Performance Prediction and Design Optimization

Performance Prediction and Design Optimization

Midn 1/c Jon P. SilverbergMidn 1/c Jon P. Silverberg

Performance PredictionPerformance Prediction

• The velocity of a ship is inherent to its mission effectiveness

• Three methods of determination– Hydrodynamic Tank Testing– Parametric Analysis– Computational Fluid Dynamics

• The velocity of a ship is inherent to its mission effectiveness

• Three methods of determination– Hydrodynamic Tank Testing– Parametric Analysis– Computational Fluid Dynamics

Mk II Navy 44 Sail Training CraftMk II Navy 44 Sail Training Craft

• Designer David Pedrick supplied:– Lines Plan– Sail Plan– Parametrically predicted speeds from the

IMS Velocity Prediction Program (VPP)

• Designer David Pedrick supplied:– Lines Plan– Sail Plan– Parametrically predicted speeds from the

IMS Velocity Prediction Program (VPP)

• Sailing craft complexities– Six Degrees of Freedom– Propulsion Systems– Lifting Surfaces

• Sailing craft complexities– Six Degrees of Freedom– Propulsion Systems– Lifting Surfaces

Performance Prediction Process

Performance Prediction Process

• Performance predicted for both motoring (upright) and sailing conditions

• Three methods of hydrodynamic analysis– Tank Testing– “FKS” Computational Fluid Dynamic (CFD) code– “SPLASH” CFD code

• Upright analysis use only hydrodynamic data• Sailing conditions necessitate aerodynamic

data and use of a Velocity Prediction Program

• Performance predicted for both motoring (upright) and sailing conditions

• Three methods of hydrodynamic analysis– Tank Testing– “FKS” Computational Fluid Dynamic (CFD) code– “SPLASH” CFD code

• Upright analysis use only hydrodynamic data• Sailing conditions necessitate aerodynamic

data and use of a Velocity Prediction Program

Initial Parametric AnalysisInitial Parametric Analysis

• Needed to determine sailing conditions and sail forces which the IMS VPP did not provide

• Needed to determine sailing conditions and sail forces which the IMS VPP did not provide

• Predictions were performed with University of Michigan’s “PCSail” developed by David Martin

• Derived conditions to test in the tow tank

• Predictions were performed with University of Michigan’s “PCSail” developed by David Martin

• Derived conditions to test in the tow tank

Basic HydrodynamicsBasic Hydrodynamics

• Two main components of Resistance– Wavemaking – determined experimentally– Viscous (friction) – calculated

• Speed of the model is scaled to reproduce wavemaking characteristics

• Turbulence stimulators are added to reproduce viscous flow conditions

• Wavemaking results scaled to ship size• Viscous resistance calculated for ship size

• Two main components of Resistance– Wavemaking – determined experimentally– Viscous (friction) – calculated

• Speed of the model is scaled to reproduce wavemaking characteristics

• Turbulence stimulators are added to reproduce viscous flow conditions

• Wavemaking results scaled to ship size• Viscous resistance calculated for ship size

Tow Tank Testing

Tow Tank Testing

• Data Recorded– Drag– Lift– Yaw Moment– Pitch

• Data Recorded– Drag– Lift– Yaw Moment– Pitch

• Tests included• Upright Conditions• Sailing Conditions• Viscous Corrections

• Performed more than 570 runs

• Tests included• Upright Conditions• Sailing Conditions• Viscous Corrections

• Performed more than 570 runs

FKS – CFDFKS – CFD• Developed by Dr. Noblesse at Carderock NSWC • Calculated the far-field wave spectrum

– Far-field waves are the totality of wave interactions– Wavemaking resistance is calculated through the

energy required to create the far-field waves

• Developed by Dr. Noblesse at Carderock NSWC • Calculated the far-field wave spectrum

– Far-field waves are the totality of wave interactions– Wavemaking resistance is calculated through the

energy required to create the far-field waves

• Hull had one degree of freedom (forward)

• Lift was not calculated• Simulations were fast• FKS was best suited for

upright calculations• Initial investigation

made on the Wigley hull

• Hull had one degree of freedom (forward)

