The effect of nose bluntness of a low-boom configuration on sonic-boom

Makino, Yoshikazu; Sugiura, Takaaki; Watanuki, Tadaharu; Kubota, Hirotoshi; Aoyama, Takashi; Iwamiya, Toshiyuki

doi:10.2514/6.1997-2213

“…3) designed by Darden's method was predicted in our previous study. 9 The dimensions of this aircraft and ight conditions are shown in Table 1. Darden's low-boom design method provides only the total equivalent-area distribution, which consists of two basic components: the actual area of the con guration and the equivalent area that is due to the distribution of lift.…”

Section: Low-boom Design Methods Based On Linear Theorymentioning

confidence: 99%

Numerical Optimization of Fuselage Geometry to Modify Sonic-Boom Signature

Makino¹,

Aoyama²,

Iwamiya³

et al. 1999

Journal of Aircraft

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A low-sonic-boom design method is developed by combining a three-dimensional Euler computational uid dynamics code with a least-squares optimization technique. In this design method, the fuselage geometry of an aircraft is modi ed to minimize the pressure discrepancies between a target low-boom pressure signature and a calculated signature. The aircraft con gurations that generate three types of low-boom pressure signatures, i.e., attop type, ramp type, and hybrid type, are successfully designed by this method. It is shown that the sonic-boom intensity of the aircraft designed by linear theory is reduced and the attop-type ground pressure signature is obtained by this method. The results of the study suggest that this method is a useful tool for low-boom design. NomenclatureA e = equivalent-area distribution of aircraft C D p = pressure drag coef cient C L = lift coef cient F.¿ / = F function H = normal distance from aircraft J = object function in optimization process K = number of design variables used in optimization process L = aircraft length M = freestream Mach number P b= baseline pressure in optimization process P t = target pressure in optimization process p 1 = freestream static pressure x = streamwise location y = spanwise location = p M 2 ¡ 1°= speci c heat ratio 1p = shock overpressure 1S = element length of pressure signature 1T R = rise time of shock overpressure ± k = kth design variable Subscript i = i th element of pressure signature in optimization process

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“…Figure 20(b) shows how the oscillations in the front part of the predicted ground signature gradually disappear as the matching errors become zero for x e ≤ x * e (= 10, 40, 70, and 100). Figure 21(a) shows the differences of A * e (x e ) generated by the second formula in equation (10) and the target distribution, with x * e = 90, 70, 40, and 10. Figure 21(b) shows that the aft part of the predicted ground signature matches the target signature when the matching errors become zero for x e ≥ 90, and it also shows how the oscillations in the front part of the predicted ground signature gradually disappear as the matching errors become zero for x e ≥ x * e (= 90, 70, 40, and 10).…”

Section: Relationship Between Area Distribution and Ground Signamentioning

confidence: 99%

“…where τ (x e ) is a piecewise linear polynomial defined by one of the following two formulas: Figure 20(a) shows the differences of A * e (x e ) generated by the first formula in equation (10) and the target distribution, with x * e = 10, 40, 70, and 100. Figure 20(b) shows how the oscillations in the front part of the predicted ground signature gradually disappear as the matching errors become zero for x e ≤ x * e (= 10, 40, 70, and 100).…”

Section: Relationship Between Area Distribution and Ground Signamentioning

confidence: 99%

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Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts

