Origination of gamma-ray burst pulses associated with the Doppler effect of spherical fireballs or uniform jet

Ryde and Petrosian have pointed out that the rise phases of gamma-ray burst (GRB) pulses originate from the widths of the intrinsic pulses and their decay phases are determined by the curvature effect of the expanding fireball surface based on their simplified formula. In this paper we investigate in detail the issue based on the formula in Ref.[20], which is derived based on a model of highly symmetric expanding fireballs, where the Doppler effect is the key factor to be concerned about, and no terms are omitted in their derivation. Our analyses show that the decay phases of the observed pulses originate from the contributions from both the curvature effect of the expanding fireball and the two timescales of the local pulses, and the rise phases of the observed pulses only come from the two timescales of the local pulses. Associated with a local pulse with both rise and decay portions, the light curve of GRBs in the rise portion is expected to undergo a concave phase and then a convex one, whereas that in the decay portion is expected to evolve by an opposite process. And the ratio of the concave timescale to the convex one in the rise phase of the observed pulse linearly increases with the ratio of the rising timescale to the decay one of the local pulse ($r_{\rm rd}$), whereas the ratio of the convex timescale to the concave timescale in its decay phase linearly decreases with $r_{\rm rd}$. The two correlations are independent of the local pulse forms and the rest-frame radiation forms. But the different forms of local pulses and the different values of $r_{\rm rd}$ gives rise to the diversity of the light curve pulse shapes. We test a sample of 86 GRB pulses detected by the BATSE instrument on board the Compton Gamma Ray Observatory and find that the characteristics do exist in the light curve of GRBs.     

起伏条件下不稳定射流压力振荡特性实验研究

蒸汽在过冷水中浸没射流凝结技术因其高效换热特性被广泛应用于陆地和海洋场景下的电力和核工业等许多工业领域中,但蒸汽凝结过程中汽液相界面变化会产生压力振荡。本文对起伏条件下不稳定射流的压力振荡特性进行了实验研究,获得了不同起伏参数对压力振荡特性的影响。结果表明,相比于静止条件下,不稳定射流在起伏运动下的压力振荡主频与压力振荡平均幅值更大,并且压力振荡主频和压力振荡平均幅值随着起伏幅值的增大而增大,随着起伏周期的增大而减小;起伏最大加速度幅度随着起伏周期的减小和起伏幅值的增大而增大,斯特劳哈尔数随着起伏最大附加加速度的增大而增大。     

逆壁射流中射流剪切层内湍流结构特性的实验研究

采用粒子图像测速技术对逆壁射流全流场进行了实验测量,射流与主流的速度比为8.89,基于射流圆管内径的雷诺数为对射流中心线上不同流向位置的脉动速度场统计分析发现:在占据主导地位.在驻点附近(尺度进行分析,在x/D=46～51总尺度向射流下游发展呈减小趋势.在x/D=35～41,参考点下游尺度大于上游尺度.在本征正交分解方法对湍流结构进行了定量分析,发现模态能量集中在低频,流场中能量最大的模态频率为f D/Uj=0.000 5,出现在再循环区.频率为产生了湍流结构,并且沿再循环区外围输运.高频结构的构型是类似的,均位于射流剪切层内,且频率越高,越接近射流出口,尺度越小.     

Pseudospectral analysis of the interfacial stability of free jets with different velocity profiles

A double fluid model for a liquid jet surrounded by a coaxial gas stream was constructed. The interfacial stability of the model was studied by Chebyshev pseudospectral method for different basic velocity profiles. The physical variables were mapped into computational space using a nonlinear coordinates transformation. The general eigenvalues of the dispersion relation obtained are solved by QZ method, and the basic characteristics and their dependence on the flow parameters are analyzed.     

第八届亚洲流体力学会议简介

１概况亚洲流体力学会议是由亚洲流体力学委员会（ＡｓｉａｎＦｌｕｉｄＭｅｃｈａｎｉｃｓＣｏｍｍｉｔｔｅｅ）主办的国际例会,轮流在亚洲各国每二年召开一次．第八届亚流会（ＴｈｅＥｉｇｈｔｈＡｓｉａｎＣｏｎｇｒｅｓｓｏｆＦｌｕｉｄＭｅｃｈａｎｉｃｓ．８ＡＣＦＭ）于１９９９年１２月６日～１０日在我国深圳召开．这是第二次在我国召开,第一次是１９８３年在北京召开的第二届亚流会．会议由中国力学学会和深圳市科学技术协会协办,中国力学学会具体承办．会议主席为亚洲流体力学委员会副主席、北京空气动力学研究所崔尔杰院士．…     

列管型射流式O2(1△)发生器的COIL出光研究

采用列管型射流式 O2 ( 1Δ)发生器在 COIL装置上做了一系列出光实验 ,对该发生器的性能、参数及相关技术等做了实验研究。实验获得化学效率最高达 2 2 .2 %。     

小型射流发生器的实验研究

通过对小型射流单重态氧发生器的稳定工作条件及射流板性能对发生器的性能影响的考察,在一个小型超音速氧碘化学激光器（COIL）中使用射流发生器成功地得到激光输出。     

影响空心旋转液体射流初始阶段运动的无量纲参数的分析

本文以描述空心旋转时流初始阶段运动规律的理论模型[1]为依据,重点讨论了影响射流运动的无量纲参数：韦伯数,液膜内外压力差,液膜初始内外环半径比,初始旋流度;初始径向速度等。从而进一步加深了对旋流喷嘴所产生的空心旋转射流初始阶段运动及发展规律的认识。     

逆向复式射流预燃室燃烧器煤粉颗粒行为预报

1引言预燃室燃烧技术是近十多年来开发研究的一种高燃烧效率低NO。的燃烧技术门．它是一种分级燃烧技术。燃料在预燃室内只是部分地燃烧,在贫氧的一次火焰区内脱挥发分,从而减少了NO。的形成。自1982年以来,我国开发研究了很多种类的预燃室,如旋流、大速差l‘］、偏置射流预燃室等。工程热物理研究所研究开发了逆向复式射流预燃室燃烧器l‘,‘］。经实验室和工业实验证明,该预燃室有极优良的火焰稳定性能和煤种适应性,能够实现较低的NOx排放。本文针对逆向射流预燃室内这一独特的流场结构,利用数值模拟来预报煤粉颗粒在其内的运…