Experimental study of flow straightening and turbulence reduction characteristics for porosity honeycomb
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摘要: 蜂窝器是安装在风洞稳定段中用来提高风洞试验段气流均匀性、降低气流偏角及湍流度的重要整流装置。普通的实壁蜂窝器需要通过提高蜂窝器单元的长径比来达到提升整流特性的目的,但同时带来了损失系数增加等问题。设计了一种在蜂窝单元壁面开孔的蜂窝器,通过蜂窝器壁面上的开孔,实现了蜂窝器单元之间的旋涡和压力的传递,可以有效地提高蜂窝器的整流效果。在0.55m×0.4m低噪声航空声学风洞闭口试验段中,在不同来流速度条件下,使用热线风速仪对普通蜂窝器和开孔壁蜂窝器下游的速度及湍流度分布特性进行了试验研究。实验结果表明,与普通的实壁蜂窝器相比,开孔率为50%的开孔壁蜂窝器下游的湍流度可降低13.8%,蜂窝器下游的速度分布得到了改善,局部气流偏角也明显减小。在风洞设计中,使用优化后的开孔壁蜂窝器可以减少阻尼网的层数或收缩段的收缩比,从而降低风洞的运行能耗,并减少风洞的建设费用。Abstract: The honeycomb is an important device which is installed in wind tunnel settling chamber to improve the flow uniformity and decrease the flow angle as well as the turbulence intensity in the wind tunnel test section. For a regular honeycomb, in order to improve the flow straightening and turbulence reduction characteristics, a large length-diameter ratio must be used in the design of the honeycomb which results in the increase of total pressure loss of the honeycomb. A new type of honeycomb with a group of small holes on the wall of honeycomb cells is designed. This type of porosity honeycomb can achieve the exchange of the vortices and pressure between different cells to significantly improve the flow quality downstream the honeycomb. In the solid wall test section of the 0.55m×0.40m low noise aeronautic acoustic wind tunnel, the 2D hot wire is used to measure the turbulence intensity and velocity distribution downstream the porosity honeycomb and the regular one respectively with different flow velocities. The experimental results indicate that the honeycomb with 50% transverse porosity can reduce the turbulence intensity by 13.8% compared against the regular one. The velocity distribution downstream the honeycomb becomes smoother and the flow angle is also reduced. The design of the flow straightening and turbulence reduction system for the wind tunnel with the optimized porosity honeycomb can reduce the number of screens or the constriction ratio of the wind tunnel, and therefore, reduce the power consumption and the construction budget of wind tunnels.
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Key words:
- wind tunnel /
- honeycomb /
- flow quality /
- turbulence intensity /
- flow angularity /
- hot wire
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表 1 蜂窝器试验件设计参数
Table 1. Honeycomb design parameter
编号 开孔数量 D0/mm L0/mm 开孔直径d/mm mod1 实壁 —— —— —— mod2 12 4 4 1.7 mod3 8 6 6 2.1 mod4 12 6 4 1.7 mod5 8 8 4 2.1 表 2 湍流度测试结果
Table 2. Turbulence intensity measurement results
试验
条件Vmean=8m/s Vmean=13m/s Vmean=18m/s Tux Tuy Tux Tuy Tux Tuy mod1 0.1085 0.0408 0.0832 0.0307 0.0807 0.0298 mod2 0.1079 0.0420 0.0797 0.0313 0.0776 0.0301 mod3 0.0877 0.0357 0.0708 0.0268 0.0722 0.0273 mod4 0.0971 0.0386 0.0758 0.0290 0.0748 0.0284 mod5 0.1042 0.0392 0.0787 0.0292 0.0786 0.0288 No honeycomb — — 0.1053 0.0920 — — -
[1] 张仲寅, 乔志德.粘性流体力学[M].北京:北京航空学院出版社, 1989.Zhang Z Y, Qiao Z D. Mechanics of viscous fluids[M]. Beijing:Beijing Aeronautics College Press, 1989. [2] 刘政崇.高低速风洞气动与结构设计[M].北京:国防工业出版社, 2003.Liu Z C. The aerodynamic and structure design of high speed and low speed wind tunnel[M]. Beijing:National Defense Industry Press, 2003. [3] 伍荣林, 王振羽.风洞设计原理[M].北京:北京航空学院出版社, 1985.Wu R L, Wang Z Y. Wind tunnel design principle[M]. Beijing:Beijing Aeronautics College Press, 1985. [4] Stanniland. Improvement of the flow quality in ARA transonic tunnel by means of a long cell honeycomb[R]. ARA-Memo-375, 1992. [5] Ahmad D Vakili. A new honeycomb for low isotropic turbulence[J]. AIAA-2003-3880, 2003. [6] 李鹏, 汤更生, 余永生, 等.航空声学风洞的声学设计研究[J].实验流体力学, 2011, 25(3):82-86. http://www.syltlx.com/CN/abstract/abstract10664.shtmlLi P, Tang G S, Yu Y S, et al. Research of acoustic design for aeroacoustic wind tunnel[J]. Journal of Experiments in Fluid Mechanics, 2011, 25(3):82-86. http://www.syltlx.com/CN/abstract/abstract10664.shtml [7] 廖达雄, 陈吉明, 彭强, 等.连续式跨声速风洞设计关键技术[J].实验流体力学, 2011, 25(4):74-78. http://www.syltlx.com/CN/abstract/abstract10640.shtmlLiao D X, Chen J M, Peng Q, et al. Key design techniques of the low noise continuous transonic wind tunnel[J]. Journal of Experiments in Fluid Mechanics, 2011, 25(4):74-78. http://www.syltlx.com/CN/abstract/abstract10640.shtml [8] 廖达雄, 黄知龙, 陈振华, 等.大型低温高雷诺数风洞及其关键技术综述[J].实验流体力学, 2014, 28(2):1-6, 20. http://www.syltlx.com/CN/abstract/abstract10710.shtmlLiao D X, Huang Z L, Cheng Z H, et al. Review on large-scale cryogenic wind tunnel and key technologies[J]. Journal of Experiments in Fluid Mechanics, 2014, 28(2):1-6, 20. http://www.syltlx.com/CN/abstract/abstract10710.shtml [9] Grunnet J, Nelson D. The new FFA T1500 transonic wind tunnel initial operation, calibration and test result[C]. AIAA 16th Aerodynamic Ground Testing Conference, Seattle, 1990. [10] 屈晓力, 余永生, 廖达雄, 等.声学引导风洞高效低噪声风扇设计[J].实验流体力学, 2013, 27(3):103-107, 112. http://www.syltlx.com/CN/abstract/abstract10442.shtmlQu X L, Yu Y S, Liao D X, et al. The design of the high-performance low-noise fan of the acoustic pilot wind tunnel[J]. Journal of Experiments in Fluid Mechanics, 2013, 27(3):103-107, 112. http://www.syltlx.com/CN/abstract/abstract10442.shtml [11] Harald Q. Hot-wire measurements in cryogenic environment[R]. AIAA-2011-880, 2011. [12] Cukurel B, Acarer S, Arts T. A novel perspective to high-speed cross-hot-wire calibration methodology[J]. Experimental Fluids, 2012, 53(4):1073-1085. doi: 10.1007/s00348-012-1344-y