Publication2

Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider, we search for the process e+e-→ηcηπ+π-. The search is performed using five large datasets recorded at center-of-mass energies of 4.23, 4.26, 4.36, 4.42, and 4.60 GeV. The ηc meson is reconstructed in 16 exclusive decay modes. No signal is observed in the ηc mass region at any center-of-mass energy. The upper limits on the reaction cross sections are determined to be 6.2, 10.8, 27.6, 22.6 and 23.7 pb at the 90% confidence level at the center-of-mass energies listed above.

In the present study rotating vaneless diffusers are considered to minimize energy losses associated with diffusion and to improve the operating range of the compressor. Depending on the speed of rotation the diffusers are classified into two types forced and free. Simulations using ANSYS CFX 17.2 are performed with free rotating diffusers, in which diffusers are rotated at fraction of impeller speed. The performance of rotating diffuser with the stationary diffuser is compared using several performance characteristics such as total pressure ratio, static pressure recovery coefficient, coefficient of torque and stagnation pressure loss coefficient are plotted in each case. Simulations are performed at different speed ratio over a range of 0.25-0.95. Among all the cases vaneless diffuser with speed ratio 0.75 has optimum performance in terms of performance characteristics and velocity streamlines are uniform with lower Mach number compared to the stationary vaneless diffuser.

Based upon the results of a literature review, a set of physical parameters suitable for quantitative comparison in experimental and numerical studies is determined. The review showed the feasibility of modeling the process of the outflow of an immersed jet of inert gas into the surrounding space and the evolution of a free shear layer formed by hot and cold gases to analyze the process of convective and diffusion transport of various types of particles. In the model formulation we consider the problem of solid destruction by a melt of the same substance, as well as by a nitrogen stream at high temperature. The test simulation of the problems of two-phase interaction of a immersed jet of molten liquid and hot gas, on the whole, qualitatively showed the reproduction of the main characteristics of the flow: The generation of large-scale vortices around the jet in the induction zone, the oscillations of the jet when it collides with an obstacle, and the shape of the cavity formed.

Sensitivity of the shape of a turbine blade shapes on its performance is more compared to the compressor blade shape. Thus, a lot of research is concentrated on design of turbine blades and wide range of methods were suggested for the same. A blade with acceptable performance should have minimum of first order continuity along the blade curve. Discontinuity on the blade geometry leads to higher pressure gradient and affects the performance drastically. Hence, in this paper a turbine blade is generated, by using Bezier control points, to obtain a smooth blade curve. The blade is divided into leading section, main section and trailing section. The middle section of the blade is formed by cubic Bezier splines ensuring the first and second order continuity on the blade geometry. New blade geometries are formed by shifting the positions of the Bezier control points. The blade geometry formed from this newly shifted Bezier control points is subjected to the same boundary conditions as the baseline profile and the pressure distribution is analysed. The different blades generated are analysed in ANSYS FLUENT 17.2. The computational domain is a two dimensional turbine cascade, consisting of a turbine blade enclosed by periodic boundaries to mimic realistic conditions. A second order upwind strategy is used for inviscid flow analysis.

We investigate the evolution of the thermal field during evaporation, a fundamental aspect of evaporating sessile drops. With numerous reports in the literature investigating the contact line dynamics, we aspire to identify generalized features in the evolution of the thermal field and ultimately correlate these with the contact line dynamics. Considering a broad range of experimental parameters such as substrate wettability, substrate temperature, initial volume of the drop, and ambient relative humidity results in a wide range of evaporation rates, in turn affecting the strength of internal convective flows. Infrared thermography is utilized to extract the thermal field at the liquid–vapor interface, and optical imaging is used to record the evolution of drop shape during evaporation. We observe that the onset and presence of a convective cell as a cold spot at the interface highlights a non-axisymmetry in the thermal field. In consequence, a hitherto unreported asymmetry in the internal flow field is observed, as evidenced by the particle image velocimetry. Among the multitude of experiments conducted, we report four distinct trends in the evolution of interfacial temperature difference depending on the presence and duration of the presence of the convective cell, which are elucidated by discussing the evolution of maximum and minimum temperatures at the interface. The interplay between heat conducted into the drop and heat released due to evaporation can result in a momentary decrease in temperature of the drop, which is not reported previously. Lastly, a theoretical estimate for the temperature difference within the drop is extracted using vapor diffusion model and energy balance during evaporation. Comparison of this theoretical temperature difference with experimental observations highlights the influence of internal convective flows in homogenizing the thermal field within the drop.