Numerical Investigations on the Water Entry of Cylindrical Projectiles with Different Initial Conditions

Gao, Jian; Chen, Zhihua; Wu, Wei‐Tao; Li, Xin

doi:10.3390/app9091858

Cited by 6 publications

(3 citation statements)

References 18 publications

(26 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hou constructed the 6DOF numerical model by using the volume of fluid (VOF) method, the large eddy simulation (LES) approach and the Eulerian multiphase model to simulate water entry physics. Gao et al (2019) investigated the dynamics of high-speed oblique water entry of different cylindrical projectiles with different initial conditions. They showed that at shallow entry angles, the projectile hits the cavity wall and makes the cavity wall less smooth and with the increase of the entry angle, it becomes possible to provide stability for the projectiles inside the cavity.…”

Section: Introductionmentioning

confidence: 99%

Stability of Oblique Water Entry of Cylindrical Projectiles

2021

JAFM

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Stability of Oblique Water Entry of Cylindrical Projectiles

2021

JAFM

View full text Add to dashboard Cite

show abstract

“…Chen applied the commercial code ANSYS Fluent to simulate the highspeed oblique water entry physics. Gao et al [22] examined the dynamics of high-speed oblique water entry of different cylindrical projectiles with different initial conditions. They have shown that, at shallow entry angles, the projectile hits the cavity wall and makes the cavity wall less smooth, and as the entry angle increases, it becomes possible for the projectile to have stability inside the cavity.…”

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.

View full text Add to dashboard Cite

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.

show abstract

“…In terms of military strikes and defense engineering, structure of walls should be thick in order to reduce the local damage effect [1][2][3][4][5][6] caused by projectile impacts, especially for structures requiring high-defense protection such as important fortifications and secret weapon storage sites; moreover, the employ space of such structures should be increased as well. A solution to this problem is using composite concrete walls [7][8][9] with a steel liner.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Numerical Investigation on Perforation Resistance of Monolithic and Segmented Concrete Targets with Steel Liners under Normal Penetration

Cheng

Xiao

Zhang

2019

Advances in Civil Engineering

View full text Add to dashboard Cite

Steel-concrete composites are important armor protective materials with the increasing power of precision-guided weapons. In this study, the formula of residual velocity as well as the ratio between residual and initial kinetic energy (Er/E0) for concrete targets with a rear steel liner was derived. By establishing finite element models of steel liner concrete targets through ANSYS/LS-DYNA, the effect of the steel liner layout on the perforation resistance was analyzed for both monolithic and segmented concrete targets, which were compared in terms of projectile kinematics characteristics, projectile energy consumption, and target damages. Four main conclusions were drawn: (1) a residual velocity prediction model of concrete targets with a rear steel liner was accurately proposed for the first time when velocity reduction coefficient η was 0.15 and the derived Er/E0 could be used to evaluate their corresponding perforation resistance; (2) moving back the steel liners enhanced the perforation resistance of both monolithic and segmented targets, but the performance of the latter was inferior to that of the former, which was reduced by 10%–16% under the same conditions; (3) during middle- and low-speed perforations, the projectile impact force was more influenced by the contact stiffness than the impact velocity; and (4) regarding the segmented targets, the perforation resistance of the 2nd target was better than the 1st target, which consumed about 10%–20% more projectile kinetic energy.

show abstract

Numerical Investigations on the Water Entry of Cylindrical Projectiles with Different Initial Conditions

Cited by 6 publications

References 18 publications

Stability of Oblique Water Entry of Cylindrical Projectiles

Stability of Oblique Water Entry of Cylindrical Projectiles

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

Theoretical and Numerical Investigation on Perforation Resistance of Monolithic and Segmented Concrete Targets with Steel Liners under Normal Penetration

Contact Info

Product

Resources

About