CHOICE - CHalmers nOIse CodE

An aircraft noise prediction framework based on empirical and semi-empirical methods found in public literature. The code is able to predict the noise at the source (aircraft) and at the certification points on the ground (so far for 2D propagation only).

If you use this framework in your work, we would kindly ask you to help us by citing CHOICE. Please use the following paper where CHOICE is described in detail and validated against noise measurements:

Thoma, E. M., Grönstedt, T., Otero, E., and Zhao, X., "Assessment of an Open-Source Aircraft Noise Prediction Model Using Approach Phase Measurements", Journal of Aircraft, 2023, https://doi.org/10.2514/1.C037332

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How to install the library

1. Download or clone the repository
2. (Optional) Create and activate a virtual environment. The following commands can be used in Anaconda prompt:

   conda create -n env_choice python==3.8
   conda activate env_choice
   

3. Navigate to the downloaded repository path (CHOICE library folder) and run the following commands in order to install all package requirements and dependencies:

   pip install -r requirements.txt
   python setup.py install
   

How to use CHOICE

A sample script to run choice is provided in main.py. Below a step-by-step guide:

1. Import the library:

   from choice import CHOICE
   

2. Set input file names and input and output folder path (absolute or relative). If they ar not provided, default names are used.

   #  Input files folder path
   input_folder = 'Input/'
   #  Output folder path and file type for noise source matrices
   output_folder = 'Output/'
   file_type = 'csv'
   #  Specify input files
   perf_file = 'performanceResults.txt'
   weight_file = 'weightAircraft.txt'
   noise_file = 'inputNoise.txt'
   

3. Instantiate a CHOICE object

   noise = CHOICE(input_folder, output_folder, perf_file, weight_file, noise_file, file_type)
   

4. Run choice

   noise.run_choice()
   

Input files:

The following files are required as input to CHOICE

inputNoise.txt --> The noise study cases are defined

• point: specify the noise certification point e.g. Approach, Cutback or Sideline
• trajectory_performance: true/false. If set to true, files for trjectory data should be provided e.g. Approach_airframe_performnce.txt. If set to false a single point performance study is perfomed using the performanceResults.txt
• use_trajectory_preparser: true/false. If set to true, the input trajectory performance files are processed to remove empty lines or zero velocity of aircraft at early or late points
• generate_noise_sources: true/false. If set to true, a 3D matrix (frequencies x directivities x trajectory points) is generated for every noise component.
• plot_source_spectra: true/false. If set to true, the total aircraft and the airframe source noise spectra are plotted.
• directivity_angle_to_plot: longitudinal directivity angle for which to plot the source spectra in deg.
• use_ground_reflection: true/false. If set to true, ground reflection is included in the propagation effects.
• use_spherical_spreading: true/false. If set to true, spherical spreading is included in the propagation effects.
• use_atmospheric_attenuation: true/false. If set to true, atmospheric absorption is included in the propagation effects.
• use_suppression_factor: true/false. If set to true, noise suppression is applied on certain components. Values should be provided on a later instance.
• no_engines: number of engines on the aircraft.
• type_nozzles: separate/mix. To define separate or mix exhaust nozzles.
• modules: specify for which components to calculate, e.g. Fan Lpc Comb Lpt cold_nozzle (Airframe is always included)
• xmic: distance of microphone from the landing point, along the runway path.
• ymic: microphone height from ground.
• zmic: lateral distance from runway.
• dt_mic: time step for the prediction of noise at the receiver. For prediction of noise in certification points 0.5 s should be used.
• ground_elevation: ground elevation at receiver location in m.
• dtIsa: deviation from ISA temperature.
• engine_height: engine height when the aircraft is on the ground in m.
• aircraft_mass: mass of aircraft in kg.
• wing_area: wing area in m**2.
• wing_span: wing span in m.
• horizontal_tail_area: horizontal tail area in m**2.
• horizontal_tail_span: horizontal tail span in m.
• vertical_tail_area: vertical tail area in m**2.
• vertical_tail_span: vertical tail span m.
• jet_aircraft_coef: constant value (in dB) that should be added to the clean wing noise prediction. According to the litterature, it shoud be 0 for aerodynamically clean sailplanes, 6 for most jet aircraft and 8 for conventional low-speed aircraft.
• noFlaps: number of flap elements.
• flap_area: flap area of each flap element. If noFlaps = 1 the total flap area should be used.
• flap_span: flap span of each flap element. If noFlaps = 1 the total flap span should be used.
• flap_type: 1slot/2slot/3slot for single, double anf tripple slotted flaps respectively.
• leading_edge_type: slat/flap for slats or leading edge flaps.
• LandingGear_vec: 0/1 for retracted or extended.
• noLG: number of landing gears.
• d_wheel: wheel diameter for each landing gear in m.
• d_strut: typical strut diameter for each landing gear in m.
• d_wire: typical wire or hydraulic pipe diameter for each landing gear in m.
• Nwheels: number of wheels on each landing gear.
• Nstruts: number of main struts on each landing gear.
• comb_ign_nozzles: ignitted nozzles for SAC (Single Annular Combustor).
• dac_nozzle_pattern: nozzle firing pattern for DAC (Dual Annular Combustor). Can be 40/30/22.5/20, see relevant literature for more information.
• fan_distortion: 0/1 to not account or account for distortion at the fan.
• ff_distortion: 0/1 to not account or account for distortion at the fan.
• fuselage_fan: false/true if fuselage fan exists or doesn't exist.
• defl_flap: flap deflection angle in rad.
• defl_slat: slat deflection angle in rad.
• fan_inlet_suppression: noise suppression constant for fan inlet.
• fan_dis_suppression: noise suppression constant for fan inlet.
• lpt_suppression: noise suppression constant for fan inlet.

