【作者】 郝志鹏；

【导师】 颜培刚；

【作者基本信息】 哈尔滨工业大学 ， 动力机械及工程， 2010， 硕士

【摘要】 高超音速边界层流动转捩的预测是二十一世纪航空航天领域的研究热点之一,同时它也是空气动力学的一大难题。转捩流动的准确预测对于飞行器气动外型和热防护措施的设计有着至关重要的影响。现代计算流体力学的发展为转捩流动的数值模拟提供了广阔的研究平台,发展出诸如直接数值模拟、大涡模拟、求解抛物化稳定性方程或线性稳定性方程以及工程转捩模式等多种转捩预测方法。在实际工程计算中,转捩模式方法由于具有对计算机资源要求不高,计算周期短等优点而得到广泛的应用。本文选用转捩模式方法,利用一种基于经验相关式的转捩模型——? ? Re?转捩模型对超音速/高超音速边界层转捩流动进行了数值模拟。该转捩模型是一种是以SST湍流模型为基础,完全基于流场当地变量的转捩模型。本文应用该模型分别对高超音速平板边界层转捩流动、高超音速尖锥体边界层转捩流动以及两款高超音速进气道模型的内流进行了数值模拟。通过与实验数据的对比分析认为,该转捩模型基本具备模拟高超音速边界层转捩的能力,能够较准确地预测出转捩的起始位置和转捩的长度,并能正确模拟出来流湍流度与粘性比对转捩起始位置的影响。同时,该转捩模型还具备对激波与边界层干扰、激波与激波干扰、激波与膨胀波干扰以及流动分离等复杂流动现象的模拟能力。但该模型对边界层层流段的模拟不够准确,究其原因可能是由于该转捩模型只是利用间歇因子?来修正湍动能的输运方程中的生成项,因此在流动的层流段并未实现对湍流的完全抑制。此外,该模型模拟转捩过冲现象的能力也稍有不足。本文还利用该模型对三种进气道设计方案进行了数值模拟,这三种方案分别是方案一三波系外压缩进气道、方案二等熵外压缩进气道和方案三单波系外压缩进气道。根据数值计算的结果对比分析了三种方案的设计工况和变工况的气动性能。在设计工况的条件下,方案二进气道由于采用等熵的外压缩型面因此喉部总压恢复系数较高,但喉部之后的扩张通道导致气流加速,使其隔离段激波串前气流马赫数较大,相应的激波损失增大,因此出口总压系数下降。而方案三进气道由于隔离段激波串损失最小,因此具有最高的出口总压恢复系数。同时方案三进气道还具有最大的进气流量和最小的外罩阻力,但该方案的出口流场畸变度也是最大的。由于方案三进气道的外压缩激波系强度不大,入射到外罩内壁面上时对进气道内流场的影响较小,因此在变工况的条件下,其特性参数变化不大,不会偏离设计点太远。即方案三进气道的速度特性曲线最为平坦,该方案具有最优良的变工况性能。更多还原

【Abstract】 The transition prediction of hypersonic boundary layer is one of the hottest issues in the field of aerospace in the 21st century as well as an unsolved problem of aerodynamics. The accurate prediction of transitional flow plays an important role in the design of the configuration and heat-protection measures of aerodynamic vehicles. The development of modern computational fluid dynamics has provide a broad research platform for the numerical simulation of transitional flows, and numerous approaches to the transition prediction have been developed,which include Direct Numerical Simulation, Large Eddy Simulation, the Solution of the Parabolized Stability Equation or the Linear Stability Equation as well as Engineering Modeling of Transition. For practical engineering computation, the approach of Engineering Modeling of Transition has been widely adopted due to its advantage with regard to the computational effort and cost.In this thesis, the approach of Engineering Modeling of Transition was choosen. A correlation-based trantion model known as ? ? Re? model,which is based on SST turbulence model and local variables, was used to simulate the transitional flow of supersonic/hypersonic boundary layer.In the first part of this thesis, the simulations of the hypersonic boundary layer transitional flow on flat plate and slender cone and the internal flow of two supersonic/hypersonic inlets model were performed. By comparision between the results of these simulations and experimental data, it has been proved that the trantion model used in this thesis has the ability to simulate the transitional flow in the hypersonic boundary layer, predicting correctly the onset location and the length of transition, and the ability to simulate the influence of turbulence intensity and viscosity ratio on the onset location of transition. Meanwhile the trantion model has the ability to simulate the complicated flow phenomena such as the shock-boundary layer interaction and the flow separation etc..However, the trantion model can not accurately simulate the laminar stage of the boundary layer flow possibly due to the use of intermittence factor to amend the production term in the transportation equation of turbulent kinetic energy, which does not completely restrain the turbulence in the laminar stage. Furthermore, the trantion model lacks the ability to simulate transitional overshoot.In the second part of this thesis, three supersonic inlet projects were proposed. The first inlet has a triple-oblique-shock external compression ramp, the second one has a isentropic external compression ramp and the third one has a single-oblique-shock external compression ramp. The numerical simulations of these three proposed inlets were performed with the use of the transition model mentioned above and sequentially the aerodynamic properties of these three inlets in both design condition and off-design condition are analyzed. In design conditionIn design condition,as the most intake flow rate and the smallest cowl drag. But, the third inlet also has the largest degree of distortion of the flow field at the outlet. In off-design condition, the velocity performance curve of the third inlet is the flattest. So when the working condition is changed, the performance of the third inlet will not vary dramaticlly, i.e. the third inlet has the best performance in off-design condition.更多还原