Examples

These examples show how to use Xfoil.jl.

• Examples
• • Manual Angle of Attack Sweep
  • Automatic Angle of Attack Sweep

Manual Angle of Attack Sweep

This first example shows how to manually perform an angle of attack sweep.

using Xfoil, Printf

# read airfoil into XFOIL
open("naca2412.dat", "r") do f
    x = Float64[]
    y = Float64[]
    for line in eachline(f)
        entries = split(chomp(line))
        push!(x, parse(Float64, entries[1]))
        push!(y, parse(Float64, entries[2]))
    end
    Xfoil.set_coordinates(x,y)
end

# repanel using XFOIL's `PANE` command
Xfoil.pane()

# set operating conditions
alpha = -10:1:10
re = 1e5
mach = 0.0

# initialize outputs
n_a = length(alpha)
c_l = zeros(n_a)
c_d = zeros(n_a)
c_dp = zeros(n_a)
c_m = zeros(n_a)
converged = zeros(Bool, n_a)
for i = 1:n_a
    c_l[i], c_d[i], c_dp[i], c_m[i], converged[i] = Xfoil.solve_alpha(alpha[i], re; mach, iter=100)
end

# print results
println("Angle\t\tCl\t\tCd\t\tCm\t\tConverged")
for i = 1:n_a
  @printf("%8f\t%8f\t%8f\t%8f\t%d\n",alpha[i],c_l[i],c_d[i],c_m[i],converged[i])
end

Angle		Cl		Cd		Cm		Converged
-10.000000	-0.464031	0.108164	-0.021557	1
-9.000000	-0.466796	0.093346	-0.026590	1
-8.000000	-0.521766	0.076927	-0.033820	1
-7.000000	-0.635832	0.034981	-0.035654	1
-6.000000	-0.568476	0.027869	-0.029951	1
-5.000000	-0.484882	0.023137	-0.026257	1
-4.000000	-0.395129	0.020376	-0.023719	1
-3.000000	-0.306835	0.018702	-0.021919	1
-2.000000	-0.144444	0.017012	-0.032525	1
-1.000000	0.084503	0.017323	-0.052484	1
0.000000	0.273953	0.016614	-0.068255	1
1.000000	0.406827	0.015799	-0.070669	1
2.000000	0.511046	0.015537	-0.066991	1
3.000000	0.608250	0.015873	-0.062339	1
4.000000	0.707389	0.016509	-0.058131	1
5.000000	0.802921	0.017368	-0.053541	1
6.000000	0.893771	0.018322	-0.048318	1
7.000000	0.975327	0.019445	-0.041884	1
8.000000	1.034578	0.022188	-0.033045	1
9.000000	1.085745	0.027443	-0.024469	1
10.000000	1.156664	0.033658	-0.019314	1

Suppose we want to find the derivative of c_l, c_d, and c_m with respect to alpha at the same angles of attack. One approach to calculate these derivatives would be to use the finite difference method.

using Xfoil, Printf

# read airfoil into XFOIL
open("naca2412.dat", "r") do f
    x = Float64[]
    y = Float64[]
    for line in eachline(f)
        entries = split(chomp(line))
        push!(x, parse(Float64, entries[1]))
        push!(y, parse(Float64, entries[2]))
    end
    Xfoil.set_coordinates(x,y)
end

# repanel using XFOIL's `PANE` command
Xfoil.pane()

# set operating conditions
alpha = -10:1:10
re = 1e5
mach = 0.0

# set step size
h = 1e-6

# initialize outputs
n_a = length(alpha)
c_l_a = zeros(n_a)
c_d_a = zeros(n_a)
c_dp_a = zeros(n_a)
c_m_a = zeros(n_a)
converged = zeros(Bool, n_a)

for i = 1:n_a
    c_l1, c_d1, c_dp1, c_m1, converged[i] = Xfoil.solve_alpha(alpha[i], re; mach, iter=100)
    c_l2, c_d2, c_dp2, c_m2, converged[i] = Xfoil.solve_alpha(alpha[i]+h, re; mach, iter=100)
    c_l_a[i] = (c_l2 - c_l1)/h * 180/pi
    c_d_a[i] = (c_d2 - c_d1)/h * 180/pi
    c_m_a[i] = (c_m2 - c_m1)/h * 180/pi
end

# print results
println("Angle\t\tdClda\t\tdCdda\t\tdCmda\t\tConverged")
for i = 1:n_a
  @printf("%8f\t%8f\t%8f\t%8f\t%d\n",alpha[i],c_l_a[i],c_d_a[i],c_m_a[i],converged[i])
end

