EVALUATION OF THE FEATURES OF THE STRUCTURE OF WATER AND AQUEOUS SOLUTIONS NEAR A SOLID SURFACE

The paper evaluates changes in the structure of water and aqueous solutions of sodium chloride in the wall layer on the basis of dielectrometry and correlation analysis. It is shown that when the distance to the solid surface decreases, there is a multi-fold nonlinear decrease in the electrical capacitance and a nonlinear change in the Sr parameter, which characterizes the magnitude of the change in the electrical capacitance of the conduction fluid when the distance to the solid surface changes. The parameters used in the work (electric capacity of liquids and Sr ) can be used to evaluate the changes in the structural organization of aqueous solutions in the wall (boundary) layer and to interpret the processes occurring in the liquid layer at the interface of the solid – aqueous solution phases.

Role of dynamic water rivulets in the excitation of rain–wind-induced cable vibration: A critical review

It has been more than 30 years since Hikami Y and Shiraishi N (1988) Rain–wind-induced vibrations of cable-stayed bridges. Journal of Wind Engineering and Industrial Aerodynamics 29: 409–418 first reported the rain–wind-induced vibration (RWIV) of stay cables in the construction stage of Meikonishi Bridge, Japan. After that, considerable research efforts have been devoted to understanding the RWIV of stay cables, and the role of the upper rivulet has been gradually realized and studied. This study presents a selective review on recent progress of RWIV and its controversial excitation mechanism. The available knowledge and up-to-date understanding of this complex fluid-structure interaction are presented in some detail. The formation, dynamics of water rivulet, and its role in affecting the near-wall boundary layer properties and in the excitation scenario of RWIV are of particular interest in this study. Finally, some limitations of previous studies are concluded, with some perspective suggestions for further study of excitation mechanism of RWIV.

One-equation turbulence models applied to practical scramjet inlet

Reynolds-averaged Navier–Stokes equations are used to simulate a practical scramjet inlet geometry using the shock-unsteadiness modified Spalart–Allmaras (SA) turbulence model. The geometry consists of fore-body ramps, expansion corners, and inlet ducts. The focus is to study the impingement of the cowl shock on the opposite wall boundary-layer. The resulting separation bubble can lead to blockage and inlet unstarts. The shock-unsteadiness correction is employed and is found to improve the computational fluid dynamics (CFD) prediction of flow separation in shock/boundary-layer interactions. The shock-unsteadiness parameter is calibrated against available experimental data of canonical flows, and the predicted flow-field is analyzed in detail. A large separation bubble size normalized to the upstream boundary-layer thickness of 4.6 is observed in the interaction region. Across the reattachment region in the interaction region, a peak value of wall pressure is observed. The inlet performance parameters are also calculated. The total pressure losses of 62% are observed across different shock waves, with an additional loss of 15% due to viscous boundary-layer effects.

Theoretical foundations of increasing the efficiency of wide-angle diffusers and practical results of new solutions to this problem

It is shown theoretically that the efficiency of wide-angle diffusers mainly depends on the method of supplying the working medium to the diffuser channel and on the nature of the interaction of this medium with the subsequent streamlined surface of the diffuser. The first condition is due to those changes in the acting force factors within the wall (boundary layer), which occur during the transition from the inlet confuser channel to the subsequent diffuser, and the second follows from the need to ensure an uninterrupted flow of the working medium moving against the increasing (in the direction of travel) static pressure. The above computational studies of wide-angle diffusers have shown that, subject to theoretically justified conditions, it is possible to ensure uninterrupted flow in flat and conical diffusers with an increase in the opening angle α of their flow path to 20° and with the same degrees of expansion ration to obtain pressure recovery coefficients commensurate with those in diffusers with an angle α = 7°.

On the influence of hypersonic flow at the speed of a reflow heat-proof surface in terms of destruction

The results on the distribution of heat flows coming to the refractory plate of a hypersonic aircraft moving at different distances from the Earth's surface with cosmic velocities are obtained. The results of studies related to the study of phase transitions in the wall boundary layer occurring during the flow of hypersonic flow ablating surface are presented. The influence of the catalytic wall on the heat flow is considered. The main attention is paid to the analysis of the surface entrainment of high-speed aircraft, based on a detailed account of the mechanism of heterogeneous catalytic reactions in the conditions of surface mass transfer. The temperature distribution over the thickness of the boundary layer at the critical point of a blunted body with a refractory coating for a particular section of the flight path is given. Mass entrainment from the surface of crystalline refractory bodies is determined. Ill. 7. Ref. 16.