COMPARISON STUDY OF SUPERCAVITATION PHENOMENA ON

DIFFERENT PROJECTILES SHAPES IN TRANSIENT FLOW BY CFD

Prof. Magdy Abu Rayan

Mechanical Power Department, Mansoura

University, Egypt

Prof. Nabil H. Mostafa

Mechanical Power Department, University,

Zagazig, Egypt

Dr. Mohamed H. Mansour

Mechanical Power Department, Mansoura

University, Egypt

Eng. Mohsen Y. Mansour

Aeronautical Eng., Mansoura University,

Egypt

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CAVITATION

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• Cavitation is the occurrence

of vapor in a fluid due to

local low pressures which

are generated by high local

flow velocities. (Hammit,

1970)

SUPERAVITATION DEFINITION

Supercavitation is the use of cavitation effects to create a bubble of gas inside a liquid large enough to encompass an object travelling through the liquid. (Mostafa, 2000)

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Supercavitation Formation 1. First, a cavity starts to grow at

the wake of the body.

2. Secondly, another cavity grows beside the nose while the cavity at the body wake continues to grow.

3. The nose cavity grows enough and the cavity at body wake starts to collapse.

4. the cavity beside the nose grows enough to merge with the cavity at the body wake forming a large one.

5. Finally, that cavity starts to fluctuate around the final. (Mostafa, 2000)

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CAVITATION NUMBER

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σ = (pr - pv) / (1/2 ρ v2)

where

σ= Cavitation number

pr = reference pressure (Pa)

pv = vapor pressure of the fluid (Pa)

ρ = density of the fluid (kg/m3)

v = velocity of fluid (m/s)

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Grids over the four projectiles

1- Hemispherical

2- Telescopic

3- Blunt

4- Conical

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FLOW SIMULATION UPON PROJECTILES

1-a- Hemispherical Using Structured Grid

Supercavitating cavities formation upon hemisphrical

projectile at speed 60 m/s, using structured mesh

domain, at t=1400x10-5 sec.

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FLOW SIMULATION UPON PROJECTILES

1-b- Hemispherical, Unstructured

Supercavitating cavities formation upon hemisphrical

projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

2-b- Telescopic, Structured

Supercavitating cavities formation upon telescopic

projectile at speed 60 m/s, using structured mesh

domain.

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FLOW SIMULATION UPON PROJECTILES

2-b- Telescopic, Unstructured

Supercavitating cavities formation upon telescopic projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION FOR BLUNT PROJECTILE

3-a- Blunt, Structured

Supercavitating cavities formation upon blunt projectile at speed 60 m/s, using structured mesh domain.

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FLOW SIMULATION FOR BLUNT PROJECTILE

3-b- Blunt, Unstructured

Supercavitating cavities formation upon blunt projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

4-a- Conical, Structured

Supercavitating cavities formation upon blunt projectile

at speed 60 m/s, using structured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

4-b- Conical, Unstructured

Supercavitating cavities formation upon conical projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

1-a- Hemispherical Using Structured Grid

Supercavitating cavities formation upon hemisphrical projectile at speed 60 m/s, using structured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

1-b- Hemispherical, Unstructured

Supercavitating cavities formation upon hemisphrical

projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

2-b- Telescopic, Structured

Supercavitating cavities formation upon telescopic projectile at speed 60 m/s, using structured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

2-b- Telescopic, Unstructured

Supercavitating cavities formation upon telescopic projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION FOR BLUNT PROJECTILE

3-a- Blunt, Structured

Supercavitating cavities formation upon blunt projectile at speed 60 m/s, using structured mesh domain.

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FLOW SIMULATION FOR BLUNT PROJECTILE

3-b- Blunt, Unstructured

Supercavitating cavities formation upon blunt projectile at speed 60 m/s, using unstructured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

4-a- Conical, Structured

Supercavitating cavities formation upon blunt projectile

at speed 60 m/s, using structured mesh domain.

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FLOW SIMULATION UPON PROJECTILES

4-b- Conical, Unstructured

Supercavitating cavities formation upon conical projectile at speed 60 m/s, using unstructured mesh domain.

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