naca_aerofoil.py

import urllib2

import numpy as np
from bs4 import BeautifulSoup


class Naca4DigitAerofoil(object):
    """
    Object to represent 4 digit NACA aerofoil generated by airfoiltools.com
    """
    def __init__(self, camber, camber_x, thickness, n):
        self.camber = camber
        self.camber_x = camber_x
        self.thickness = thickness
        self.url = "http://airfoiltools.com/airfoil/naca4digit?" \
                   "MNaca4DigitForm%5Bcamber%5D={}" \
                   "&MNaca4DigitForm%5Bposition%5D={}" \
                   "&MNaca4DigitForm%5Bthick%5D={}" \
                   "&MNaca4DigitForm%5BnumPoints%5D={}" \
                   "&MNaca4DigitForm%5BcosSpace%5D=0&MNaca4DigitForm%5BcosSpace%5D=1" \
                   "&MNaca4DigitForm%5BcloseTe%5D=1&yt0=Plot".format(self.camber, self.camber_x, self.thickness, n - 1)
        self.data = np.empty((n, 2))
        self.page = None

    def __call__(self, *args, **kwargs):
        self._get_html()
        self._parse_data()

    def _get_html(self):
        self.page = urllib2.urlopen(self.url)

    def _parse_data(self):
        soup = BeautifulSoup(self.page, 'html.parser')
        dat = soup.find('pre')
        dat = dat.text.split('\n')
        dat = dat[2:-1]     # Fudge to remove header and whitespace rows

        for i, row in enumerate(dat):
            ascii = row.encode('ascii')
            values = ascii.split(' ')
            x_y = [float(val) for val in values if len(val)]
            self.data[i] = x_y

    def write_dat(self):
        """
        Function to write .dat file containing x, y coordinates.
        """
        data = self.get_data()
        data.savetxt('{}.dat'.format(self.get_name()))

    def get_data(self):
        return self.data

    def get_name(self):
        return 'NACA{}{}{}'.format(self.camber, self.camber_x, self.thickness)