scholarly journals The transition from sheet to cloud cavitation

2017 ◽  
Vol 817 ◽  
pp. 439-454 ◽  
Author(s):  
P. F. Pelz ◽  
T. Keil ◽  
T. F. Groß
Keyword(s):  
Reynolds Number ◽  
Cavitation Number ◽  
Wall Friction ◽  
Bubble Collapse ◽  
Penetration Length ◽  
Cloud Cavitation ◽  
Viscous Film ◽  
History Of ◽  
Good Agreement

Recent studies indicate that the transition from sheet to cloud cavitation depends on both cavitation number and Reynolds number. In the present paper this transition is investigated analytically and a physical model is introduced. In order to include the entire process, the model consists of two parts, a model for the growth of the sheet cavity and a viscous film flow model for the so-called re-entrant jet. The models allow the calculation of the length of the sheet cavity for given nucleation rates and initial nuclei radii and the spreading history of the viscous film. By definition, the transition occurs when the re-entrant jet reaches the point of origin of the sheet cavity, implying that the cavity length and the penetration length of the re-entrant jet are equal. Following this criterion, a stability map is derived showing that the transition depends on a critical Reynolds number which is a function of cavitation number and relative surface roughness. A good agreement was found between the model-based calculations and the experimental measurements. In conclusion, the presented research shows the evidence of nucleation and bubble collapse for the growth of the sheet cavity and underlines the role of wall friction for the evolution of the re-entrant jet.

Some Characteristics of Cavity Flow Past Cylindrical Inducers in a Venturi

1976 ◽  
Vol 98 (3) ◽  
pp. 461-466 ◽  
Author(s):  
B. C. Syamala Rao ◽  
D. V. Chandrasekhara
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Cavity Flow ◽  
Cavitation Number ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Wall Effects ◽  
Maximum Width ◽  
Shedding Frequency

The characteristic dimensions of the steady cavity and the shedding frequency of vortices behind six circular cylinders in a two-dimensional venturi have been studied. The normalized length and maximum width of cavity for cavitation sources of different sizes indicated unified trends with a modified cavitation number km. The angles of detachment θ increased with cavitation number k and decreased with increasing Reynolds number R. The Strouhal number Sd reached minimum values for all cavitation sources at small values of k. The possible role of wall effects on the investigations are discussed.

Turbulent Lubrication Flow in an Annular Channel

1986 ◽  
Vol 108 (2) ◽  
pp. 185-192 ◽  
Author(s):  
H. G. Polderman ◽  
G. Velraeds ◽  
W. Knol
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Diffusion Model ◽  
Annular Channel ◽  
Velocity Profiles ◽  
Experimental Results ◽  
Wall Friction ◽  
Number Range ◽  
Gradient Diffusion ◽  
Good Agreement

An analytical and experimental study is presented of the lubrication flow in an annular channel with a moving core. Velocity profiles and wall friction were determined over a Reynolds number range up to 3 × 104 and radius ratios of 0.6 and 0.85. The experimental results are shown to be in good agreement with the predictions of a three-layer gradient-diffusion model.

Ripple and dune formation in rivers

2011 ◽  
Vol 673 ◽  
pp. 121-131 ◽  
Author(s):  
M. COLOMBINI ◽  
A. STOCCHINO
Keyword(s):  
Reynolds Number ◽  
Flow Model ◽  
Phase Lag ◽  
Bed Shear Stress ◽  
Particle Reynolds Number ◽  
Ripple Formation ◽  
Bed Elevation ◽  
Two Dimensional Flow ◽  
Good Agreement

A linear stability analysis for dune and ripple formation is presented that implements a rotational two-dimensional flow model valid in the smooth as well as in the transitional and rough flow regimes. Sediment is assumed to be transported as bedload, disregarding the role of suspension. Therefore, the main mechanism driving instability, for both ripples and dunes, is the phase lag between bed shear stress and bed elevation. Ripples are shown to be confined to relatively low values of the Shields parameter and of the particle Reynolds number. For higher values of the Shields parameter and of the particle Reynolds number (and thus of the Froude number and of the roughness Reynolds number), ripples are replaced by dunes. The present analysis ultimately allows for a successful unification of the theories of dune and ripple formation and for a clarification of the debated role of ripples on the formation of dunes. A good agreement between predicted and observed wavelengths for both ripples and dunes is found.

Elaborating the role of reflection and individual differences in the study of folk-economic beliefs

2018 ◽  
Vol 41 ◽  
Author(s):  
Kevin Arceneaux
Keyword(s):  
Decision Making ◽  
Individual Differences ◽  
Cognitive Processes ◽  
Evolutionary History ◽  
Behavioral Responses ◽  
History Of ◽  
Economic Beliefs

AbstractIntuitions guide decision-making, and looking to the evolutionary history of humans illuminates why some behavioral responses are more intuitive than others. Yet a place remains for cognitive processes to second-guess intuitive responses – that is, to be reflective – and individual differences abound in automatic, intuitive processing as well.

