In this article the formation of mineral-wool fibers is studied on a real industrial production process. The results presented indicate the presence of a melt instability that is formed as a complex quasi-periodic oscillation of the structures on the surface of the film. In addition to the melt oscillation, which coincides with the rotating frequency of the spinner wheel and its higher harmonics, aperiodic melt structures also appear. These structures result from the Taylor instability, which is inherent to liquid movement and is one of the basic mechanisms for the formation of melt ligaments that solidify into mineral-wool fibers. The results indicate the characteristic influence of melt film dynamics on the fiber formation and, indirectly, on the quality of the end product.
COBISS.SI-ID: 12424987
A visualization method was employed for accurate non-intrusive measurement of velocity fields at a physical model of a sharp-crested rectangular sideweir under subcritical flow. The experimental observation of velocity vectors at various horizontal planes over the entire width of the main channel confirms that the flow conditions at sideweir are non-uniform. The coefficients of non-uniform velocity distribution were in the range from 1 to 1.1. The present study focuses on the relation between the longitudinal components of the overflow velocities and the corresponding cross-sectional average velocities in the main channel, detailed as a function of flow depth and of location along the sideweir crest. For different sideweir geometries, these coefficients varied between 1 and 1.2.
COBISS.SI-ID: 12227611
CFD becomes an everyday tool in the development process of water turbines and pumps. The development of new models for steady state and unsteady calculations is very fast, but unfortunately some procedures in the development process are still very time-consuming. Some special numerical analysis takes more than a month of the CPU time although a huge number of processors are used. Hereafter are presented some new ideas on how computational time for steady state and unsteady calculations for incompressible fluids can be reduced by orders of magnitude for some particular cases. In the development process of new hydraulic turbines when high energetic and cavitation characteristics are expected, usually a huge number of different geometries and a lot of operating regimes should be analysed. To obtain accurate results the mesh needs to follow some quality criteria and should be fine enough. Considering all above mentioned facts, the computational time can be a bottleneck for efficient accomplishment of industrial projects.
COBISS.SI-ID: 26520615