Problems of optimizing multilayered spherical vessels

The problem of calculating a composite construction possessing defined optimal properties when compared with other constructions of the given type is considered in this paper in the case of spherical vessels in the domain of elastic strains.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 86–94, March–April, 1972.     

Comparison of Combustion Models and Assessment of Their Applicability to the Simulation of Premixed Turbulent Combustion in IC-Engines

In order to simulate the turbulent combustion process occurring in spark-ignition (IC) engines, it is necessary to provide suitable and numerically economical models, the latter being particularly important in the application to industrial problems. Moreover, these models must deliver sufficiently accurate results for the unsteady operation of spark combustion engines, concerning variable geometries, temperatures, pressures and charge development in different configurations. In this work different turbulent combustion models for premixed hydrocarbon combustion are compared with respect to their ability to accurately predict the propagation of turbulent perfectly premixed flames. As a first configuration a cylinder of constant volume was studied. Transient calculations were used to simulate the propagation of the turbulent flame and to evaluate the resulting turbulent burning velocity. These calculations were performed for a perfect mixture of air and hydrocarbons at stoichiometric mixture and different initial conditions concerning pressure, temperature and turbulence intensity. As a second configuration a stationary turbulent bunsen-type flame with methane fuel was used to validate the turbulent combustion model of [Lindstedt and Vaos, Combust. Flame 116 (1999) 461] at different pressures. Calculated results were then compared to experimental data of [Kobayashi, Tamura, Maruta and Niioka. In: Proceedings of the 26th Symposium on Combustion, 1996, p. 389] and show excellent agreement for the turbulent burning velocity at several pressure levels using only a single set of model parameters.     

Obtaining the shear stress shear rate relationship and yield stress of liquid foods from Couette viscometry data

A method based on Tikhonov regularisation is used to convert the Couette viscometry data of a number of liquid foods into shear stress vs shear rate relationships. For liquid foods that have a yield stress and if the viscometry data cover the appropriate range of shear stress, Tikhonov regularisation is used to compute simultaneously the yield stress. The versatility of Tikhonov regularisation is demonstrated by applying it to process data from wide as well as narrow gap Couette viscometers. The results generated by Tikhonov regularisation are compared against that obtained by methods currently employed by rheologists.     

Experimental measurements and computational modeling of the flow field in an idealized human oropharynx

The velocity field in the central sagittal plane of an idealized representation of the human oropharynx (HOP) during steady inspiration, simulating oral inhalation through an inhaler mouthpiece, was measured experimentally using endoscopic particle image velocimetry (PIV). Measurements were made at three flow rates: 15, 30, and 90 L/min, which correspond to a wide range of physiological conditions. Extensive tests were performed to verify the veracity of the PIV data. The flow was also modeled computationally using Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) methods. The PIV data clearly indicate the complex nature of HOP flow, with three-dimensionality and several regions of separation and recirculation evident. Comparison of the experimental and computational results shows that, although the RANS CFD reproduces the basic features of the flow, it does not adequately capture the increased viscous effects at lower Reynolds numbers. The results demonstrate the need for more development and validation of CFD modeling, in particular RANS methods, in these flows.     

Deformation of a Peridynamic Bar

The deformation of an infinite bar subjected to a self-equilibrated load distribution is investigated using the peridynamic formulation of elasticity theory. The peridynamic theory differs from the classical theory and other nonlocal theories in that it does not involve spatial derivatives of the displacement field. The bar problem is formulated as a linear Fredholm integral equation and solved using Fourier transform methods. The solution is shown to exhibit, in general, features that are not found in the classical result. Among these are decaying oscillations in the displacement field and progressively weakening discontinuities that propagate outside of the loading region. These features, when present, are guaranteed to decay provided that the wave speeds are real. This leads to a one-dimensional version of St. Venant's principle for peridynamic materials that ensures the increasing smoothness of the displacement field remotely from the loading region. The peridynamic result converges to the classical result in the limit of short-range forces. An example gives the solution to the concentrated load problem, and hence provides the Green's function for general loading problems.     

Some features of flexural-gravity wave propagation in the presence of a crack in sheet ice

The effect of a crack in an ice sheet on the propagation of surface flexural-gravity waves in a basin of constant depth is analyzed. The ice sheet is simulated by two floating semi-infinite fragments of a thin elastic isotropic plate. As the boundary-contact conditions on the line of contact between the parts of the plate the conditions of continuity of displacements for arbitrary slopes simulating one ice-floe overlying on another and free-edge conditions (crack) are considered. The dependence of the amplitude characteristics of the perturbations on the thickness of the ice, its degree of compression, the incident wave frequency, the depth of the basin, and the form of the boundary-contact conditions is investigated. Problems of wave diffraction on inhomogeneities of an elastic plate were solved in [1, 2], and on a crack in the ice sheet in [3, 4].Sevastopol. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 144–150, March–April, 1996.     

Dynamic compression-shear response of brittle materials with specimen recovery

A new configuration for compression-shear soft-recovery experiments is presented. This technique is used to investigate various failure mechanisms during dynamic multiaxial loading of an Al₂O₃/SiC nanocomposite and TiB₂. Velocity profiles of the target surface are measured with a variable sensitivity displacement interferometer, yielding normal and transverse velocity-time histories. A dynamic shear stress of approximately 280 MPa is obtained, in the Al₂O₃/SiC nanocomposite, for an imposed axial stress of about 3.45 GPa on a 540 m thick sample. This dynamic shear stress is well below the value predicted by elastic wave propagation theory. This could be the result of stress-induced damage and inelasticity in the bulk of the sample or inelasticity on the sample surface due to frictional sliding. To gain further insight into the possible failure mechanisms, an investigation of compression-shear recovery techniques, with simultaneous trapping of longitudinal and lateral release waves, is conducted.     

Carrier testing program in a high-risk cystic fibrosis population from northeastern Italy. Active recruitment of relatives via probands' parents

OBJECTIVE: To assess the practicability and monitor the results of an active carrier testing program among relatives of cystic fibrosis (CF) patients. METHODS: Parents of CF patients in the Veneto and Trentino regions of northeastern Italy were asked to help recruit relatives aged between 18 and 45 years for CF mutation testing. RESULTS: Of 409 enrolled CF parents, 59.6% agreed to send to the CF Center family composition data of relatives up to the third degree, and 28.8% recruited relatives to carrier testing, providing names and addresses of those who, being contacted, expressed a willingness to be tested. The participation of parents was higher if they were young and had a child recently diagnosed with CF. Recruiting parents indicated 333 close relatives (59%) for testing. When contacted by the CF Center, 170 of these 333 (51%) attended for testing. The percentage of close relatives who spontaneously asked for the test was 5.4% before the carrier testing program started; it rose to 25.3% following the introduction of the active strategy. CONCLUSIONS: The participation of the parents of CF patients is an important factor affecting the utilization of testing by relatives. Besides this, the influence of a favorable medical and cultural context (participation of gynecologists and family doctors in testing programs, genetic education of the general population) has to be considered.     

Weakly nonlinear magnetosonic waves and structure of low-intensity discontinuities in magnetohydrodynamics

Mathematical techniques are proposed which make it possible to reduce the system of magnetohydrodynamic equations for a viscous heat-conducting gas with finite electric conductivity and a general equation of state to the model Burgers equation. On the basis of this equation the structure of weakly nonlinear magnetohydrodynamic shock waves is studied. In particular, the width of the shock wave is estimated.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.4, pp. 43–48, May–June, 1993.