Numerical and experimental investigations on the cavitating flow in a cascade of hydrofoils

The cavitating flow in a cascade of three hydrofoils was investigated by experimental means and numerical simulation. Experiments on the 2D-hydrofoils cascade were carried out at Darmstadt University of Technology in a rectangular test section of a cavitation tunnel. A numerical model developed at LEGI (Grenoble) to describe the unsteady behaviour of cavitation including the shedding of vapour structures was applied to the hydrofoils cascade geometry. Results of both experimental and numerical studies show a strong interaction between the cavities of each flow channel besides the typical self-oscillation of cloud cavitation. A detailed comparison of the results allows proposing an interpretation of the interaction mechanisms

Experimental and numerical studies on a centrifugal pump with 2D-curved blades in cavitation condition

In the presented study a special test-pump with 2D curvature blade geometry in cavitating and non-cavitating conditions was investigated using different experimental techniques and a 3D numerical model of cavitating flows. Experimental and numerical results concerning pump characteristics and performance breakdown were compared at different flow conditions. Appearing types of cavitation and the spatial distribution of vapour structures within the runner were also analysed

Experimental and numerical studies of a centrifugal pump in cavitating conditions

In the presented study a special test pump with two-dimensional curvature blade geometry was investigated in cavitating and noncavitating conditions using different experimental techniques and a three-dimensional numerical model implemented to study cavitating flows. Experimental and numerical results concerning pump characteristics and performance breakdown were compared at different flow conditions. Appearing types of cavitation and the spatial distribution of vapor structures within the impeller were also analyzed. These results show the ability of the model to simulate the complex three-dimensional development of cavitation in a rotating machinery, and the associated effects on the performance

Development of a Standardized Approach to Assess the Energy Efficiency of Booster Pump Units in the Sense of an Extended Product

With regard to the so called extended product approach (EPA), an appropriate methodology to qualify respectively verify these extended products has been successfully developed at the Institute for Fluid Systems of Technische Universität Darmstadt – supported by Europump – for single pump units. The EPA is a measure to meet the energy related products (ErP) and energy using products (EuP) requirements of the European Commission. Based on the experience of this work Europump decided to expand the EPA also to booster pump units, which normally consist of multiple pumps as well as further hydraulic and electric components to ensure the specific demands of pressure boosting within buildings. A characteristic rating is needed to compare and quantify the energy efficiency of booster pump units in a standardized way. The development of a draft standard proposal for further regulation is the final objective of this work. As a result the energy efficiency index (EEI) as a normalized weighted average of the electrical input power for a booster pump unit operating at different duty points at part load is introduced. A standardized load-time profile and a pressure control curve are defined in order to compare lifetime efficiency and part load behaviour. The EEI will be determined using both an experimental and semi-analytical approach. Main task of the experimental work is the development of a measurement procedure for the EEI determination, which can be summarized as a realization of sensitivity studies in order to deduce all major effects on the EEI for a subsequent standard elaboration. This includes the definition of needed accuracy and acceptable tolerances of flow-adjustment and used sensors as well as the examination of parameters affecting the power consumption of the booster pump unit. Besides, steady state operation for each duty point has to be guaranteed. A method for non-adjustable duty points within the given constraints has to be implemented which is attended by the exertion of penalties in EEI for overshooting. The tasks of the Institute for Fluid Systems of Technische Universität Darmstadt are the development and neutral assessment of all required measurement procedures. Besides the experimental work, a semi-analytical approach is developed which allows calculating the electrical input power and thus the EEI with reduced experimental effort in future. The resulting semi-analytical model (SAM) is based on empirical data for frequency converters, motors and pumps as well as analytical laws describing the physics of booster system behaviour. A further advantage of SAM is the possibility of systematic determination of EEI values for booster units consisting of components delivered by different manufacturers

Determination of the Tensile Strength and the Nuclei Concentration by Means of the In-Situ-Nozzle

In this paper a new method for the determination of the tensile strength in combination with the underlying distribution of free cavitation nuclei is presented. This method is based on the advancement of the in-situ-measuring of the tensile strength by means of the so-called “in-situ-nozzle” originally presented at the CAV2006 Symposium. The in-situ-nozzle works as a cavitation susceptibility meter that is based on the venturi principle. In contrast to several previously presented cavitation susceptibility meters the in-situ-nozzle can be used to measure the tensile strength “in-situ ” i.e. directly within a hydraulic pipe, without the need for any bypass connections. Consequently the in-situ-nozzle serves as a measuring device for the detection of the tensile strength at basically any position within a hydraulic circuit. The adjacent analysis method that has been developed to evaluate the collected data allows for providing additional information on the freely distributed cavitation nuclei in an operating test installation. For this purpose the measured tensile strength is associated with the critical size of gas bubbles acting as cavitation nuclei. Following this approach it is possible to give an approximation of the currently existing nuclei size distribution respectively the nuclei concentration at the mounting position of the in-situ-nozzle. By installing two identically constructed in-situ-nozzles in a centrifugal pump test rig the tensile strength and the nuclei concentration at two positions with different boundary conditions are determined. One nozzle is mounted directly upstream of the test pump, whereas the other one is installed in the pressure pipe downstream of the pump. This is done first of all, to examine the capability of the measuring device of being sensitive enough for a change in the boundary conditions in general. If this is verified, the two nozzles can be adopted to particularly investigate the influence of specifically chosen operating points of the test pump on the tensile strength as well as on the underlying nuclei concentration

Human papillomavirus vaccination of girls in the German model region Saarland: Insurance data-based analysis and identification of starting points for improving vaccination rates

