Sonic boom reduction has been a major obstacle in the aviation industry for the last 20 years, scientists from all over the world strive to find a solution for reduction of the impact sonic boom on the ground, hence bring back Supersonic travel back to life after the retirement of the first supersonic civil transport airplane, concord, in 2011. To do so, the emphasis in latest research has been on supersonic plane shape optimization to decrease the sound signature on the floor resulting from a supersonic aircraft's Sonic boom in cruise flight at elevated altitude. CFD technology offers an appealing option to help in the design and optimization of supersonic cars due to the constraints of in-flight testing and laboratory scale testing costs. Due to the significant rise in computing power, the predictive capacity of CFD technology has considerably enhanced over the past decade, enabling the treatment of more complicated geometries with bigger meshes, better numerical algorithms and enhanced turbulence models for Reynolds-averaged Navier-Stokes (RANS). As computing energy continues to rise, numerical optimization techniques were coupled with CFD to further assist in the design phase. But first we must understand the phenomena. This thesis provides a careful study of the sonic boom and its signature on the ground. The study is conducted following three approaches of analysis: Analytical, computational and experimental. Once the understanding of the phenomena is all done, we move into finding the flight conditions and shape that minimize the sonic boom and provide the required lift.

1. Experimental and Computational Study on
Sonic Boom Reduction
Presented by:
Anas LAAMIRI
Ayoub BOUDLAL
Supervised by:
Pr. Mohammed Khalil IBRAHIM

2. Outline
I. Introduction
1. What is Sonic Boom?
2. Impact of Sonic Boom in community
3. Historical background
4. Prevision attempt to reduce Sonic Boom
II. Methodology
1. Experimental (Wind Tunnel)
2. Analytical (BASS theory)
3. Computational (CFD)
III. Results
1. Experimental results (Wind tunnel)
2. Computational results (ANSYS)
3. Analytical Results (BASS_Matlab)
IV. Minimization to reduce Sonic Boom
1. Based on analytical results obtained from Matlab
2. The added Spike
V. Conclusion

3. I. Introduction
1. What is Sonic Boom?
2. Impact of Sonic Boom in community
3. Historical background
4. Prevision attempt to reduce Sonic Boom

4. Introduction
1. What is Sonic Boom?
 When the object travels faster than the speed of sound, the produced sound waves can not migrate from each
other as the velocity is beyond that of the sound — thus colliding with each other.
 This causes the waves to force themselves or combine to travel in a single shock wave at a critical speed
known as ‘Mach 1’ or 1,235 km/h.
 So, because of this compression of the sound waves, a "boom" is heard. These are known as Sonic booms.
Figure Illustration of the shock wave

5. Introduction
1. What is Sonic Boom?
The path of a primary and secondary sonic boom
Pressure signature on the ground

6. Introduction
2. Impact of Sonic Boom in community
 The boom intensity can be measured in pounds of air pressure per square foot (PSF).
 It is the amount of pressure that the normal pressure around us increases to 2,116 psf.
 The booms triggered by big supersonic aircraft can be noisy, capturing the attention of people, and the sound
of livestock can be upset.
 Strong booms can cause the construction systems to suffer minor harm.
 The chances of structural harm and greater government response are also improved if the overpressure rises.
Figure Spread of the distribution for actual pressure

7. Introduction
3. Historical background
 On October 14, 1947; test pilot Chuck Yeager became the first human to break the sound barrier,
achieving Mach 1 in the BellX-1 rocket-powered aircraft.
 To make supersonic transport possible, Concorde technicians contracted to work on parts of the
aviation had to create fresh techniques or refine ancient ones, from fly-by-wire controls in the cockpit
to heat-resistant tires.
Figure First pilot to reach the sound barrier

8. Introduction
4. Prevision attempt to reduce Sonic Boom
 To evaluate sonic booms, NASA launched the Shaped Sonic Boom Experiment in 2001. In an attempt to reduce the
effects of sonic booms during test flights, they modified the fuselage of a Northrop F-5E Tiger II
 Aerion has intended a supersonic LFC wing that decreases drag over the wing by 50 percent.
Figure Spike technique Figure Aerion Aircraft

