def __init__(self):
self._db = pth.db.airfoil
self.name = None
self.pts = None
self.ptsUp = None
self.ptsLo = None
self.thickness = None
self.camber = None
self.camberLocation = None
self.leRadius = None
self.zTrailingEdge = 0.0
self._curveUp = None
self._curveLo = None
self.polar = AirfoilPolar()
self._distribution = 'cos'
class Airfoil:
def __init__(self):
self._db = pth.db.airfoil
self.name = None
self.pts = None
self.ptsUp = None
self.ptsLo = None
self.thickness = None
self.camber = None
self.camberLocation = None
self.leRadius = None
self.zTrailingEdge = 0.0
self._curveUp = None
self._curveLo = None
self.polar = AirfoilPolar()
self._distribution = 'cos'
def read_db(self,name,xlsPath=None):
"""
Reads airfoil from xls database. If additional geometry information
and aerodynamic tables exist then existing tables are used
otherwise information will be created using internal tools of module.
"""
if xlsPath==None:
xlsPath = pth.db.airfoil
db = db_tools.ReadDatabase(xlsPath,name)
self.name = name
xCoord = db.read_row(0,1)
yCoord = db.read_row(1,1)
self.pts = np.transpose([xCoord,yCoord])
self._separate_coordinates()
# geometry
i = db.find_header('GEOMETRY')
if i==-1:
self._analyze_geometry()
else:
self.thickness = db.read_row(i+1,1)
self.camber = db.read_row(i+2,1)
self._analyze_geometry()
# analysis
i = db.find_header('ANALYSIS')
if i==-1:
self.build_aero_table()
else:
self.polar.source = db.read_row(i+1,1)
i = db.find_header('LIFT COEFFICIENT')
nAlpha = db.find_header('DRAG COEFFICIENT') - i-2
self.polar.Mach = np.array(db.read_row(i+1,1))
self.polar.alpha = np.array(db.read_column(0,i+2,nAlpha))
self.polar.cl = db.read_row_range(i+2,1,nAlpha)
i = db.find_header('DRAG COEFFICIENT')
self.polar.cd = db.read_row_range(i+2,1,nAlpha)
i = db.find_header('MOMENT COEFFICIENT')
self.polar.cm = db.read_row_range(i+2,1,nAlpha)
self.polar.cl = np.transpose(self.polar.cl)
self.polar.cd = np.transpose(self.polar.cd)
self.polar.cm = np.transpose(self.polar.cm)
self.polar._create_splines()
self.polar._calc_clmax()
def write_db(self,xlsPath=None,includePolars=True):
"""
Writes airfoil to xls format database.
"""
if xlsPath==None:
xlsPath=pth.db.airfoil
db = db_tools.WriteDatabase(xlsPath,self.name)
db.write_row('X',self.pts[:,0])
db.write_row('Y',self.pts[:,1])
db.write_row('GEOMETRY')
db.write_row('thickness',self.thickness)
db.write_row('camber' ,self.camber)
if includePolars:
db.write_row('ANALYSIS')
db.write_row('method', self.polar.source)
db.write_row('LIFT COEFFICIENT')
db.write_row('Mach list',self.polar.Mach)
i = db._irowPrev
db.write_column(self.polar.alpha)
db._irowPrev = i
db.write_row_range(np.transpose(self.polar.cl),-1,1)
db.write_row('DRAG COEFFICIENT')
db.write_row('Mach list',self.polar.Mach)
i = db._irowPrev
db.write_column(self.polar.alpha)
db._irowPrev = i
db.write_row_range(np.transpose(self.polar.cd),-1,1)
db.write_row('MOMENT COEFFICIENT')
db.write_row('Mach list',self.polar.Mach)
i = db._irowPrev
db.write_column(self.polar.alpha)
db._irowPrev = i
db.write_row_range(np.transpose(self.polar.cm),-1,1)
db.save()
def read_txt(self,airfoilPath):
"""
Reads airfoil coordinates from text file. Two formats of coordinates
are supported.
