# The configuration file

The .conf file contains different options which specify the problem that APM will solve. The contents of an example .conf file are shown below:
c_ref = 1
b_ref = 1
S_ref = 1
x_cg = 0
y_cg = 0
z_cg = 0
trailing_edge_angle = 150
p_ref = 101325
rho_ref = 1.225
mu_ref = 1.789e-5
norm_V_ref = 1
M_ref = 0
alpha = 0
beta = 0
p = 0
q = 0
r = 0
dt = 1
N_timesteps = 1
restart_from_checkpoint = 0
wake_alignment = 0
wake_angle = 0
wake_rollup = 1
output_frequency = 1
paraview_output = 1
tecplot_output = 0
json_output = 0
 Option Dimension Description Default value c_ref ​$L$​ Reference chord, used for non-dimensionalisation of the aerodynamic coefficients 1 b_ref ​$L$​ Reference span, used for non-dimensionalisation of the aerodynamic coefficients 1 S_ref ​$L^2$​ Reference area, used for non-dimensionalisation of the aerodynamic coefficients 1 x_cg, y_cg, z_cg ​$L$​ Location of the centre of gravity 0 trailing_edge_angle - Edges sharper than the trailing edge angle in degrees are identified as trailing edges 150 p_ref ​$M/(L{\cdot}T^2)$​ Reference pressure 101325 rho_ref ​$M/L^3$​ Reference density 1.225 mu_ref ​$M/(L{\cdot}T)$​ Reference dynamic viscosity 1.789e-5 norm_V_ref ​$L/T$​ Reference freestream speed 1 M_ref - Reference Mach number (used for compressibility corrections) 0 alpha, beta - Angle of attack and angle of sideslip with respect to the freestream in degrees 0 p, q, r ​$1/T$​ Roll, pitch, and yaw rates in degrees/sec 0 dt ​$T$​ Time step 1 N_timesteps - Number of timesteps 1 restart_from_checkpoint - Instructs the solver to restart the solution from a checkpoint 0 wake_alignment, wake_angle - Specifies how the wake aligns with respect to the trailing edges 0 wake_rollup - If disabled the induced velocities from the body on the wake and on the wake iteslf wont be calculated. The wake will be translated with the reference freestream speed. 1 json_output, paraview_output, tecplot_output - Enables or disables JSON, ParaView, and Tecplot output 0 doublet_gradient_scheme - Instructs the solver how to calculate the doublet gradient​ 0 neighbour_tolerance - Specifies the neighbour tolerance criteria 1e-6 tip_panels - Instructs the solver to label specific panels as type 6 Empty symmetry - Enables symmetry across the x-y plane. The solutions 2x faster and the memory requirements are 2x lower. 0