Experimental investigation on trajectory stability of high-speed water entry projectiles

Chen, Tuo; Huang, Wei; Zhang, Wei; Qi, Yafei; Guo, Zitao

doi:10.1016/j.oceaneng.2019.02.021

Cited by 93 publications

(15 citation statements)

References 15 publications

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“…Akbari et al [9] studied the hydrodynamic characteristics of supercavitating projectiles launched obliquely into water, and found that the supercavitating projectiles were subjected to a significant normal impact force which was closely related to the wet area. The experimental results of Chen et al [10] showed that supercavitating projectiles could fly stably in a tail-slap mode, indicating that an approximately periodic hydrodynamic force acts on the supercavitating projectile during the underwater motion process. The alternating load can result in a high-frequency structural vibration, and even a sympathetic vibration, which exerts significant influence on the flow field in high-speed conditions.…”

Section: Introductionmentioning

confidence: 99%

Motion Characteristics of High-Speed Supercavitating Projectiles Including Structural Deformation

Huang

Liu

et al. 2022

Energies

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High-speed supercavitating projectiles receive tremendous hydrodynamic force when flying underwater in tail-slap mode, and have obvious structural deformation and structural vibration. To study the motion characteristics of high-speed supercavitating projectiles, a bidirectional fluid-structure interaction model was established, and validated by comparing with the existing results. The motion, supercavitation flow field, and structural deformation response process of a supercavitating projectile were numerically investigated under the conditions of initial speed within 800–1600 m/s. It was found that the tail-slap motion of high-speed supercavitating projectiles is correlated with a high-frequency structural vibration. Further, the amplitude of the structural vibration increases with the initial speed. When flying with an initial speed higher than 1200 m/s, supercavitating projectiles encounter a great structural deformation under the action of the huge hydrodynamic load, which exerts a significant influence on the motion characteristic, and even destroys the trajectory stability. Thus, the supercavitating projectile cannot be regarded as a rigid body any more, and the structural response effect must be considered.

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Section: Introductionmentioning

confidence: 99%

Motion Characteristics of High-Speed Supercavitating Projectiles Including Structural Deformation

Huang

Liu

et al. 2022

Energies

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“…They have also shown that oblique water entry of projectiles with small L/D will end up in a ricochet. Chen et al (2019b)) studied the influences of entry angle, entry speed and cavitator area on the axial force of three types of vehicles with a disk cavitator experimentally and numerically. Their article investigated the axial force which is exerted on the projectile at entry process and attempted to figure out a relationship between the peak axial force and other entry parameters.…”

Section: Introductionmentioning

confidence: 99%

Stability of Oblique Water Entry of Cylindrical Projectiles

2021

JAFM

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Water entry is an interesting subject but many of its physical aspects have remained unknown so far. Using computational fluid dynamics (CFD), this study investigates the dynamic stability of cylindrical projectiles in the oblique water entry at shallow angles in the presence of three phases of air, water and water vapor. The three-dimensional and transient numerical model has been verified using the former experimental results in the literature. In this study, the effects of projectile length-to-diameter ratio (L/D) and water entry angle on the projectile stability within cavity were investigated. Accordingly, the water entry of six projectiles was simulated with aspect ratios of 2 to 6 at three water entry angles of 6, 9 and 12 degrees with respect to the free surface with an initial velocity of 280 m/s. At each of the aforementioned angles, the critical L/D, where the projectile avoids tumbling inside the cavity at a larger value, was determined. This study showed that in the oblique water entry of a cylindrical projectile at the angles of 6, 9 and 12 degrees, the projectile tumbled within the cavity with a L/D of less than 5, 4 and 3.5, respectively. The simulation results showed that increasing the L/D as well as the water entry angle relative to the free surface resulted in the improvement of the cylindrical projectile motion stability, which is in agreement with the experimental results. By analyzing the details of each simulation, it was found that the projectile stability within the cavity is correlated with the magnitude of the angular momentum which is generated in the projectile by the impact of the cavitator on the free surface and it was shown that the projectile with a specific L/D can withstand destabilizing angular momentum to a certain extent. Considering the fact that the atmospheric ballistics of gyroscopically stabilized projectiles lead to a limit for increasing L/D, this study showed that, for aluminum cylindrical projectiles in which air stability is achieved via the gyroscopic effect, the minimum water entry angle is 6° to attain the gyroscopic stability of the projectile in the air and stable motion inside the cavity. This fact is very important from a practical point of view.

