small script that runs XFOIL to generate polars

src/airfoil_data/calc_polar.py

+# -*- coding: utf-8 -*-
+
+import numpy as np
+from xfoil import calc_polar
+
+NACA = "0021"
+REYNOLDS = [re * 1000000 for re in [0.02, 0.1, 0.2, 0.5, 1, 2, 5, 10]]
+
+
+for re in REYNOLDS:
+    
+    filename = f"polar_{re}.txt"
+    
+    calc_polar(NACA, re, filename, alfaseq= np.arange(-20,30,0.5), clseq=[], refine=False, max_iter=500, n=None)

src/airfoil_data/xfoil.py

+# -*- coding: utf-8 -*-
+
+import os
+import numpy as np
+import subprocess as sp
+import re
+
+
+def polar(afile, re, *args,**kwargs):
+    """calculate airfoil polar and load results
+    
+    Parameters
+    ----------
+    afile: string
+        path to aifoil dat file
+    re: float
+        fixed reynoldsnumber for polar calculation
+    *args, **kwargs
+        have a look at calcpolar for further information
+        
+    Returns
+    -------
+    dict
+        airfoil polar
+    """
+    calc_polar(afile, re,'polar.txt', *args, **kwargs)
+    data = read_polar('polar.txt')
+    delete_polar('polar.txt')
+    return data
+
+
+def calc_polar(afile, re, polarfile, alfaseq=[], clseq=[], refine=False, max_iter=200, n=None):
+    """run xfoil to generate polar file
+    
+    Parameters
+    ----------
+    afile: string
+        path to airfoil dat file
+    re: float
+        fixed reynoldsnumber
+    alfaseq: iterateable, optional
+        sequence of angles of attack
+    clseq: iterateable, optional
+        sequence of lift coefficients (either those or alfaseq must be defined)
+    refine: bool
+        shall xfoil refine airfoil
+    maxiter: int
+        maximal number of boundary layer iterations
+    n: int
+        boundary layer parameter
+    """
+    
+    import subprocess as sp
+    import numpy as np
+    import sys,os
+    
+    if(os.name == 'posix'):
+        xfoilbin = 'xfoil'
+    elif(os.name == 'nt'):
+        xfoilbin = 'xfoil.exe'
+    else:
+        print('Betriebssystem %s wird nicht unterstützt'%os.name)   
+    
+    
+    pxfoil = sp.Popen([xfoilbin], stdin=sp.PIPE, stdout=None, stderr=None)
+    
+    def write2xfoil(string):
+        if(sys.version_info > (3,0)):
+            string = string.encode('ascii')
+            
+        pxfoil.stdin.write(string)
+        
+    if(afile.isdigit()):
+        write2xfoil('NACA ' + afile + '\n')
+    else:
+        write2xfoil('LOAD ' + afile + '\n')
+        
+        if(refine):
+            write2xfoil('GDES\n')
+            write2xfoil('CADD\n')
+            write2xfoil('\n')
+            write2xfoil('\n')
+            write2xfoil('\n')
+            write2xfoil('X\n ')
+            write2xfoil('\n')
+            write2xfoil('PANEL\n')
+
+    write2xfoil('OPER\n')
+    if n != None:
+        write2xfoil('VPAR\n')
+        write2xfoil('N '+str(n)+'\n')
+        write2xfoil('\n')
+    write2xfoil('ITER '+str(max_iter)+'\n')
+    write2xfoil('VISC\n')
+    write2xfoil(str(re) + '\n')
+    write2xfoil('PACC\n')
+    write2xfoil('\n')
+    write2xfoil('\n')
+    for alfa in alfaseq:
+        write2xfoil('A ' + str(alfa) + '\n')
+    for cl in clseq:
+        write2xfoil('CL ' + str(cl) + '\n')
+    write2xfoil('PWRT 1\n')
+    write2xfoil(polarfile + '\n')
+    write2xfoil('\n')
+
+    pxfoil.communicate(str('quit').encode('ascii'))
+
+def read_polar(infile):
+    """read xfoil polar results from file
+    
+    Parameters
+    ----------
+    infile: string
+        path to polar file
+     
+    Returns
+    -------
+    dict
+        airfoil polar splitted up into dictionary
+    """
+    
+    regex = re.compile('(?:\s*([+-]?\d*.\d*))')
+    
+    with open(infile) as f:
+        lines = f.readlines()
+        
+        a           = []
+        cl          = []
+        cd          = []
+        cdp         = []
+        cm          = []
+        xtr_top     = []
+        xtr_bottom  = []
+        
+        
+        for line in lines[12:]:
+            linedata = regex.findall(line)
+            a.append(float(linedata[0]))
+            cl.append(float(linedata[1]))       
+            cd.append(float(linedata[2]))
+            cdp.append(float(linedata[3]))
+            cm.append(float(linedata[4]))
+            xtr_top.append(float(linedata[5]))
+            xtr_bottom.append(float(linedata[6]))
+            
+        data = {'a': np.array(a), 'cl': np.array(cl) , 'cd': np.array(cd), 'cdp': np.array(cdp),
+             'cm': np.array(cm), 'xtr_top': np.array(xtr_top), 'xtr_bottom': np.array(xtr_bottom)}
+        
+        return data
+
+
+def delete_polar(infile):
+    """ deletes polar file """
+    os.remove(infile)
+