Sonic Boom Focusing - Case 1 

This test case is intended to provide an as-simple-as-possible validation case to evaluate and verify the capability of sonic boom simulation codes
to predict sonic boom focussing situation, caustics location in space and pressure signatures near caustics. For that, we use a simple trajectory
corresponding to a constantly-accelerated rectilinear level flight and assume that the near-field pressure waveform is constant in time (despite 
the acceleration along trajectory), axisymmetrical which actually corresponds to the mean value of RANS solutions on the AXIE test case from 
AIAA Sonic Boom Prediction Workshop II (https://lbpw.larc.nasa.gov/sbpw2/nearfield/axie/), extracted at R/L=3 with R=32.92m
 
The near-field dp/p data is provided as X (meters) vs dp/p in file: Case1_dpp.plt

The atmosphere is the standard atmosphere (no wind) defined in file : Case1_atm.txt 

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Simulation Conditions for Propagation in Focussing condition:

a)	accelerated level flight around Mach number = 1.2 (focusing condition corresponds exactly to Mach 1.2)
b)	Cruise altitude = 10300 meters
c)	Propagation starting distance from the body = 98.76 meters
d)	R/L = 3.0
e)	Ground reflection factor = 2.0
f)	Ground altitude = 0. meters
g)	Acceleration is constant, rectilinear, aligned with the initial velocity vector, corresponding to a level flight (horizontal, constant altitude). Value of the acceleration is positive 1 m.s^-2, corresponding to a time derivative of Mach number: dM/dt= 0.003355821846 s^-1 
h)	Heading (defined as degrees clockwise from East) is zero
i)	Standard atmosphere (defined in file: Case1_atm.txt )
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

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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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