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“…Chen et al [17] experimentally investigated the effect of cavitator shape and entry angle on projectile's trajectory stability of a slender projectile. They concluded that, in contrast with the ogival projectile, flat nose projectile exhibits a perfect trajectory stability.…”

Section: Introductionmentioning

confidence: 99%

“…Numerical studies can rarely be quantitatively validated against experiment. Chen et al [17] considered the oblique water entry impact of three different cylindrical geometry vehicles with the same length but different cavitator diameters experimentally and numerically. Chen applied the commercial code ANSYS Fluent to simulate the highspeed oblique water entry physics.…”

Section: Introductionmentioning

confidence: 99%

A dynamic study of the high-speed oblique water entry of a stepped cylindrical-cone projectile

Akbari

Mohammadi

Fereidooni

2020

J Braz. Soc. Mech. Sci. Eng.

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High-speed oblique water entry is an interesting subject, many physical aspects of which remain unknown up to now. Among high-speed air-to-water projectiles, the supercavitating cylindrical-cone (SCC) ones have economic and operational advantages over the other types. However, maintaining stability of the SCC projectiles inside the cavity at shallow entry angles is a challenging issue from both practical and design-related points. The first section of the present study proposes a novel and unique scheme of air-to-water supercavitating projectile design which is called the supercavitating stepped cylindrical-cone (SSCC) projectile. The SSCC scheme is analyzed numerically to investigate the projectile stability improvement at shallow entry angles. The 6DOF dynamics of the SSCC projectile are investigated using the Star-CCM+ commercial code in the presence of three phases of air, water and vapor in a three-dimensional and transient model. Accuracy of numerical results and the model's ability to simulate the physical phenomena of water entry is validated using experimental results from the literature, and both are in good agreement. In the present study, the high-speed oblique water entry dynamics of the SSCC projectile are investigated for five certain entry angles varying from 10° to 60°. The results show that the SSCC projectile faces intensive unstabilizing forces in the water entry process which leads to a heavy pitching moment and, hence, intensive angular velocity (̇) on the projectile. This study also proves that the presence of step enhances the projectile stability in the entry process. The present study shows that, based on their geometry and mass characteristics, each SSCC projectile is capable of withstanding instability up to a critical value of the angular velocity (̇C r). Therefore, projectile stability inside the cavity can be achieved when the value of maximum angular velocity (|̇| max) experienced by the projectile is lower that ̇C r (i.e., |̇| max <̇C r). The results of this study also show that |̇| max is inversely correlated with the , and that it follows a simple equation which is proposed in this study. Therefore, projectile stability inside the cavity can also be practically achieved by adjusting the shooting mechanism at an angle higher than the minimum stable entry angle (min). This study also proposes an effective numerical approach to evaluate min of a supercavitating projectile. It should be noted that determining the value of min is an important factor from both a practical and design-related points of view.

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Experimental investigation on trajectory stability of high-speed water entry projectiles

Cited by 93 publications

References 15 publications

Motion Characteristics of High-Speed Supercavitating Projectiles Including Structural Deformation

Motion Characteristics of High-Speed Supercavitating Projectiles Including Structural Deformation

Stability of Oblique Water Entry of Cylindrical Projectiles

A dynamic study of the high-speed oblique water entry of a stepped cylindrical-cone projectile

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