Source code for RCAIDE.Library.Methods.Aerodynamics.Common.Drag.compressible_mixed_flat_plate
# ----------------------------------------------------------------------
# Imports
# ----------------------------------------------------------------------
# package imports
import numpy as np
# ----------------------------------------------------------------------
# Compressible Mixed Flat Plate
# ----------------------------------------------------------------------
[docs]
def compressible_mixed_flat_plate(Re,Ma,Tc,xt):
"""Computes the coefficient of friction for a flat plate given the
input parameters. Also returns the correction terms used in the
computation.
Assumptions:
Reynolds number between 10e5 and 10e9
xt between 0 and 1
Source:
adg.stanford.edu (Stanford AA241 A/B Course Notes)
Inputs:
Re (Reynolds number) [Unitless]
Ma (Mach number) [Unitless]
Tc (temperature) [K]
xt (turbulent transition point as a proportion of chord length) [Unitless]
Outputs:
cf_comp (coefficient of friction) [Unitless]
k_comp (compressibility correction) [Unitless]
k_reyn (Reynolds number correction) [Unitless]
Properties Used:
N/A
"""
if xt < 0.0 or xt > 1.0:
raise ValueError("Turbulent transition must be between 0 and 1")
Rex = Re*xt
Rex[Rex==0.0] = 0.0001
theta = 0.671*xt/(Rex**0.5)
xeff = (27.78*theta*Re**0.2)**1.25
Rext = Re*(1-xt+xeff)
cf_turb = 0.455/(np.log10(Rext)**2.58)
cf_lam = 1.328/(Rex**0.5)
if xt > 0.0:
cf_start = 0.455/(np.log10(Re*xeff)**2.58)
else:
cf_start = 0.0
cf_inc = cf_lam*xt + cf_turb*(1-xt+xeff) - cf_start*xeff
# compressibility correction
Tw = Tc * (1. + 0.178*Ma*Ma)
Td = Tc * (1. + 0.035*Ma*Ma + 0.45*(Tw/Tc - 1.))
k_comp = (Tc/Td)
# reynolds correction
Rd_w = Re * (Td/Tc)**1.5 * ( (Td+216.) / (Tc+216.) )
k_reyn = (Re/Rd_w)**0.2
# apply corrections
cf_comp = cf_inc * k_comp * k_reyn
return cf_comp, k_comp, k_reyn
