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 Ms. Hong Sun, Doctoral Graduate Student Mr. Yumin Deng, Graduate student

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD2 Topics ► MPUF/HULLFPP.vs. PROPCAV/HULLFPP ► Effective wake evaluation at blade control points ► Modeling of cavitating ducted propeller ► Blade design using optimization method

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD3 MPUF3A- and PROPCAV- /HULLFPP (Steady wetted case: H03861 Propeller) * 4 blades * 4 blades * User input thickness * User input thickness * User input camber * User input camber ► Propeller and hull geometries * uniform wake * Froude number Fr= * Froude number Fr= * Advance Ratio Js =0.976 * Advance Ratio Js =0.976 * IHUB = OFF * IHUB = OFF

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD4 ► From MPUF3A/HULLFPP ► From PROPCAV/HULLFPP MPUF3A- and PROPCAV- /HULLFPP (Pressure distribution on the hull)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD5 MPUF3A- and PROPCAV- /HULLFPP ► Circulations from MPUF3A and PROPCAV * Not considering induced velocity effect * Not considering induced velocity effect * Match the transition wake geometry from PROPCAV with that from MPUF3A * Match the transition wake geometry from PROPCAV with that from MPUF3A

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD6 MPUF3A- and PROPCAV- /HULLFPP ► Field Point Potential from MPUF3A and PROPCAV

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD7 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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD8 MPUF-3A/HULLFPP ► General wake geometry

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD9 * Cavitation number * Froude number Fr = * Advance Ratio Js =1.177 ► Hull geometry and run conditions * Uniform wake * IHUB =ON * TLC = ON MPUF-3A/HULLFPP (Steady cavitating case)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD10 MPUF-3A/HULLFPP (Pressure distribution on the hull) ► Improved Approximation ► Using decay function

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD11 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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD12 MPUF-3A/HULLFPP (Pressure distribution on the hull) ► Improved approximation ► Using decay function

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD13 NEW EFFECTIVE WAKE CALCULATION

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.

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

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.

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

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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD19 CAVITATING DUCTED PROPELLER

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

Modeling of ducted propeller ► NACA0015 Duct

Modeling of ducted propeller ► NACA0010 Duct Straight PanelPaneled with pitch angle (45 o )

Modeling of ducted propeller ► NACA0010 Duct

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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD25 BLADE DESIGN VIA OPTIMIZATION

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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD27 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 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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD28 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)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD29 ► 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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD30 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.

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD31 In current case, the problem reduces to: The function to be minimized is, while x is the vector (X1, X2, X3), and are Lagrange multipliers, and are penalty function coefficients. With: and are user defined. Augmented Lagrange function:

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

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD33 -- Database and Interpolation :

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD34

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD35 How good is the interpolation method?

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD36 -- Optimum solution and comparisons with CAVOPT-3D 3rd order functions are used to approximate both KT and KQ codeKT10KQEfficiency OPT CAVOPT-3D The solution of OPT are : X1 = X2 = X3 =

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD37 Propeller geometry comparison: OPT vs. CAVOPT-3D

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD38 Circulation comparison: OPT vs. CAVOPT-3D

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD39 Pressure distribution comparison: OPT vs. CAVOPT-3D

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD40 Blade geometry comparison: OPT vs. CAVOPT-3D

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD41 Sample 2: Cavitating run based on N4148 propeller and presribed skew distribution -- Design conditions: -- Range of variables:, to be minimized,, effective wake file 10x9 and 20x9 grid size

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD42 -- Wake file used:

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD43

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD44

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD45 -- Database and Interpolation :

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD46 -- 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 codeKT10KQCAEfficiency OPT (10x9) %86.6% CAVOPT-3D %83.4% The solution of OPT are : X1 = X2 = X3 = Initial guess: ( 0.8, 1.0, 1.0 ) Several initial guesses were tested, they led to the almost same optimization results.

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD47 Propeller geometry comparison: OPT (10x9) vs. CAVOPT-3D (10x9)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD48 Circulation comparison: OPT (10x9) vs. CAVOPT-3D (10x9)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD49 Blade geometry comparison: OPT (10x9) vs. CAVOPT-3D (10x9)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD50 Cavitations comparison: OPT (10x9) vs. CAVOPT-3D (10x9) %18.51 %

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD51 -- Optimization solution of OPT (20x9) 4th order functions are used for KT, KQ and CAMAX Initial guess: ( 0.8, 1.0, 1.0 ) codeGridKT10KQCAEfficiency OPT20x %85.8% CAVOPT-3D10x %83.4% The solution of OPT are :X1 = X2 = X3 = Several initial guesses were tested, they led to almost the same optimization results.

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD52 Propeller geometry of OPT (20x9):

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD53 Circulation of OPT

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD54 Blade geometry and cavity of OPT (20x9)

10/18/2004SNAME panel H-8 mtg. No. 124, NSWC-CD55 Conclusions and Future work (on optimization) ► The interpolation scheme can approximate the database very well using higher order functions. ► The optimization scheme works well for the fully wetted run. For cavitating runs, both CAVOPT-3D and OPT should be improved. ► Include more parameters in current optimization scheme. ► Improve the approximation of cavity area.