物体与容器底壁部分紧密接触时的浮力情况

针对"物体与容器底壁部分紧密接触时所受浮力与哪些因素有关"这一问题,引入不紧密接触系数k,在不考虑大气压力作用下,选取规则圆柱体和不规则柱体倒圆台为对象展开讨论.从理论分析求出物体所受浮力的表达式,通过图像给出浮力与各变量间的关系.得出结论,物体与容器底壁部分紧密接触时浮力不仅与p液,V排,g有关,还与物体表面积s、浸...     

气浮结构的浮态和运动特性分析与试验

研究了筒型基础结构气浮的浮态和运动特性。假设浮筒内的空气为理想气体 ,导出了气浮力的计算式 ,建立了气浮结构静稳态的分析方法和浮态参数的计算方法。按单自由度刚体弹簧体系求得了气浮结构升沉运动的固有周期 ,并对气浮结构的动态特性进行了分析。浮态理论计算结果与模型试验和现场试验数据吻合。文中引进的气浮力折减因数体现了气浮体的恢复力刚度系数与普通浮体的差异 ,该参数对气浮体的浮态、稳性、运动特性都有很大的影响。     

The stratification phenomena in the thermal and solutal fields of double-diffusive convection in a circular cylinder

Natural convection due to spatial variations of fluid density is of fundamental importance in many scientific and engineering problems. In the past, investigators always pay attention to convection driven by thermal buoyancy force induced by temperature g…     

Numerical simulations of buoyant reactive jets with sidewall effects

The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant ambient environment in a corner configuration with sidewall boundaries.Simulation results are presented for two cases with different jet nozzle geometries: a corner-round reactive jet and a cor-ner-square reactive jet with the same cross-sectional area on the nozzle plane. Buoyancy-induced large vortical structures evolve spatially in the flow field and transition to turbulence occurs downstream. Calculation of the mean flow properties shows that entrainment of the corner-round jet is stronger than that of the corner-square jet due to the stronger vortex deformation in the corner-round case.     

Studying the stability of the middle atmosphere (30―60km) over Wuhan by Rayleigh lidar

The stability of the middle atmosphere ranging from 30 km to 60 km over Wuhan is elementarily studied, according to the observational data obtained in about one year through the WIPM Rayleigh lidar. The stability parameter (buoyancy frequency squared), which was obtained through the temperature field, shows that the middle atmosphere over Wuhan is stable all the year round, but the sta- bility appears variable because the stability of sum- mer and winter is lower, and that of spring and au- tumn is higher.     

AFG-90基固体浮力材料的固化动力学与性能研究

为了确定N,N-二缩水甘油对氨基苯酚缩水甘油醚环氧树脂（AFG-90）/四氢邻苯二甲酸酐（THPA）的固化工艺,采用非等温DSC法研究了固化反应动力学,制备了添加空心玻璃微珠（HGM）的固体浮力材料.结果表明, m_AFG-90:m_THPA=1:1为最佳配比;Kissinger法计算的表观活化能E为67.72 kJ·mol-1,指前因子lgA为8.20 s-1;最概然机理函数为Avrami-Erofeev方程;固化工艺为100℃,1.0 h,125℃,2.5 h;添加HGM的固体浮力材料的密度为0.90 g·cm-3,压缩强度为113 MPa.      

单室火灾中浮力修正的雷诺应力模型

本文用场模化法研究了浮升流在室内的运动规律.推导了有浮力修正的雷诺应力方程,结合相匹配的数值方法,编制了专门的计算机程序,求解了单个房间,单个热源,火灾烟气发生、发展各时刻的温度场和速度场,并用绘图软件处理.验证了烟气运动的几个典型现象,并与用普通雷诺应力模型的求解做了比较,认为推导的浮力修正雷诺应力模型能给出更为符合实际的结果.     

热分层湍流计算机模拟的数学模型研究

以湍流标准k－ε模型为基础,综合考虑代数应力模型（ASM）及湍流热流输运方程,建立了热分层流动的热浮力湍流修正数学模型。理论及在液纳空腔内的热分层湍流计算机模拟中的应用表明,该模型在一程度上反映了由于流动过程中温度不均而导致的各向异性特征,并为解决热分层流中温度随时间变化的计算机模拟难题提供了一个较为简单、稳定的模型。     

关于浮力教学的探讨

本文讨论了关于浮力的一些问题,给出了有意义的结果。     

对双向应力椭圆理论的质疑

目前在套管柱强度设计中广泛应用的双向应力椭圆 (塑性椭圆 )理论 ,在其推导过程中忽略了与周向应力σt 具有同等地位、同等重要性的径向应力σr,这在理论上是不正确的 ,并由此导致了椭圆的 4个象限出现违背第四强度理论的自相矛盾现象。双向应力椭圆理论曲线与实验数据符合程度不高。所以 ,应当重新评价双向应力椭圆的正确性 ,研究套管柱组合强度设计的新理论。