WANG Yan, ZHOU Chun-gui, WANG Zhi-jun

(College of Mechatronic Engineering, North University of China, Taiyuan 030051, China)

王 妍, 周春桂, 王志軍

(中北大學(xué) 機(jī)電工程學(xué)院, 山西 太原 030051)

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Numerical simulation of subsonic and transonic flow flieds and aerodynamic characteristics of anti-tank intelligent mine

WANG Yan, ZHOU Chun-gui, WANG Zhi-jun

(CollegeofMechatronicEngineering,NorthUniversityofChina,Taiyuan030051,China)

Anti-tank intelligent mine is a kind of new intelligent anti-tank bomb relying on high precision detector. It can effectively capture and damage targets with wind resistance coefficient and other factors affecting its flight characteristics under consideration. This article is based on the three-dimensional model of intelligent mine. To analyze its subsonic and transonic flow fields and the change law of aerodynamic force factor with the growth of the angle of attack, computational fluid dynamics software is used for intelligent mine flow field numerical calculation and the change law of pressure center. The results show that the large drag coefficient is conducive to the stability of scanning. Drastic changes of the flow field near the intelligent mine will disable its scanning movement. The simulation results can provide a reference for scanning stability analysis, overall performance optimization and appearance improvement.

anti-tank intelligent mine; flow flied; aerodynamic characteristics; numerical simulation

Anti-tank intelligent mine is a kind of new smart ammunition. After the intelligent mine is laid into battle area, when the scanning device on the mine body detects tanks marching in recognition zone, transmitting device will shoot out intelligent mines aiming at the weakest part of the target.

Intelligent mine usually has two components: mine body and scanner, during the aerodynamic characteristics study[1]. The latter is fixedly connected with the body. Shaped charge liner and initiating explosive device are in the head of intelligent mine. The body is simplified as a cylindrical and scanner is simplified as a cube.

Anti-tank intelligent mine technology development is the common effort of scholars at home and abroad. Western countries have adopted high technologies to upgrademine it for larger fight radius, farther distance and better effect. YIN Jian-ping, et al. analyzed vulnerability of tank from the perspective of kill efficiency of intelligent mine[2-5]. ZHANG Yong-sheng, et al. determined the optimum operational time and place according to target speed and target distance with the intelligent mine[6-8]. CHANG Bian-hong, et al. changed initial conditions, mine body mass and shell parameters by means of simulation software to discuss their influence on intelligent mine flight process[9-10]. LIU Ji-dong, et al. evaluated combat effectiveness of intelligent mines exchanging information with other systems[11]. YIN Jian-ping has found that multiple explosively formed penetrator (MEFP) warhead technology used in intelligent mine can improve the effect of battle on cluster tanks and armored vehicles[12].

But there is few research about anti-tank intelligent mine aerodynamic parameters and flow field analysis. Considering that the kill radius of 100-200 m and scanning speed of 20-100 m/s may not meet mobility requirements of future standardized battle, flight velocity, sweeping speed and flight stability larger improvement. Therefore, three-dimensional model based on typical anti-tank intelligent mine is used to obtain flow field and aerodynamic characteristics at different angles of attack, and then what angle of attack can influence stability of intelligent mine in flight is discussed. Speed range is Mach number of 0.13-1.0.

1 Calculation model

1.1 Geometric model

Intelligent mine while flying head down generally has small slenderness ratio. The head is flat or blunt. Mine body is a cylinder. This study uses short cylinder (slenderness ratio of 0.8) as geometric model of the body, regardiess of the internal components such as shaped charge liner, fuse, etc. The shape of the intelligent mine is presented in Fig.1.

Fig.1 Shape of intelligent mine

The length(x) of the cube computational domain is 25 times as long as the intelligent mine diameter, the width(y) is 20 times as long as the length of the intelligent mine and the height(z) is 20 times as long as the diameter. Then the computational domain is divided into two layers. The model is located at the center of the inner computational domain. Unstructured grids of 780 000 are used. Mine body surface grid is shown in Fig.2.

Fig.2 Local grid of mine body

The grid quality report is showed in Fig.3.

Fig.3 Grid quality report

1.2 Calculation model

The simulation assumes that the intelligent mine flies without rotational speed. We chose density based explicit solver as basic solver. Boundary of half model calculation domain adopts pressure far field. If aerodynamic coefficients converge to a stable state, the results converge without setting residual convergence criteria for each equation. Since this case mainly discusses the flow field around mine from subsonic to transonic, Spalart-Allmaras (S-A) single equation model which is an equation about eddy viscosity variable is selected as the turbulence model[13]. S-A equation is

(1)

(2)

(3)

(4)

(5)

g=r+Cw2(γ6-γ),

Thevaluesofconstantsintheformulaeare

2 Flow field and aerodynamic performance of intelligent mine

2.1 Aerodynamic characteristics of intelligent mine

This study calculates the flow field and aerodynamic characteristics with Mach number of 0.13-1.0; The range of angles of attack is from -15° to 15°.

Aerodynamic coefficient curve is depicted in Fig.4. When the airflow velocity is a constant value, drag coefficient changes in shape of a parabola. Since the greater the absolute value of angle of attack is, the greater windward areas of the body and scanner are, drag coefficient increases with the increase of absolute value of angle of attack. After intelligent mine is launched to the air, if the speed is not reduced quickly, it will soon fall to the ground and be broken. Therefore, the larger drag coefficient is indispensable for stable flight of intelligent mine. Simulation results show that drag coefficient will be over 0.6 if Mach number is greater than 0.6, which results in very good movement slowing effect.

