﻿ 单体热射流水团浮升扩散规律研究
 舰船科学技术  2001, Vol. 44 Issue (6): 72-75    DOI: 10.3404/j.issn.1672-7649.2022.06.015 PDF

Study on the law of floating and diffusion of water mass of single thermal jet
ZHANG Ze-hua, DU Yong-cheng, WANG Bao-lin, WU Ting-feng, YANG Li
School of Power Engineering, Naval University of Engineering, Wuhan 430033, China
Abstract: The thermal jet emission of underwater vehicle may form certain infrared characteristics on the water surface, which will affect its stealth performance. Therefore, it is of great significance to study the buoyancy and diffusion mechanism of thermal wake. In this paper, a two-dimensional mathematical model is established to study the buoyancy and diffusion law of single thermal jet water mass. The two-dimensional numerical simulation of buoyancy and diffusion law of thermal jet water mass is carried out by using Fluent software. The buoyancy and diffusion law and temperature distribution characteristics of single thermal jet water mass are obtained by using SST k-omega turbulence model and finite volume method. By using this mathematical model, the influence of initial velocity, direction and temperature difference on the buoyancy and diffusion of single hot jet water mass is further studied and compared, and the temperature distribution and motion trajectory of single hot jet water under the influence of several factors are obtained.
Key words: jet     temperature distribution     floating law     Fluent
0 引　言

1 数学模型及计算方法

 $\frac{{\partial p}}{{\partial t}} + \frac{{\partial \left( {\rho {u_i}} \right)}}{{\left( {\partial {x_i}} \right)}} = 0 。$ (1)

 $\begin{split} \rho \frac{{\partial {u_i}}}{{\partial t}} +& \rho {u_j}\frac{{\partial {u_i}}}{{\partial {x_j}}} + \frac{{\partial p}}{{\partial {x_i}}} - \left( {{\rho _0} - \rho } \right){g_i} =\\ &\frac{\partial }{{\partial {x_j}}}\left[ {\mu \left( {\frac{{\partial {u_i}}}{{\partial {u_j}}} + \frac{{\partial {u_j}}}{{\partial {u_i}}}} \right)} \right] - \frac{2}{3}\frac{\partial }{{\partial {x_i}}}\left( {\mu \frac{{\partial {u_j}}}{{\partial {x_j}}}} \right) \end{split}。$ (2)

 $\rho {c_p}\frac{{\partial T}}{{\partial t}} + \rho {c_p}{u_j}\frac{{\partial T}}{{\partial {x_j}}} = {u_j}\frac{{\partial p}}{{\partial {x_j}}} + \frac{\partial }{{\partial {x_j}}}\left( {\lambda \frac{{\partial T}}{{\partial {x_j}}}} \right) 。$ (3)

 $\rho \frac{{{\rm{D}}k}}{{{\rm{D}}t}} + \rho \frac{{\partial \left( {k{u_i}} \right)}}{{\partial {x_f}}} = \frac{\partial }{{\partial {x_f}}}\left( {{T_k}\frac{{\partial k}}{{\partial {x_f}}}} \right) + {G_k} - {Y_k}。$ (4)

 $\rho \frac{{{\rm{D}}\omega }}{{{\rm{D}}t}} + \rho \frac{{\partial \left( {\omega {u_i}} \right)}}{{\partial {x_i}}} = \frac{\partial }{{\partial {x_f}}}\left( {{T_\omega }\frac{{\partial \omega }}{{\partial {x_f}}}} \right) + {G_\omega } - {T_\omega } + {D_\omega }。$ (5)

2 网格及边界条件

3 结果与讨论 3.1 单体热射流水团浮升运动轨迹

 图 1 5 s时的速度矢量图 Fig. 1 Velocity vector diagram at 5 seconds

 图 2 前85 s的温度云图 Fig. 2 Temperature cloud image of the first 85 seconds

3.2 横向与纵向的浮升扩散对比

 图 3 4种工况D值变化曲线 Fig. 3 Variation curve of D value under four working conditions

3.3 浮升速度及温度变化规律

4种工况在前90 s内的的最大速度、最高温度及Y方向浮升距离变化如图4图6所示。

 图 4 最高温度变化曲线 Fig. 4 Maximum temperature curve

 图 5 最大速度变化曲线 Fig. 5 Maximum speed curve

 图 6 Y方向偏移变化曲线 Fig. 6 Y-direction offset curve

4 结　语

1）单体热射流水团在浮升过程中会产生旋转涡对，不同的是无初始动量的热水团产生一对对称的旋转涡对，而具有初始动量的热水团则产生一对不对称的旋转涡对，且旋转将会持续较长的时间。

2）具有水平初始动量的单体热射流水团因其产生的旋转涡对使其在X方向的扩散更强，但也因此，其各个时刻的最高温度始终略高于其他工况。

3）温差对静止状态下射流的浮升扩散有一定影响，适当降低温差能降低热射流的浮升速率，延迟热射流浮升到水面的时间，增强水下热射流与背景水域的掺混换热。

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