Angle		dClda		dCdda		dCmda		Converged
-10.000000	3.779719	-0.604610	0.342606	1
-9.000000	2.626080	-0.687377	0.207316	1
-8.000000	1.006273	-0.792112	0.301047	1
-7.000000	2.642149	-0.399279	0.532187	1
-6.000000	4.343322	-0.211069	0.375840	1
-5.000000	5.022881	-0.158689	0.205753	1
-4.000000	5.134982	-0.084520	0.150924	1
-3.000000	5.158002	-0.019555	0.078398	1
-2.000000	9.126479	-0.035567	-0.320871	1
-1.000000	10.271401	-0.023298	-0.912901	1
0.000000	12.325168	-0.091335	-1.041678	1
1.000000	8.742740	-0.089399	-0.226087	1
2.000000	3.010501	0.095911	0.575110	1
3.000000	6.005368	0.009855	0.220494	1
4.000000	3.444125	0.110609	0.458157	1
5.000000	6.530404	0.033534	0.153271	1
6.000000	4.517164	0.061409	0.380156	1
7.000000	4.538258	0.086789	0.398239	1
8.000000	2.098868	0.317527	0.617265	1
9.000000	3.166303	0.322161	0.398941	1
10.000000	3.873508	0.340185	0.341636	1

A better approach might be to use the complex step method.

using Xfoil, Printf

# read airfoil into XFOIL
open("naca2412.dat", "r") do f
    x = Float64[]
    y = Float64[]
    for line in eachline(f)
        entries = split(chomp(line))
        push!(x, parse(Float64, entries[1]))
        push!(y, parse(Float64, entries[2]))
    end
    Xfoil.set_coordinates_cs(x,y)
end

# repanel using XFOIL's `PANE` command
Xfoil.pane_cs()

# set operating conditions
alpha = -10:1:10
re = 1e5
mach = 0.0

# set step size
h = 1e-20im

# initialize outputs
n_a = length(alpha)
c_l_a = zeros(n_a)
c_d_a = zeros(n_a)
c_dp_a = zeros(n_a)
c_m_a = zeros(n_a)
converged = zeros(Bool, n_a)

for i = 1:n_a
    c_l, c_d, c_dp, c_m, converged[i] = Xfoil.solve_alpha_cs(alpha[i]+h, re; mach, iter=100)
    c_l_a[i] = imag(c_l)/imag(h) * 180/pi
    c_d_a[i] = imag(c_d)/imag(h) * 180/pi
    c_m_a[i] = imag(c_m)/imag(h) * 180/pi
end

# print results
println("Angle\t\tdClda\t\tdCdda\t\tdCmda\t\tConverged")
for i = 1:n_a
  @printf("%8f\t%8f\t%8f\t%8f\t%d\n",alpha[i],c_l_a[i],c_d_a[i],c_m_a[i],converged[i])
end

Angle		dClda		dCdda		dCmda		Converged
-10.000000	3.836778	-0.606239	0.338542	1
-9.000000	-308.222983	-90.101663	30.291607	1
-8.000000	1.015039	-0.792379	0.301010	1
-7.000000	2.646253	-0.399401	0.531807	1
-6.000000	4.350507	-0.211193	0.374933	1
-5.000000	5.032753	-0.158907	0.204315	1
-4.000000	5.147571	-0.084773	0.148990	1
-3.000000	5.174246	-0.019851	0.075819	1
-2.000000	9.134179	-0.035749	-0.321986	1
-1.000000	10.271136	-0.023432	-0.912764	1
0.000000	12.326638	-0.091378	-1.041800	1
1.000000	8.744871	-0.089444	-0.226340	1
2.000000	3.012825	0.095849	0.574821	1
3.000000	6.007896	0.009783	0.220178	1
4.000000	3.446835	0.110536	0.457792	1
5.000000	6.534067	0.033438	0.152758	1
6.000000	4.521577	0.061297	0.379486	1
7.000000	4.544736	0.086650	0.397209	1
8.000000	2.108494	0.317512	0.615544	1
9.000000	3.184692	0.322179	0.395689	1
10.000000	3.899871	0.340231	0.337307	1

Automatic Angle of Attack Sweep

For performing angle of attack sweeps, the function alpha_sweep may also be used.

using Xfoil, Printf

# extract geometry
x = Float64[]
y = Float64[]

f = open("naca2412.dat", "r")

for line in eachline(f)
    entries = split(chomp(line))
    push!(x, parse(Float64, entries[1]))
    push!(y, parse(Float64, entries[2]))
end

close(f)

# set operating conditions
alpha = -10:1:10
re = 1e5

c_l, c_d, c_dp, c_m, converged = Xfoil.alpha_sweep(x, y, alpha, re, iter=100, zeroinit=false, printdata=true)