9. Sonic Boom in the past and the prediction for the future (F-18)

10. II. Methodology
1. Experimental (Wind Tunnel)
2. Analytical (BASS theory)
3. Computational (CFD)

11. Methodology
1. Experiment – UIR Supersonic Wind Tunnel Facility

12. The Schlieren and Shadowgraph System
Visualizing density gradient (1st and 2nd)

13. Methodology
Shadowgraph System
Shadow System setup
Flat mirror
Pin hole
Test section
Flat mirror
Light Source
knife edge
Camera
Shadow Photo at M∞ = 1.8 and
𝜶 = 0o
 The shadowgraph is the second derivative of density.
Shadow glass

14. Schlieren system Setup
Light Source
Pin hole
Test section
Flat mirror
Flat mirror
Camera Knife edge

15. Methodology
Visualization Results
Schlieren Shadowgraph

16. Methodology
Measurement System Setup
 Pressure measurement system Setup (VDAS)

17. Methodology
Measurement System Setup
Versatile Data Acquisition
System (VDAS) software

18. Methodology
The Model
t = 2.1872 mm
c = 25 mm
𝑡
𝑐
= 0.0874
5°
Test section
Body
Measurement
tube

19. Theoretical Flow Filed around the model
 The flow filed around diamond wedge with 5° angle of attack and 0° angle of attack:
△P
Ground
Ground
△P

20. Sample Results (Wind Tunnel)
Number of Point
P (bar)
N-wave

21. Methodology
2. Analytical – The Bakker Asymptote Shock Strength
(BASS)
 The BASS is a nonlinear theory makes use of the characteristic equations for a 2D, steady, inviscid, and
isentropic supersonic flow.
 The BASS measure represents a relation between the body geometry and the asymptotic shock strength it
produces.
 A measure for the sonic boom strength is based on the asymptotic behavior of the interaction between the shock
and expansion waves caused by a body moving with the speed of sound.

22. Methodology
2. Analytical – The Bakker Asymptote Shock Strength (BASS)
 The figure below illustrates the details of an object with geometry y = f(x) in a supersonic
flow field.
 TheΓ+
: characteristics are straight lines and have a slope of
 P(x,y) is an arbitrary point in the upper domain of the profile, the value v for this point is :

23. Methodology
2. Analytical – The Bakker Asymptote Shock Strength (BASS)
Figure: Small part of a profile with length (dx)
• A measure for the sonic boom strength is based on the asymptotic behavior of the interaction between the shock and
expansion waves determined by BASS measure: ( 𝜃 characteristic angle)
• A more conventional way to express shock strengths is :
With 𝐴𝐿 = 𝐴

24. 3. Methodology CFD
 Computational Hardware and Software
 Application
 Computational domain
 Grid

25. Computational Hardware and Software
 Asus intel Core i7, NVIDIA GFORCE 720m
 Apple MacBook Pro 2.6 GHz Intel Core i5, Memory: 8 GB 1600 MHz DDR3
 Software:

26. Methodology
Computation
ANSYS Fluent
Pressure plot Pressure contour

27. CFD
Geometry: Input of the geometry and setting the
computational domain
Meshing: Setting up a dynamic mesh is needed for any
coupled analysis
Setup : Setting up boundary conditions and restrictions.
Solution: Mainly this part of the analysis is reserved to
plotting the variables, such as the pressure distribution
along a surface or the body.
Results: Visual representation of the flow and variable
variation, for example pressure.