In Germany, the incidence of cervical cancer, a disease caused by human papillomaviruses (HPV), is higher than in neighboring European countries. HPV vaccination has been recommended for girls since 2007. However, it continues to be significantly less well received than other childhood vaccines, so its potential for cancer prevention is not fully realized. To find new starting points for improving vaccination rates, we analyzed pseudonymized routine billing data from statutory health insurers in the PRÄZIS study (prevention of cervical carcinoma and its precursors in women in Saarland) in the federal state Saarland serving as a model region. We show that lowering the HPV vaccination age to 9 years led to more completed HPV vaccinations already in 2015. Since then, HPV vaccination rates and the proportion of 9- to 11-year-old girls among HPV-vaccinated females have steadily increased. However, HPV vaccination rates among 15-year-old girls in Saarland remained well below 50% in 2019. Pediatricians vaccinated the most girls overall, with a particularly high proportion at the recommended vaccination age of 9–14 years, while gynecologists provided more HPV catch-up vaccinations among 15-17-year-old girls, and general practitioners compensated for HPV vaccination in Saarland communities with fewer pediatricians or gynecologists. We also provide evidence for a significant association between attendance at the children´s medical check-ups “U11” or “J1” and HPV vaccination. In particular, participation in HPV vaccination is high on the day of U11. However, obstacles are that U11 is currently not financed by all statutory health insurers and there is a lack of invitation procedures for both U11 and J1, resulting in significantly lower participation rates than for the earlier U8 or U9 screenings, which are conducted exclusively with invitations and reminders. Based on our data, we propose to restructure U11 and J1 screening in Germany, with mandatory funding for U11 and organized invitations for HPV vaccination at U11 or J1 for both boys and girls

Plasma folate levels are associated with the lipoprotein profile: a retrospective database analysis

BACKGROUND: Several studies demonstrated an association of homocysteine plasma levels and the plasma lipoprotein profile. This cross-sectional pilot study aimed at analyzing whether blood levels of the two important cofactors of homocysteine metabolism, folate and vitamin B12, coincide with the lipoprotein profile. METHODS: In a retrospective single center approach, we analyzed the laboratory database (2003-2006) of the University Hospital Bonn, Germany, including 1743 individuals, in whom vitamin B12, folate and at least one lipoprotein parameter had been determined by linear multilogistic regression. RESULTS: Higher folate serum levels were associated with lower serum levels of low density lipoprotein cholesterol (LDL-C; Beta = -0.164; p < 0.001), higher levels of high density lipoprotein cholesterol (HDL-C; Beta = 0.094; p = 0.021 for trend) and a lower LDL-C-C/HDL-C-ratio (Beta = -0.210; p < 0.001). Using ANOVA, we additionally compared the individuals of the highest with those of the lowest quartile of folate. Individuals of the highest folate quartile had higher levels of HDL-C (1.42 +/- 0.44 mmol/l vs. 1.26 +/- 0.47 mmol/l; p = 0.005), lower levels of LDL-C (3.21 +/- 1.04 mmol/l vs. 3.67 +/- 1.10 mmol/l; p = 0.001) and a lower LDL-C/HDL-C- ratio (2.47 +/- 1.18 vs. 3.77 +/- 5.29; p = 0.002). Vitamin B12 was not associated with the lipoprotein profile. CONCLUSION: In our study sample, high folate levels were associated with a favorable lipoprotein profile. A reconfirmation of these results in a different study population with a well defined status of health, diet and medication is warranted

MicroRNA-96 Directly Inhibits γ-Globin Expression in Human Erythropoiesis

Fetal hemoglobin, HbF (α2γ2), is the main hemoglobin synthesized up to birth, but it subsequently declines and adult hemoglobin, HbA (α2β2), becomes predominant. Several studies have indicated that expression of the HbF subunit γ-globin might be regulated post-transcriptionally. This could be confered by ∼22-nucleotide long microRNAs that associate with argonaute proteins to specifically target γ-globin mRNAs and inhibit protein expression. Indeed, applying immunopurifications, we found that γ-globin mRNA was associated with argonaute 2 isolated from reticulocytes that contain low levels of HbF (<1%), whereas association was significantly lower in reticulocytes with high levels of HbF (90%). Comparing microRNA expression in reticulocytes from cord blood and adult blood, we identified several miRNAs that were preferentially expressed in adults, among them miRNA-96. The overexpression of microRNA-96 in human ex vivo erythropoiesis decreased γ-globin expression by 50%, whereas the knock-down of endogenous microRNA-96 increased γ-globin expression by 20%. Moreover, luciferase reporter assays showed that microRNA-96 negatively regulates expression of γ-globin in HEK293 cells, which depends on a seedless but highly complementary target site located within the coding sequence of γ-globin. Based on these results we conclude that microRNA-96 directly suppresses γ-globin expression and thus contributes to HbF regulation

Measurement of Cavitation Erosive Aggressiveness by Means of Structure Born Noise

A measuring system was developed to estimate the cavitation erosive aggressiveness in a centrifugal pump during operation. The system is based on acoustical means. Acoustic pressure waves in water and vibrations of machine casings underlie several disturbances especially by changes of the transmission behaviour of the fluid during operation. Thus, an approach based on the structure born noise measured directly on the mechanical structure exposed to the cavitation was chosen to minimise this problems. The sensor, the amplifier and the signal processing and transmission devices have then to be placed within the rotating part of the machine. The measurements of the system have been compared with results of measurements using material specimen and coatings of soft copper. The physical relation between the acoustical event amplitudes detected by the system and the sizes of pits found on the specimen is discussed