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SNAME H-8 Panel Meeting No. 124 Oct. 18, 2004 NSWC-CD Research Update from UT Austin

SNAME H-8 Panel Meeting No. 124 Oct. 18, 2004 NSWC-CD Research Update from UT Austin. Ocean Engineering Group Department of Civil Engineering The University of Texas at Austin Prof. Spyros A. Kinnas Dr. Hanseong Lee, Research Associate Mr. Hua Gu, Doctoral Graduate Student

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SNAME H-8 Panel Meeting No. 124 Oct. 18, 2004 NSWC-CD Research Update from UT Austin

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  1. SNAME H-8 Panel Meeting No. 124Oct. 18, 2004 NSWC-CDResearch Update from UT Austin Ocean Engineering Group Department of Civil Engineering The University of Texas at Austin Prof. Spyros A. Kinnas Dr. Hanseong Lee, Research Associate Mr. Hua Gu, Doctoral Graduate Student Ms. Hong Sun, Doctoral Graduate Student Mr. Yumin Deng, Graduate student

  2. Topics • MPUF/HULLFPP .vs. PROPCAV/HULLFPP • Effective wake evaluation at blade control points • Modeling of cavitating ducted propeller • Blade design using optimization method SNAME panel H-8 mtg. No. 124, NSWC-CD

  3. MPUF3A- and PROPCAV- /HULLFPP(Steady wetted case: H03861 Propeller) • Propeller and hull geometries * 4 blades * User input thickness * User input camber * uniform wake * Froude number Fr=9999.0 * Advance Ratio Js =0.976 * IHUB = OFF SNAME panel H-8 mtg. No. 124, NSWC-CD

  4. From MPUF3A/HULLFPP From PROPCAV/HULLFPP MPUF3A- and PROPCAV- /HULLFPP(Pressure distribution on the hull) SNAME panel H-8 mtg. No. 124, NSWC-CD

  5. MPUF3A- and PROPCAV- /HULLFPP • Circulations from MPUF3A and PROPCAV * Not considering induced velocity effect * Match the transition wake geometry from PROPCAV with that from MPUF3A SNAME panel H-8 mtg. No. 124, NSWC-CD

  6. MPUF3A- and PROPCAV- /HULLFPP • Field Point Potential from MPUF3A and PROPCAV SNAME panel H-8 mtg. No. 124, NSWC-CD

  7. MPUF3A/HULLFPP(Effects of the ultimate wake singularities) • Previously, it was assumed that only the steady part of the circulation at the blade TE shed into the ultimate wake, and a decay function was applied to the transition wake • In the improved approximation the unsteady vorticity is shed into the ultimate wake • This improvement was verified by several cases using uniform inflow SNAME panel H-8 mtg. No. 124, NSWC-CD

  8. MPUF-3A/HULLFPP • General wake geometry SNAME panel H-8 mtg. No. 124, NSWC-CD

  9. MPUF-3A/HULLFPP(Steady cavitating case) • Hull geometry and run conditions * Uniform wake * IHUB =ON * TLC = ON * Cavitation number * Froude number Fr = 3.0789 * Advance Ratio Js =1.177 SNAME panel H-8 mtg. No. 124, NSWC-CD

  10. Improved Approximation Using decay function MPUF-3A/HULLFPP(Pressure distribution on the hull) SNAME panel H-8 mtg. No. 124, NSWC-CD

  11. MPUF-3A/HULLFPP (Unsteady cavitating case) • Cavitating run conditions * Effective wake * Cavitation number * Froude number Fr=4.0 * Advance Ratio Js =1.0 * IHUB = OFF * TLC = ON • Cavity patterns 20x18 SNAME panel H-8 mtg. No. 124, NSWC-CD

  12. Improved approximation Using decay function MPUF-3A/HULLFPP(Pressure distribution on the hull) SNAME panel H-8 mtg. No. 124, NSWC-CD

  13. NEW EFFECTIVE WAKE CALCULATION SNAME panel H-8 mtg. No. 124, NSWC-CD

  14. Effective wake evaluation at blade control points Previous method: evaluates effective wake at a plane ahead (by one cell) of the blade. New method: Evaluates the effective wake at the blade control points.

  15. Effective wake evaluation at blade control points Interpolation of total axial velocity on control points Interpolation of total tangential velocity on control points

  16. Effective wake evaluation at blade control points At the MPUF-3A control points, the induced velocity may be in error due to the local effect of blade singularities. The bad points need to be removed before the induced velocity is (time) averaged. The figure shows the induced velocity at a control point at chord index 9 and span index 8.

  17. Effective wake evaluation at blade control points At each control point, Ue = Ua -Uin is applied, the expected effective wake should be 1.00 at all points, there is still a maximum of 4% error in this case.

  18. Effective wake evaluation at blade control points The error brings lower circulation for this case, which still needsimprovement.

