Cavitation Evolution around a NACA0015 Hydrofoil with Different Cavitation Models Based on Level Set Method

Yu, An; Tang, Qinghong; Zhou, Daqing

doi:10.3390/app9040758

Cited by 16 publications

(12 citation statements)

References 16 publications

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“…Therefore, this cavitation model can be used for mass transfer simulation between the liquid and vapor phases. Within the cavitation process, the equation for the vapor volume fraction has the following form (Zwart et al (2004), Yu et al (2019)):…”

Section: Governing Equations Of Fluid Flowmentioning

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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Section: Governing Equations Of Fluid Flowmentioning

confidence: 99%

Stability of Oblique Water Entry of Cylindrical Projectiles

2021

JAFM

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“…As a result, this cavitation model can be used for mass transfer simulation between liquid and vapor phases. For the cavitation process, the vapor volume fraction's equation is as follows [29,30]:…”

Section: Governing Equations Of Fluid Flowmentioning

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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“…Transport equation for vapor volume fraction was used to simulate vapor generation and condensation rate in the cavitating flow, expressed as follows [16][17][18]:…”

Section: Governing Equationsmentioning

confidence: 99%

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

Gao

Chen

et al. 2019

Applied Sciences

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In this paper, coupled with Reynolds-averaged Navier–Stokes equations and ballistic equations, the numerical simulations of high-speed water entry of projectiles under different conditions have been conducted. The water-gas flow was modeled by the mixture multiphase model. The numerical results indicated that the simulations agree well with analytical solutions by two cavity models, which validates the model applied. Then the effects of variations of project length, entry angle and velocity on the entry process of projectiles were further investigated. The results show that, for small water entry angles, the cavity wall interacts with the projectile, affects the trajectory of the projectile, and even ricochets for projectiles with small length (5D). On the other hand, the projectile vibrates during the whole process of water entry; the vibration amplitude decreases with the increase of projectile length and entry angle; however, it is the contrary for the vibration period. Furthermore, after the initial impact period, the influence of these parameters on the drag coefficient is not obvious.

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Cavitation Evolution around a NACA0015 Hydrofoil with Different Cavitation Models Based on Level Set Method

Cited by 16 publications

References 16 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

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

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