Li

¹

,

Shields

²

,

Le

³

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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There are several research papers on how to design a supersonic configuration that has desirable low-boom characteristics as determined by the Seebass-George-Darden boom minimization theory (SGD theory). The low-boom signatures predicted by the SGD theory could be realized by wing-fuselage configurations. However, for a given low-boom signature generated by the SGD theory, it is still an open question whether one could develop a feasible aircraft configuration with nacelles and tails that has a similar low-boom ground signature as that predicted by the SGD theory.Past attempts indicated that no feasible aircraft configuration with nacelles and tails would have a total equivalent area distribution matching one of the equivalent area distributions corresponding to the low-boom ground signatures determined by the SGD theory. There are essentially three alternative methods for generating a supersonic concept with a shaped boom ground signature: (i) use a direct optimization method that minimizes numerical figures of merit for low-boom characteristics, (ii) construct new "realizable" target equivalent area distributions (or near-field pressure distributions) that result in shaped boom ground signatures, and (iii) develop new tools to help designers find acceptable low-boom configurations. There were many attempts, with mixed results, using the first two methods to obtain supersonic configurations that have shaped boom ground signatures.This paper introduces a tool called BOSS (Boom Optimization using Smoothest Shape modifications). BOSS utilizes interactive inverse design optimization to develop a fuselage shape that yields a low-boom aircraft configuration. The paper also demonstrates how BOSS could be used to help design realistic aircraft concepts with low-boom ground signatures. A fundamental reason for developing BOSS is the need to generate feasible low-boom conceptual designs that are appropriate for further refinement using CFD-based preliminary design methods. BOSS was not developed to provide a numerical solution to the inverse design problem. Instead, BOSS was intended to help designers find the "right" configuration among infinitely many possible configurations that are equally good using any numerical figure of merit.BOSS uses the smoothest shape modification strategy for modifying the fuselage radius distribution at 100 or more longitudinal locations to find a smooth fuselage shape that reduces the discrepancies between the design and target equivalent area distributions over any specified range of effective distance. For any given supersonic concept (with wing, fuselage, nacelles, tails, and/or canards), a designer can examine the differences between the design and target equivalent areas, decide which part of the design equivalent area curve needs to be modified, choose a desirable rate for the reduction of the discrepancies over the specified range, and select a parameter for smoothness control of the fuselage shape. BOSS will then generate a fuselage shape based on the designer's inputs in a matter ...

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Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts

Li

¹

,

Shields

²

,

Le

³

2008

Journal of Aircraft

View full text Add to dashboard Cite

There are several research papers on how to design a supersonic configuration that has desirable low-boom characteristics as determined by the Seebass-George-Darden boom minimization theory (SGD theory). The low-boom signatures predicted by the SGD theory could be realized by wing-fuselage configurations. However, for a given low-boom signature generated by the SGD theory, it is still an open question whether one could develop a feasible aircraft configuration with nacelles and tails that has a similar low-boom ground signature as that predicted by the SGD theory.Past attempts indicated that no feasible aircraft configuration with nacelles and tails would have a total equivalent area distribution matching one of the equivalent area distributions corresponding to the low-boom ground signatures determined by the SGD theory. There are essentially three alternative methods for generating a supersonic concept with a shaped boom ground signature: (i) use a direct optimization method that minimizes numerical figures of merit for low-boom characteristics, (ii) construct new "realizable" target equivalent area distributions (or near-field pressure distributions) that result in shaped boom ground signatures, and (iii) develop new tools to help designers find acceptable low-boom configurations. There were many attempts, with mixed results, using the first two methods to obtain supersonic configurations that have shaped boom ground signatures.This paper introduces a tool called BOSS (Boom Optimization using Smoothest Shape modifications). BOSS utilizes interactive inverse design optimization to develop a fuselage shape that yields a low-boom aircraft configuration. The paper also demonstrates how BOSS could be used to help design realistic aircraft concepts with low-boom ground signatures. A fundamental reason for developing BOSS is the need to generate feasible low-boom conceptual designs that are appropriate for further refinement using CFD-based preliminary design methods. BOSS was not developed to provide a numerical solution to the inverse design problem. Instead, BOSS was intended to help designers find the "right" configuration among infinitely many possible configurations that are equally good using any numerical figure of merit.BOSS uses the smoothest shape modification strategy for modifying the fuselage radius distribution at 100 or more longitudinal locations to find a smooth fuselage shape that reduces the discrepancies between the design and target equivalent area distributions over any specified range of effective distance. For any given supersonic concept (with wing, fuselage, nacelles, tails, and/or canards), a designer can examine the differences between the design and target equivalent areas, decide which part of the design equivalent area curve needs to be modified, choose a desirable rate for the reduction of the discrepancies over the specified range, and select a parameter for smoothness control of the fuselage shape. BOSS will then generate a fuselage shape based on the designer's inputs in a matter ...

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The effect of nose bluntness of a low-boom configuration on sonic-boom

Cited by 3 publications

References 3 publications

Numerical Optimization of Fuselage Geometry to Modify Sonic-Boom Signature

Numerical Optimization of Fuselage Geometry to Modify Sonic-Boom Signature

Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts

Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts

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