  19. CAVITATING DUCTED PROPELLER SNAME panel H-8 mtg. No. 124, NSWC-CD

  20. Modeling of cavitating ducted propeller(duct: panel method, propeller: PROPCAV) • NACA0015 Duct Straight Panel Paneled with pitch angle (45o)

  21. Modeling of ducted propeller • NACA0015 Duct

  22. Modeling of ducted propeller • NACA0010 Duct Straight Panel Paneled with pitch angle (45o)

  23. Modeling of ducted propeller • NACA0010 Duct

  24. Modeling of ducted propeller • NACA0015 Duct + N3745 Propeller * Uniform wake * Advance ratio Js =0.6 Circulation Distribution

  25. BLADE DESIGNVIA OPTIMIZATION SNAME panel H-8 mtg. No. 124, NSWC-CD

  26. CAVOPT-3D (CAVitating Propeller Blade OPTimization method)Mishima (PhD, MIT, ’96), Mishima & Kinnas (JSR ’97), Griffin & Kinnas (JFE’98)

  27. CAVOPT-3D • Allows for design of propeller in non-axisymmetric inflow and includes the effects of sheet cavitation DURING the design process • MPUF-3A is running inside the optimization scheme until all requirements and constraints are satisfied • Takes about 600-1000 MPUF-3A runs to produce the final design (3-6 hrs) • New versions of MPUF-3A (that include duct, pod, etc) can be incorporated • Not practical as a web based instructional tool SNAME panel H-8 mtg. No. 124, NSWC-CD

  28. New Optimization Method • Start with a base propeller geometry. • Given conditions are: Js, inflow (can be non-axisymmetric), cavitation number, Froude number, and thrust coefficient. • The optimum design is searched for within a family of propeller geometries such that: X1, X2, X3 are factors (constant initially, to be varied later) SNAME panel H-8 mtg. No. 124, NSWC-CD

  29. Hydrodynamic coefficients and cavity planform area are expressed in terms of polynomial functions of X1, X2 and X3. While: The function coefficients are determined by Least Square Method (LSM), using the predictions of a large array (e.g. 10x10x10) of MPUF-3A runs SNAME panel H-8 mtg. No. 124, NSWC-CD

  30. The Optimization Scheme (based on CAVOPT-2D, optimization method for cavitating 2-D hydrofoils) • The optimization problem of the propeller design is : Minimize : Subject to : Where is the objective function to be minimized. is the solution vector of n components. ( i=1…m ) are inequality constrains and ( i=1…l ) are equality constrains. The constrained optimization problem is changed to an unconstrained optimization problem by using Lagrange multipliers and penalty functions. For more information, please refer to the JSR paper by Mishima & Kinnas, 1996. SNAME panel H-8 mtg. No. 124, NSWC-CD

  31. In current case, the problem reduces to: Augmented Lagrange function: With: and are user defined. The function to be minimized is , while x is the vector (X1, X2, X3), and are Lagrange multipliers, and are penalty function coefficients. SNAME panel H-8 mtg. No. 124, NSWC-CD

  32. Sample 1: Fully wetted run based on N4148 propeller (with prescribed skew distribution) Optimization Samples: -- Design conditions: • , to be minimized • , , • uniform inflow • 20x9 grid size -- Range of variables:

  33. -- Database and Interpolation : SNAME panel H-8 mtg. No. 124, NSWC-CD

  34. SNAME panel H-8 mtg. No. 124, NSWC-CD

  35. How good is the interpolation method? SNAME panel H-8 mtg. No. 124, NSWC-CD

  36. -- Optimum solution and comparisons with CAVOPT-3D 3rd order functions are used to approximate both KT and KQ The solution of OPT are : X1 = 1.28865 X2 = 0.80000 X3 = 2.00000 SNAME panel H-8 mtg. No. 124, NSWC-CD

  37. Propeller geometry comparison: OPT vs. CAVOPT-3D SNAME panel H-8 mtg. No. 124, NSWC-CD

  38. Circulation comparison: OPT vs. CAVOPT-3D SNAME panel H-8 mtg. No. 124, NSWC-CD

  39. Pressure distribution comparison: OPT vs. CAVOPT-3D SNAME panel H-8 mtg. No. 124, NSWC-CD

  40. Blade geometry comparison: OPT vs. CAVOPT-3D SNAME panel H-8 mtg. No. 124, NSWC-CD

  41. Sample 2: Cavitating run based on N4148 propeller and presribed skew distribution -- Design conditions: • , to be minimized • , , • effective wake file • 10x9 and 20x9 grid size -- Range of variables: SNAME panel H-8 mtg. No. 124, NSWC-CD

  42. -- Wake file used: SNAME panel H-8 mtg. No. 124, NSWC-CD

  43. SNAME panel H-8 mtg. No. 124, NSWC-CD

  44. SNAME panel H-8 mtg. No. 124, NSWC-CD

  45. -- Database and Interpolation : SNAME panel H-8 mtg. No. 124, NSWC-CD

  46. -- Optimization solution from OPT (MPUF-3A: 10X9) and comparisons with CAVOPT-3D (MPUF-3A: 10X9) 4th order functions are used for KT, KQ and CAMAX Initial guess: ( 0.8, 1.0, 1.0 ) The solution of OPT are : X1 =1.43586 X2 =2.00000 X3 =1.89869 Several initial guesses were tested, they led to the almost same optimization results. SNAME panel H-8 mtg. No. 124, NSWC-CD

  47. Propeller geometry comparison: OPT (10x9) vs. CAVOPT-3D (10x9) SNAME panel H-8 mtg. No. 124, NSWC-CD

  48. Circulation comparison: OPT (10x9) vs. CAVOPT-3D (10x9) SNAME panel H-8 mtg. No. 124, NSWC-CD

  49. Blade geometry comparison: OPT (10x9) vs. CAVOPT-3D (10x9) SNAME panel H-8 mtg. No. 124, NSWC-CD

  50. Cavitations comparison: OPT (10x9) vs. CAVOPT-3D (10x9) 18.51 % 18.97 % SNAME panel H-8 mtg. No. 124, NSWC-CD

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