weightAircraft.txt --> Engine sizing data. Metric system is used

• GBX_ratio: gear box ratio. If the engine is direct driven, set this parameter to 1.0.
• FanR1BDiaOuter: fan outer diameter.
• FanA2: fan annulus area.
• FanR1BNb: number of fan rotor blades.
• FanRss: rotor stator spacing parameter. See the relevant literature for definition.
• MtipFan: relative tip Mach number of fan in design point (typically the top-of-climb point during a flight mission).
• xnl: fan rotation speed in design point in rps.
• FanVsOgvNb: number of fan stator blades.
• stages_LPC: number of LPC stages.
• r_compr: LPC radius.
• rh_compr: LPC hydraulic radius.
• RSS_compr: rotor stator spacing parameter.
• MtipLpc: relative tip Mach number of lpc in design point (typically the top-of-climb point during a flight mission).
• N_compr: number of rotor blades for first stage rotor.
• S_compr: number of stator blades for first stage stator.
• CombType: SAC/DAC, combustor type.
• maxNo_nozzles_dac: total number of fuel nozzles in DAC.
• A_comb_exit: combustor exit area.
• Deff_comb: exhaust nozzle exit plane effective diameter.
• Dhyd_comb: exhaust nozzle exit plane hydraulic diameter.
• Lc_comb: combustor nominal length.
• h_annulus_comb: annulus height at combustor exit.
• LptStgLastBNb: number of blades at the last rotor stage of the LPT.
• stages_LPT: number of LPT stages.
• LptStgLastDiaOuter: outer diameter of the last stage of the LPT.
• LptStgLastAExit: exit area of the last stage of the LPT.
• SRS: rotor stator spacing.
• A_core: core nozzle area.
• A_bypass: bypass nozzle are.

performanceResults.txt or trajectory performance files --> engine and aircraft performance data for every point

Fan performance:

• Mtip_fan: relative tip Mach number. In single point mode it is computed from inlet temperature, pressure mass flow area, diameter and rotational speed.
• Mu_fan: blade Mach number. In single point mode it is computed from inlet temperature, pressure mass flow area, diameter and rotational speed.
• xnl_fan: rotational speed in rps.
• dt_fan: stage temperature rise over fan rotor.
• g1_fan: mass flow at fan face in kg/s.

IPC/LPC performance:

• Mtip_lpc: relative tip Mach number. In single point mode it is computed from inlet temperature, pressure mass flow area, diameter and rotational speed.
• Mu_lpc: blade Mach number. In single point mode it is computed from inlet temperature, pressure mass flow area, diameter and rotational speed.
• xnl_fan: rotational speed in rps.
• dt_lpc: temperature rise over entire LPC. In single point mode it is computed from a stage loading parameter (0.70 for non-geared and 0.45 for geared).
• g1_lpc: mass flow at LPC in kg/s.

Combustor performance:

• P3: combustor inlet pressure in Pa.
• P4: combustor exit pressure in Pa.
• P7: turbine exit pressure in Pa.
• T3: combustor inlet temperature in K.
• T4: combustor exit temperature in K.
• T5: turbine exit temperature in K.
• W3: combustor inlet flow in kg/s.

LPT performance:

• V_TR: relative tip speed of turbine last rotor in m/s.
• T_LPT_exit: turbine exhaust temperature in K.
• n_LPS: rotational speed in rps.
• m_core: mass flow in kg/s.
• Cax: axial velocity in m/s. In single point mode it is computed from the previous parameters and the LPT exit area.

Jet performance:

• dmdt_1_hot: mass flow rate of inner stream or circular jet in kg/s.
• dmdt_2_cold: mass flow rate of outer stream in kg/s.
• v_1: nozzle exit flow velocity of inner stream or circular jet in m/s.
• v_2: nozzle exit flow velocity of outer stream in m/s.
• T_1: nozzle exit flow total temperature of inner stream or circular jet in K.
• T_2: nozzle exit flow total temperature of outer stream in K.

Airframe performance:

• psi: aircraft pitch angle in rad.
• defl_flap: flap deflection angle in rad.
• defl_slat: slat deflection angle in rad.
• LandingGear: landing gear position, 0 or 1.