| Title: | Direct numerical simulation of hypersonic boundary layer transition over a blunt cone with a small angle of attack |
| Authors: | Li XL(李新亮); Fu DX(傅德薰); Ma YW(马延文) |
| Issue Date: | 2010 |
| Abstract: | The direct numerical simulation of boundary layer transition over a 5° half-cone-angle blunt cone
is performed. The free-stream Mach number is 6 and the angle of attack is 1°. Random wall
blow-and-suction perturbations are used to trigger the transition. Different from the authors’
previous work [Li et al., AIAA J. 46, 2899(2008)],
the whole boundary layer flow over the cone
is simulated (while in the author’s previous work, only two 45° regions around the leeward and the
windward sections are simulated). The transition location on the cone surface is determined through
the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a
nonmonotonic curve and the transition is delayed in the range of 0° ≤ θ ≤ 30° (θ = 0° is the leeward
section). The mechanism of the delayed transition is studied by using joint frequency spectrum
analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the
second mode are suppressed in the range of 20° ≤ θ ≤ 30°, which leads to the delayed transition
location. Very low frequency waves VLFWs� are found in the time series recorded just before the
transition location, and the periodic times of VLFWs are about one order larger than those of
ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves,
and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves
when they are strong enough.The direct numerical simulation of boundary layer transition over a 5° half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1°. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors’ previous work [ Li et al., AIAA J. 46, 2899 (2008) ], the whole boundary layer flow over the cone is simulated (while in the author’s previous work, only two 45° regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 20° ≤ θ ≤ 30° (θ = 0° is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20° ≤ θ ≤ 30°, which leads to the delayed transition location. Very low frequency waves (VLFWs) are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough. |
| URI: | http://dspace.imech.ac.cn/handle/311007/33062 |
| discipline: | 流体力学 |
| Citation: | Physics of Fluids.2010,22(2):025105-1-18 |
| Appears in Collections: | 高温气体动力学重点实验室_期刊论文
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| PhysFluids_22_025105[1].pdf | | 3867Kb | Adobe PDF | View/Open |
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