CHOICE

class choice.CHOICE(input_folder='Input/', output_folder='Output/', perf_file='performanceResults.txt', weight_file='weightAircraft.txt', noise_file='inputNoise.txt', file_type=None)

Instantiate input files and folders to be used for the noise calculation.

Parameters:

• input_folder (str) – input files folder path

• output_folder (str) – output files folder path

• perf_file (str) – file containing the engine performance parameters

• weight_file (str) – file containing engine sizing data

• noise_file (str) – file that is used to define the noise calculation study

• file_type (str) – file type for noise source matrices (csv, m, None)

run_choice()

Sets the required parameters and performs the noise calculation

Reading and editing input files

Module choice_read_and write

Used to read and edit external / input files.

class choice.choice_read_and_write.MultptPerfData(pf)

Instantiate the multipoint performance data for each point.

Parameters:

pf (list) – A list of data from the performance file

static load_dict(spos, pf)

Returns a dictionary with all the data for a given operating point.

class choice.choice_read_and_write.ReadFiles(weight_file, noise_file, perf_file)

Instantiate files to be read.

Parameters:

• weight_file (str) – File with data on engine sizing

• noise_file (str) – File to define the cases to be run and required inputs for noise prediction

• perf_file (str) – File containing the engine performance data for every point

open_performance_file()

Reads a given performance file into a list.

static retrieve_file(file)

Reads the data from the given file and creates a dictionary.

set_modules()

Returns a list of the modules in the inputNoise.txt file

choice.choice_read_and_write.isfloat(num)

Checks if the provided string is a float number.

choice.choice_read_and_write.preparse_trajectories(traj_perf, opPnt, modules, input_folder)

Preparses the trajectory and component performance files by removing data corresponding to stationary points.

choice.choice_read_and_write.save_noise_points(fname, opPoint, fuselage_fan, EPNL)

Saves the EPNL for each component and for the total in output file.

Interface

Module choice_interf

Choice interface: used to set the required parameters for the noise calculation and call the physics-based methods from the module choice_physics.

class choice.choice_interf.NoiseChoice(noiseFile)

Instantiate the required input arguments for the noise prediction cases to be run.

Parameters:

noiseFile (dict) – Definition of the noise cases to be performed.

class choice.choice_interf.NoiseMatrices(modules=None)

A class that defines the noise level for each aircraft noise component.

Parameters:

modules (list) – Fan, Lpc, Lpt, etc.

class choice.choice_interf.NoiseMatricesCerification(modules=None)

A class that defines the noise level for each aircraft noise component.

Parameters:

modules (list) – Fan, Lpc, Lpt, etc.

class choice.choice_interf.NoiseSources(prms, theta, fband)

Instantiate noise source object

Parameters:

• prms (Prms) – Acoustic pressure arrays for each aircraft noise component

• theta (ndarray) – 1D array containg directivity angles

• fband (ndarray) – 1D array containg the 1/3 octave band frequencies

classmethod compute(traj, modules, noise, weight, performance, nop, output_folder, ext=None)

Compute the acoustic pressure for each noise component.

Parameters:

• traj (Trajectory) – A Trajectory object with the trajectory data

• modules (list) – Fan, Lpc, Lpt, etc.

• noise (NoiseChoice) – A NoiseChoice object with the required input arguments for the noise prediction

• weight (WeightChoice) – A WeightChoice object with the engine size and architecture

• performance (PerformanceChoice) – A PerformanceChoice object with the engine performance data

• nop (int) – Number of operating point

• output_folder (str) – Output folder path

• ext (str) – File extension for noise source matrices

Return NoiseSources:

A Prms object with the rms acoustic pressure for each component, the directivity angles and the 1/3 octave band frequencies

static include_multiple_engines(no_engines, prms)

Account for multiple engines on the aircraft.

class choice.choice_interf.PerformanceChoice(ptr, trajPerf, point, n_traj, weight_choice, mpd, input_folder)

Instantiate the engine performance data.