Fig.4 Computational aerodynamic force coefficients

Fig.4(b) is lift coefficient changing with the angle of attack. Lift coefficient increases faster within a small angle of attack, and then growth is relatively stable. Lift is small on the whole.

Pitching moment coefficients in Fig.4(c) demonstrat that the range of values forMzis very small and pitching moments of different Mach number have little change.

The fact that the pressure center coefficient decreases with the increase of Mach number indicates that the stability of the intelligent mine gradually reduces.

Fig.5 Pressure coefficients varied with attack angle

2.2 Flow field analysis

Isopiestic line of flow field in the plane of the angle of attack withv=1 Ma andα∈[-15°,15°] is illustrated in Fig.6. Atα= 0°, when the wind blows from the left side of the intelligent mine, a high pressure area is formed from the windward side. After the stream flows around the intelligent mine, a low pressure area is formed in the mine head, the tail and the right respectively for flow expansion. With the increase of attack angle, the windward side high pressure zone moves towards the head, mine-tail low pressure zone expands the scope and integrates with the leeward-side low pressure zone on the right side at the same time. The head low pressure zone disappears. This phenomenon can make intelligent-mine raise head. With the attack angle decreasing, the windward side high pressure area on the left moved to the mine tail and the tail low pressure area disappeared, making the mine bow its head. Furthermore, low pressure area of the head gradually expands and integrats with low pressure area of the right leeward side. External flow field of the body changes greatly, as is demonstrated by the results in Fig.6. The change of the surrounding pressure will undermine flight stability of the intelligent mine, especially when its speed increases.

Fig.6 Pressure contours at different angles of attack at v=1 Ma

Figs.7(a)-(c) are velocity contours of the attack angle plane with streamline. Air flow stagnation point is located on the left side of the body. Then air flows along the axis of the body, bypassing the head and the tail. Vortex is formed in the head and the tail at attack angle of 0°. A small vortex appears when the airflow just bypasses the head at attack angle of 15°, while it appears when the airflow just bypasses the tail at attack angle of -15°.

Fig.7 Velocity contour of attack angle plane with streamline

Airflows converes on the right and form trailing vortex whose rough position is behind of the scanner and right near the head of the mine. So the existence of the scanner damages vortexes of the mine. In the intelligent mine velocity field, the maximum speed occurrs when air just flows around the body, while the minimum speed occurrs after air flows around the body. With the positive and negative angles of attack, the flow velocity is 1.5 times greater than the speed of sound, forming the shock wave in the head and the tail[14].

Fig.8 shows that flow separation occurs as air flows around two-thirds of the mine body contour, a series of vortexes forming in the leeward side.

Fig.8 Three-dimensional flow chart of smart ray

3 Conclusion

This paper discusses the influenceof the change of attack angle on the aerodynamic characteristics of the anti-tank intelligent mine. Numerical calculation results can reflect the aerodynamic characteristics of the intelligent mine to some extent and provide basis and reference for further improvement and optimization of intelligent mine steady-state scanning platform. There is a need for a systematic wind tunnel experiment, combining with numerical simulation method to study the aerodynamic characteristics of the anti-tank intelligent mine.

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反坦克智能雷亞、跨音速氣動(dòng)特性數(shù)值仿真

反坦克智能雷是一種依托高精度探測(cè)器件的新型智能反坦克炸彈。 智能雷實(shí)現(xiàn)高效捕獲、 毀傷目標(biāo)時(shí)， 應(yīng)考慮風(fēng)阻系數(shù)等因素其飛行特性的影響。 本文基于智能雷的三維模型, 分析了亞、 跨音速智能雷流場(chǎng)以及氣動(dòng)力因數(shù)隨迎角的增長(zhǎng)規(guī)律。 應(yīng)用計(jì)算流體力學(xué)軟件對(duì)智能雷外流場(chǎng)進(jìn)行數(shù)值計(jì)算, 得到智能雷壓心位置的變化規(guī)律。 結(jié)果顯示阻力系數(shù)的值比較大, 有利于智能雷維持穩(wěn)定掃描狀態(tài)。 智能雷附近劇烈的流場(chǎng)變化可能導(dǎo)致其掃描運(yùn)動(dòng)失效。 仿真結(jié)果能夠作為智能雷掃描穩(wěn)定性分析、 總體性能優(yōu)化和外形改良的參照。

反坦克智能雷； 流場(chǎng)； 氣動(dòng)特性； 數(shù)值仿真

WANG Yan, ZHOU Chun-gui, WANG Zhi-jun. Numerical simulation of subsonic and transonic flow flieds and aerodynamic characteristics of anti-tank intelligent mine. Journal of Measurement Science and Instrumentation, 2015, 6(3)： 264-269. [

王 妍, 周春桂, 王志軍

(中北大學(xué) 機(jī)電工程學(xué)院, 山西 太原 030051)

10.3969/j.issn.1674-8042.2015.03.011]

Received date： 2015-05-03 Foundation items： National Natural Science Foundation of China (No.1157229)；Graduate Student Education Innovation Project of Shanxi Province (No.2015SY58)

WANG Yan (495082493@qq.com)

1674-8042(2015)03-0264-06 doi： 10.3969/j.issn.1674-8042.2015.03.011

CLD number： TJ51+2.1 Document code： A