实验研究了螺管内绝热和沸腾汽液两相流动时压力波动特性，分析了热流密度对压力波动的影响规律。结果表明沸腾时波动的均方根和分形参数（分维数、关联维数和Kolmogorov熵）与绝热两相流明显不同，加热热流密度的大小影响各特征参数的大小及其随干度的变化规律。未考虑流密度影响的流型图或流型转变准则只能在小热流密度时使用。

运用现代数字信号处理技术，对垂直上升管水/水蒸气两相流不同流型时的压美波动信号特性进行了分析研究，提出了基于压差波动特征的两相流型的客观识别方法。通过提取压差波动信号的功率谱分布特征，表明利用功率谱随频率的分布特性的均方根可客观识别的泡状流、间歇流和环状流。

从理想的单气泡运动物理模型和离散正交小波与统计相结合的信号处理技术研究了泡状流压力波动的机理与多尺度的频规律，得到以下结论：泡状流的压力波动主要来源于气泡的运动和诱导湍及液相湍流，其中在低流速下前者产生的压力波动幅度大于后两者；存在一个临界频率，低于该频率压力信号均方根随频率的增加面增加，高于该频率压力信号均方根随频率的增加而减少；发生流型转变时压力信号的时频特征发生明显改变，最大均方根出现在更低的频率区。

Byu singa ne nsemble-avem gedt wo-fluid model, with validc losurec onditionso fin terfacialtu omenturne xchanged uet ovirtual mass force, visco us shears tressand dragf orce, amodelfo rp ressurew avep ropagation in a horizontal gas-liquid bubbly flow is proposed. Accordingt ot hes mallp erturbationt heorya nds olvablec onditiono fo eorderlinearu niform equations, ad spersione quationo fpressurew aveis in duced. The pressue wave speedc alculatedf rom the modelis compare danding oods greem entwithe xistingdata. According to the dispersion equation, the propagation and attenuation of pressure wave are investigated systemicaly. The factors affecting pressure wave, sucha sv oidf raction, pressure, wallsh ears tress, perturbationf requency, virtualm ass for ceandd ragforce, are analyzed. The result shows that the decrease in system pmmare, the increase in void fraction and the existence of wall shear stress, will cause a decre inp ressurew avesp eeda nda nIn eressein the a tenuationc oefficientin the horizontalga s-liquidb ubblyflow. Thee ffectso fp erturbstion frequency, virtual mess and drag force on pressure wave in the horizontal gas-liquid bubbly flow at low perturbation frequency are different from that at high perturbation frequency.

A simple method is developed in this paper to solve two-dimensional nonlinear steady inverse heat conduction problems. The unknown boundary conditions can be numerically obtained by using the iteration and modification method. The effect of measurement errors of the wall temperature on the algorithm is numerically tested. The results prove that this method has the advantages of fast convergence, high precision, and good stability. The method is successfully applied to estimate the convective heat transfer coefficient in the case of a fluid flowing in an electrically heated helically coiled tube