openplaning 0.4.5

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

You can run the example below, plus an optimization case study, online with Binder:

from openplaning import PlaningBoat

#Vessel particulars (from the Savitsky '76 example)
speed = 13.07 #m/s
weight = 827400 #N
beam = 7.315 #m
length = 24.38 #m, vessel LOA
lcg = 10.67 #m, long. center of gravity
vcg = beam/7 #m, vert. center of gravity
r_g = 0.25*length #m, radius of gyration
beta = 15 #deg, deadrise

#Propulsion
epsilon = 0 #deg, thrust angle w.r.t. keel
vT = vcg #m, thrust vertical distance
lT = lcg #m, thrust horizontal distance

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

#Seaway
H_sig = 1.402 #m, significant wave height

#Additional options
wetted_lengths_type = 3 #1 = Use Faltinsen 2005 wave rise approximation, 2 = Use Savitsky's '64 approach, 3 = Use Savitsky's '76 approach. Defaults to 1.
roughness_penalty_type = 2 #1 = Use Mosaad's '86 regression, 2 = Use Townsin's '84 regression. Defaults to 1.

#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=wetted_lengths_type, roughness_penalty_type=roughness_penalty_type)

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

boat.print_description()

Output:

---VESSEL---
Speed            13.07 m/s
V_k              25.40808 knot
Fn (beam)        1.543154 
Fn (volume)      2.001392 
V_m              12.96912 m/s, mean bottom fluid speed
Rn               2.550646e+08 based on V_m and mean wetted-length

Weight           827400 N
Mass             84371.75 kg
Volume           82.24409 m³
Beam             7.315 m
LCG              10.67 m from stern
VCG              1.045 m from keel
R_g              6.095 m
Deadrise         15 deg

LOA              24.38 m
AHR              150 10⁻⁶m, average hull roughness

---ATTITUDE---
z_wl             0.1384811 m, vertical distance of center of gravity to the calm water line
tau              2.878945 deg, trim angle
η₃               0 deg, additional heave
η₅               0 deg, additional trim

---PROPULSION---
Thrust angle     0 deg w.r.t. keel (CCW with body-fixed origin at 9 o'clock)
LCT              10.67 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---
wetted_lengths_type 3 (1 = Use Faltinsen 2005 wave rise approximation, 2 = Use Savitsky's '64 approach, 3 = Use Savitsky's '76 approach)
z_max_type       1 (1 = Uses 3rd order polynomial fit (faster, recommended), 2 = Use cubic interpolation)

---RUNNING GEOMETRY---
L_K              28.69256 m, keel wetted length
L_C              17.67617 m, chine wetted length
L_C2             15.05145 m, side chine wetted length
λ                3.199428 mean wetted-length to beam ratio (L_K+L_C)/(2*beam)
x_s              11.0164 m, distance from keel/water-line intersection to start of wetted chine
z_max            0.7704615 maximum pressure coordinate coefficient (z_max/Ut)
alpha            18.36643 deg, spray line angle w.r.t. keel in plan view
LCP              11.05546 m, longitudinal center of pressure from stern
T                1.441111 m, draft of keel at transom
wetted_bottom_area 175.5762 m², bottom wetted surface area

---ROUGHNESS DRAG PENALTY---
roughness_penalty_type 2 (1 = Use Mosaad's '86 regression, 2 = Use Townsin's '84 regression)
ΔC_f             0.2485087 10⁻³ change in friction coefficient
ΔL/ΔD            None roughness induced change of hull lift to change of hull drag ratio
ΔC_L             0 10⁻³ change in lift coefficient

---FORCES [F_x (N, +aft), F_z (N, +up), M_cg (N*m, +pitch up)]---
Hydrodynamic Force =
[39245.86 780400.3 301189.8]

Skin Friction =
[31893.98 -1603.929 -18962.39]

Roughness Lift Change =
[0 0 0]

Air Resistance =
[0 0 0]

Flap Force =
[1840.949 44933.51 -282227.4]

Net Force =
[72980.79 2.573734e-08 2.535526e-07]

Resultant Thrust =
[-72980.79 3670.16 0]

---THURST & POWER---
Thrust Magnitude 73073.02 N
Effective Thrust 72980.79 N
Eff. Power       953.859 kW
Eff. Horsepower  1279.146 hp

---EOM MATRICES---
Mass matrix, [kg, kg*m/rad; kg*m, kg*m²/rad] =
[[501800.8 67648.82]
 [67648.82 2.046024e+07]]

Damping matrix, [kg/s, kg*m/(s*rad); kg*m/s, kg*m²/(s*rad)] =
[[447299.8 -8182636]
 [3078703 2.909537e+07]]

Restoring matrix, [N/m, N/rad; N, N*m/rad] =
[[1325673 -2390482]
 [4940227 5.375431e+07]]

---PORPOISING---
[[Eigenvalue check result, Est. pitch settling time (s)],
 [Savitsky chart result, Critical trim angle (deg)]] =
[[0 7.097941]
 [0 9.955598]]

---BEHAVIOR IN WAVES---
H_sig            1.402 m, significant wave heigth
R_AW             38406.03 N, added resistance in waves
Average impact acceleration [n_cg, n_bow] (g's) =
[0.3082269 0.754686]

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 was presented as a conference paper at the SNAME FAST Conference 2021:

• Castro-Feliciano, E. L., 2021, "OpenPlaning: Open-Source Framework for the Hydrodynamic Design of Planing Hulls," SNAME FAST '21 Conference Proceedings

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
• Fridsma, G., 1971, "A Systematic Study of the Rough-Water Performance of Planing Boats (Irregular Waves - Part II)," Tech. Rep. 1495, Stevens Institute of Technology
• Hadler, J. B., 1966, "The Prediction of Power Performance on Planing Craft," SNAME Trans., 74, pp. 563–610
• ITTC, 1978, "15th International Towing Tank Conference (Proceedings - Part 1)," Netherlands Ship Model Basin, Wageningen, pp. 273–277
• Mosaad, M. A., 1986, "Marine Propeller Roughness Penalties," PhD Thesis, University of Newcastle, p. 193
• 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