# Source code for bladedesigner.camberlines.n2dcamberline

#!/usr/bin/env python
# -*- coding: utf-8 -*-

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# *   Copyright (C) 2011-2012 by Andreas Kührmann [kuean@users.sf.net]      *
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import numpy as np

import bladedesigner.baseclasses as bcls
import bladedesigner.foundation as fdn

__all__ = ['N2DCamberLine']

[docs]class N2DCamberLine(bcls.AnalyticalCamberLine):
r"""

The NACA 2-digit camber line is characterized by two attributes :math:m
and :math:p where :math:m is the maximum camber and :math:p is the
chordwise location of maximum camber. This camber line is formed by two
parabolic segments that match in value and slope at :math:p. The camber
line equation is:

.. math::

y = \Bigg\{ \begin{array}{ll} m p^{-2} x (2 p - x) & \mbox{if } x \leq p
\\ m (1 - p)^{-2} (1 - 2 p + x (2 p - x)) & \mbox{if } x > p \end{array}

.. tip::

Jacobs, Eastman N.; Ward, Kenneth E. and Pinkerton, Robert M.:
*The Characteristics of 78 Related Airfoil Sections From Tests in the
Variable-Density Wind Tunnel.* NACA Rep. 460, 1933

Ladson, Charles L.; Brooks, Cuyler W.; Hill, Acquilla S. and Sproles
Darrell W.: *Computer Program To Obtain Ordinates for NACA Airfoils*
NACA TM 4741, 1996.
"""

def __init__(self):
super(N2DCamberLine, self).__init__()
# properties (initialized by user)
self.__max_camber = fdn.Uninit('max_camber')
self.__max_camber_position = fdn.Uninit('max_camber_position')
# add user properties to initialization summary
self._properties.extend(['max_camber', 'max_camber_position'])

@property
def max_camber(self):
"""
Type: int or float
"""
return self.__max_camber

@max_camber.setter
@fdn.restrict(new_max_camber=(int, float))
[docs]    def max_camber(self, new_max_camber):
if self.__max_camber != new_max_camber:
self.__max_camber = new_max_camber
self.update()

@property
def max_camber_position(self):
"""
Type: float - values between (exclusive) 0 and 1 only
"""
return self.__max_camber_position

@max_camber_position.setter
@fdn.restrict(new_max_camber_position=fdn.OpenInterval(0, 1))
[docs]    def max_camber_position(self, new_max_camber_position):
if self.__max_camber_position != new_max_camber_position:
self.__max_camber_position = new_max_camber_position
self.update()

@fdn.memoize
[docs]    def get_derivations(self):
"""
get_derivations()

Returns: ndarray

Calculates camber line derivations and returns them in an array.

.. note::

The return value will be cached. Recalling this method returns the
cached value, if the attribues are unchanged.
"""
self._check_initialization()
self._cached = True
p = self.max_camber_position
m = self.max_camber
x = self.distribution(self.sample_rate)
index = np.where(x <= p)[0]
if index.size:
dydx_1 = 2 * m / np.power(p, 2) * (p - x[index])
index = np.where(x > p)[0]
if index.size:
dydx_2 = m / (1 - p) ** 2 * 2 * (p - x[index])
return np.append(dydx_1, dydx_2)

@fdn.memoize
[docs]    def as_array(self):
"""
as_array()

Returns: ndarray

Calculates camber line coordinates and returns them in an array.

.. note::

The return value will be cached. Recalling this method returns the
cached value, if the attribues are unchanged.
"""
self._check_initialization()
self._cached = True
p = self.max_camber_position
m = self.max_camber
x = self.distribution(self.sample_rate)
index = np.where(x <= p)[0]
if index.size:
z = x[index]
y1 = m / p ** 2 * (z * (2 * p - z))
index = np.where(x > p)[0]
if index.size:
z = x[index]
y2 = m / (1 - p) ** 2 * (1 - 2 * p + z * (2 * p - z))
y = np.append(y1, y2)
return np.reshape(np.append(x, y), (-1, 2), "F")