Parameters:

• ptr (int) – Operating point (trajectory) number in order of appearance in the inputNoise.txt

• trajPerf (bool) – If true, trajectory data are used, else, single point study is performed

• point (str) – Operating point

• n_traj (int) – Number of trajectory points

• Weight_choice (WeightChoice) – Engine sizing data

• mpd (MultptPerfData) – Multipoint performance data

• input_folder (str) – Input files folder path

coAxialJet()

Sets the jet performance parameters.

coAxialJet_ffn()

Sets the jet performance parameters for fuselage fan nozzle .

getIsOpenRotor(modules)

Checks if it is an open rotor.

get_variable(point, name)

Returns the value of the item with the specified key for the provided point.

classmethod set(ptr, modules, n_traj, mpd, noise_choice, weight_choice, input_folder)

Sets the performance data for each component.

Parameters:

• ptr (int) – Operating point (trajectory) number in order of appearance in the inputNoise.txt

• modules (list) – Engine components

• n_traj (int) – Number of trajectory points

• mpd (MultptPerfData) – Multipoint performance data

• noise_choice (NoiseChoice) – Noise prediction input data

• weight_choice (WeightChoice) – Engine sizing data

• input_folder (str) – Input files folder

Return PerformanceChoice:

A PerformanceChoice object

setAirfrm(noise_choice)

Sets the airframe performance parameters.

setComb()

Sets the combustor performance parameters.

setFan()

Sets the fan performance parameters.

setLpc()

Sets the low pressure compressor performance parameters.

setLpt()

Sets the low pressure turbine performance parameters.

setff()

Sets the fuselage fan performance parameters.

class choice.choice_interf.Prms(npts)

Instantiate rms acoustic pressure for each aircraft noise component.

Parameters:

npts (int) – Number of trajectory points

class choice.choice_interf.Trajectory(ipnt, opPnt, noise_choice, input_folder)

Instantiate the trajectory data of the aircraft.

Parameters:

• ipnt (int) – Operating point (trajectory) number in order of appearance in the inputNoise.txt

• opPnt (str) – Operating point (trajectory), e.g. Approach, Cutback, Sideline

• noise_choice (NoiseChoice) – Noise prediction input data

static get_dx(x1, y1, z1, dt, gamma, c0, Va, tnext)

Computes distance travelled until the location of the next noise sample generation.

Parameters:

• x1 (float) – x coordinate of first sample (in relation to microphone)

• y1 (float) – y coordinate (height) of first sample (in relation to microphone)

• z1 (float) – z coordinate of microphone

• dt (float) – Time interval between sounds reaching the microphone

• gamma (float) – Flight path angle

• c0 (float) – Speed of sound at aircraft location

• Va (float) – Aircraft speed

• tnext (float) – Next sampling time

Return float:

The distance that the aircraft travelled

get_xsi(xmic, ymic, zmic)

Computes the angle between the direction of the aircraft’s motion and the sound propagation path.

Parameters:

• xmic (float) – Microphone/observer horizontal distance (m)

• ymic (float) – Microphone/observer height (m)

• zmic (float) – Microphone/observer lateral horizontal distance (m)

read_trajectory_input(opPnt, input_folder, h_engine)

Reads and stores the trajectory data (position, velocity and angle of attack) for the provided operating point

Parameters:

opPnt (str) – Operating point

classmethod set(ipnt, opPnt, noise_choice, input_folder)

Sets the required trajectory details for the noise calculation.

Parameters:

• ipnt (int) – Operating point (trajectory) number in order of appearance in the inputNoise.txt

• opPnt (str) – Operating point (trajectory), e.g. Approach, Cutback, Sideline

• noise_choice (NoiseChoice) – NoiseChoice object

Return Trajectory:

A trajectory object

set_time_vector(ipnt, noise_choice)

Computes the retarded time.

Parameters:

• ipnt (int) – Operating point (trajectory) number in order of appearance in the inputNoise.txt

• noise_choice (NoiseChoice) – NoiseChoice object

set_velocity(dtIsa)

Computes ambient temperature (ta), speed of sound (a) and Mach number (Ma) along the trajectory

Parameters:

dtIsa (float) – Deviation from ISA temperature

class choice.choice_interf.WeightChoice(weightFile)

Instantiate the engine size and architecture data.