• Lift was not calculated• Simulations were fast• FKS was best suited for

upright calculations• Initial investigation

made on the Wigley hull

Wavemaking ComparisonWavemaking Comparison

Scale effects in tank testingScale effects in tank testing

Spray and pitchSpray and pitch

Viscous interaction in wavemaking

Viscous interaction in wavemaking

SPLASH – CFDSPLASH – CFD

• Calculated inviscid fluid velocities across a discretized hull

• Hull had six degrees of freedom

• Calculations included upright testing and sailing conditions

• SPLASH ran on a high resource system

• Calculated inviscid fluid velocities across a discretized hull

• Hull had six degrees of freedom

• Calculations included upright testing and sailing conditions

• SPLASH ran on a high resource system

Development was by Bruce Rosen of South Bay Simulations and Joe Laiosa from Navair at Patuxent River

Development was by Bruce Rosen of South Bay Simulations and Joe Laiosa from Navair at Patuxent River

All Upright DataAll Upright Data

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 2 4 6 8 10 12

Velocity [knots]

Res

ista

nce

[lb

s]

Tank

FKS

SPLASH

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 2 4 6 8 10 12

Velocity [knots]

Res

ista

nce

[lb

s]

Tank

FKS

SPLASH

Different method of viscous calculations

Different method of viscous calculations

Pitch EffectsPitch Effects

Sailing Hydrodynamic

Data

Sailing Hydrodynamic

Data

SPLASHSPLASH

Tank Testing

Tank Testing

Utilized MATLAB and MAPLE to interpolate through sailing matrices

Utilized MATLAB and MAPLE to interpolate through sailing matrices

Mk II Navy 44 VPPMk II Navy 44 VPP• Aerodynamics

– Analyzed sail forces using basic wing theory– Force coefficients from sails derived from IMS VPP

• Aerodynamics– Analyzed sail forces using basic wing theory– Force coefficients from sails derived from IMS VPP

• Solution– Draghydro= Driveaero

– Lifthydro= Sideforceaero

– RightingMomenthydro = HeelingMomentaero

– YawingMomenthydro = YawingMomentaero

• Solution– Draghydro= Driveaero

– Lifthydro= Sideforceaero

– RightingMomenthydro = HeelingMomentaero

– YawingMomenthydro = YawingMomentaero

Custom VPP had a complex hydrodynamic model and solution but a simplified aerodynamic model

Custom VPP had a complex hydrodynamic model and solution but a simplified aerodynamic model

• Custom VPP written in Excel using Visual Basic• Created three VPPs from Tow Tank data, SPLASH

data, and FKS data (which proved unusable)• Predicted speed for any wind condition and angle

• Custom VPP written in Excel using Visual Basic• Created three VPPs from Tow Tank data, SPLASH

data, and FKS data (which proved unusable)• Predicted speed for any wind condition and angle

Solved by simultaneous equations using finite-difference iteration

Solved by simultaneous equations using finite-difference iteration

Performance PredictionsPerformance Predictions

Low wind speeds showed variable results due to simplifications in the aerodynamic model

Low wind speeds showed variable results due to simplifications in the aerodynamic model

All other wind speeds showed excellent correlation between all velocity predictions

All other wind speeds showed excellent correlation between all velocity predictions

Performance Prediction ConclusionsPerformance Prediction Conclusions

• Tow tank method was limited by scale factors at low model speeds

• FKS was limited to upright testing• SPLASH proved a valuable tool

when its accuracy was increased with tank data

• IMS and PCSail VPP’s provide reliable trends based on extensive hydrodynamic data

• Custom VPP provided best results using complex hydrodynamic models

• Polars constructed as best fit of all VPP data

• Tow tank method was limited by scale factors at low model speeds

• FKS was limited to upright testing• SPLASH proved a valuable tool

when its accuracy was increased with tank data

• IMS and PCSail VPP’s provide reliable trends based on extensive hydrodynamic data

• Custom VPP provided best results using complex hydrodynamic models

• Polars constructed as best fit of all VPP data

Rudder DesignRudder Design

• Designer David Pedrick provided an unfinished rudder design for the Mk II Navy 44