The role of a family history of adenocarcinomas in patients with Barrett oesophagus

2001 ◽  
Vol 120 (5) ◽  
pp. A442-A442
Author(s):  
P TSIBOURIS ◽  
M HENDRICKSE ◽  
P ISAACS
Keyword(s):  
Family History ◽  
History Of ◽  
Barrett Oesophagus

Protective Factors and Suicidality in Members of Arab Kindred

Crisis ◽  
2012 ◽  
Vol 33 (2) ◽  
pp. 80-86 ◽  
Author(s):  
Sami Hamdan ◽  
Nadine Melhem ◽  
Israel Orbach ◽  
Ilana Farbstein ◽  
Mohammad El-Haib ◽  
...  
Keyword(s):  
Risk Factors ◽  
Protective Factors ◽  
Suicidal Behavior ◽  
Composite International Diagnostic Interview ◽  
Diagnostic Interview ◽  
Suicidal Risk ◽  
Arab Population ◽  
Psychiatric Interview ◽  
History Of

Background: Relatively little is known about the role of protective factors in an Arab population in the presence of suicidal risk factors. Aims: To examine the role of protective factors in a subsample of in large Arab Kindred participants in the presence of suicidal risk factors. Methods: We assessed protective and risk factors in a sample of 64 participants (16 suicidal and 48 nonsuicidal) between 15 and 55 years of age, using a comprehensive structured psychiatric interview, the Composite International Diagnostic Interview (CIDI), self-reported depression, anxiety, hopelessness, impulsivity, hostility, and suicidal behavior in first-degree and second-relatives. We also used the Religiosity Questionnaire and suicide attitude (SUIATT) and multidimensional perceived support scale. Results: Suicidal as opposed to nonsuicidal participants were more likely to have a lifetime history of major depressive disorder (MDD) (68.8% vs. 22.9% χ2 = 11.17, p = .001), an anxiety disorder (87.5% vs. 22.9, χ2 = 21.02, p < .001), or posttraumatic stress disorder (PTSD) (25% vs. 0.0%, Fisher’s, p = .003). Individuals who are otherwise at high risk for suicidality have a much lower risk when they experience higher perceived social support (3.31 ± 1.36 vs. 4.96 ± 1.40, t = 4.10, df = 62, p < .001), and they have the view that suicide is somehow unacceptable (1.83 ± .10 vs. 1.89 ± .07, t = 2.76, df = 60, p = .008). Conclusions: Taken together with other studies, these data suggest that the augmentation of protective factors could play a very important role in the prevention of incidental and recurrent suicidal behavior in Arab populations, where suicidal behavior in increasing rapidly.

THE ROLE OF RECTAL EUS-FNA/B IN PRE-SACRAL UNDEFINED LESIONS IN PATIENTS WITH HISTORY OF LOWER GI NEOPLASIA

2020 ◽  
Author(s):  
B Mangiavillano ◽  
S Carrara ◽  
E Dabizzi ◽  
F Auriemma ◽  
V Cennamo ◽  
...  
Keyword(s):  
History Of

The problem of periodization of the history of religion

1997 ◽  
pp. 3-8
Author(s):  
Borys Lobovyk
Keyword(s):  
Religious Studies ◽  
Human Being ◽  
Religious Development ◽  
History Of Religion ◽  
The Social ◽  
The World ◽  
History Of ◽  
Role Of Religion

An important problem of religious studies, the history of religion as a branch of knowledge is the periodization process of the development of religious phenomenon. It is precisely here, as in focus, that the question of the essence and meaning of the religious development of the human being of the world, the origin of beliefs and cult, the reasons for the changes in them, the place and role of religion in the social and spiritual process, etc., are converging.

ROLE OF LIPID PROFILE IN OVARIAN CARCINOMA PATIENTS

2019 ◽  
Vol 3 (8) ◽  
Author(s):  
Dr. Manisha ◽  
Dr. Ruchi Jindal
Keyword(s):  
Ovarian Cancer ◽  
Lipid Profile ◽  
Cancer Patients ◽  
Ovarian Tumor ◽  
Ovarian Cancer Risk ◽  
Low Level ◽  
Medical College ◽  
Group I ◽  
History Of

Background: The term "ovarian cancer" includes several different types of cancer that  arise from cells of the ovary, most commonly, tumors arise from the epithelium or lining cells of the ovary.  Ovarian cancer risk is positively associated with higher consumption of dietary cholesterol and eggs, and inversely associated with a higher intake of vegetables. High consumption of fats may increase circulating estrogen levels, thus increasing the possibility of cell damage and proliferation that is responsible for cancerous growth. Material & Methods: The present study was conducted at Geetanjali Medical College and Hospital, Udaipur (Rajasthan). Total  100 cases (females) attending the obstetrics and gynecology department for some gynecological and other problem  were selected for this study between the age of 40-60 years, who were attending cancer centre at GEETANJALI MEDICAL COLLEGE AND  HOSPITAL, Udaipur (Rajasthan).                GROUP I: - It consisted of healthy females control subjects (n=50) .By routine examination and tests, we ensured that all the subjects were healthy and there were no signs and symptoms or history of ovarian tumor and diseases GROUP II: - It consisted of ovarian cancer females subjects (n=50) with a history of ovarian tumor. Results:   Higher level of cholesterol, LDL, VLDL and low level of HDL are found in ovarian cancer patients. Conclusion: The present study we highlights the importance and role of serum lipid profile in diagnosis, prognosis and recurrence of the disease. The study shows that serum level of cholesterol, LDL, VLDL was elevated in  patients of ovarian cancer while low level of HDL are found in ovarian cancer patients. Key words: lipid profile, ovarian cancer.

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