Sanetrik, Mark D.

NASA Technical Reports Server

Sonic Boom Calculations for the N+2 
Configuration!
Mark D. Sanetrik 
 
NASA Langley Research Center 
 
 
 
 
 
 
 
 
 
\ 
 
 
Presented at ASE Summit 
NASA Ames Research Center 
April 14, 2015 
https://ntrs.nasa.gov/search.jsp?R=20160007032 2019-08-31T02:35:05+00:00Z
Outline 
•  Introduction 
•  Requirements for Sonic Boom Calculations 
•  Challenges of Sonic Boom Calculations 
•  Sample Solutions 
•  Sonic Boom Results 
–  Effect of Grid Resolution 
–  Effect of Domain Extent 
–  Effect of Near-Field Pressure Extraction Location 
–  Effect of Static Aeroelastic Deflections 
–  Effect of Engines 
•  Concluding Remarks and Future Work 
Introduction 
•  Low sonic boom flight a major requirement for N+2 Program 
•  Extensive work done to optimize sonic boom signature 
•  Optimization done on a rigid structure 
•  Structure will deflect aeroelastically under aerodynamic loads 
•  How will static aeroelastic deflections change the sonic boom signature? 
Requirements for Sonic Boom Calculations 
•  Conventional Static Aeroelastic domain is rectangular 
•  Body is defined at 0o angle of attack 
•  Same grid can be used for multiple flow conditions 
•  Sonic Boom domain must be shock aligned 
•  Conical-shaped domain with angle of cone dictated by Mach angle 
•  Body must be rotated to proper angle of attack 
•  Separate grid  for each flow condition 
CAE Computational Domain 
CAE Computational Domain Detail 
Sonic Boom Computational Domain 
Sonic Boom Computational Domain 
Challenges of Sonic Boom Calculations 
•  Separate grid for every flow condition 
•  Extremely fine near-field grid required 
•  Where to extract pressure signature? 
–  Too close and the pressure signature not fully developed 
–  Too far away and the pressure signature is dissipated 
–  Current practice is 3 body lengths 
•  Use of external program to propagate shock to ground level (sBOOM)  
•  Interpretation of ground signatures 
Conventional CAE Solution 
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
11.8 MGP, CL = 0.14343, CD = 0.09220 
Conventional CAE Solution with Grid  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
11.8 MGP, CL = 0.14343, CD = 0.09220 
Sonic Boom Coarse Solution  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
15.9 MGP, CL = 0.14342, CD = 0.09252 
Sonic Boom Coarse Solution with Grid  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
115.9 MGP, CL = 0.14342, CD = 0.09252 
Sonic Boom Medium Solution  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
46.5 MGP, CL = 0.14343, CD = 0.09251 
Sonic Boom Medium Solution with Grid  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
46.5 MGP, CL = 0.14343, CD = 0.09251 
Sonic Boom Fine Solution  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
89.9 MGP, CL = 0.14342, CD = 0.09256 
Sonic Boom Fine Solution with Grid  
Inviscid, No Engines, Mach = 1.70, α = 2.25ο 
89.9 MGP, CL = 0.14342, CD = 0.09256 
Sonic Boom Grid Resolution Study 
5000 6000 7000 8000 9000
x (in.)
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
Coarse Grid
Medium Grid
Fine Grid
Near-field Pressure Signature
No Engines, Undeformed, Mach = 1.7, Alpha = 2.25
Sonic Boom Grid Resolution Study (cont.) 
0 50 100 150 200 250 300
time, ms
-1
-0.5
0
0.5
1
1.5
Ov
erp
res
su
re,
 ps
f
Coarse Grid
Medium Grid
Fine Grid
Ground Level Boom Signature
No Engines, Undeformed, Mach = 1.7, Alpha = 2.25
Sonic Boom Domain Size Study 
5000 6000 7000 8000 9000 10000 11000
x, inches
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
dp/p
Coarse Grid Short Domain
Coarse Grid Long Domain
Medium Grid Short Domain
Medium Grid Long Domain
Near-field Pressure Signature
No Engines, Undeformed, Mach = 1.7, Alpha = 2.25
Sonic Boom Domain Size Study (cont.) 
0 50 100 150 200 250 300
time, ms
-1
-0.5
0
0.5
1
1.5
Ov
erp
res
su
re,
 ps
f
Coarse Grid Short Domain
Coarse Grid Long Domain
Medium Grid Short Domain
Medium Grid Long Domain
Ground Level Boom Signature
No Engines, Undeformed, Mach = 1.7, Alpha = 2.25
Sonic Boom Extraction Position Study 
2000 4000 6000 8000 10000
x (in)
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
dp
/p
1.00 Body Length
1.38 Body Lengths
2.00 Body Lengths
3.00 Body Lengths
Near-field Pressure Signature
No Engines, Meduim Grid, Undeformed, Mach = 1.7, Alpha = 2.25
Sonic Boom Extraction Position Study (cont.) 
0 50 100 150 200 250 300
Time (ms)
-1.0
-0.5
0.0
0.5
1.0
1.5
Ov
erp
res
su
re 
(ps
f)
1.00 Body Length
1.38 Body Lengths
2.00 Boby Lengths
3.00 Body Lengths
Ground Level Boom Signature
No Engines, Medium Grid, Undeformed, Mach = 1.7, Alpa 2.25
Sonic Boom Effect of Deflections Study 
5000 6000 7000 8000 9000
x (in.)
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
dp/p
Undeformed
Deformed
Near-field Pressure Signature
No Engines, Medium Grid, Mach = 1.7, Alpha = 2.25
Sonic Boom Effect of Deflections Study (cont.) 
0 100 200 300
Time (ms)
-1.0
-0.5
0.0
0.5
1.0
1.5
Ov
erp
res
su
re 
(ps
f)
Undeformed
Deformed
Ground Level Boom Signature
Medium Grid, No Engines, Mach = 1.7, Alpa 2.25
Sonic Boom Effect of Engines Study 
5000 6000 7000 8000 9000
x (in.)
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
No Engines
Engines
Near-field Pressure Signature
Meduim Grid, Undeformed, Mach = 1.7, Alpha = 2.25
Sonic Boom Effect of Engines Study (cont.) 
0 50 100 150 200 250 300
Time (ms)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Ov
erp
res
su
re 
(ps
f)
No Engines
Engines
Ground Level Boom Signature
Medium Grid, Undeformed, Mach = 1.7, Alpa 2.25
Concluding Remarks 
•  Sonic boom signatures have been computed for the N+2 configuration 
•  Still a work in progress; much learning to be done 
•  Major questions to be answered 
–  Exactly what is the configuration are we analyzing? 
–  What is the best procedure for static aeroelastic computations? 
•  Future Work 
–  Additional computations with engines 
–  More realistic engines? 
–  Viscous Calculations 
•  A good start has been made in the investigation of the aeroelastic 
effects on the sonic boom signature 
Mark.D.Sanetrik@nasa.gov 
29 


Sonic Boom Calculations for the N+2 Configuration

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