復(fù)雜流動機(jī)理及預(yù)測方法研究

陸利蓬　柳陽威

摘 要：針對氣動噪聲計算問題，經(jīng)過2年的研究，主要進(jìn)展如下：（1）研究了高精度湍流模擬技術(shù)的數(shù)值方法。首先發(fā)展了一套基于高階有限差分格式的流場求解器，并進(jìn)行了系統(tǒng)測評；在此基礎(chǔ)上，針對激波模擬精度，提出了帶寬耗散優(yōu)化方法（BDOM），發(fā)展了MP-LD格式，結(jié)果表明MP-LD格式對小尺度流動結(jié)構(gòu)的捕捉能力以及對湍流的模擬效率要顯著優(yōu)于常規(guī)的高階激波捕捉格式。（2）采用高精度湍流模擬技術(shù)研究了復(fù)雜流動機(jī)理。利用MP-LD格式和ASTR程序，對激波/各向同性湍流干涉（SITI）和激波/湍流邊界層干涉（SBLI）等進(jìn)行了DNS和機(jī)理性的研究。結(jié)果表明：湍流脈動之間的非線性作用使得大尺度湍流結(jié)構(gòu)向各向同性恢復(fù)的過程更加復(fù)，而小尺度脈動結(jié)構(gòu)則更容易恢復(fù)各向同性；由于來流速度脈動的影響，激波表面形狀會發(fā)生變形，較高的來流速度脈動會導(dǎo)致當(dāng)?shù)丶げㄎ恢酶拷掠危⒃黾蛹げǖ膹?qiáng)度。（3）研究了壓氣機(jī)三維角區(qū)分離流動機(jī)理和湍流模型改進(jìn)。針對角區(qū)分離流動，首先開展了先進(jìn)實(shí)驗(yàn)測量和高精度數(shù)值模擬，為機(jī)理研究和湍流模型改進(jìn)提供豐富的數(shù)據(jù)庫。其次，提出了基于湍流非平衡輸運(yùn)特性改進(jìn)湍流模型的新方法，并針對SA湍流模型，提出了兩種改進(jìn)方法：一是修正模型系數(shù)Cb1；二是基于當(dāng)?shù)芈菪扔嬋胪牧髂芰糠磦魑锢頇C(jī)制。其中，基于螺旋度改進(jìn)可以“自適應(yīng)”計入湍流非平衡輸運(yùn)特性，可以“自適應(yīng)”實(shí)現(xiàn)對不同工況下壓氣機(jī)三維角區(qū)分離流動的準(zhǔn)確模擬。（4）研究了壓氣機(jī)轉(zhuǎn)靜干涉機(jī)理和時均模擬方法。針對轉(zhuǎn)靜干涉噪聲，團(tuán)隊(duì)提出了時均模擬技術(shù)和線性諧波法相結(jié)合的快速非定常數(shù)值模擬思路。該課題首先采用非定常數(shù)值模擬技術(shù)，研究了轉(zhuǎn)靜干涉機(jī)理；其次改進(jìn)了交界面處理方法，深入分析了確定性相關(guān)項(xiàng)的分布特點(diǎn)和對時均流場的影響特性，發(fā)展了確定性相關(guān)項(xiàng)模型，發(fā)展完善了時均模擬技術(shù)，為下一步和線性諧波法相結(jié)合，實(shí)現(xiàn)對轉(zhuǎn)靜干涉噪聲源的快速非定常計算，提供堅(jiān)實(shí)的基礎(chǔ)。（5）建立了氣動聲學(xué)知識庫系統(tǒng)和噪聲機(jī)理知識。首先建立了國際上首套氣動聲學(xué)知識庫系統(tǒng)；其次對大攻角超音速流動，發(fā)現(xiàn)了機(jī)翼上表面存在一種激波/滑移面共存結(jié)構(gòu)，發(fā)現(xiàn)了一種新的氣動噪聲來源；最后針對氣動聲學(xué)重要來源之一的點(diǎn)渦與物體的相互作用，建立了一套點(diǎn)渦群對多物體受力影響的基本理論。

關(guān)鍵詞：復(fù)雜流動機(jī)理 數(shù)值方法 氣動噪聲

Abstract：The mainly development of the research work in the first two years is divided into five parts. （1）A high-fidelity flow solver is developed and evaluated in the study. To improve numerical scheme for shocks， the bandwidth dissipation optimization method （BDOM） is developed. A high-order MP-LD scheme， based on BDOM is developed and assessed. The results show that MP-LD scheme is much better than the conventional high-order shock-capturing schemes in resolving small-scale flow structures and turbulent motions. （2）The DNS researches of shock/isotropic turbulence interaction and shock/turbulent boundary layer interaction are conducted. The return to isotropy of the turbulence downstream the normal shock is complex due to the nonlinear interaction between turbulence fluctuations. The shock surface is distorted by the inlet turbulence velocity fluctuations. Higher velocity fluctuations will make the local shock surface further downstream and increase the shock strength. （3）To investigate the corner separation in compressors， advanced experimental techniques and high-fidelity numerical simulations are conducted， and abundant database are achieved. A new modification approach for turbulence model is proposed based on turbulence transport nature. Two effective modified methods for SA model are achieved： one is to modify constant Cb1； the other is to take account of the energy backscatter by using relative helicity density. The result indicates that the modification based on helicity is self-adaptive for different conditions. （4）Investigation for rotor-stator interaction （RSI） noise prediction method is studied. Firstly， unsteady simulation is conducted to study RSI mechanism. Then the influence of rotor-stator interface treatment is improved. The distribution characteristics of deterministic correlations are analyzed and the influence of some factors on the time-averaged flow field is further studied. Based on above studies， an exponent decay deterministic correlation model is proposed. （5）Knowledge management system for aero-acoustics is set up and some acoustic flow mechanisms are studied. A new triple flow structure exists for a supersonic flow around a F15 fighter model at the high angle of attack. The Kelvin Helmholtz instability for the slip line would provide a new source of noise. The role of the body by including image vortex rings in the vortex ring model is studied and the body image effect reduces the lift force is found.

Key Words： Complex flow mechanisms； Numerical methods； Aero-acoustics

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