Numerical study on the transient behavior of water-entry supercavitating flow around a cylindrical projectile influenced by turbulent drag-reducing additives

Jiang, Chenxing; Shuai, Zhi-Jun; Zhang, Xiang-Yuan; Li, Wanyou; Li, Feng‐Chen

doi:10.1016/j.applthermaleng.2016.05.102

Cited by 25 publications

(5 citation statements)

References 16 publications

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“…14, the moment applied on the projectile produces the angular velocity of − 217 and − 28 rad/s at entry angles of 10° and 40°, respectively, and it can be deduced that the maximum absolute value of the projectile angular velocity ( |̇| max ) will be achieved after the projectile impacts with the water surface. Figures 17,18,19,20 show the projectile axial force, normal force, pitching moment and angular velocity at different entry angles. It is evident that as the entry angle decreases, the duration of the projectile's impact with the free surface increases and, therefore, the duration of the force and unstabilizing pitching moment applied to the projectile increases.…”

Section: The Sscc Projectile Dynamics At Two Entry Angles Of 10° and mentioning

confidence: 99%

“…However, main numerical studies on water entry concentrated on vertical entry. Jiang et al [18] simulated of the unsteady vertical water entry supercavitating projectile in viscous incompressible domain using ANSYS FLUENT CFD commercial code. It was obtained that the numerical simulation results are in good accuracy with experimental data and verifying the established numerical method procedures.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: The Sscc Projectile Dynamics At Two Entry Angles Of 10° and mentioning

confidence: 99%

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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“…In Li's study, he recorded the trajectories of bullets projected into cetyltrimethyl ammonium chloride aqueous solution of different mass fraction by using highspeed CCD camera, and finally observed the supercavities configuration around bullets. Jiang [28,29,34] also conducted experimental and numerical study on the effects of drag-reducing additives on supercavities. In his investigation, he used cross-viscosity model to calculate the dynamic viscosity of the drag-reducing solution and then simulated the supercavities' behavior.…”

Section: Insteadmentioning

confidence: 99%

Numerical investigation on the orifice cavitating water jet considering the fluid viscosity’s effects on bubbles’ growth and collapse

Deng

Guan

2017

J Braz. Soc. Mech. Sci. Eng.

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The initial radius of bubble t Time ρ m The density of mixture u m The velocity of mixture μ m The viscosity of mixture α The volume fraction of vapor phase ρ v The density of vapor phase u v The velocity of vapor phase R e Mass transfer source term connected to the growth of the vapor bubbles R c Mass transfer source term connected to the collapse of the vapor bubbles n Bubble number density F vap Evaporation coefficient F cond Condensation coefficient ℜ B Bubble radius 1 Introduction Cavitation is a common hydraulic phenomenon in nature, and the collapse of the bubbles will generate a significant force of impact. So, cavitating water jets are widely used in many engineering fields such as cleaning, cutting, mining and improving the fatigue strength of materials [1-5]. Many experiments and simulations have been conducted to investigate cavitating water jets [6-11]. Since the computational fluid dynamics (CFD) was put forward in 1950s, Abstract This paper attempts to investigate the effects of fluid viscosity on cavitation generation. Different from the traditional cavitation models in which the Rayleigh-Plesset equation is simplified neglecting the second-order term and the surface tension force term, the primitive R-P equations with different dynamic viscosity values are solved by mathematical software and numerical solutions are obtained. Then, the method of curve fitting is selected to get the approximate expressions of bubble radius about time. Based on the expressions, the rate of change of bubble radius about time under different viscous conditions can be approximately obtained which will be written as in-house code to enhance the traditional cavitation models by UDFs. Numerical simulations of high-speed water jets issuing from a nozzle are carried out. The simulated cavitation characteristics match the supercavity experiments very well. The result shows a more homogenous distribution of vapor volume fraction while the viscosity of fluid increases. The pressure and velocity also change more slowly and smoothly along the nozzle under more viscous conditions. Simulations of external flow fields are also made based on the modified model to show the cavitation characteristics under submerged condition.

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“…Truscott et al (2014) provided a review of the cavity formation, the depth and time of pinch-off, forces, and trajectories of the projectiles of different shapes and materials from the various experimental, theoretical, and numerical studies on low-speed water entry to high-speed ballistics. Jiang et al (2016) performed numerical simulations to study the transient behavior of waterentry supercavitating flow around a cylindrical projectile at different impact velocities in the presence of turbulent drag-reducing additives. They compared the cavity lengths, velocity attenuations, penetration distances, and drag coefficients for water and drag-reducing solution cases at high and low impact velocity cases.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of water entry of hydrophobic spheres

Singh,

Pal

2024

Fluid Dyn. Res.

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We perform numerical simulations to study the dynamics of the entry of hydrophobic spheres in a pool of water. To track the air-water interface during the translation of the sphere in the pool of water, we use the volume of fluid (VOF) model. The continuum surface force (CSF) method computes the surface tension force. To represent the hydrophobic surface properties, we use wall adhesion in terms of a static contact angle. We perform simulations with different diameters and impact speeds of the sphere. Our simulations capture the formation of different types of air cavities, pinch-offs of these cavities, and other finer details similar to the experiments performed at the same parameters. Finally, we compare the drag force among the different hydrophobic cases. We further perform simulations of hydrophilic spheres impacting the pool of water and compare the drag force with the analogous hydrophobic cases. We conclude that the spheres with hydrophobic surfaces encounter a lower drag than their hydrophilic counterparts. This lower drag of the hydrophobic spheres is attributed to the formation of the air cavity by the hydrophobic surfaces while translating through the pool of water, which reduces the area of the sphere in contact with water. In contrast, no such air cavity forms in the case of hydrophilic spheres.

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Numerical study on the transient behavior of water-entry supercavitating flow around a cylindrical projectile influenced by turbulent drag-reducing additives

Cited by 25 publications

References 16 publications

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

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

Numerical investigation on the orifice cavitating water jet considering the fluid viscosity’s effects on bubbles’ growth and collapse

Numerical investigation of water entry of hydrophobic spheres

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