• Three design comparisons– Size (Tow tank and SPLASH)– Planform (SPLASH)– Location and Depth

(SPLASH)

• Designer David Pedrick provided an unfinished rudder design for the Mk II Navy 44

• Three design comparisons– Size (Tow tank and SPLASH)– Planform (SPLASH)– Location and Depth

(SPLASH)

Size ComparisonSize Comparison • Comparison of the Pedrick and “Beaver” rudders

• Beaver rudder provided better turning ability and upwind ability in high wind speeds

• Comparison of the Pedrick and “Beaver” rudders

• Beaver rudder provided better turning ability and upwind ability in high wind speeds

• SPLASH and Tank testing results were similar• SPLASH was used for the rest of the testing

based on its accuracy and precision

• SPLASH and Tank testing results were similar• SPLASH was used for the rest of the testing

based on its accuracy and precision

Planform ComparisonPlanform Comparison

• Picked different shapes to determine the resulting flow patterns

• Each shape was analyzed in SPLASH in under two hours

• Picked different shapes to determine the resulting flow patterns

• Each shape was analyzed in SPLASH in under two hours

BaselineBaseline BulgeBulge EllipticalElliptical TipTip ZoidZoid

Planform ResultsPlanform Results

• Picked different shapes to determine the resulting flow patterns

• Each shape was analyzed in SPLASH in under two hours

• Picked different shapes to determine the resulting flow patterns

• Each shape was analyzed in SPLASH in under two hours

BaselineBaseline BulgeBulge EllipticalElliptical TipTip • The Tip rudder was the most efficient rudder

• The Tip moved the induced vortex away from the main lifting surface

• The Tip rudder was the most efficient rudder

• The Tip moved the induced vortex away from the main lifting surface

The Tip rudder showed a drag reduction of 0.8% in turning and 0.2% while sailing upwind

The Tip rudder showed a drag reduction of 0.8% in turning and 0.2% while sailing upwind

Location and Depth ComparisonLocation and Depth Comparison

• Compared rudders– Moved forward 1.6 ft– Moved forward 3.2 ft– Increased size to

maximum draft (85% total draft)

• Compared rudders– Moved forward 1.6 ft– Moved forward 3.2 ft– Increased size to

maximum draft (85% total draft)

• Forward movement thought to reduce drag caused by wavemaking

• Size increase thought to increase efficiency by reducing the relative induced drag

• Forward movement thought to reduce drag caused by wavemaking

• Size increase thought to increase efficiency by reducing the relative induced drag

• Forward movement interfered with wake from the keel

• Increased depth interfered with keel vortex

• No rudder proved better than the baseline

• Forward movement interfered with wake from the keel

• Increased depth interfered with keel vortex

• No rudder proved better than the baseline

Rudder Design ConclusionsRudder Design Conclusions

• The Beaver rudder provided better turning and upwind ability, but was slower downwind

• Moving the rudder forward or increasing its maximum draft increased drag

• By adding a tip onto the Baseline rudder, the overall performance of the Mk II Navy 44 would be improved

• CFD was more effective and efficient at redesigning appendages than tow tank testing

• The Beaver rudder provided better turning and upwind ability, but was slower downwind

• Moving the rudder forward or increasing its maximum draft increased drag

• By adding a tip onto the Baseline rudder, the overall performance of the Mk II Navy 44 would be improved

• CFD was more effective and efficient at redesigning appendages than tow tank testing

Future WorkFuture Work

• Integrate the rudder results into the custom VPP• Larger models should be tested to validate tow

tank results• Viscid CFD codes should be used to evaluate the

rudder comparisons• An improved Aerodynamic model should be

used in the custom VPP• Full-scale testing would validate all of the data

once a prototype is built

• Integrate the rudder results into the custom VPP• Larger models should be tested to validate tow

tank results• Viscid CFD codes should be used to evaluate the

rudder comparisons• An improved Aerodynamic model should be

used in the custom VPP• Full-scale testing would validate all of the data

once a prototype is built

Questions?Questions?