3rd AIAA Sonic Boom Prediction Workshop
Propagation Workshop
Case 2

The propagation case pressure waveform corresponds to C609, which is an earlier version of the NASA's Low Boom Flight Demonstrator X-59 aircraft

The near-field dp/p data (-90.0 to 90 degrees in 2 degree increments) is provided as X (meters) vs dp/p in file: Case2_dpp.plt

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Simulation Conditions for Propagation:

a)	Mach number = 1.4
b)	Cruise altitude = 16459.2 meters
c)	Propagation starting distance from the body = 82.296 meters
d)	R/L = 3.0
e)	Ground reflection factor = 1.9
f)	Ground altitude = 110.011 meters
g)	Acceleration, turn- and climb- rates are all zero
h)	Heading (defined as degrees clockwise from East) is zero
i)	X (East) and Y (North) components of wind represent the direction the wind is blowing toward.
j)	X and Y Coordinates for ray ground interception point are defined as positive in East and South respectively, and with origin (0,0) at the aircraft position at the emmision time
k)	The azimuthal angles are given in degrees
l)	Dimensionalize the off-body pressures using linear interpolation of the provided atmospheric pressures

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NOTE on Wind and azimuthal angle conventions:

1. Azimuthal Angle: From the point of view of the pilot, positive azimuths are defined as being to his right and negative azimuths are to his left.

2. For the wind convention, the positive X-wind is tail-wind since the aircraft is flying East. Positive Y-wind is going North i.e. from a pilot's point of view, positive Y-wind is blowing toward his left. Put another way, IF aircraft were flying North, positive Y-wind is tail-wind.

Please see https://lbpw-ftp.larc.nasa.gov/sbpw3/propagation/Conventions_SBPW3.pdf for detailed graphics on wind and azimuthal angle conventions 

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For loudness calculations, the minimum sampling frequency is 50 kHz

Near-field: Near-field X (meters) vs. dp/p's to be used for propagation supplied in Case2_dpp.plt. 

atmospheric_profiles: 

1. The first atmospheric profile is a balloon measured actual profile and the data corresponding to this profile is provided in separate files for Temperature, Relative Humidity and Winds

The altitudes in atmospheric profiles are in meters.

i. 	Case2_temperature_degC.txt
ii. Case2_relativeHumidity_percent.txt
ii. Case2_eastwardVectorWindSpeed_m_per_second.txt
iv. Case2_northwardVectorWindSpeed_m_per_second.txt
v. 	Case2_pressure.txt


2. In addition, standard atmospheric profile is also included in file: Case2_standard_atmo.txt. Use that for propagating under standard conditions.


NOTES: 
1.	If the participant uses a non-uniform sampling during propagation, the ground signatures submitted should be resampled to a uniform distribution.
2.	Participants can optionally include curved-earth/diffraction or other advanced effects in their results if they have such capabilities in their propagation model.


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Desired Runs

1.  For the measured atmospheric profile, use near-field dp/p at the following azimuthal angles to predict the ground signatures. If a specific azimuthal angle is beyond your computed lateral cut-off, submit (0.0 0.0) as the ground signature
i. 		From -60 to 60  in 10 degree increments (with 0 being under-track)
ii. 	From -70 to -60  in 2 degree increments
iii. 	From 60 to 70  in 2 degree increments

2. For both the standard atmospheric profile and the measured atmospheric profile, determine lateral cut-off angles on both sides

3. Using near-field pressure data as given below, compute ground signatures, ground intersection locations and loudness metrics associated with the lateral cut-off angles computed.
i. 		For the measured atmospheric profile, use -70 and 70 degrees from Case2_dpp.plt
ii.  	For the standard atmospheric profile, use -50 and 50 degrees from Case2_dpp.plt

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Submission data:
1. Ground signatures (Time (seconds) vs. Pressure (Pascals))
2. The lateral cut-off angles on both sides of the carpet
3. Loudness metrics (PL, ASEL, BSEL, CSEL) corresponding to all the ground signatures
4. The ground intersections should be specified in meters and propagation time in seconds

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