【摘要】：脊?fàn)畋砻鏈p阻作為仿生減阻的重要技術(shù)之一,以其低能耗和減阻效果明顯而著稱(chēng),是一種高效、實(shí)用的邊界層減阻技術(shù)。目前,該技術(shù)在航海、交通工具、航空航天、流體機(jī)械、油氣輸運(yùn)、體育、醫(yī)療等領(lǐng)域得到了較為廣泛應(yīng)用。本文通過(guò)數(shù)值模擬的方法,以三維槽道為研究對(duì)象,研究在不同速度下脊?fàn)罱Y(jié)構(gòu)頂角β對(duì)流動(dòng)阻力的影響。該部分從脊?fàn)罱Y(jié)構(gòu)對(duì)局部壓力的影響入手,逐步分析脊?fàn)罱Y(jié)構(gòu)對(duì)近壁面速度分布、速度梯度分布、壁面剪切應(yīng)力分布、摩擦阻力系數(shù)等基本流動(dòng)參數(shù)影響,得到不同工況下的減阻效果。為了對(duì)減阻效果進(jìn)行更好的解釋,研究了脊?fàn)罱Y(jié)構(gòu)對(duì)法向速度脈動(dòng)、流向渦的影響,從渦結(jié)構(gòu)的角度對(duì)減阻機(jī)理進(jìn)行探索分析。結(jié)果表明:溝槽內(nèi)形成的漩渦結(jié)構(gòu)可以有效的減小脊?fàn)罱Y(jié)構(gòu)布置區(qū)域速度梯度和壁面剪切應(yīng)力,最終減小摩擦阻力。脊?fàn)罱Y(jié)構(gòu)頂角β=90°,25m/s的速度下取得的最大減阻率為9.71%。在脊?fàn)罱Y(jié)構(gòu)布置的區(qū)域,流向渦的渦頭上揚(yáng)的角度變大,致使由流向渦引起的“上揚(yáng)”和“下掃”事件減弱,有效的減小了摩擦阻力。此外,脊?fàn)罱Y(jié)構(gòu)布置區(qū)域流向渦的失穩(wěn)破碎明顯;流經(jīng)脊?fàn)罱Y(jié)構(gòu)段后,流向渦的空間密度分布顯著減小,這個(gè)可能是因?yàn)榧範(fàn)罱Y(jié)構(gòu)影響了y+在20?60范圍內(nèi)自維持過(guò)程中流向渦的再生,同樣達(dá)到了減小壁面的摩擦阻力的效果。在得到脊?fàn)罱Y(jié)構(gòu)減阻機(jī)理后,本文研究了脊?fàn)罱Y(jié)構(gòu)布置位置和壓力梯度對(duì)NACA0018翼型流動(dòng)及噪聲特性的影響。主要分析了脊?fàn)罱Y(jié)構(gòu)對(duì)翼型邊界層速度分布、尾跡速度分布、表面壓力系數(shù)、升阻比的影響,并且通過(guò)熵產(chǎn)分析的方法研究了脊?fàn)罱Y(jié)構(gòu)對(duì)能量耗散的控制作用,最后對(duì)監(jiān)視點(diǎn)處噪聲信號(hào)的時(shí)域和頻率進(jìn)行分析,研究了脊?fàn)罱Y(jié)構(gòu)對(duì)NACA0018翼型噪聲特性的影響。結(jié)果表明:α=6°攻角下,riblet-H脊?fàn)罱Y(jié)構(gòu)翼型可以有效的減小邊界層的分離區(qū)域,減小尾跡速度虧損,此外還可以提高翼型的升力系數(shù),減少翼型阻力系數(shù),24m/s的工況下升阻比相對(duì)光滑翼型而言提高了53.418%。在噪聲方面,riblet-H翼型模型有效的減少了0-3000Hz頻率范圍內(nèi)的噪聲。通過(guò)對(duì)漩渦結(jié)構(gòu)及熵產(chǎn)的分析發(fā)現(xiàn),在α=6°攻角下riblet-H翼型可以有效的控制漩渦結(jié)構(gòu)的生成和高熵產(chǎn)結(jié)構(gòu)的能量耗散。
[Abstract]:As one of the important bionic drag reduction techniques, ridged surface drag reduction is known for its low energy consumption and obvious drag reduction effect. It is an efficient and practical boundary layer drag reduction technology. At present, the technology has been widely used in navigation, transportation, aerospace, fluid machinery, oil and gas transportation, sports, medical treatment and other fields. In this paper, the effect of the top angle 尾 of the ridge structure on the flow resistance at different velocities is studied by means of numerical simulation. Starting with the influence of ridge structure on local pressure, the influence of ridge structure on velocity distribution, velocity gradient distribution, wall shear stress distribution, friction resistance coefficient and other basic flow parameters are analyzed step by step. The drag reduction effect under different working conditions is obtained. In order to better explain the drag reduction effect, the effect of ridged structure on normal velocity pulsation and flow vortex is studied, and the mechanism of drag reduction is analyzed from the point of view of vortex structure. The results show that the vortex structure formed in the groove can effectively reduce the velocity gradient and wall shear stress in the arrangement area of the ridge structure, and finally reduce the friction resistance. The maximum drag reduction rate obtained at the velocity of 25m/s is 9.71 for the ridge structure with a parietal angle 尾 = 90 擄. In the region with ridged structure, the angle of vortex head rising becomes larger, which weakens the "upward" and "downward sweep" events caused by the flow vortex, and effectively reduces the friction resistance. In addition, the instability and breakage of vortex flow direction in the arrangement area of ridged structure is obvious. The spatial density distribution of the flow vortex decreases significantly after flowing through the ridge structure, which may be due to the fact that the ridge structure affects the regeneration of the flow vortex in the self-sustaining process of y in the range of 20 ~ 60, and also achieves the effect of reducing the friction resistance of the wall. After obtaining the drag reduction mechanism of the ridged structure, the effects of the position of the ridged structure and the pressure gradient on the flow and noise characteristics of the NACA0018 airfoil are studied in this paper. The effects of ridge structure on velocity distribution of boundary layer, wake velocity distribution, surface pressure coefficient and lift-drag ratio of airfoil are analyzed. The control effect of ridged structure on energy dissipation is studied by entropy production analysis. Finally, the time domain and frequency of the noise signal at the surveillance point are analyzed, and the influence of the ridge structure on the noise characteristics of the NACA0018 airfoil is studied. The results show that when 偽 = 6 擄angle of attack, riblet-H ridge structure airfoil can effectively reduce the separation area of boundary layer and the wake velocity loss, in addition, it can also increase the lift coefficient of airfoil and reduce the drag coefficient of airfoil. The rise-to-drag ratio of 24m/s is increased by 53.418 in comparison with the smooth airfoil. In the aspect of noise, riblet-H airfoil model can effectively reduce the noise in the range of 0-3000Hz frequency. Through the analysis of vortex structure and entropy production, it is found that riblet-H airfoil can effectively control the formation of swirl structure and the energy dissipation of high entropy production structure at the angle of attack of 偽 = 6 擄.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TB53

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