Parameters:

weightFile (dict) – Engine sizing data.

choice.choice_interf.certificationLimits(noEngines, MTOW)

Computes EPNL certification limits.

choice.choice_interf.compute_SPLi(prmsi)

Computes Sound Pressure Level matrix from rms acoustic pressure.

choice.choice_interf.get_version_num(fname)

Writes CHOICE version number in output file.

choice.choice_interf.interpolate_to_t_source(traj, modules, prms)

Computes the Sound Pressure Level for the times that the sound reaches the microphone.

Parameters:

• traj (Trajectory) – A Trajectory object with the trajectory data

• modules (list) – Fan, Lpc, Lpt, etc.

• prms (Prms) – A Prms object with the rms acoustic pressure for each component

Returns:

For the times that the sound reaches the microphone, a NoiseMatrices object with the Sound Pressure Level for each component, the observation angle, the Mach number and the angle of attack

choice.choice_interf.set_rotational_speeds_choice(mpd, weightChoice, comp)

Estimates absolute speeds from relative rotating speeds (from performance) using several points.

Parameters:

• mpd (MultptPerfData) – Multipoint performance data

• weightChoice (WeightChoice) – Engine sizing data

• comp (str) – Engine component

Return MultptPerfData:

Updated multipoint performance data

choice.choice_interf.source_interpolation(prms, traj)

Interpolate the rms acoustic pressure for the times that reach the microphone.

Methods for noise prediction

Module choice_physics

Physics and methods for the noise prediction broken down in modules.

class choice.choice_physics.Airframe(opPoint, N_wheels, N_struts, nlg, d_wheel, d_strut, d_wire, NoFlap, S_flap, span_flap, Sw, span, ND, span_hor_tail, Sht, span_ver_tail, Svt, flap_type, slat_type, theta, fband)

Instantiate airframe source noise prediction.

Parameters:

• opPoint (list) – Approach, Cutback, Sideline

• N_wheels (int) – Array containing the number of wheels in each landing gear system

• N_struts (int) – Array containing the number of main struts in each landing gear system

• nlg (int) – Number of landing gear systems

• d_wheel (ndarray) – 1D array containing the diameters of landing gear wheels (in)

• d_strut (ndarray) – 1D array containing typical diameter of landing gear struts (in)

• d_wire (ndarray) – 1D array containing typical diameter of landing gear wire/small pipes (in)

• NoFlap (int) – Number of flap elements

• S_flap (ndarray) – 1D array containing the area of each flap (m**2)

• span_flap (ndarray) – 1D array containing the span of each flap (m)

• Sw (float) – Aircraft reference area (m**2)

• span (float) – Wing span (m)

• ND (int) – Coefficient for jet aircraft (1 => + 6dB in wing trailing edge OASPL)

• span_hor_tail (float) – Horizontal tail span (m)

• Sht (float) – Horizontal tail area (m)

• span_ver_tail (float) – Vertical tail span (m)

• Svt (float) – Vertical tail area (m)

• flap_type (str) – Flap type: 1slot, 2slot, 3slot

• slat_type (str) – Leading edge high-lift system type: slat, le_flap

• theta (ndarray) – 1D array containing the longitudinal directivity angles (deg)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

calc(Ta, Ha, Ma, Va, phi, defl_flap, defl_slat, LG)

Airframe source noise model based on a combination of methods found in public literature. Trailing-edge and landing gear noise are modelled separately. The references for each method are found in the description of the corresponding functions.

