openplaning 0.0.1

Hydrodynamic evaluation of planing hulls based on the Savitsky empirical methods.

OpenPlaning

OpenPlaning is a Python library for the hydrodynamic evaluation of planing hulls based on the Savitsky empirical methods.

Installation

Use the package manager pip to install openplaning.

pip install openplaning

Examples

from openplaning import PlaningBoat

#Vessel particulars
speed = 13.07 #m/s, Fn = 2 : 13.07 m/s | Fn = 3 : 19.60 m/s
weight = 827369 #N
beam = 7.315 #m
lcg = 10.668 #m
vcg = beam/7 #m (rough estimate)
r_g = 1.3*beam #m (rough estimate)
beta = 15 #deg
epsilon = 0 #deg
vT = vcg #m
lT = lcg #m
length = 24.384 #m

#Trim tab particulars
sigma = 1.0 #flap span-beam ratio
delta = 5 #deg, flap deflection
Lf = 0.3048 #m, flap chord

#Seaway
H_sig = 1.4021 #m, significant wave height

#Create boat object
boat = PlaningBoat(speed, weight, beam, lcg, vcg, r_g, beta, epsilon, vT, lT, length, H_sig, Lf=Lf, sigma=sigma, delta=delta, wetted_lengths_type=3)

#Calculates the equilibrium trim and heave, and updates boat.tau and boat.z_wl
boat.get_steady_trim()

boat.print_description()
# RETURNS:
# ---VESSEL---
# Speed            13.07 m/s
# V_k              25.40808 knot
# Fn (beam)        1.543154 
# Fn (volume)      2.001405 

# Weight           827369 N
# Mass             84368.59 kg
# Volume           82.24101 m³
# Beam             7.315 m
# LCG              10.668 m from stern
# VCG              1.045 m from keel
# R_g              9.5095 m
# Deadrise         15 deg

# LOA              24.384 m
# AHR              0.00015 m, average hull roughness

# ---ATTITUDE---
# z_wl             0.1384483 m, vertical distance of center of gravity to the calm water line
# tau              2.880351 deg, trim angle
# η₃               0 deg, additional heave
# η₅               0 deg, additional trim
# Transom draft    1.441303 m, draft of keel at transom

# ---PROPULSION---
# Thrust angle     0 deg w.r.t. keel (CCW with body-fixed origin at 9 o'clock)
# LCT              10.668 m from stern, positive forward
# VCT              1.045 m from keel, positive up

# ---FLAP---
# Chord            0.3048 m
# Span/Beam        1 
# Angle            5 deg w.r.t. keel (CCW with body-fixed origin at 9 o'clock)

# ---AIR DRAG---
# l_air            0 m, distance from stern to center of air pressure
# h_air            0 m, height from keel to top of square which bounds the air-drag-inducing shape
# b_air            0 m, transverse width of square which bounds the air-drag-inducing shape
# C_shape          0 area coefficient for air-drag-inducing shape. C_shape = 1 means the air drag reference area is h_air*b_air
# C_D              0.7 air drag coefficient

# ---ENVIRONMENT---
# ρ                1025.87 kg/m³, water density
# ν                1.19e-06 m²/s, water kinematic viscosity
# ρ_air            1.225 kg/m³, air density
# g                9.8066 m/s², gravitational acceleration

# ---WETTED LENGTH OPTIONS---
# LC_type          3 (1 = Use Faltinsen 2010 wave rise approximation, 2 = Use Savitsky's '64 approach, 3 = Use Savitsky's '76 approach)
# zmax_type        1 (1 = Uses 3rd order polynomial fit (faster, recommended), 2 = Use cubic interpolation)

# ---WETTED LENGTHS---
# L_K              28.6824 m, keel wetted length
# L_C              17.67158 m, chine wetted length
# λ                3.19842 mean wetted-length to beam ratio (L_K+L_C)/(2*beam)
# x_s              11.01082 m, distance from keel/water-line intersection to start of wetted chine
# z_max            0.770493 maximum presssure coordinate coefficient (z_max/Ut)

# ---FORCES [F_x (N, +aft), F_z (N, +up), M_cg (N*m, +pitch up)]---
# Hydrodynamic Force =
# [39263.4 780367.3 301094.5]

# Skin Friction =
# [31885.2 -1604.272 -18956.96]

# Air Resistance =
# [0 0 0]

# Flap Force =
# [1841.278 44933.51 -282137.5]

# Net Force =
# [72989.88 2.725164e-08 2.635643e-07]

# Resultant Thrust =
# [-72989.88 3672.413 0]


# ---THURST & POWER---
# Thrust Magnitude 73082.21 N
# Effective Thrust 72989.88 N
# Eff. Power       953.9777 kW
# Eff. Horsepower  1279.305 hp

# ---EOM MATRICES---
# Mass matrix, [kg, kg*m/rad; kg*m, kg*m²/rad] =
# [[501671.6 67071.08]
#  [67071.08 2.493895e+07]]

# Damping matrix, [kg/s, kg*m/(s*rad); kg*m/s, kg*m²/(s*rad)] =
# [[447265.2 -8180477]
#  [3076884 2.908446e+07]]

# Restoring matrix, [N/m, N/rad; N, N*m/rad] =
# [[1325190 -2393769]
#  [4937876 5.370457e+07]]


# ---PORPOISING---
# [[Eigenvalue check result, Est. pitch settling time (s)],
#  [Savitsky chart result, Critical trim angle (deg)]] =
# [[0 8.803258]
#  [0 9.95532]]


# ---BEHAVIOR IN WAVES---
# H_sig            1.4021 m, significant wave heigth
# R_AW             38407.17 N, added resistance in waves
# Average impact acceleration [n_cg, n_bow] (g's) =
# [0.3084043 0.7553826]

Dependencies

• NumPy
• SciPy
• ndmath

Contributing

Contributions and feedback are welcome and greatly appreciated. Feel free to open an issue first to discuss what you would like to change.

License

MIT

Citing

This package is scheduled to be presented as a conference paper at the SNAME FAST Conference 2021:

• Castro-Feliciano, E. L., 2021, "OpenPlaning: An Open-Source Python-Based Framework for the Hydrodynamic Design, Exploration and Optimization of Planing Hulls," SNAME FAST '21 Conference Proceedings [Abstract Accepted]

References

• Castro-Feliciano, E. L., Sun, J., and Troesch, A. W., 2017, "First Step Toward the Codesign of Planing Craft and Active Control Systems," J. Offshore Mech. Arct. Eng., 139(1)
• Faltinsen, O. M., 2005, "Planing Vessels," Hydrodynamics of High-Speed Marine Vehicles, Cambridge University Press, New York, p. 342.
• Hadler, J. B., 1966, "The Prediction of Power Performance on Planing Craft," SNAME Trans., 74, pp. 563–610.
• Savitsky, D., 1964, "Hydrodynamic Design of Planing Hulls," Mar. Technol., 1(1), pp. 71–94.
• Savitsky, D., and Brown, P. W., 1976, "Procedures for Hydrodynamic Evaluation of Planing Hulls in Smooth and Rough Water," Mar. Technol., 13(4), pp. 381-400