Sonic Boom Focusing - Case 2 

This test case is representative of C608, which is a early variant of the NASA X-59 Low Boom Flight Demonstrator.
This concepty was previously used in the 3rd Sonic Boom Prediction Workshop (SBPW3) as part of the CFD portion of the workshop. 
The trajectory information is loosely based on one of the performance trajectories for the X-59.
As such, the trajectory is much more complicated than the first case, with non-zero flight path angle and changing acceleration.


The near-field pressures were computed using turbulent FUN3D simulations leveraging the design cruise grid generation per the AIAA Sonic Boom Prediction Workshop III (https://lbpw.larc.nasa.gov/sbpw3/c608-low-boom-flight-demonstrator-test-case/), extracted at R/L=3 with R=27.432m
 
The near-field dp/p data is provided as X (meters) vs dp/p in file: Case2_dpp.plt

The atmosphere is the standard atmosphere (no wind) defined in file : Case2_atm.txt 

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Simulation Conditions for Propagation in Focussing condition:

a)	accelerated level flight around Mach number = 1.19423965
b)	Cruise altitude = 13789.45 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 = 0. meters
g)	Acceleration corresponds to a time derivative of Mach number: dM/dt= 0.001144274 s^-1 
h)	Rate of change of acceleration corresponds to a time derivative of dM/dt number: d^2M/dt^2= -2.95e-6 s^-2 
i)	Flight path angle (FPA) = 2.0515 degrees
j) 	Rate of change of FPA = -0.004 degrees/s
k)	Heading (defined as degrees clockwise from East) is zero
l)	Standard atmosphere (defined in file: Case2_atm.txt )
m)	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
n)	The azimuthal angles are given in degrees

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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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Desired Runs

1) Identification of caustic formed in the above specified conditions (trajectory and atmosphere)
2) Calculation of the ground time-pressure waveform near the interection of the caustic with the ground

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Submission data:
1. Caustic surface geometry: X-Y location of ground intersection of caustic, radii of curvature of the caustic, caustic diffraction layer thickness (delta) 
2. Ground pressure pressure (in Pa) as a function of time (in second) at different location on the ground: on the caustics, at +/- delta/2, at +/- delta and at location where max. overpressure is maximum (delta: diffraction layer thickness of the caustic)
3. Location and pressure waveforms at the interface between Augmented Burgers and Tricomi solvers
4. Loudness metrics to be submitted include PL, A/B/C/D/S SEL and ISBAP

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