Experimental and Numerical Study of Cavitation Number Limitations for Hydrodynamic Cavitation Inception Prediction

Hydrodynamic cavitation is the formation, growth and subsequent collapse of vapor bubbles in a moving liquid. It is extremely important to determine conditions of cavitation inception and when it starts damaging industrial equipment. In some cases, such as hydrodynamic cleaning it is important to understand how to improve the cavitation phenomenon in order to enhance cleaning properties. The cavitation number is a parameter used to predict cavitation and its potential effects. In this paper we discuss limitations of this parameter and demonstrate that it cannot be considered sufficient to predict cavitation inception and development in the fluid flow. The experimental setup was designed and built to study cavitation inception in various nozzles. RANS SST k–ω turbulence model was used in this study to model turbulent flow in ANSYS Fluent. CFD calculations were compared to experimental results. It was shown that cavitation inception was sensitive to change in nozzle geometry and, since geometrical parameters are not included in cavitation number formula, scenarios of cavitation inception can be different at the same cavitation number

Experimental and Numerical Study of Cavitation Number Limitations for Hydrodynamic Cavitation Inception Prediction

Hydrodynamic cavitation is the formation, growth and subsequent collapse of vapor bubbles in a moving liquid. It is extremely important to determine conditions of cavitation inception and when it starts damaging industrial equipment. In some cases, such as hydrodynamic cleaning it is important to understand how to improve the cavitation phenomenon in order to enhance cleaning properties. The cavitation number is a parameter used to predict cavitation and its potential effects. In this paper we discuss limitations of this parameter and demonstrate that it cannot be considered sufficient to predict cavitation inception and development in the fluid flow. The experimental setup was designed and built to study cavitation inception in various nozzles. RANS SST k–ω turbulence model was used in this study to model turbulent flow in ANSYS Fluent. CFD calculations were compared to experimental results. It was shown that cavitation inception was sensitive to change in nozzle geometry and, since geometrical parameters are not included in cavitation number formula, scenarios of cavitation inception can be different at the same cavitation number

The Scythian World of M.I. Rostovtzeff and E.H. Minns

Публикация переписки М.И. Ростовцева с английским археологом-классиком, палеографом и историком-славистом Э.Х Минзом освещает контакты двух ученых с 1913 по 1952 гг. и демонстрирует эволюцию их отношений.Примечания: с. 516-544. Публикация подготовлена при финансовой поддержке Российского фонда фундаментальных исследований (РФФИ). Проект № 02-06-87075

Semen microbiota and cytokines of healthy and infertile men

In this study, we determined the levels of cytokine secretory inhibitors and the microbiota biofilms of semen from healthy and infertile subjects. A total of 118 clinical bacterial isolates were isolated and tested. Cytokine secretory inhibitors were determined based on the difference in cytokine content between the control and experimental samples of cell-free supernatants of isolated microorganisms. Biofilm formation was studied by determining the adhesion of microorganisms to the surface of a 96-well sterile plate and expressed as the optical density at 630 nm (OD630). Cell-free supernatants of Staphylococcus contained higher levels of secretory inhibitor of cytokines in conditionally healthy than in infertile patients. In contrast, in infertile men, the ability to reduce cytokine levels was more characteristic of Enterococcus and Corynebacterium. Seminal Staphylococcus, Corynebacterium, and Enterococcus isolated from infertile subjects showed a greater ability to form biofilms than the same bacteria isolated from healthy men. Further research is needed on this topic, since it is necessary to determine the relationships between decreased secretory inhibitors of cytokines, production of biofilms by bacteria in semen, and infertility. It is likely that the ability of microorganisms to change the concentration of cytokines and increase the level of biofilm formation in semen may be associated with minimal impairments of fertilizing ability, which are not detected using other methods