xfoil_interface.py

import subprocess as sp
import pandas as pd
import os

def get_curve_com_default(Rey, a1, a2, astep, afile = 'airfoils\\airfoil.txt', timeout = 5, \
    xfoilpath = 'xfoil.exe', itr = 250, M = 0):

    if Rey == 0:
        return [], [], []
    
    if a1*a2 < 0:
        a_list1, cl_list1, cd_list1 = get_curve_com_default(Rey, 0, a1, -astep, afile = afile, timeout = timeout, xfoilpath = xfoilpath, itr = itr, M = M)
        a_list2, cl_list2, cd_list2 = get_curve_com_default(Rey, 0, a2, astep, afile = afile, timeout = timeout, xfoilpath = xfoilpath, itr = itr, M = M)
        if len(a_list1) > 0:
            a_list1.pop(0)
            cl_list1.pop(0)
            cd_list1.pop(0)
        a_list1.reverse()
        cl_list1.reverse()
        cd_list1.reverse()
        a_list1.extend(a_list2)
        cl_list1.extend(cl_list2)
        cd_list1.extend(cd_list2)
        return a_list1, cl_list1, cd_list1

    ps = sp.Popen(xfoilpath, universal_newlines = True, stdin = sp.PIPE, stdout = sp.PIPE)

    try:
        output, _ = ps.communicate(input = f'plop\ng f\n\nload {afile}\n\noper\niter {itr}\nvisc {Rey}\nM {M}\naseq {a1} {a2} {astep}\n\n\n\nquit \n', timeout = timeout) 
    except: 
        ps.kill()
    list = output.split()
    i = 0
    id_remember = 0
    cl_list = []
    cd_list = []
    a_list = []
    length = len(list)
    for i in range(length):
        if list[i].lower() == "cl":
            cl = list[i + 2]
        if list[i].lower() == "cd":
            cd = list[i + 2]
        if list[i].lower() == "a":
            a = list[i + 2]
        
        if id_remember < itr:
            skip = False

        if list[i].lower() == "rms:":
            if (id_remember >= itr) and (not skip):
                skip = True
            elif (int(list[i - 1]) < id_remember) and (not skip):
                try:
                    a_list.append(float(a))
                    cl_list.append(float(cl))
                    cd_list.append(float(cd))
                except:
                    pass
                skip = True
            id_remember = int(list[i - 1])
        
        if (i == len(list) - 1) and (id_remember < itr):
            try:
                a_list.append(float(a))
                cl_list.append(float(cl))
                cd_list.append(float(cd))
            except:
                pass
    try:
        ps.kill()
        return a_list, cl_list, cd_list
    except:
        ps.kill()
        return [], [], []

def GetXfoilCurves(Reynolds, Mach, Ncrit, InitialAlpha_deg, FinalAlpha_deg, AlphaStep_deg, AirfoilFile):
    Timeout_s = 25
    OutputFile = "XfoilOutput.txt"

    try:
        os.remove(OutputFile)
    except:
        pass
    
    if (InitialAlpha_deg*FinalAlpha_deg < 0):
        AlphaList1, ClList1, CdList1, CmList1 = GetXfoilCurves(Reynolds, Mach, Ncrit, 0, InitialAlpha_deg, -AlphaStep_deg, AirfoilFile)
        AlphaList2, ClList2, CdList2, CmList2 = GetXfoilCurves(Reynolds, Mach, Ncrit, 0, FinalAlpha_deg, AlphaStep_deg, AirfoilFile)
        if (len(AlphaList1) > 0) and (len(AlphaList2) > 0) and (AlphaList1[0] == AlphaList2[0]):
            AlphaList1.pop(0)
            ClList1.pop(0)
            CdList1.pop(0)
            CmList1.pop(0)
        AlphaList1.reverse()
        ClList1.reverse()
        CdList1.reverse()
        CmList1.reverse()
        AlphaList1.extend(AlphaList2)
        ClList1.extend(ClList2)
        CdList1.extend(CdList2)
        CmList1.extend(CmList2)
        return AlphaList1, ClList1, CdList1, CmList1
    
    XfoilCommand = f'plop\ng f\n\nload {AirfoilFile}\n\noper\nvpar\nn {Ncrit}\n\niter 250\nvisc {Reynolds}\nM {Mach}\n'
    if InitialAlpha_deg != 0:
        XfoilCommand += f'aseq 0 {InitialAlpha_deg} 1\n'
    XfoilCommand += f'pacc\n{OutputFile}\n\naseq {InitialAlpha_deg} {FinalAlpha_deg} {AlphaStep_deg}\n\n\n\nquit\n'
    
    SubProcess = sp.Popen("xfoil.exe", universal_newlines = True, stdin = sp.PIPE, stdout = sp.PIPE)
    try:
        Output, _ = SubProcess.communicate(XfoilCommand, timeout = Timeout_s)
    except:
        pass
    SubProcess.kill()
    Dataframe = pd.read_csv(OutputFile, header=5, delim_whitespace=True)

    AlphaList = [float(Placeholder) for Placeholder in list(Dataframe['alpha'])[1:]]
    ClList = [float(Placeholder) for Placeholder in list(Dataframe['CL'])[1:]]
    CdList = [float(Placeholder) for Placeholder in list(Dataframe['CD'])[1:]]
    CmList = [float(Placeholder) for Placeholder in list(Dataframe['CM'])[1:]]

    try:
        os.remove(OutputFile)
    except:
        pass

    return AlphaList, ClList, CdList, CmList