THE APPLICATION OF COMPUTATIONAL FLUID DYNAMICS (CFD) TO RIVER TOWBOAT DESIGN

Smart Rivers 2011PIANCNew Orleans, LAUSA

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Authors:

Brant R. Savander, Ph.D., P.E.Principal Research ScientistMaritime Research Associates, LLCAnn Arbor, MIUSA

Gregory LeeNaval ArchitectMarine Design CenterUS Army Corps of EngineersPhiladelphia, PAUSA

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Acknowledgements:

Sergio FifiNaval ArchitectJensen Maritime Consultants, Inc.

Johan SperlingNaval ArchitectJensen Maritime Consultants, Inc.

OVERVIEWThe Application of CFD to River Towboat Design

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• USACE Towboat Example: EVANICK

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• 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.

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• 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

USACE 114-FT TOWBOAT APPLICATION

The Application of CFD to River Towboat Design

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• 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.

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Outboard Profile

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

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• General Arrangement

NUMERICAL TOWING TANK – FULL SCALE

The Application of CFD to River Towboat Design

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Computational Geometry

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Computational Domain: Full Scale Tank

Lateral Symmetry

Bottom Boundary

Velocity Inlet

Pressure Outlet

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Computational Domain: Full Scale Tank

Lateral Symmetry

Bottom Boundary

Velocity Inlet

Free Surface

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Rudder and Propeller Mesh

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Rudder and Propeller Mesh

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Results: Full Resolution of Pressure Field

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Results: Full Resolution of Velocity Field

-7.2o

-3.3o

-5.9o

2.3o

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Stock Appendages: Axial Velocity

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Wake Adapted App.: Axial Velocity

USACE TOWBOAT PROPELLER

The Application of CFD to River Towboat Design

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Propeller Drawing

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Propeller Distributions

RUDDER ANGLE VARIATION

The Application of CFD to River Towboat Design

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Example: Steering Rudders – 20 deg.

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Free Surface: Steering 20-deg

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Streamlines: Steering 20-deg

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Steering Angle Force Summary

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Flanking Rudder Angle Force Summary

RESULTS & CONCLUSIONSThe Application of CFD to River Towboat Design

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• 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.

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• 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.

Overview 114-ft Towboat Numerical Towing Tank Propeller Rudder AOA Closure

• Closure

Thank You .