Angle		Cl		Cd		Cm		Converged
-10.000000	-0.464031	0.108164	-0.021557	1
-9.000000	-0.466796	0.093346	-0.026590	1
-8.000000	-0.521766	0.076927	-0.033820	1
-7.000000	-0.635832	0.034981	-0.035654	1
-6.000000	-0.568476	0.027869	-0.029951	1
-5.000000	-0.484882	0.023137	-0.026257	1
-4.000000	-0.395129	0.020376	-0.023719	1
-3.000000	-0.306835	0.018702	-0.021919	1
-2.000000	-0.144444	0.017012	-0.032525	1
-1.000000	0.084503	0.017323	-0.052484	1
0.000000	0.273953	0.016614	-0.068255	1
1.000000	0.406827	0.015799	-0.070669	1
2.000000	0.511046	0.015537	-0.066991	1
3.000000	0.608250	0.015873	-0.062339	1
4.000000	0.707389	0.016509	-0.058131	1
5.000000	0.802921	0.017368	-0.053541	1
6.000000	0.893771	0.018322	-0.048318	1
7.000000	0.975327	0.019445	-0.041884	1
8.000000	1.034578	0.022188	-0.033045	1
9.000000	1.085745	0.027443	-0.024469	1
10.000000	1.156664	0.033658	-0.019314	1

A version of alpha_sweep has also been implemented for use with the complex step version of XFOIL.

using Xfoil, Printf

# extract geometry
x = Float64[]
y = Float64[]

f = open("naca2412.dat", "r")

for line in eachline(f)
    entries = split(chomp(line))
    push!(x, parse(Float64, entries[1]))
    push!(y, parse(Float64, entries[2]))
end

close(f)

# set operating conditions
alpha = -10:1:10
re = 1e5
mach = 0.0

# set step size
h = 1e-20im

c_l, c_d, c_dp, c_m, converged = Xfoil.alpha_sweep_cs(x, y, alpha .+ h,
    re, mach=mach, iter=100, zeroinit=false, printdata=true)

println("Angle\t\tdClda\t\tdCdda\t\tdCmda\t\tConverged")
for i = 1:length(alpha)
    @printf("%8f\t%8f\t%8f\t%8f\t%d\n", alpha[i], imag(c_l[i])/imag(h)*180/pi, imag(c_d[i])/imag(h)*180/pi, imag(c_m[i])/imag(h)*180/pi, converged[i])
end

Angle		Cl		Cd		Cm		Converged
-10.000000	-0.464031	0.108164	-0.021557	1
-9.000000	-0.466796	0.093346	-0.026590	1
-8.000000	-0.521766	0.076927	-0.033820	1
-7.000000	-0.635832	0.034981	-0.035654	1
-6.000000	-0.568476	0.027869	-0.029951	1
-5.000000	-0.484882	0.023137	-0.026257	1
-4.000000	-0.395129	0.020376	-0.023719	1
-3.000000	-0.306835	0.018702	-0.021919	1
-2.000000	-0.144444	0.017012	-0.032525	1
-1.000000	0.084503	0.017323	-0.052484	1
0.000000	0.273953	0.016614	-0.068255	1
1.000000	0.406827	0.015799	-0.070669	1
2.000000	0.511046	0.015537	-0.066991	1
3.000000	0.608250	0.015873	-0.062339	1
4.000000	0.707389	0.016509	-0.058131	1
5.000000	0.802921	0.017368	-0.053541	1
6.000000	0.893771	0.018322	-0.048318	1
7.000000	0.975327	0.019445	-0.041884	1
8.000000	1.034578	0.022188	-0.033045	1
9.000000	1.085745	0.027443	-0.024469	1
10.000000	1.156664	0.033658	-0.019314	1
Angle		dClda		dCdda		dCmda		Converged
-10.000000	3.836778	-0.606239	0.338542	1
-9.000000	-308.222983	-90.101663	30.291607	1
-8.000000	1.015039	-0.792379	0.301010	1
-7.000000	2.646253	-0.399401	0.531807	1
-6.000000	4.350507	-0.211193	0.374933	1
-5.000000	5.032753	-0.158907	0.204315	1
-4.000000	5.147571	-0.084773	0.148990	1
-3.000000	5.174246	-0.019851	0.075819	1
-2.000000	9.134179	-0.035749	-0.321986	1
-1.000000	10.271136	-0.023432	-0.912764	1
0.000000	12.326638	-0.091378	-1.041800	1
1.000000	8.744871	-0.089444	-0.226340	1
2.000000	3.012825	0.095849	0.574821	1
3.000000	6.007896	0.009783	0.220178	1
4.000000	3.446835	0.110536	0.457792	1
5.000000	6.534067	0.033438	0.152758	1
6.000000	4.521577	0.061297	0.379486	1
7.000000	4.544736	0.086650	0.397209	1
8.000000	2.108494	0.317512	0.615544	1
9.000000	3.184692	0.322179	0.395689	1
10.000000	3.899871	0.340231	0.337307	1