Investigation rear-end of flow structures on a 6:1 prolate spheroid by using the magnetic suspension and balance system

Ambo, Takumi; Otsuki, Takaya; Taniguchi, Shuhei; Numata, Daiju; Asai, Keisuke

doi:10.2514/6.2016-4158

Cited by 5 publications

(6 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 95% con dence intervals are also shown as error bars. The C D and C L are de ned by equation ( 1) and ( 2), while the C m is de ned by equation (3).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Is the pitching moment acting on a Javelin always nose-down?

Seo

Okuizumi

Konishi

et al. 2022

Preprint

View full text Add to dashboard Cite

The rules governing the dimensions of the Javelin were substantially changed in 1986. It was considered that this new design guaranteed there was zero pitching moment at 0° angle of attack and that the pitching moment decreased (became negative) with increasing angle of attack. The objective of this study is to investigate if the pitching moment remains always negative (nose-down rotation). To measure accurate aerodynamic forces acting on a Javelin, the world’s largest 1m magnetic suspension and balance system was used. The magnetic suspension and balance system was able to measure aerodynamic forces without support interference in the wind tunnel. In addition, computational fluid dynamics were carried out to estimate the pitching moment coefficients. It was found that the pitching moment coefficient of a commercially available Javelin becomes positive (nose-up rotation) at lower angles of attack, less than 12°. The pitching moment becomes positive if the upstream side of the center of gravity receives more inflow than the downstream side. This situation can be attained by, for example, increasing the thickness of the upstream side when compared with that of the downstream side.

show abstract

“…The 95% con dence intervals are also shown as error bars. The C D and C L are de ned by equation ( 1) and ( 2), while the C m is de ned by equation (3).…”

Section: Resultsmentioning

confidence: 99%

“…However, the supporting rod disturbs the ow and this is known as support interference. For example, the separation line on the ellipsoid has been observed to drastically move backwards when using a thin rod whose diameter is 0.5 mm 3 . Generally, in the case of the equipment of sports, the sizes are comparable with hands or feet.…”

Section: Introductionmentioning

confidence: 99%

Is the pitching moment acting on a Javelin always nose-down?

Seo

Okuizumi

Konishi

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…The lift force and pitching moment are controlled by the currents flowing through upper and lower coils 1, 3, 5, and 7, while the side and yawing motions are controlled by currents flowing through coils 2, 4, 6, and 8. 31) The positions and attitudes of the model in the supportfree, levitated test were detected by an optical sensor subsystem oriented orthogonally to the model (Fig. A1(b)).…”

Section: Discussionmentioning

confidence: 99%

Effect of Boattail Angle on Pressure Distribution and Drag of Axisymmetric Afterbodies under Low-Speed Conditions

Ambo

Chen

Nonomura

et al. 2019

Trans. Japan Soc. Aero. S Sci.

Self Cite

View full text Add to dashboard Cite

This study is focused on the effect of boattail angle on the pressure distribution and drag force of axisymmetric afterbodies under low-speed conditions. Experiments were conducted on three conical boattails with angles of 10°, 14°and 20°. The diameter-based Reynolds number is approximately 4.3 © 10 4 under the experimental conditions. Two types of flows, a fully-attached flow (¢ = 10°) and a flow with a separation bubble (¢ = 14°, 20°), were observed. The aerodynamic drag measurements were conducted using both a strut-supported model and a support-free (levitated) model. The results show that boattail model with the angle of 20°has a relatively large effect on the pressure distribution. The pressure drag resulting from pressure distribution on the vertical plane indicates that the model with a boattail angle of 14°has the lowest drag. A good trend in agreement between afterbody drag (measured using pressure taps) and total aerodynamic drag (measured using the levitated system) was obtained. The effect of strut support on pressure distribution at different polar angles is also explained in this study.

show abstract

“…The cross-flow separation is not only influenced by α but is also dependent on Re. Ambo et al (2016) observed laminar flow separation of an inclined prolate spheroid for Re = 0.5 × 10 6 using oil flow visualizations. Ahn (1992) performed a series of studies over a wide Re range (1.39 × 10 6 ≤ Re ≤ 4.2 × 10 6 ) and defined a critical Reynolds number of Re c = 2.5 × 10 6 .…”

Section: Introductionmentioning

confidence: 97%

Vortex-wake formation and evolution on a prolate spheroid at subcritical Reynolds numbers

Guo

Kaiser

Rival

2023

Preprint

View full text Add to dashboard Cite

Three-dimensional (3D) flow reconstruction over a 6:1 prolate spheroid using scanning stereoscopic particle image velocimetry has been conducted in a towing-tank facility. Forces, moments, surface pressure and reconstructed 3D vortical-flow structures are acquired in order to characterize the separated flow within the subcritical regime at three Reynolds numbers (Re = 0.5 × 106, 1.0 × 106 and 1.5 × 106), and at four incidence angles (α = 5◦, 10◦, 15◦ and 20◦). Key flow features are evaluated through the reconstructed 3D flowfield data. In particular, the interaction of the crossflow vortices and the surface-pressure distribution are discussed. It is shown that the crossflow vortices consist of helical vortex tubes as the dominant coherent structures, which are more distinct at large α. For α ≥ 15◦, four high-vorticity regions were observed. A pair of upper vortex tubes, originate on the windward side of the model, while a lower vortex tube is formed on the strong curvature region on the leeward side of the model. The vortex dynamics are further characterized through stretching and tilting terms via the vorticity-transport equation. Larger incidence angles α lead to a stronger alignment of the crossflow vortices with the mean flow direction, which is reflected in the tilting terms. A weak Re dependency of the loads and flow structures within the range 1.0 × 106 ≤ Re ≤ 1.5 × 106 is reported, while a significantly different result was captured for separation at Re = 0.5 × 106. An increase in separation size at Re = 0.5 × 106 at 20◦ results in an additional flow structure; a pair of secondary vortices is formed, leading to a change in the pressure distribution on the model surface when compared to higher Re.

show abstract

Investigation rear-end of flow structures on a 6:1 prolate spheroid by using the magnetic suspension and balance system

Cited by 5 publications

References 8 publications

Is the pitching moment acting on a Javelin always nose-down?

Is the pitching moment acting on a Javelin always nose-down?

Effect of Boattail Angle on Pressure Distribution and Drag of Axisymmetric Afterbodies under Low-Speed Conditions

Vortex-wake formation and evolution on a prolate spheroid at subcritical Reynolds numbers

Contact Info

Product

Resources

About