Source code for RCAIDE.Library.Methods.Aeroacoustics.Semi_Empirical.Turbofan.mixed_noise_component
# RCAIDE/Methods/Aeroacoustics/Semi_Empirical/Engine/mixed_noise_component.py
#
#
# Created: Jul 2023, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# Python package imports
import numpy as np
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# Mixed Noise Component
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def mixed_noise_component(Velocity_primary, theta_m, sound_ambient, Velocity_secondary,
Velocity_aircraft, Area_primary, Area_secondary, DSPL_m, EX_m, Str_m, Velocity_mixed, XBPR):
"""
This function calculates the noise contribution of the mixed jet component.
Parameters
----------
Velocity_primary : float
Velocity of the primary jet [m/s].
theta_m : float
Angle for the mixed jet [rad].
sound_ambient : float
Ambient sound level [SPL].
Velocity_secondary : float
Velocity of the secondary jet [m/s].
Velocity_aircraft : float
Velocity of the aircraft [m/s].
Area_primary : float
Area of the primary jet [m^2].
Area_secondary : float
Area of the secondary jet [m^2].
DSPL_m : float
Decibel Sound Pressure Level for the mixed jet [SPL].
EX_m : float
Excess noise level for the mixed jet.
Str_m : float
Strouhal number for the mixed jet.
Velocity_mixed : float
Velocity of the mixed jet [m/s].
XBPR : float
Bypass ratio adjustment factor.
Returns
-------
SPL_m : float
Sound Pressure Level for the mixed jet component [dB].
Notes
-----
The function uses semi-empirical methods to calculate the noise contribution of the mixed jet component.
**Definitions**
'SPL_m'
Sound Pressure Level for the mixed jet component.
References
----------
[1] SAE ARP876D: Gas Turbine Jet Exhaust Noise Prediction (original)
[2] de Almeida, Odenir. "Semi-empirical methods for coaxial jet noise prediction." (2008). (adapted)
"""
#Calculation of the velocity exponent
velocity_exponent = (Velocity_mixed/sound_ambient)**0.5*(0.6+(0.2/(0.2+Str_m) * \
np.exp(-0.3*(theta_m+(Str_m/(1+Str_m))-2.7)**2)))
#Calculation of the Source Strengh Function (FV)
FV = ((Velocity_mixed-Velocity_aircraft)/sound_ambient)**velocity_exponent * \
((Velocity_mixed+Velocity_aircraft)/sound_ambient)**(1-velocity_exponent)
#Determination of the noise model coefficients
Z1 = -30*((1.8*theta_m/np.pi)-0.6)**2
Z2 = -9 -4*((Velocity_primary-Velocity_secondary)/sound_ambient)-38*((1.8*theta_m/np.pi)-0.6)**3 + \
30*(0.6-np.log10(1+Area_secondary/Area_primary))*(1.8*theta_m/np.pi - 0.6)
Z3 = 1-0.4*((1.8*theta_m/np.pi)-0.6)**2
Z4 = 0.44-0.5/np.exp(((4.5*theta_m/np.pi)-4)**2) + 0.2*Velocity_primary/sound_ambient - \
0.7*Velocity_mixed/sound_ambient - 0.2*np.log10((1+Area_secondary)/Area_primary) + \
0.05*(XBPR)*np.exp(-5*(theta_m-2.4)**2)
Z5 = 34 + 81*theta_m/np.pi - 20*((1.8*theta_m/np.pi)-0.6)**3
Z6 = 108 + 37.8*theta_m/np.pi + 5*Velocity_mixed*(Velocity_primary-Velocity_secondary)/(sound_ambient**2) - \
np.exp(-5*(theta_m-1.8)**2) + 7*Velocity_mixed/sound_ambient*(1-0.4*(Velocity_primary/sound_ambient) * \
np.exp(-0.7*np.abs(Str_m-0.8))) / np.exp(8*(theta_m-2.4)**2) + 0.8*(XBPR)*np.exp(theta_m-2.3-Velocity_mixed/sound_ambient) + \
DSPL_m + EX_m
#Determination of Sound Pressure Level for the mixed jet component
SPL_m = (Z1*np.log10(FV)+Z2)*(np.log10(Str_m)-Z3*np.log10(FV)-Z4)**2 + Z5*np.log10(FV) + Z6
return SPL_m
