Fracture and buckling of thin panels with edge crack in tension

This study is concerned with the buckling and/or cracking of thin aluminium panels with an edge crack in tension. Two types of end conditions are considered. In the first case, the ends of the panel are clamped such that they would extend in parallel. In the second case, the ends are permitted to rotate when extended in tension. The cracked edge would open while the smooth edge is compressed that could lead to out-of-plane deflection if the panels are sufficiently thin. An empirical relation is obtained for the critical tensile stress. Relations among the geometrical parameters for which buckling occurs are also derived.     

Acoustic Waves in Channels with Porous and Permeable Walls

The propagation of acoustic disturbances in a porous medium crossed by numerous cracks (double porosity medium) is a complex problem that we here simplify by investigating the acoustics of a permeable channel. We consider a fluidfilled channel in two possible geometries, a slit or a cylindric pipe. The channel is surrounded by a porous medium (saturated with the same fluid) and is itself surrounded by an external medium. To simulate the average properties of the cracked rock, the external medium is either nonpermeable (few connections between cracks) or highly permeable (numerous connections). We present analytical and numerical results concerning acoustic disturbances of small amplitude generated in the channel, such as harmonic waves, step disturbanses and pulses.     

Numerical study of a swirled turbulent flow in the separation zone of a centrifugal air separator

A mathematical model of a swirled turbulent flow in the separation zone of a pneumatic centrifugal device is presented. The model is based on the known k-? model of turbulence proposed by Wilcox. The influence of rotation of the separation-zone walls, input swirl of the gas flow, and other characteristic parameters on the mean velocity field is demonstrated. A comparison of parameters is performed, which reveals good agreement between the numerical and experimental results for a turbulent fluid flow between parallel disks.     

Vanadyl Sulfate (VOSO4.3H2O). An Efficient Catalyst for Acylation of Alcohols and Phenols under Solvent Free Condition

Alcohols and phenols were efficiently acylated with acetic anhydride in the presence of vanadyl sulfate (VOSO₄.3H₂O) at room temperature in high yields.     

Local buckling of extended plates containing cracks and cracklike defects, subject to the influence of geometrical parameters of the plates and the defects

An experimental study of the local buckling of plates containing cracks and cracklike defects is reported, where the influence of the geometrical parameters of the plate and the defect are taken into account. An empirical curve is plotted to estimate the critical stresses at which buckling takes place. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 12, pp. 80–84, December, 1999.     

Explosive discharge of a gas-saturated liquid from channels and tanks

A mathematical model for the discharge of a gas-saturated liquid from cylindrical channels is developed. Two limiting cases of linear and quadratic, relations between the flow friction force and the flow velocity are considered. It is established that the process of evacuation, from a semi-infinite channel consists of two stages. In the initial stage, the flow drag can be ignored, and the process of discharge is described by a Riemann wave solution. For the next stage, in which inertia is insignificant, nonlinear equations are obtained and self-similar solutions are constructed for them. The problem of flow through a slot in a tank of finite volume is solved. It is shown that the discharge proceeds either in a gas-dynamic choking regime or in a subsonic regime, depending on the conditions inside the tank and at the outlet. Examples of numerical calculations are given. Institute of Mechanics, Ufa Scientific Center, Russian Academy of Sciences, Ufa 450000 Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 1, pp. 64–73, January–February, 1999.