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| 1 | Experimental investigation of boundary layer transition over a delta wing at Mach number 6显示文摘An experimental study on the boundary layer transition over a delta wing was carried out at Mach number 6 in a quiet wind tunnel.The Nano-tracer-based Planar Laser Scattering(NPLS)and Temperature-Sensitive Paints(TSP)techniques were used to measure the fine flow field structure and the wall Stanton number of the delta wing.The influence of factors such as the angle of attack and the Reynolds number was studied.The following results were obtained.The boundary layer transition between the leading edge and the centerline was dominated by the crossflow instability.At the location of the initial appearance of the traveling crossflow waves,the Stanton number began to rise.The Stanton number reached a maximum when the crossflow waves were broken up to turbulence.Increasing the angle of attack increased the spanwise pressure gradient at the windward side of the delta wing,thereby increasing the crossflow instability and advancing the boundary layer transition front.However,increasing the angle of attack caused the transition front to move backward at the leeward side.In addition,the sensitivity of the boundary layer transition to the Reynolds number varied with the angle of attack and the region. | Haibo NIU Shihe YI Xiaolin LIU Xiaoge LU Dundian GANG | 2020 | Chinese Journal of Aeronautics2020，33，7： | 9 |
| 2 | A swept fin-induced flow field with different height mounting gaps显示文摘In order to apply the air fin successfully and ensure the maneuverability of hypersonic vehicle, a key problem to be studied urgently is the heat flux brought by the fin mounting gap.The appearance of mounting gap and fin shaft can induce many complex flow structures which need more attentions to be investigated. Under Ma 6, Nano-tracer-based Planar Laser Scattering(NPLS)and Temperature Sensitive Paints(TSP) were applied to visualize and measure transient flow structures and heat flux distribution of a swept fin-induced flow field with different height mounting gaps. Complementarily, Reynolds-averaged N-S equations were solved with k-x SST turbulent model. The heat flux distribution results of numerical simulation and TSP observed the change of high heat flux region with different mounting gap, both in position and magnitude. The streamlines based on Computational Fluid Dynamics(CFD) and flow visualization results obtained by NPLS revealed the cause of high heat flux region. The high heat flux region in this flow field is mainly related to the reattachment of vortex and flow stagnation. The increase of gap height can lead to stronger gap overflow and shaft-induced horseshoe vortex, which are source of the high heat flux around the fin. The case with the highest mounting gap(4 mm) en-counters the most severe aerodynamic heating, both on the surface of fin and plate. Thus, under the premise of ensuring the flexibility of the fin, the gap should be set as small as possible. | Feng ZHANG Shihe YI Xiwang XU Haibo NIU Xiaoge LU | 2021 | Chinese Journal of Aeronautics2021，34，1： | 2 |
| 3 | Integrating polygenic and clinical risks to improve stroke risk stratification in prospective Chinese cohorts显示文摘The utility of the polygenic risk score(PRS)to identify individuals at higher risk of stroke beyond clinical risk remains unclear,and we clarified this using Chinese population-based prospective cohorts.Cox proportional hazards models were used to estimate the 10-year risk,and Fine and Gray’s models were used for hazard ratios(HRs),their 95%confidence intervals(CIs),and the lifetime risk according to PRS and clinical risk categories.A total of 41,006 individuals aged 30–75 years with a mean follow-up of 9.0 years were included.Comparing the top versus bottom 5%of the PRS,the HR was 3.01(95%CI 2.03–4.45)in the total population,and similar findings were observed within clinical risk strata.Marked gradients in the 10-year and lifetime risk across PRS categories were also found within clinical risk categories.Notably,among individuals with intermediate clinical risk,the 10-year risk for those in the top 5%of the PRS(7.3%,95%CI 7.1%–7.5%)reached the threshold of high clinical risk(≥7.0%)for initiating preventive treatment,and this effect of the PRS on refining risk stratification was evident for ischemic stroke.Even among those in the top 10%and 20%of the PRS,the 10-year risk would also exceed this level when aged≥50 and≥60 years,respectively.Overall,the combination of the PRS with the clinical risk score improved the risk stratification within clinical risk strata and distinguished actual high-risk individuals with intermediate clinical risk. | Qingmei Cui Fangchao Liu Jianxin Li Xiaoge Niu Zhongying Liu Chong Shen Dongsheng Hu Keyong Huang Shufeng Chen Jie Cao Xiaoqing Liu Ling Yu Fanghong Lu Xianping Wu Liancheng Zhao Jianfeng Huang Ying Li Zhibin Hu Hongbing Shen Dongfeng Gu Xiangfeng Lu | 2023 | Science China(Life Sciences)2023，66，7： | 0 |
| 4 | Experimental investigation of expansion effect on shock wave boundary layer interaction near a compression ramp显示文摘The experiment is conducted to investigate the effect of expansion on the shock wave boundary layer interaction near a compression ramp. The small-angle expansion with an angle degree of 5° occurs at different positions in front of the compression ramp. The particle image velocimetry and flow visualization technology show the flow structures, velocity field, and velocity fluctuation near the compression ramp. The mean pressure distribution, pressure fluctuation, and power spectral density are measured by high-frequency response pressure transducers. The experimental results indicate that the expansion before the compression ramp position affects the shock wave boundary layer interaction to induce a large-scale separation. But the velocity fluctuation and pressure fluctuation are attenuated near the large-scale flow separation region. When the expansion occurs closer to the compression ramp, the expansion has a more significant impact on the flow. The fluctuation of velocity and pressure is significantly attenuated, and the wall pressure rise of the separation point is reduced obviously. And the characteristic low-frequency spectrum signal related to the unsteadiness of the shock wave boundary layer interaction is significantly suppressed. In addition, variation of the separation region scale at different compression angle degrees is distinctive with the effect of expansion. | Junjie HUO Shihe YI Wenpeng ZHENG Haibo NIU Xiaoge LU Dundian GANG | 2022 | Chinese Journal of Aeronautics2022，35，12： | 0 |
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