Parameters:

• Ta (float) – Atmospheric static temperature (K)

• Ha (float) – Flight altitude (m)

• Ma (float) – Aircraft Mach number

• Va (float) – Aircraft speed (m/s)

• phi (float) – Lateral directivity angle (deg)

• defl_flap (float) – Flap deflection angle (rad)

• defl_flap – Slat deflection angle (rad)

• LG (int) – Landing gear position (0 => retracted, 1 => extended)

Return ndarray:

2D array of Rms or effective acoustic pressure for airframe component

full_matrix(mato, nl)

Computes the coefficients that are required for the landing gear calculation for every directivity angle and returns a nc x nthet array where nc is the order of the equation of each noise component.

getLandingGear(Nt, Ns, M, c0, dl, dh, dtire)

Landing gear source noise model based on the method presented by Sen et al. (R. Sen, B. Hardy, K. Yamamoto, Y. Guo., G. Miller “Airframe Noise Sub-Component Definition and Model”. NASA/CR-2004-213255.)

Parameters:

• Nt (int) – Number of wheels/tires

• Ns (int) – Number of main struts

• M (float) – Aircraft Mach number

• c0 (float) – Speed of sound (m/s)

• dl (float) – Representative length scale for low frequency noise component (ft)

• dh (float) – Representative length scale for high frequency noise component (ft)

• dtire (float) – Representative length scale for tire noise component (ft)

Return ndarray:

2D array of Rms or effective acoustic pressure for landing gear

get_le_slats(Va, ny, S, b, dir_factor, ND, slat_type)

Leading edge high-lift system source noise model developed by Fink (M.R. Fink, “Airframe Noise Prediction Method”, FAA-RD-77-29 and M.R. Fink, “Noise Component Method for Airframe Noise”).

Parameters:

• Va (float) – Aircraft speed (m/s)

• ny (float) – Kinematic viscocity (m**2/s)

• S (float) – Wing or tail area (m**2)

• b (float) – Wing or tail span (m)

• dir_factor (float) – Equals cos(phi) where phi is lateral directivity calculated from the flyover plane

• ND (int) – Coefficient for jet aircraft (1 => + 6dB in wing trailing edge OASPL)

Return ndarray:

2D array of Rms or effective acoustic pressure for leading edge flaps

get_te_flaps(Va, Sf, bf, defl_flap, flap_type, phi)

Trailing edge flap source noise model developed by Fink (M.R. Fink, “Airframe Noise Prediction Method”, FAA-RD-77-29 and M.R. Fink, “Noise Component Method for Airframe Noise”).

Parameters:

• Va (float) – Aircraft speed (m/s)

• Sf (float) – Flap area (m**2)

• bf (float) – Flap span (m)

• defl_flap (float) – Flap deflection angle (rad)

• phi (float) – Lateral directivity calculated from the flyover plane

Return ndarray:

2D array of Rms or effective acoustic pressure for trailing edge flaps

get_wing_and_tail(Va, ny, S, b, dir_factor, ND)

Trailing edge source noise model for wing and tail surfaces developed by Fink (M.R. Fink, “Noise Component Method for Airframe Noise”).

Parameters:

• Va (float) – Aircraft speed (m/s)

• ny (float) – Kinematic viscocity (m**2/s)

• S (float) – Wing or tail area (m**2)

• b (float) – Wing or tail span (m)

• dir_factor (float) – Equals cos(phi) where phi is lateral directivity calculated from the flyover plane

• ND (int) – Coefficient for jet aircraft (1 => + 6dB in wing trailing edge OASPL)

Return ndarray:

2D array of Rms or effective acoustic pressure for wing and tail airframe component

class choice.choice_physics.Combustor(type_comb, Aec, De, Dh, Lc, h, Nfmax, theta, fband)

Instantiate combustor source noise prediction.

Parameters:

• type_comb (str) – Combustor type, SAC or DAC

• Aec (float) – Combustor exit area (ft^2)

• De (float) – Exhaust nozzle exit plane effective diameter (ft)

• Dh (float) – Exhaust nozzle exit plane hydraulic diameter (ft)

• Lc (float) – Combustor nominal length (ft)

• h (float) – Annulus height at combustor exit (ft)

• Nfmax (int) – Total number of DAC fuel nozzles

• theta (ndarray) – 1D array containing the directivity angles (deg)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

calc(Nf, pattern, pa, p3, p4, p7, ta, t3, t4, t5, w3)

Combustor source noise model based on the method for low-emissions combustors developed by Gliebe et al. (P. Gliebe, R. Mani, H. Shin, B. Mitchell, G. Ashford, S. Salamah and S. Connel. “Aeroacoustic Prediction Codes”. NASA-CR-210244). Includes model for SAC (Single-Annular Combustor) and DAC (Dual-Annular Combustor).

