Source code for RCAIDE.Library.Methods.Aeroacoustics.Semi_Empirical.Turbofan.ground_proximity_effect
# RCAIDE/Methods/Aeroacoustics/Semi_Empirical/Engine/external_plug_effect.py
#
#
# Created: Jul 2023, M. Clarke
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# IMPORT
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# Python package imports
import numpy as np
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# Ground Proximity Effect
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[docs]
def ground_proximity_effect(Velocity_mixed, sound_ambient, theta_m, engine_height, Diameter_mixed, frequency):
"""
This function calculates the ground proximity effect, in decibels, for full-scale engine test stands.
Parameters
----------
Velocity_mixed : float
Velocity of the mixed jet [m/s].
sound_ambient : float
Ambient sound level [SPL].
theta_m : float
Angle for the mixed jet [rad].
engine_height : float
Height of the engine above the ground [m].
Diameter_mixed : float
Diameter of the mixed jet [m].
frequency : float
Frequency of the sound wave [1/s].
Returns
-------
GPROX_m : float
Ground proximity effect adjustment for the mixed jet [dB].
Notes
-----
The function assumes that the ground proximity effect is significant for the mixed jet component and calculates the noise adjustments accordingly.
**Definitions**
'GPROX_m'
Ground Proximity Effect, the adjustment in decibels due to the proximity of the ground.
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)
"""
# Ground proximity is applied only for the mixed jet component
GPROX_m = (5*Velocity_mixed/sound_ambient)*np.exp(-(9*(theta_m/np.pi)-6.75)**2- \
((engine_height/Diameter_mixed)-2.5)**2)*(1+(np.sin((np.pi*engine_height*frequency/sound_ambient)-np.pi/2))**2)/ \
(2+np.abs((engine_height*frequency/sound_ambient)-1))
return GPROX_m
