Cavitation Inception Observations on Six Axisymmetric Headforms

1981 ◽  
Vol 103 (2) ◽  
pp. 273-279 ◽  
Author(s):  
T. T. Huang
Keyword(s):  
Static Pressure ◽  
Water Tunnel ◽  
Air Bubbles ◽  
Flow Transition ◽  
Laminar Separation ◽  
Cavitation Inception ◽  
Air Content ◽  
Natural Flow ◽  
The Individual ◽  
Made In

Cavitation inception observations on a series of axisymmetric headforms were made in the DTNSRDC 36-in. water tunnel. Cavitation inception observed on headforms with natural flow transition is characterized by the growth and collapse of the individual undissolved air bubbles in the water when traveling through the low pressure regions of flow transition. Cavitation inception observed on headforms with laminar separation is characterized by an attached band or bubble-ring cavitation starting at the separation point. The traveling bubble type cavitation inception is significantly affected by the microbubble population. However, the effect of total air content and size distribution of the bubbles on attached cavitation inception is less pronounced. Attached spot or ring/band cavitation never occur at the location of minimum static pressure but are observed first in the regions of natural flow transition or laminar separation.

Cavitation Inception Tests on Axisymmetric Headforms

1981 ◽  
Vol 103 (2) ◽  
pp. 268-272 ◽  
Author(s):  
Sen-sen Pan ◽  
Zhan-ming Yang ◽  
Pei-shuen Hsu
Keyword(s):  
Scientific Research ◽  
Flow Regimes ◽  
Flow Patterns ◽  
The Body ◽  
Research Center ◽  
Water Tunnel ◽  
Cavitation Inception ◽  
Air Content ◽  
Flow Past ◽  
Wall Flow

Six axisymmetric headforms were tested in the 350-mm dia water tunnel at China Ship Scientific Research Center (CSSRC) for observation and measurement of cavitation inception. Among them, three of the flow patterns were displayed and analyzed by holography. Results of the tests show that cavitation inception on the headforms was closely related to the structure of the near-wall flow past the body with different flow regimes corresponding to different features of cavitation inception. By carefully fitting a trip wire of suitable height on a hemispherical headform, it was observed that under conditions of low air content, this artificial means of boundary transition may bring about a significant reduction in cavitation inception number.

Analysis of Flow Separation in an Annular Expansion—Contraction With Inner Cylinder Rotating

1973 ◽  
Vol 95 (4) ◽  
pp. 485-492 ◽  
Author(s):  
G. F. Dailey ◽  
G. E. Geiger
Keyword(s):  
Turbulent Flow ◽  
Numerical Solution ◽  
Steady Flow ◽  
Flow Separation ◽  
Static Pressure ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Air Bubbles ◽  
Theoretical Computer ◽  
Laminar Separation

A three-dimensional incompressible isothermal laminar separation of a Newtonian fluid in transient and steady flow was investigated. The geometry chosen for this study was an annular expansion-contraction chamber with a rotating inner cylinder. It was found that an adaptation of a numerical solution first proposed by Fromm gave converged solutions for all Reynolds numbers in the laminar range. Theoretical computer plotted streamline patterns were superimposed on time exposure photographs of air bubbles in transparent oil. Measured static pressure differentials were compared with laminar theory. Turbulent flow was studied experimentally.

Rough Surface Effects on Cavitation Inception

1968 ◽  
Vol 90 (2) ◽  
pp. 249-261 ◽  
Author(s):  
Roger E. A. Arndt ◽  
A. T. Ippen
Keyword(s):  
Skin Friction ◽  
Boundary Layers ◽  
Bubble Dynamics ◽  
Static Pressure ◽  
Skin Friction Coefficient ◽  
Water Tunnel ◽  
Mean Square ◽  
Mean Velocity ◽  
Cavitation Inception ◽  
Rough Boundaries

Cavitation inception and the associated bubble dynamics in turbulent boundary layers adjacent to surfaces roughened with triangular grooves is investigated in a two-dimensional recirculating water tunnel. The experiments result in the significant conclusion that the cavitation inception index is directly related to the skin friction coefficient for both smooth and rough boundaries. Cavitation is observed to occur away from the wall approximately in the center of the boundary layer, and is apparently the result of negative peaks in static pressure having a magnitude which exceeds 5 times the expected value of root mean square wall pressure. Mean velocity and skin friction data are correlated with existing theory for equilibrium boundary layers.

Effect of Air Content on Cavitation Inception as Investigated by Depressurizing Still Water

2003 ◽  
Author(s):  
Hidetake Tanibayashi ◽  
Yoshinori Matsuura ◽  
Kimihito Inoue ◽  
Kenji Ogura
Keyword(s):  
Coulter Counter ◽  
Air Bubbles ◽  
Reduced Pressure ◽  
Cavitation Inception ◽  
Air Content ◽  
Free Air

It has been recognized that air content in water affects inception of cavitation and its development. Number of nuclei in the water which are considered to trigger cavitation, however, has been found to be almost independent of air content, as far as the nuclei are counted by a coulter counter. In this study, the mechanisms of cavitation inception are investigated with emphasis on the role of air content in water. As a result, it is shown that nuclei in water increase with air content when the water is supersaturated with air by depressurization. This was proved by experiments both in atmospheric and reduced pressure conditions. From this study the effect of air content on cavitation may be interpreted as follows: free air bubbles are formed when the water is supersaturated by depressurization and they become nuclei which induce cavitation inception.