Parameters:

• Nf (int) – Number of ignited fuel nozzles

• pattern (int/float) – Fuel nozzle firing pattern

• pa (float) – Atmospheric pressure (Pa)

• p3 (float) – Combustor inlet pressure (Pa)

• p4 (float) – Combustor exit pressure (Pa)

• p7 (float) – Turbine last stage exit pressure (Pa)

• ta (float) – Atmospheric temperature (K)

• t3 (float) – Combustor inlet temperature (K)

• t4 (float) – Combustor exit temperature (K)

• t5 (float) – Turbine last stage exit temperature (K)

• w3 (float) – Combustor inlet flow (kg/s)

Return ndarray:

2D array of Rms or effective acoustic pressure for combustor component

getDAC(pattern, Pa, P3, P4, P7, T3, T4, T5, W3, AA)

Calculate the noise level from a Dual Annular Combustor.

getSAC(Nf, Pa, P3, P4, P7, T3, T4, T5, W3, AA)

Calculate the noise level from a Single Annular Combustor.

class choice.choice_physics.FanCompressor(component, MtipD, N_rotors, N_stators, rss, theta, fband, f, distortion=None)

Instantiate fan or compressor source noise prediction.

Parameters:

• component (str) – Compressor component, fan, LPC, IPC

• MtipD (float) – Rotor tip relative inlet Mach number at design point

• N_rotors (int) – Number of rotors

• N_stators (int) – Number of stators

• rss (float) – Rotor-stator spacing

• theta (ndarray) – 1D array containing the directivity angles (deg)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

• f (ndarray) – 1D array containing frequencies (Hz)

calc(operatingPoint, Mtip, Mu, dT, xnl, g1)

Fan and compressor source noise model based on the methods developed by Heidman (M. F. Heidmann. “Interim Prediction Method for Fan and Compressor Source Noise”. NASA-TM-X71763) and updated by Kontos et al. (K. B. Kontos, B. A. Janardan and P. R. Gliebe. “Improved NASA-ANOPP Noise Prediction Computer Code for Advanced Subsonic Propulsion Systems”. NASA-CR-195480).

Parameters:

• operatingPoint (str) – Approach, Cutback, Sideline

• Mtip (float) – Rotor tip relative inlet Mach number at operating point

• Mu (float) – Blade Mach number

• dT (float) – Temperature rise across fan or compressor stage

• xnl (float) – Fan rotational speed (rps)

• g1 (float) – Mass flow rate passing through fan or compressor (kg/s)

Return ndarray:

2D array of Rms or effective acoustic pressure for tone, broadband and combination tone noise

fanCompr_broadband(operatingPoint, Mtr, fb, dT, g1)

Fan and compressor broadband noise estimation.

fanCompr_comb_tone(Mtr, dT, g1, fb)

Fan and compressor combination tone noise estimation.

fanCompr_tone(operatingPoint, acc, Mtr, dT, g1, delta_cutoff, fb)

Fan and compressor discrete tone noise estimation.

get_C(nthet)

C coefficient from eq. 12 in Heidmann

get_Fig10a(M_tr)

Get characteristic peak sound pressure level of fundamental discrete tone for inlet duct according to Fig. 10(a) in Heidmann and eq. 5 in Kontos.

get_Fig10b(M_tr)

Get characteristic peak sound pressure level of fundamental discrete tone for discharge duct according to Fig. 10(b) in Heidmann.

get_Fig3a(f_over_fb)

Creating F4 according to eq. 2 in Heidmann

get_Fig4a(M_tr)

Get peak broadband sound pressure levels from Fig 4(a) for inlet duct according to Heidmann.

get_Fig4b(M_tr)

Get peak broadband sound pressure levels from Fig 4(b) for discharge duct according to Heidmann and eq. 3a-3b in Kontos.

get_Fig8(igv, Mtr, k, delta)

Get rotor-stator interaction discrete tone harmonic levels from Fig 8 in Heidmann and eq. 7a-8c in Kontos.

get_Fig9(no_fan_stages, k)

Get inlet flow distortion discrete tone harmonic levels for inlet duct from Fig 9 in Heidmann.

class choice.choice_physics.Jet(A_core_caj, A_bypass_caj, type, theta, fband)

Instantiate jet source noise prediction.