"""
fid = open(airfoilPath,'rt')
self.name = str(fid.readline()[:-1])
lines = fid.readlines()
fid.close()
seg = lines[0].split()
if float(seg[0])>3 and float(seg[1])>3:
iup = int(round(float(seg[0])))
ilo = int(round(float(seg[1])))
self._read_txt_type2(lines[1:],iup,ilo)
else:
self._read_txt_type1(lines)
self._analyze_geometry()
def write_txt(self,filePath,tab=True,writeName=True):
"""
writes airfoil coordinates to text file.
Parameters
----------
filePath : path
airfoil text file path to write coordinates
tab : bool
white space parameter. If True then x,y coordinates are separated
by tabbing otherwise
separated by 4 spacings as required for X-foil input.
writeName : bool
if True then airfoil name will be written to the text file header
otherwise only coordinates will be stored
"""
afFile = open(filePath,'wt')
if writeName:
afFile.write('%s\n'%self.name)
if tab:
whiteSpace = '\t'
else:
whiteSpace = ' '
for point in self.pts:
afFile.write('%.6f%s%.6f\n'%(point[0],whiteSpace,point[1]))
afFile.close()
def _line_coord_to_float(self,lines):
output = list()
for line in lines:
if line.strip()!='':
seg = line.split()
outline = np.zeros(2)
outline[0] = float(seg[0])
outline[1] = float(seg[1])
output.append(outline)
return np.array(output)
def _separate_coordinates(self):
self.ptsUp, self.ptsLo = geom.separate_coordinates(self.pts)
def _join_coordinates(self):
self.pts = geom.join_coordinates(self.ptsUp, self.ptsLo)
def _read_txt_type1(self,lines):
"""
reads airfoil coordinates from text file stored in xfoil and javafoil
like format.
Text format as follows:
1. airfoil name
2. coordinates starting from upper curve trailing edge (xx yy)
Parameters
----------
filePath : path
airfoil coordinates file path
Returns
-------
coord : 2d array
airfoil coordinates
name : string
airfoil name
"""
self.pts = self._line_coord_to_float(lines)
self._separate_coordinates()
def _read_txt_type2(self,lines,nPtsUp,nPtsLo):
"""
reads airfoil coordinates from text file stored in format similar to
uiuc db file format.
Text format as follows:
1. airfoil name
2. number of upper and lower curve points (n n)
3. upper curve points starting from leading edge (xx yy)
4. lower curve points starting from leading edge (xx yy)
Parameters
----------
filePath : path
airfoil coordinates file path
Returns
-------
coord : 2d array
airfoil coordinates
name : string
airfoil name
"""
coordRaw = self._line_coord_to_float(lines)
self.ptsUp = coordRaw[:nPtsUp]
self.ptsLo = coordRaw[nPtsUp:nPtsUp+nPtsLo]
self._join_coordinates()
def display(self,linetype='ko-'):
fig = plt.figure()
ax = fig.add_subplot(111)
ax.grid(True)
ax.axis('equal')
ax.set_title(self.name)
ax.plot(self.pts[:,0],self.pts[:,1],linetype)
plt.show()
def _create_splines(self):
"""
create cubic splines for x and y coordinate with respect to curve
length parameter
"""
# parametric splines x = x(t), y = y(t)
lenUp = geom.curve_pt_dist_normalized(self.ptsUp)
lenLo = geom.curve_pt_dist_normalized(self.ptsLo)
self._curveUp = CurveXyt(self.ptsUp[:,0],self.ptsUp[:,1],lenUp)
self._curveLo = CurveXyt(self.ptsLo[:,0],self.ptsLo[:,1],lenLo)
ptsUp,ptsLo = self._sort_pts()
