PyResis package

Submodules

PyResis.propulsion_power module

class PyResis.propulsion_power.Ship[source]

Bases: object

Class of ship object, can be initialize with zero argument.

dimension(length, draught, beam, speed, slenderness_coefficient, prismatic_coefficient)[source]

Assign values for the main dimension of a ship.

Parameters:
  • length – metres length of the vehicle
  • draught – metres draught of the vehicle
  • beam – metres beam of the vehicle
  • speed – m/s speed of the vehicle
  • slenderness_coefficient – Slenderness coefficient dimensionless \(L/(∇^{1/3})\) where L is length of ship, ∇ is displacement
  • prismatic_coefficient – Prismatic coefficient dimensionless \(∇/(L\cdot A_m)\) where L is length of ship, ∇ is displacement Am is midsection area of the ship
get_reynold_number()[source]

Return Reynold number of the ship

Returns:Reynold number of the ship
maximum_deck_area(water_plane_coef=0.88)[source]

Return the maximum deck area of the ship

Parameters:water_plane_coef – optional water plane coefficient
Returns:Area of the deck
prop_power(propulsion_eff=0.7, sea_margin=0.2)[source]

Total propulsion power of the ship.

Parameters:
  • propulsion_eff – Shaft efficiency of the ship
  • sea_margin – Sea margin take account of interaction between ship and the sea, e.g. wave
Returns:

Watts shaft propulsion power of the ship
resistance()[source]

Return resistance of the vehicle.

Returns:newton the resistance of the ship
PyResis.propulsion_power.frictional_resistance_coef(length, speed, **kwargs)[source]

Flat plate frictional resistance of the ship according to ITTC formula. ref: https://ittc.info/media/2021/75-02-02-02.pdf

Parameters:
  • length – metres length of the vehicle
  • speed – m/s speed of the vehicle
  • kwargs – optional could take in temperature to take account change of water property
Returns:

Frictional resistance coefficient of the vehicle
PyResis.propulsion_power.froude_number(speed, length)[source]

Froude number utility function that return Froude number for vehicle at specific length and speed.

Parameters:
  • speed – m/s speed of the vehicle
  • length – metres length of the vehicle
Returns:

Froude number of the vehicle (dimensionless)
PyResis.propulsion_power.residual_resistance_coef(slenderness, prismatic_coef, froude_number)[source]

Residual resistance coefficient estimation from slenderness function, prismatic coefficient and Froude number.

Parameters:
  • slenderness – Slenderness coefficient dimensionless \(L/(∇^{1/3})\) where L is length of ship, ∇ is displacement
  • prismatic_coef – Prismatic coefficient dimensionless \(∇/(L\cdot A_m)\) where L is length of ship, ∇ is displacement Am is midsection area of the ship
  • froude_number – Froude number of the ship dimensionless
Returns:

Residual resistance of the ship
PyResis.propulsion_power.reynolds_number(length, speed, temperature=25)[source]

Reynold number utility function that return Reynold number for vehicle at specific length and speed. Optionally, it can also take account of temperature effect of sea water.

Parameters:
  • length – metres length of the vehicle
  • speed – m/s speed of the vehicle
  • temperature – degree C
Returns:

Reynolds number of the vehicle (dimensionless)

Module contents