Parameters:

• A_core_caj (float) – Nozzle exit flow area of inner stream or circular jet (m^2)

• A_bypass_caj (float) – Nozzle exit flow area of outer stream (m^2)

• type (str) – Nozzle type, mix or separate

• theta (ndarray) – 1D array containing the directivity angles (deg)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

calc(dmdt_1, dmdt_2, v_1, v_2, T_1, T_2, Ta, Pa)

Jet source noise model for circular and coaxial jets based on the methods presented by Russel (J. W. Russel. “An empirical Method for Predicting the mixing Noise Levels of Subsonic Circular and Coaxial Jets”. NASA-CR-3786).

Parameters:

• dmdt_1 (float) – Mass flow rate of inner stream or circular jet (kg/s)

• dmdt_2 (float) – Mass flow rate of outer stream (kg/s)

• v_1 (float) – Nozzle exit flow velocity of inner stream or circular jet (m/s)

• v_2 (float) – Nozzle exit flow velocity of outer stream (m/s)

• T_1 (float) – Nozzle exit flow total temperature of inner stream or circular jet (K)

• T_2 (float) – Nozzle exit flow total temperature of outer stream (K)

• Ta (float) – Ambient static temperature (K)

• Pa (float) – Ambient pressure (Pa)

Return ndarray:

2D array of Rms or effective acoustic pressure for jet component

class choice.choice_physics.PropagationEffects(ymic, use_ground_refl, spherical_spr, atm_atten, fband, xsii, Mai, xsi_alphai, dTisa, elevation)

Instantiate noise estimation at microphone/observer.

Parameters:

• ymic (float) – Microphone height (m)

• use_ground_refl (bool) – True to account for ground reflection or False else

• spherical_spr (bool) – True to account for spherical spreading or False else

• atm_atten (bool) – True to account for atmospheric attenuation or False else

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

• xsii (ndarray) – 1D array containing observation angles (rad)

• Mai (ndarray) – 1D array containing Mach number

• xsi_alphai (ndarray) – 1D array containing directivity angle accounting for angle of attack (deg)

• dTisa (float) – Deviation from ISA temperature (K)

• elevation (float) – Ground elevation at microphone location (m)

static atmospheric_attenuation(t_k, pa, relHum, r, fband, third_octave_band=False)

Computes the absorption for a sound wave travelling through the atmosphere. Modelled according to the ISO 9613-1:1993 report.

Parameters:

• t_k – 1D array containing atmospheric temperature (K)

• pa – 1D array containing atmospheric pressure (Pa)

• relHum (float) – Relative humidity

• r – 1D array containing distance between source and observer (m)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

• third_octave_band (bool) – If True 1/3 octave bands are used and coefficients are estimated using the Volpe method (E. D. Rickley, G. G. Fleming, C. Roof. “Simplified procedure for computing the absorption of sound by the atmosphere”)

Return ndarray:

1D array containing the atmospheric absorption in dB.

convert_to_3rd_octave_bands(spl_dop, fdop_u, fdop_l)

Convert dopplerized frequency spectrum to 1/3 octave bands

convert_to_narrowband(Lp, fupper, flower, fc_new)

Compute the narrowband spectrum

flightEffects(nti, theta, x, y, r1, tai, SPLi, comp, phi)

Computes the sound pressure level and the acoustic pressure matrices accounting for propagation effects.