self._curveUp2 = interp1d(ptsUp[:,0],ptsUp[:,1],'cubic')
self._curveLo2 = interp1d(ptsLo[:,0],ptsLo[:,1],'cubic')
self._xmin = max([ptsUp[0,0],ptsLo[0,0]])
self._xmax = min([ptsUp[-1,0],ptsLo[-1,0]])
def _analyze_geometry(self):
"""
calculates airfoil geometry parameters
"""
self._create_splines()
tc = lambda x: self._curveLo2(x) - self._curveUp2(x)
camber = lambda x: -(self._curveLo2(x) + self._curveUp2(x))
self.thicknessLocation = fminbound(tc,self._xmin,self._xmax)
self.camberLocation = fminbound(camber,self._xmin,self._xmax)
self.thickness = -tc(self.thicknessLocation)
self.camber = -camber(self.camberLocation)/2.0
n = len(self.pts)-1
L = np.zeros(n)
for i in range(n):
L[i] = ((self.pts[i,0]-self.pts[i+1,0])**2.0 + (self.pts[i,1]-self.pts[i+1,1])**2.0)**0.5
self.length = L.sum()
self.zTrailingEdge = self.ptsUp[-1,1] - self.ptsLo[-1,1]
# self._calc_leadingedge_radius()
#
# def _calc_leadingedge_radius(self):
# dt = 1e-5
# pt1 = self._curveLo(dt)
# pt2 = self._curveLo(0.0)
# pt3 = self._curveUp(dt)
# dx1,dx2 = pt3[0]-pt2[0], pt2[0]-pt1[0]
# print dx1, dx2
def _sort_pts(self):
xmin = 0.05
xmax = 0.95
def sort_pts(pts,xmin,xmax):
for i,pt in enumerate(pts):
if pt[0]>=xmin:
idxStart = i
break
for i,pt in enumerate(pts[idxStart:]):
if pt[0]>=xmax:
idxEnd = i+idxStart
break
return pts[idxStart:idxEnd]
ptsUp = sort_pts(self.ptsUp,xmin,xmax)
ptsLo = sort_pts(self.ptsLo,xmin,xmax)
return ptsUp,ptsLo
def _get_point_distribution(self,nPts=30,distribution=None):
if distribution==None:
distribution = self._distribution
if distribution=='sin':
return geom.get_sine_distribution(nPts)
elif distribution=='cos':
return geom.get_cosine_distribution(nPts)
def redim(self,nPts,overwrite=True,distribution='sin'):
"""
Redimension and redistribution of airfoil points using cosine function.
More points are located at leading and trailing edge.
Parameters
----------
numPts : integer
number of points for target airfoil. If number of points is same
as source airfoil, points will be redistributed to make smooth
surface
overwrite : bool
If True then self.pts, self.upPts and self.loPts will be
overwritten, otherwise will return array of redimensioned points
in format of self.pts
"""
if nPts%2==0:
nPts1 = nPts/2
nPts2 = nPts/2+1
else:
nPts1 = (nPts+1)/2
nPts2 = nPts1
#nPts *= 0.5
t1 = self._get_point_distribution(nPts1,distribution)
t2 = self._get_point_distribution(nPts2,distribution)
self._create_splines()
xUp, yUp = self._curveUp(t1)
xLo, yLo = self._curveLo(t2)
upPts = np.transpose(np.vstack([xUp,yUp]))
loPts = np.transpose(np.vstack([xLo,yLo]))
coord = geom.join_coordinates(upPts,loPts)
if overwrite:
self.pts = coord
self.ptsUp = upPts
self.ptsLo = loPts
else:
return coord
def scale_thickness(self,thicknessNew,analysis=False):
"""
Scales airfoil in Y-direction to achieve required thickness. Useful
to be used with propeller analysis when same airfoil has different
thickness at different *x* stations.
Parameters
----------
newThickness: float
thickness/chord of result airfoil
analysis : bool
If True then aerodynamic table will be generated using
self.build_aero_table, otherwise only geometry will be changed.
