Repetition Frequency Dependence of Wave Drag Reduction Induced by Laser-Pulse-Energy Depositions

Iwakawa, Akira; Sakai, Takeharu; Sasoh, Akihiro

doi:10.2322/tastj.11.53

Cited by 7 publications

(5 citation statements)

References 23 publications

(37 reference statements)

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“…In this simulation, the distance between the model surface of the cylinder and the center of the energy source is fixed; s=4×r, shown in Figure 1. Absorption efficiency; η a and energy deposition area radius; r 0 are set to η a =0.4, r 0 =1.0mm obtained by previous investigations 7 . These values are fitted by the experimental results of the temporal pressure history.…”

Section: Experimental Setup and Calculation Methodsmentioning

confidence: 99%

Supersonic Drag Reduction Performance of Blunt-Body with Conical Spike using with Energy Depositions

Iwakawa

Hasegawa

Osuka

et al. 2013

44th AIAA Plasmadynamics and Lasers Conference

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The blunt-body with conical spike model was suggested and demonstrated by experimentally and numerically. The results obtained from calculation was qualitatively agreed with measured results. The major purposes of this model are maintaining axisymmetric flow, achieving small baseline drag and keeping vortex residence time in shock layer. An experimenal visualization indicate that the axisymmetric flow was maintained by the effect of the conical spike. The measured and calculated results indicated the baseline drag become smaller by attaching conical spike than the cylinder model. The analyzed results obtained from calculation shows the vortex residence time in shock layer of attaching conical spike model have kept almost same time of the cylinder model under same repetition frequency of energy deposition. The drag and drag reduction performance shows that the tendency have less dependence of attaching conical spike but certain condition achieved better performance than cylinder model. The best performance achieved l cone =8.7mm, d cone /d cylinder =0.50 and f=60kHz.Nomenclature η = efficiency of energy deposition U = flow speed ΔD = drag reduction D = drag D 0 = baseline drag of cylinder model f = frequency E = deposited energy per pulse d cone = bottom radius of conical spike d cylinder = radius of cylinder part l cone = length of conical spike δ = shock stand-off distance s = distance of energy deposition area from model head of cylinder part Q = spatial distribution of deposited energy source λ = step function q 0 = total input power per unit mass x 0 = center position of deposited energy source r 0 = radius of deposited energy source t = elapsed time τ = deposited energy pulse duration η a = effectively-deposited energy ratio

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Section: Experimental Setup and Calculation Methodsmentioning

confidence: 99%

Supersonic Drag Reduction Performance of Blunt-Body with Conical Spike using with Energy Depositions

Iwakawa

Hasegawa

Osuka

et al. 2013

44th AIAA Plasmadynamics and Lasers Conference

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“…[22][23][24] The drag reduction mechanisms enabled by energy deposition have been discussed using computational fluid dynamics. 12,15,25) Applying energy deposition a high-temperature low-density bubble, a so-called "thermal bubble" generated upstream, and the shock-wave is weakened when interacting with the bubble; the acoustic impedance of which is lower than that of the post-shock flow. As a result, the shock-wave extrudes upstream (lens effect 26) ).…”

Section: Introductionmentioning

confidence: 99%

“…15,27) The pressure in the shock layer is mitigated in the vortex ring, thereby reducing the drag. 25) This is the basic mechanism of drag reduction using energy deposition.…”

Section: Introductionmentioning

confidence: 99%

Mach Number Effect on Supersonic Drag Reduction using Repetitive Laser Energy Depositions over a Blunt Body

Iwakawa

Shoda

Majima

et al. 2017

Trans. Japan Soc. Aero. S Sci.

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Supersonic drag reduction performance using repetitive pulse energy depositions over blunt bodies was experimentally studied under two Mach numbers. The normalized drag reduction and energy deposition efficiency of Mach-1.92 over a 10-mm-dia. blunt-cylinder model were 8% and 1.2 at most, respectively. On the other hand, these values at Mach-3.20 over the same model were 22% and 6.2, respectively. The shock-wave deformation period using single-pulse energy deposition at Mach-3.20 was 64 ®s. This duration was shorter than that of 80 ®s at Mach-1.92, but the deformation magnitude on the model center axis of 40% at Mach-3.20 was larger than that of 15% at Mach-1.92. These experimental characteristics were consistent as solutions of the Riemann problem. Moreover, a drag reduction performance was much improved with a larger model diameter of 20 mm. Therefore, it has been experimentally demonstrated that the drag reduction performance due to energy deposition improves much at a high Mach number and with large model dimensions.

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“…The absorption efficiency η and the laser-heated radius 𝑟𝑟 0 in Eq. ( 9) are set to 0.4 and 1.0 mm, respectively, based on the research of Iwakawa et al, [37][38] in which the same experimental equipment was used. The experimental measurements of the change in diameter of the bubble with different laser deposition energies are shown in Table I.…”

Section: 𝑓𝑓(𝑀𝑀mentioning

confidence: 99%

Numerical and experimental study on the behavior of vortex rings generated by shock–bubble interaction

et al. 2022

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In this study, three-dimensional numerical simulations and experiments of the interaction between a normal shock and bubbles generated by the repetitive energy depositions of a laser pulse in a Mach 1.92 flow was conducted. As a result of the shock–bubble interaction, a vortex ring, caused by a baroclinic effect, was generated. Owing to the self-induced velocity field, the advection velocity of the vortex rings decreased with increasing laser pulse energy. In the experiments, when interactions among the vortex rings became strong, separations in transverse directions between adjacent bubbles were induced. This was reproduced through numerical simulations by imposing an artificial disturbance in the initial positions of the bubbles, i.e., by 5% of the bubble diameter in a transversal direction. The asymmetric behaviors of a row of vortex rings were classified into three patterns based on the ratio of the distance between the vortex rings to the size of the vortex rings ( λ: inverse Strouhal number). In pattern 1, with λ >2.9, there was negligible interference between the vortex rings because the interval of the vortex rings was sufficiently large. In pattern 2, with λ = 0.97–1.2, separation in the vortex-ring rows appeared, and the separation angle increased as λ decreased. In pattern 3, with λ <0.62, the interference intensified, and the vortex rings collapsed, forming a turbulent flow behind the shock wave.

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Repetition Frequency Dependence of Wave Drag Reduction Induced by Laser-Pulse-Energy Depositions

Cited by 7 publications

References 23 publications

Supersonic Drag Reduction Performance of Blunt-Body with Conical Spike using with Energy Depositions

Supersonic Drag Reduction Performance of Blunt-Body with Conical Spike using with Energy Depositions

Mach Number Effect on Supersonic Drag Reduction using Repetitive Laser Energy Depositions over a Blunt Body

Numerical and experimental study on the behavior of vortex rings generated by shock–bubble interaction

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