可压混合层涡并放热效应的涡动力分析

 基于双元单步不可逆燃烧动力学简化模型 ,采用紧致差分算法直接求解二维可压 Navier-Stokes方程 ,研究了时间发展非预混扩散火焰平面反应混合层流动。拟序结构由数值线性稳定性分析方法设定的粘性可压最不稳定小扰动初场促生。随放热强度增大 ,得到了基频涡卷撕裂现象。涡动力分析表明 ,放热主要通过膨胀和斜压这两种强非线性过程抑制大尺度剪切涡的演化     

ALGEBRAIC TURBULENCE MODEL WITH MEMORY FOR COMPUTATION OF 3-D TURBULENT BOUNDARY LAYERS WITH VALIDATION

Additional equations were found based on experiments for an algebraic turbulence model to improve the prediction of the behavior of three dimensional turbulent boundary layers by taking account of the effects of pressure gradient and the historical variation of eddy viscosity, so the model is with memory. Numerical calculation by solving boundary layer equations was carried.out for the five pressure driven three dimensional turbulent boundary layers developed on flat plates, swept-wing, and prolate spheroid in symmetrical plane. Comparing the computational results with the experimental data, it is obvious that the prediction will be more accurate if the proposed closure equations are used, especially for the turbulent shear stresses.     

主流倾斜的引射器试验研究

作者设计了 4种主流倾斜的引射器模型,分别在 5种主气流倾斜角和 4种排气反压下,完成了模型冷流试验。试验表明,4种模型中具有等直管的模型 3,4引射系数普遍高于大头模型 1,2。在零气流角和反压为大气压时,约高 10%左右,最高引射系数为 3.379。试验还表明,具有等直管的模型3和模型4能承受的反压较大。引射系数 N为零的反压可高至 900mm水柱左右。 4种引射器模型中,模型 4的综合性能最好      

Flap contour optimization for highly integrated SERN nozzles

The performance of a Single Expansion Ramp Nozzle (SERN) for hypersonic cruise vehicles is examined with focus on the flow at the nozzle flap and the corresponding separation of the boundary layer. Two wind tunnel models are used to analyze the interaction of the free stream and the nozzle flow and the flow at the flap in detail. A finite element flow code is employed to support the design of the flap model and the analysis of the flow.Comparative contour studies show that the size and the location of the separation at the flap cowl and therefore the aerodynamic quality can be influenced by optimizing the flap cowl contour. The position of the separation is measured for different contours and varying Reynolds numbers at laminar, transitional and turbulent flow conditions. Numerical studies of a nozzle/afterbody configuration suggest an improvement of up to 3.5% in axial thrust for optimized flap contours in the examined Mach range between 1.64 and 6. At the same time the rotation of the thrust vector is reduced by up to 5° at lower Mach numbers.     

重庆与兰州电离层Es出现率的比较研究

对重庆(29.5,106.6)与兰州(36,103.9)f₀E_s>5MHz的Es出现率和E层临界频率f₀E进行了详细对比研究.结果表明:(1)此两地Es出现率的变化特征显著.白天重庆高于兰州;晚上则正相反.(2)出现率的这种变化与Es环境电离密度的变化趋势十分一致.(3)上述特征的形成,除了此两地纬度上的差异外,与兰州地处地磁S_q电流系的焦点很有关系.      

脉冲爆震燃烧器混合室研究

利用CFD程序分别对切向、轴向和径向供气方式的混合室中油、气的混合特性进行了三维数值模拟.切向进气有助于油气的充分混合,但是油、气分布不均;轴向进气时油、气分布比较均匀,但是油气的混合不够充分;而径向进气的油气分布、混合程度介于切向与轴向进气之间.能耗较大.设计了四种混合室结构,进行了基于两相无阀脉冲爆震燃烧器(PDC)的热态试验研究,找到了利于点火、起爆迅速的混合室结构.     

STUDY OF SWEPT SHOCK WAVE AND BOUNDARY LAYER INTERACTIONS

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用柔性微型传感器阵列测量边界层分离点的实验研究

结合边界层分离点附近的剪应力变化规律,提出了在飞行器外表面贴附微型传感器阵列的分离点检测方法,并给出了相应微型剪应力传感器阵列的设计方案.同时提出了基于三极管恒流源电流镜驱动电源设计和滤波衰减电路设计方案,并在NAGA0012标准翼型上实现了边界层分离检测系统集成,最后,在低速风洞实验中对传感器阵列的性能和传感器阵列输出信号的处理判断方式进行验证,对实验结果的分析表明本研究制造的微型热敏传感器阵列能够实现对流体边界层分离位置的在线测量.     

用GAO-YONG湍流模型计算激波/边界层干扰

采用GAO-YONG可压缩湍流方程组,模拟了平板激波/湍流边界层干扰现象.运用SIMPLE算法求解方程组,并分别采用三阶精度的QUICK格式和中心格式离散对流项和扩散项.计算结果较好预测了入射斜激波在平直壁面引起湍流附面层分离的流动特征: 分离点的反射激波、分离包引起的膨胀扇以及再附点的反射激波.对流场的时均参数与实验值进行了比较,计算得到的壁面压力分布、摩阻系数分布和速度型与实验值比较吻合很好.结果表明GAO-YONG可压缩湍流方程组能够高精度模拟平板激波/湍流边界层干扰流动.      

ATN中的数据压缩算法分析及进一步完善

针对航空电信网移动通信中的数据压缩问题,详细分析了无连接网络层协议(CLNP,Connectionless Network Layer Protocol)报头压缩过程和压缩性能,得出传输效率、报头压缩效率与报文长度的关系.在缺省域间路由方式下,结合ESIS(End System to Intermediate System )协议,提出了CLNP报头数据的压缩完善方案,并分析了算法的压缩性能、给出了压缩效率和数据包长的关系.仿真结果表明,该算法进一步提高了压缩效率,提高了无线信道传输效率.