"""
scale = thicknessNew / self.thickness
self.name = self.name + '_tc%.2f'%(thicknessNew*100.0)
self.pts[:,1] = self.pts[:,1]*scale
self._separate_coordinates()
self.redim(50,overwrite=True)
if analysis:
self.build_aero_table()
def build_aero_table(self,MachSeq=[0.1,0.9,0.1],alphaSeq=[-20,20,1.0],
mode='javafoil'):
"""
builds full table of aerodynamic coefficients using *fast* solvers
Coefficients to be caclulated are as follows:
- lift coefficient vs. alpha, Mach
- drag coefficient vs. alpha, Mach
- moment coefficient vs. alpha, Mach
Parameters
----------
MachSeq : array float
array of Mach number to be analyzed in format [start, end, step]
alphaSeq : array float
array of angle of attack sequence to be analyzed in format
[start, end, step]
mode : string
if mode='javafoil' then coefficients will be generated using
javafoil, if 'xfoil' then using xfoil
"""
Mach = np.arange(MachSeq[0], MachSeq[1], MachSeq[2])
Re = list()
for i,M in enumerate(Mach):
Re.append(fc.FlightConditions(M,0.0).Re)
if mode=='javafoil':
tmpPolar = self.get_jfoil_polar(M, Re[i], alphaSeq)
elif mode=='xfoil':
tmpPolar = self.get_xfoil_polar(M, Re[i], alphaSeq, 200)
if i==0:
self.polar.cl = tmpPolar.cl
self.polar.cd = tmpPolar.cd
self.polar.cm = tmpPolar.cm
else:
self.polar.cl = np.vstack([self.polar.cl, tmpPolar.cl])
self.polar.cd = np.vstack([self.polar.cd, tmpPolar.cd])
self.polar.cm = np.vstack([self.polar.cm, tmpPolar.cm])
self.polar.Re = Re
self.polar.source = 'javafoil'
self.polar.Mach = Mach
self.polar.alpha = tmpPolar.alpha
self.polar._create_splines()
def get_xfoil_polar(self,Mach,Re,alphaSeq=[-15,15,1],nIter=10,graphic=False,smooth=False,
flapChordRatio=0.3,flapDefl=None):
"""
Calculates aerodynamic coefficients at given flight conditions using Xfoil.
Parameters
----------
Mach : float
Mach number
Re : float
Reynolds number
alphaSeq : array float
array of angle of attack sequence to be analyzed in format
[start, end, step]
nIter : integer
number of xfoil iterations. Default value is that is enough for
conventional airfoil configurations. For complex airfoil shapes
this number should be increased (for example while optimization
using genetic algorithm)
Returns
-------
polar : AirfoilPolar
airfoil polar with all aerodynamic data at specified flight
conditions
"""
return xf.get_xfoil_analysis(self,Mach,Re,alphaSeq,nIter,graphic,smooth,flapChordRatio,flapDefl)
def get_jfoil_polar(self,Mach,Re,alphaSeq=[-15,15,1],
stall='eppler',transition='drelaAfter1991',surface='NACAstandard',
flapDefl=None,flapChordRatio=30.0):
"""
Calculates aerodynamic coefficients at given flight conditions using Xfoil.
Parameters
----------
Mach : float
Mach number
Re : float
Reynolds number
alphaSeq : array float
array of angle of attack sequence to be analyzed in format
[start, end, step]
stall : string
stall model. Available options: calcfoil, eppler
transition : string
transition model. Availabel options: epplerStandard, epplerExtended,
michel1, michel2, H12Re, granville, drelaBefore1991, drelaAfter1991,
arnal
surface : string
surface type. Available options: smooth, paintedFabrid,
NACAstandard, bugsDirt
Returns
-------
polar : AirfoilPolar
airfoil polar with all aerodynamic data at specified flight
conditions
Note
----
Javafoil requires path to java installed in system in
:file:`javapath.txt`. For linux OS file should contain *java*
