of surface pressure curves on the flow facing side of secondary vehicles with different launch sequences(U=0.25, Z2=1)

Fig.12 Comparison of surface pressure curves on the side facing against the flow of secondary vehicles with different launch sequences (U=0.25, Z2=1)

Fig.13 Comparison of surface pressure curves on the flow facing side of secondary vehicles with different launch sequences (U=0.25, Z2=2)

Fig.14 Comparison of surface pressure curves on the side facing against the flow of secondary vehicles with different launch sequences (U=0.25, Z2=2)

Fig.15 Trajectory curves under different launch sequences

Fig.16 Pitch angle curves under different launch sequences

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