Analysis of Laminar Boundary-Layer Separation in Retarded Flow over Bodies of Revolution

Laminar boundary-layer separation phenomenon is one of the interesting and important aspects of boundary-layer flows. It occurs in various physical situations because of decreasing wall shear stress. Retarded flow velocities are one of the reasons to happen this event. Flow separation can be prevented or delayed by utilizing bodies of revolution as surface transverse curvature produces the effects of the nature of favorable pressure-gradient which in turn increases wall shear stress that keeps the flow attached to the surface. Bodies of revolution whose body contour follows power-law form also play a vital role to delay flow separation. Bodies of revolution of varying cross-sections and involving surface transverse curvature (TVC) are utilized to examine their effects on flow separation. Particularly, a convex transverse curvature has been considered due to its effects of the nature of favorable pressure-gradient which causes to delay the flow separation. A retarded flow velocity of Görtler’s type is considered in this study to investigate flow separation process. A detailed analysis is provided to understand the flow separation by calculating separation points under various assumptions. It has been observed that the body contours exponent n and the convex transverse curvature parameter k play an assistive role in the delaying of boundary-layer separation even under the influence of strong retardation. Results are presented through various Tables and graphs in order to highlight the role of the power-law exponent of external velocity m, the convex transverse curvature parameter k, and the body contours exponent n on separation points.

Study on the Stability Principle of Mechanical Structure of Roadway with Composite Roof

With the typical composite roof roadway and roof fall accidents in the Guizhou Province of China as the research background, the expression of damage parameters of composite roof was deduced according to Weibull statistical distribution, generalized Hooke’s law and Mises yield criterion, and the influence of shape and scale parameters of Weibull on damage characteristic was discussed. Based on the infinite slab theory, the expressions of deflection and layer separation of each layer of the composite roof were obtained, the critical load expression of each delamination was determined, and the influence of roadway width, overlying strata load, elastic modulus, shape parameters and scale parameters on the stability of composite roof was explored. The research shows that the bolt support can effectively reduce the layer separation between the composite roofs and enhance the stability of the composite roof. On this basis, it is proposed that for the surrounding rock control problem of roadways with composite roof, the active support technology with bolts as the core should be adopted.

Evaluation of Changes and Characteristics of Hair According to the Application of the Hair Dryer Plasma Functional Module

Hairdryers are commonly known to cause hair damage such as “roughness”, “dryness”, and “hair color loss”. while using it. So, numerous studies have tried to find ways to dry hair with no damage or minimized level. In this study, we examined hair damage levels by varying drying applications during the process and analyzed hair changes either in essential characteristics such as “oil and moisture balance” or “microstructure”. As a result, hair was severely damaged when treated with a general hot air dryer for 90 minutes, causing cuticle crack or layer separation. In contrast, the plasma hairdryer caused just a little or even no damage to hair for the same exposure time. It may be because ions and moisture molecules generated when using a plasma hairdryer can protect hair structure from the harsh hot air condition.