Parameters:

• nti (int) – Number of trajectory points

• theta (ndarray) – 1D array containing the directivity angles (deg)

• x (ndarray) – 1D array containing aircraft horizontal distance relative to the microphone (m)

• y (ndarray) – 1D array containing aircraft altitude relative to the microphone (m)

• r1 (ndarray) – 1D array containing aircraft distance relative to the microphone (m)

• tai (ndarray) – 1D array containing atmospheric temperature (K)

• SPLi (ndarray) – 3D array containing Sound pressure level at the source (dB)

• comp (string) – Noise component

Returns:

An SPL and a prms array

getDopplerShift(fband, xsii, Mai)

Computes the frequency shift due to the movement of the aircraft.

ground_reflection(y_plane, r1, ta, fband)

Computes the ground effects factor for a sound wave that does not travel directly from the source to the observer.

Parameters:

• y_plane (float) – Aircraft altitude relative to the microphone (m)

• r1 (float) – Aircraft distance relative to the microphone (m)

• ta (float) – Atmospheric static temperature (K)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

Return array:

1D array containing ground effects factor

lateral_attenuation(phi, engine='wing')

Calculation of engine-installation effects (lateral directional effects attributed to wing or fuselage mounted engines) for conventional aircraft. The method is based on the SAE AIR 5662 report, “Method for Predicting Lateral Attenuation of Airplane Noise”.

Parameters:

• phi – depression angle (deg)

• engine – wing or fus depending on where the engine is mounted

subband_combination(prms_subband)

Combine into subband prms.

subband_division(prms)

Divide into subbands to be used in the ground effects application.

tones_to_3rd_octave_bands(spl_dop, DF)

Convert dopplerized frequency spectrum of tonal components to 1/3 octave bands

class choice.choice_physics.Turbine(N_rotors, SRS, theta, fband, f)

Instantiate turbine source noise prediction.

Parameters:

• N_rotors (int) – Number of rotors

• SRS (float) – Stator-rotor spacing

• theta (ndarray) – 1D array containing the directivity angles (deg)

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

• f (ndarray) – 1D array containing frequencies (Hz)

calc(Vtr, Texit, xnl, mcore, Cax)

Turbine source noise model based on the method developed by Dunn and Peart (D. G. Dunn and N. A. Peart. “Aircraft Noise Source and Contour Estimation”. NASA-CR-114649).

Parameters:

• Vtr (float) – Relative tip speed of turbine last rotor

• Texit (float) – Exhaust temperature (K)

• xnl (float) – Rotational speed (rps)

• mcore (float) – Mass flow (kg/s)

• Cax (float) – Axial velocity (m/s)

Return ndarray:

2D array of Rms or effective acoustic pressure for turbine component

General functions

Module choice_aux

Choice auxiliary routines such as error handling and file editing and writing.

choice.choice_aux.SPL2prms(SPL)

For a given SPL matrix computes the acoustic mean square pressure.

class choice.choice_aux.chapter3(noEngines, MTOW)

Instantiate the EPNL certification limits for every operating point.

Parameters:

• noEngines (int) – Number of engines

• MTOW (float) – Maximum take-off weight (tn)

get_EPNL_approach()

Computes EPNL limit for Approach.

get_EPNL_cutback()

Computes EPNL limit for Cutback.

get_EPNL_lateral()

Computes EPNL limit for Sideline.

choice.choice_aux.containsStars(fname)

Checks if the file contains stars instead of data.

choice.choice_aux.gen_noise_source_matr_subr(output_folder, operatingPoint, nfreq, nthet, n_traj_pts, prms, ext)

Save component SPL matrices to files.

Parameters:

• operatingPoint (str) – Approach, Cutback, Sideline

• nfreq (int) – Number of frequencies

• nthet (int) – Number of directivity angles

• n_traj_pts (int) – Number of trajectory points

• prms (Prms) – Rms or effective acoustic pressure for all components

• ext (str) – File extension for noise source matrices

choice.choice_aux.getTotLevel(L)

Computes the total PNLT for all noise sources.

choice.choice_aux.get_Cax(gam, p, t, w, A)

Computes the axial flow speed from pressure, temperature, mass flow and area.

choice.choice_aux.get_M(gam, xfunc0)

Computes the Mach number in the fan and compressor components.

choice.choice_aux.get_R(fa)

Computes gas constant.

choice.choice_aux.loadStorageMat(fname, ndata, nvars)

Reads data from file and returns a 2D array.

