Source code for RCAIDE.Library.Methods.Aeroacoustics.Semi_Empirical.Turbofan.secondary_noise_component
# RCAIDE/Methods/Aeroacoustics/Semi_Empirical/Engine/secondary_noise_component.py
#
#
# Created: Jul 2023, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# Python package imports
import numpy as np
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# Secondary Noise Component
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def secondary_noise_component(Velocity_primary, theta_s, sound_ambient, Velocity_secondary, Velocity_aircraft,
Area_primary, Area_secondary, DSPL_s, EX_s, Str_s):
"""
This function calculates the noise contribution of the secondary jet component.
Parameters
----------
Velocity_primary : float
Velocity of the primary jet [m/s].
theta_s : float
Angle for the secondary jet [rad].
sound_ambient : float
Ambient sound level [dB].
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_s : float
Decibel Sound Pressure Level for the secondary jet [dB].
EX_s : float
Excess noise level for the secondary jet.
Str_s : float
Strouhal number for the secondary jet.
Returns
-------
SPL_s : float
Sound Pressure Level for the secondary jet component [dB].
Notes
-----
The function uses semi-empirical methods to calculate the noise contribution of the secondary jet component.
**Definitions**
'SPL_s'
Sound Pressure Level for the secondary 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 = 0.5 * 0.1*theta_s
# Calculation of the Source Strengh Function (FV)
FV = ((Velocity_secondary-Velocity_aircraft)/sound_ambient)**velocity_exponent *\
((Velocity_secondary+Velocity_aircraft)/sound_ambient)**(1-velocity_exponent)
# Determination of the noise model coefficients
Z1 = -18*((1.8*theta_s/np.pi)-0.6)**2
Z2 = -14-8*((1.8*theta_s/np.pi)-0.6)**3
Z3 = -0.7
Z4 = 0.6 - 0.5*((1.8*theta_s/np.pi)-0.6)**2+0.5*(0.6-np.log10(1+Area_secondary/Area_primary))
Z5 = 51 + 54*theta_s/np.pi - 9*((1.8*theta_s/np.pi)-0.6)**3
Z6 = 99 + 36*theta_s/np.pi - 15*((1.8*theta_s/np.pi)-0.6)**4 + \
5*Velocity_secondary*(Velocity_primary-Velocity_secondary)/(sound_ambient**2) + DSPL_s + EX_s
# Determination of Sound Pressure Level for the secondary jet component
SPL_s = (Z1*np.log10(FV)+Z2)*(np.log10(Str_s)-Z3*np.log10(FV)-Z4)**2 + Z5*np.log10(FV) + Z6
return SPL_s
