def get_clipped_section_data(cls, sectiondata, inlet_height, angle):
'''Function to get a SectionAIRFOILData instance from a SectionData as
required for a parafoil by clipping the front portion as specified by
the inlet height and angle of cut
'''
dx = sectiondata.data_points[:, 0]
xmin, xmax = numpy.min(dx), numpy.max(dx)
xchange = numpy.argmax(dx) if dx[1] > dx[0] else numpy.argmin(dx)
x = numpy.unique(dx)
# datax, datay
dxu, dyu = sectiondata.data_points[:xchange+1, 0], sectiondata.data_points[:xchange+1, 1]
a = numpy.argsort(dxu)
dxu, dyu = dxu[a], dyu[a]
dxl, dyl = sectiondata.data_points[xchange:, 0], sectiondata.data_points[xchange:, 1]
a = numpy.argsort(dxl)
dxl, dyl = dxl[a], dyl[a]
angle_r = angle * numpy.pi / 180
#def err_angle
err_angle = lambda x,x1,y1: angle_r - numpy.arctan2(y1 - numpy.interp(x, dxl, dyl), x1 - x)
get_err_angle = lambda x1,y1: lambda x: err_angle(x,x1,y1)
def get_inlet_height(x, angle):
x1 = x
y1 = numpy.interp(x1, dxu, dxu)
x2 = false_position_method(get_err_angle(x1,y1), x1, x1 + 0.01, angle_r / 100, max_iter=100)
y2 = numpy.interp(x, dxl, dyl)
return y1 - y2
err_height = lambda x: get_inlet_height(x, angle) - inlet_height
x1 = x_inlet = false_position_method(err_height, 0.1, 0.11, inlet_height / 1000, max_iter=100)[0]
x2_inlet = false_position_method(get_err_angle(x1,numpy.interp(x1, dxu, dxu)), x1, x1 + 0.01, angle_r / 100, max_iter=100)[0]
dxu_new = dxu[dxu>x_inlet]
dxu_new = numpy.concatenate(([x_inlet],dxu_new))
dyu_new = numpy.interp(dxu_new, dxu, dyu)
dxl_new = dxl[dxl>x2_inlet]
dxl_new = numpy.concatenate(([x2_inlet],dxl_new))
dyl_new = numpy.interp(dxl_new, dxl, dyl)
dx_new = numpy.concatenate((dxl_new[::-1],dxu_new))
dy_new = numpy.concatenate((dyl_new[::-1],dyu_new))
# now translate the data to get x_le = 0.0
dx_new = dx_new-x_inlet
# now scale to get initial chord to compensate for the cut
dx_new = dx_new/(1-x_inlet)
dy_new = dy_new/(1-x_inlet)
data_points = numpy.array([dx_new,dy_new]).T
print data_points.shape
ret = SectionAIRFOILData(data_points=data_points)
return ret
def get_inlet_height(x, angle):
x1 = x
y1 = numpy.interp(x1, dxu, dxu)
x2 = false_position_method(get_err_angle(x1,y1), x1, x1 + 0.01, angle_r / 100, max_iter=100)
y2 = numpy.interp(x, dxl, dyl)
return y1 - y2