Parameters:

• fname (str) – File name

• ndata (int) – Number of data loaded along the trajectory

• nvars (int) – Number of variables stored for particular module

Return ndarray:

2D array with the data

choice.choice_aux.plot_airframe_source(fband, theta, prms_airframe, prms_wing, prms_hor_tail, prms__flap, prms_slat, prms_lg_m, prms_lg, prms_lg_n, theta_plot, point)

Plot airframe source spectrum.

Parameters:

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

• theta (ndarray) – 1D array containing the longitudinal directivities (deg)

• prms_airframe (ndarray) – 1D array containing the mean square (rms) acoustic pressure for the trailing edge (Pa)

• prms_wing (ndarray) – 1D array containing the rms acoustic pressure for the wing (Pa)

• prms_hor_tail (ndarray) – 1D array containing therms acoustic pressure for the horizontal tail (Pa)

• prms__flap (ndarray) – 1D array containing the rms acoustic pressure for the flaps (Pa)

• prms_slat (ndarray) – 1D array containing the rms acoustic pressure for the slats (Pa)

• prms_lg_m (ndarray) – 1D array containing the rms acoustic pressure for the main landing gear (Pa)

• prms_lg (ndarray) – 1D array containing the rms acoustic pressure for all landing gears (Pa)

• prms_lg_n (ndarray) – 1D array containing the rms acoustic pressure for the nose landing gear (Pa)

• theta_plot (ndarray) – Directivity angle for which to plot the source (deg)

• point (int) – Point in the trajectory

choice.choice_aux.plot_source(fband, theta, prms, theta_plot, point, modules)

Plot total source spectrum.

Parameters:

• fband (ndarray) – 1D array containing the 1/3 octave band frequencies (Hz)

• theta (ndarray) – 1D array containing the longitudinal directivities (deg)

• prms (ndarray) – A Prms object

• theta_plot (ndarray) – Directivity angle for which to plot the source (deg)

• point (int) – Point in the trajectory

• modules (list) – Fan, Lpc, Lpt, etc.

choice.choice_aux.preProcessFanFile(fname, d1, a2)

Computes missing data from fan performance file and saves new file. (This routine is only called if the file has stars)

choice.choice_aux.preProcessLptFile(fname, de, ae)

Computes missing data from lpt performance file and saves new file. (This routine is only called if the file has stars)

choice.choice_aux.prms2SPL(prms)

Converts rms acoustic pressure to Sound Pressure Level.

choice.choice_aux.save_3D_matrix(fname, n_rows, n_cols, n_2d_mat, mat, ext=None)

Saves a 3D matrix for in output file.

choice.choice_aux.setMachNumbers(p1, t1, g1, Ain, D1, xnl, gamma)

Computes the blade Mach numbers for a component.

Parameters:

• p1 (float) – Pressure (Pa)

• t1 (float) – Temperature (K)

• g1 (float) – Mass flow (kg/s)

• Ain (float) – Area (m**2)

• D1 (float) – Diameter (m)

• xnl (float) – Rotational speed (rps)

• gamma (float) – Heat capacity ratio

Returns:

Blade and relative tip Mach number and mid point speed

choice.choice_aux.set_frequencies(nb, nfreq, fmin=50, fmax=10000)

Computes the 1/3 octave band frequency, the mid-frequency of each band and all the frequencies from the given minimum to the maximum value.

Parameters:

• nb (int) – Number of bands

• nfreq (int) – Number of frequencies

• fmin (float) – The minimum frequency value (Hz)

• fmax (float) – The maximum frequency value (Hz)

Return ndarray:

The computed frequencies in 1D array form

Data

Module choice_data

Contains default data for components and tabulated data for noise empirical models.