28. Computational domain

29. Computational domain
200mm
100mm
M=1.8
P∞= 0.23 bar
25mm
WALL
100 mm
Velocity-Inlet
Pressure-outlet

30. Computational Grid – 2D
 Number of elements: 17200
 Quality ration: 0.604209 < 0.9
 Run time: 10 minutes

31. Computational Grid – 3D
 Number of elements : 80 K
 Quality ratio :0.7856 < 0.9
 Run time : 15 minutes

32. Fluent analysis scheme

33. III. Results
1. Experimental results (Wind tunnel)
2. Computational results (ANSYS)
3. Analytical Results (BASS_Matlab)

34. Results
1. Experimental (Wind Tunnel): (⍺= 0°) Non-lifting case
N-wave
P (bar)
Number of points

35. Results
1. Experimental (Wind Tunnel): (⍺= 5°) lifting case
N-wave
P (bar)
Number of points

36. 2. Results (CFD)- 2D
Non-lifting case (0° degree angle of attack)
P (bar)
X (m)

37. 2. Non-lifting case: 3D
P (bar)
X (m)

38. 2. Results verification
P (bar)
X (m)

39. Body results (Non-lifting case) – 2D
P (bar)
X (m)

40. Body results (Non-lifting case) – 3D
P (bar)
X (m)

41. Pressure contour
Density gradient
Pressure (contour) and density gradient

42. Pressure contour
Density gradient
Angle measurement (comparison)

43. Results
 Lifting case (5° angle of attack)
P (bar)
X (m)

44. Comparison with experimental (5°)
P (bar)
X (m)

45. Pressure contour
Density gradient
5° angle of attack (Lifting case)
Contour plots

46. 3. Analytical Results
Flight conditions (Matlab prediction tool)

47. IV. Minimization to reduce Sonic Boom
 Based on analytical results obtained from Matlab
 The added Spike

48. Sketch of the Diamond wedge (Lambda and t)
“t” Modification
λ Modification
 Optimized Shape

49. Results
Lift Coefficient
Mach 1.8
5° Angle of attack
P∞= 0.23 bar
CL = L/0.5/Gamma/P0/M0/M0/c;
From Matlab:
Flight conditions:

50. Results
Drag Coefficient
Mach 1.8
5° Angle of attack
P∞= 0.23 bar
From Matlab:
CD = D/0.5/Gamma/P0/M0/M0/c;
Flight conditions:

51. Results
Pressure signature and Lift coefficient
Flight conditions:
From Matlab:
DP(i,j) = BASS(M0,M1,M2,alpha,c,t,lamda,h)
BASS is an under function developed in Matlab
M=1.8
P∞= 0.23 bar
5° angle of attack

52. Minimization to reduce Sonic Boom
The Minimized Pressure Signature (Lifting case)
CFD

𝑡
𝑐
= 0.05

𝜆
𝑐
= 0.72

53. Shape corresponding to:
t=0.05c
λ= 0.72c
𝑡
2
= 0.025c
λ = 0.72c
Scheme of the new optimized shape

54. Geometry of the new shape

55.  Number of elements : 50 k roughly
 Quality ratio : 0.6 < 0.9
 Run time : less than 10 minutes
Grid generated

56. Results pressure plot on ground
P (bar)
X (m)
15% reduction

57. Pressure contour

58. Minimization using Spike
Introduction to the idea
 Added spike to the F-15b
 Spike divided into several parts

59. Geometry of the shape with added Spike
M=1.8
P∞= 0.23 bar
0° Angle of attack

60.  Number of elements :100 k
 Quality ratio : 0.85
 Run time : roughly 10 minuttes
New Grid generated

61. Pressure plot on the Ground
P (bar)
X (m)

62. Comparison with Normal model
P (bar)
X (m)
7% reduction

63. Pressure contour for the shape with added spike

64.  Strong initial Shock waves
 Several follow-up shockwaves
Close up look on the spike :

65. V. Conclusion and recommendations
Conclusion:
 The shape “N-wave” which characterizes the “sonic boom” is presented and is in excellent agreement with the
experimental.
 The compute the Lift Coefficient, Drag Coefficient and pressure signature of a Diamond Wedge Airfoil to several
dimensions (t and lamda) are presented using the shock-expansion theory for Lift/Drag Coefficient computation and BASS
theory for pressure signature.
 t=0.05c and lamda = 0.72c for optimized shape:
Recommendations:
• The BASS measure used in this project is first order, the higher order terms was neglected. it is recommend to include also
the higher order terms.
• A measure for validation could be obtained by comparing the BASS results with results from the linear Whitham theory
[Whitham (1952)].

66. Thank You