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Variable Shape Cavitator Design for a Supercavitating Torpedo

Variable Shape Cavitator Design for a Supercavitating Torpedo. E. Alyanak, R. Grandhi, R. Penmetsa, V. Venkayya Wright State University. 10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference. ONR Grant N00014-03-1-0057 Dr. Kam Ng, Program Manager. Outline.

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Variable Shape Cavitator Design for a Supercavitating Torpedo

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  1. Variable Shape Cavitator Design for a Supercavitating Torpedo E. Alyanak, R. Grandhi, R. Penmetsa, V. Venkayya Wright State University 10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference ONR Grant N00014-03-1-0057 Dr. Kam Ng, Program Manager

  2. Outline • Supercavitating torpedo and cavitator introduction • Technique utilized for supercavity fluid modeling • Cavitator Shape definition • Optimization problem formulation • Constraint discussion • Modeling acceleration • Results of the optimization problem • Suggestions for a variable shape cavitator

  3. What is a Supercavitating Torpedoand a Cavitator? * Figures are artist’s impression Figure From a Water Tunnel Test at Penn State Cavity Water Vapor “Bubble” formation behind the cavitator Cavitator Initiates Cavity Formation

  4. Outside boundaries Given a Cavitator Shape, the Cavity is defined by meeting two conditions on the cavity boundary: r Cavity boundary element Cavitator boundary element Cavity Radius = 0.5 x Cavitator Reentrant jet y Multiple cavity boundary shapes Cavitator shape Cavity boundary x V∞ Boundary conditions 1 and 2 Two-Phase Flow Analysis Cavitation Number: Developed by: Dr. Uhlman

  5. y y Design variable points fixed point Spline through design points 0.5 x Cosine spaced points X1 X2 x Resulting x coordinates Cavitator Definition Two Design Variables define the Shape with a spline constructed through them After the spline is created through the design variables, any number of points can be created to define the cavitator shape

  6. P = 1 Flat Disk Decreasing P Extended Curve Cavitator Shape Optimization Formulation • Min{CD = f(Shape Variables)} • Subject to Formulation Constraint Behavior Cd where Cavity Number

  7. Cavity Growth and Torpedo Acceleration • = 0.6 x 10-6 (m2/s) U = Velocity (m/s) D = Cavitator Diameter

  8. Cavity Growth Vs Torpedo Acceleration Cavitator Shape Results P = 0.75 thus: All Cavitator Shapes behave as a flat disk w.r.t. cavity length and percent increase/decrease in cavitation number

  9. Relaxation of sconstraint Optimization results for increasing velocity and cavity length Cavitator shapes Increase in cavity length and velocity Non-Dimensional Length Non-Dimensional Length

  10. Suggested Shape Change Cavitator profile for given cavity length to

  11. Conclusion • Modeled supercavitating flow • Defined shape optimization problem to determine cavitator shape • Solved optimization problem through the entire range of torpedo speeds • Presented possible variable shape cavitator

  12. Thank You E. Alyanak, R. Grandhi, R. Penmetsa, V. Venkayya Wright State University ealyanak@cs.wright.edu 10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference ONR Grant N00014-03-1-0057 Dr. Kam Ng, Program Manager

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