keyword only
"""
return jf.get_javafoil_analysis(self,Mach,Re,alphaSeq,stall,transition,
surface,flapChordRatio,flapDefl)
def create_cst(self,Au,Al,nPts=25,zTE=None):
self.upCurve = geom.CstCurve(Au)
self.loCurve = geom.CstCurve(Al)
x = self._get_point_distribution(nPts)
self.ptsUp = self.upCurve.get_coordinates(x)
self.ptsLo = self.loCurve.get_coordinates(x)
self._join_coordinates()
if not zTE==None:
self.set_trailing_edge(zTE)
self._analyze_geometry()
self.name = 'CST airfoil'
def create_naca4(self,thickness=12.0,camber=0.0,camberLoc=0.0,nPts=25):
t = thickness / 100.0
m = camber / 100.0
p = camberLoc / 100.0
x = self._get_point_distribution(nPts)
y = t/0.2*(0.2969*x**0.5 - 0.1281*x - 0.3516*x*x + 0.2843*x**3.0 - 0.1015*x**4.0)
self.thickness = t
self.camber = m
self.camberLocation = p
self.name = 'NACA%.0f%.0f%.0f'%(camber,camberLoc/10.0,thickness)
if not m*p==0.0:
yc = np.zeros(len(x))
tanTheta = np.zeros(len(x))
for i,xpt in enumerate(x):
if xpt<=p:
yc[i] = m*xpt/(p*p)*(2.0*p - xpt)
tanTheta[i] = 2.0*m/(p*p)*(p-xpt)
else:
yc[i] = m*(1.0-xpt)/((1.0-p)**2.0)*(1.0+xpt-2.0*p)
tanTheta[i] = -2.0*m/((1.0-p)**2.0)*(xpt-p)
theta = np.arctan(tanTheta)
xu = x - y*np.sin(theta)
xl = x + y*np.sin(theta)
yu = yc + y*np.cos(theta)
yl = yc - y*np.cos(theta)
self.ptsUp = np.transpose(np.vstack([xu,yu]))
self.ptsLo = np.transpose(np.vstack([xl,yl]))
else:
self.ptsUp = np.transpose(np.vstack([x,y]))
self.ptsLo = np.transpose(np.vstack([x,-y]))
self._join_coordinates()
def set_trailing_edge(self,zTEnew=0.0):
zTEcurrent = self.ptsUp[-1,1] - self.ptsLo[-1,1]
dzTE = zTEnew - zTEcurrent
ptsUpNew = self.ptsUp[:,1] + self.ptsUp[:,0]*dzTE/2.
ptsLoNew = self.ptsLo[:,1] - self.ptsLo[:,0]*dzTE/2.
self.ptsUp[:,1] = ptsUpNew
self.ptsLo[:,1] = ptsLoNew
self._join_coordinates()
self._analyze_geometry()
def get_clmax(self,velocity,altitude,flapToChord,flapDefl):
"""
analysis using javafoil since it's more robust than xfoil
with calcfoil stall model. Note that only plain flap are possible.
Parameters
----------
velocity : m/sec or Mach
airspeed
altitude : m
flapToChord : [0;1]
flap to chord ratio
flapDefl : deg
flap deflection angle.
"""
fc1 = fc.FlightConditions(velocity,altitude,1.0)
Mach = fc1.Mach
Re = fc1.Re
pol = self.get_jfoil_polar(Mach,Re,[0,20,1],'eppler',
flapChordRatio=flapToChord, flapDefl=flapDefl)
return float(pol.clmax), pol.alphaClmax
def fit_cst(self, nBPO=3):
"""
generates CST coefficients of given BPO for current airfoil.
Parameters
----------
nBPO : int
Bernstein polynomial order
"""
nvar = nBPO*2+1
# ----
def get_error(curve,pts):
sqErr = np.zeros(len(pts[:,0]))
for i,x in enumerate(pts[:,0]):
ynew = curve(x)
sqErr[i] = (ynew-pts[i,1])**2.0
return sqErr
def obj(x):
n = len(x)
if n%2==0:
Au = x[:n/2]
Al = x[n/2:]
else:
Au = np.array(x[:int(n/2)+1])
Al = np.hstack([-x[0],x[int(n/2)+1:]])
upCurve = geom.CstCurve(Au,TEgap=self.zTrailingEdge)
loCurve = geom.CstCurve(Al,TEgap=self.zTrailingEdge)
sqErrUp = get_error(upCurve,self.ptsUp)
sqErrLo = get_error(loCurve,self.ptsLo)
err = np.sum(sqErrUp) + np.sum(sqErrLo)
return err
# ----
xl = -0.5*np.ones(nvar)
xu = 0.5*np.ones(nvar)
bnds = np.vstack([xl,xu])
bnds = np.transpose(bnds)
x0 = np.zeros(nvar)
rslt = minimize(obj,x0,bounds=bnds,method='SLSQP')
xopt = rslt.x
return xopt, obj(xopt)/(len(self.pts)+1)