Smart Rivers 2011 PIANC New Orleans, LA USA THE APPLICATION OF COMPUTATIONAL FLUID DYNAMICS (CFD) TO RIVER TOWBOAT DESIGN

Smart Rivers 2011 PIANC New Orleans, LA USA THE APPLICATION OF COMPUTATIONAL FLUID DYNAMICS (CFD) TO RIVER TOWBOAT DESIGN

Authors: Brant R. Savander, Ph.D., P.E. Principal Research Scientist Maritime Research Associates, LLC Ann Arbor, MI USA Gregory Lee Naval Architect Marine Design Center US Army Corps of Engineers Philadelphia, PA USA

Acknowledgements: Sergio Fifi Naval Architect Jensen Maritime Consultants, Inc. Johan Sperling Naval Architect Jensen Maritime Consultants, Inc.

The Application of CFD to River Towboat Design OVERVIEW

USACE Towboat Example: EVANICK

Towboat Design Attributes & Challenges 1. Hull form incorporates propeller tunnels. 2. Steering and flanking rudders ahead and aft of propeller. 3. Thrust and steering equally important in ahead and astern operation. 4. Propeller diameter limited and heavily loaded. 5. Large Variation in barge tow size gives large range of propeller operating points.

USACE: 114-ft, 1500-hp per shaft Steering & Flanking Rudders Strut Propeller Diameter & Tip Clearance Wake Adapted Blade Shape Wake Aligned Appendages Comparison to Z-Drives

The Application of CFD to River Towboat Design USACE 114-FT TOWBOAT APPLICATION

Design & Analysis Objectives: 1. Wake alignment of struts and rudders. 2. Wake adapted propeller design. 3. Propeller diameter trade-off analysis: efficiency vs. pressure pulse levels. 4. Match propeller and hull to a wide operating speed range rated engine. 5. Evaluate maximum forces on steering and flanking rudders at hard over angles.

Outboard Profile LOA: 114-0 BOA: 35-0 Depth: 10-3 (molded) Max. Air Draft: 60-6

General Arrangement

The Application of CFD to River Towboat Design NUMERICAL TOWING TANK FULL SCALE

Computational Geometry

Computational Domain: Full Scale Tank Pressure Outlet Lateral Symmetry Bottom Boundary Velocity Inlet

Computational Domain: Full Scale Tank Free Surface Velocity Inlet Lateral Symmetry Bottom Boundary

Rudder and Propeller Mesh

Rudder and Propeller Mesh

Results: Full Resolution of Pressure Field

Results: Full Resolution of Velocity Field -7.2 o -5.9 o 2.3 o -3.3 o

Stock Appendages: Axial Velocity

Wake Adapted App.: Axial Velocity

The Application of CFD to River Towboat Design USACE TOWBOAT PROPELLER

Propeller Drawing

Propeller Distributions

The Application of CFD to River Towboat Design RUDDER ANGLE VARIATION

Example: Steering Rudders 20 deg.

Free Surface: Steering 20-deg

Streamlines: Steering 20-deg

Steering Angle Force Summary

Flanking Rudder Angle Force Summary

The Application of CFD to River Towboat Design RESULTS & CONCLUSIONS

Results: Struts & Rudders 1. Inboard Flanking Rudder: LE outboard 3.3 deg. 2. Outboard Flanking Rudder: LE outboard 7.2 deg. 3. Inboard Steering Rudder: LE inboard 2.3 deg. 4. Outboard Steering Rudder: LE outboard 5.9 deg. 5. Maximum Rudder Side Force: 40-45 deg. 6. Struts Wake Aligned at ahead speed of 8.7 kts.

Results: Propeller 1. Compared w/ flat face geometry a. 35 % reduction in unsteady shaft thrust and torque amplitude. b. 25 % reduction in radiated pressure pulse levels. c. 3 % increase in openwater efficiency. d. Tip clearance reduced from 15% D to 10% D. e. Propeller diameter increase from 79 to 82.5 2. Full 3D CNC propeller models. ABS Class.

Closure Thank You.