Effect of semi-open impeller side clearance on centrifugal pump cavitation inception

2018 ◽  
Vol 1 (2) ◽  
pp. 24-39
Author(s):  
A. Farid ◽  
A. Abou El-Azm Aly ◽  
H. Abdallah
Keyword(s):  
Centrifugal Pump ◽  
Static Pressure ◽  
Rotation Speed ◽  
Centrifugal Pumps ◽  
Severe Condition ◽  
Cavitation Inception ◽  
Total Input ◽  
Input Pressure ◽  
Pump Head ◽  
Pump Pressure

Cavitation in pumps is the most severe condition that centrifugal pumps can work in and is leading to a loss in their performance.  Herein, the effect of semi-open centrifugal pump side clearance on the inception of pump cavitation has been investigated.  The input pump pressure has been changed from 80 to 16 kPa and the pump side clearance has been changed from 1 mm to 3 mm at a rotation speed of 1500 rpm. It has been shown that as the total input pressure decreased; the static pressure inside the impeller is reduced while the total pressure in streamwise direction has been reduced, also the pump head is constant with the reduction of the total input pressure until the cavitation is reached. Head is reduced due to cavitation inception; the head is reduced in the case of a closed impeller with a percent of 1.5% while it is reduced with a percent of 0.5% for pump side clearance of 1mm, both are at a pressure of 20 kPa.   Results also showed that the cavitation inception in the pump had been affected and delayed with the increase of the pump side clearance; the cavitation has been noticed to occur at approximate pressures of 20 kPa for side clearance of 1mm, 18 kPa for side clearances of 2mm and 16 kPa for 3mm.

A Handbook to Eddic Poetry: Myths and Legends of Early Scandinavia, ed. Carolyne Larrington, Judy Quinn, and Brittany Schorn. Cambridge: Cambridge University Press, 2016, xii, 413 pp., 12 b/w ill.

Mediaevistik ◽  
2018 ◽  
Vol 31 (1) ◽  
pp. 366-366
Author(s):  
Albrecht Classen
Keyword(s):  
Old Norse ◽  
Entire Volume ◽  
Cambridge University ◽  
Critical Studies ◽  
Individual Contributions ◽  
The Many ◽  
The Individual ◽  
Made In ◽  
Scandinavian Literature

Eddic poetry constitutes one of the most important genres in Old Norse or Scandinavian literature and has been studied since the earliest time of modern-day philology. The progress we have made in that field is impressive, considering the many excellent editions and translations, not to mention the countless critical studies in monographs and articles. Nevertheless, there is always a great need to revisit, to summarize, to review, and to digest the knowledge gained so far. The present handbook intends to address all those goals and does so, to spell it out right away, exceedingly well. But in contrast to traditional concepts, the individual contributions constitute fully developed critical article, each with a specialized topic elucidating it as comprehensively as possible, and concluding with a section of notes. Those are kept very brief, but the volume rounds it all off with an inclusive, comprehensive bibliography. And there is also a very useful index at the end. At the beginning, we find, following the table of contents, a list of the contributors, unfortunately without emails, a list of translations and abbreviations of the titles of Eddic poems in the Codex Regius and then elsewhere, and a very insightful and pleasant introduction by Carolyne Larrington. She briefly introduces the genre and then summarizes the essential points made by the individual authors. The entire volume is based on the Eddic Network established by the three editors in 2012, and on two workshops held at St. John’s College, Oxford in 2013 and 2014.

The Chemical Effect in Medicine Interaction Determining the Form and Speed of Psychical Involution in the Prosthetic Restauration in the Edentulous

2018 ◽  
Vol 69 (8) ◽  
pp. 2306-2310
Author(s):  
Aureliana Caraiane ◽  
Razvan Leata ◽  
Veronica Toba ◽  
Doina Vesa ◽  
Luana Andreea Macovei ◽  
...  
Keyword(s):  
Practical Importance ◽  
Psychosocial Problems ◽  
Well Being ◽  
The Elderly ◽  
Chemical Effect ◽  
Special Importance ◽  
Dramatic Form ◽  
Specific Disorders ◽  
The Individual ◽  
Made In

The progress made in dentistry during the latest decades is due, conceptually, to the new, systemic vision of man, which has also taken place in this field of medicine. In this context, the link between organic and psychic is indestructible. Thus illness is understood as a drama in which the somatic process has a psychic value, and the mental one has a body value. It is known that the morphological and functional integrity of the dental system, health and vigorousness, gives the individual a state of well-being that affects his somatic and psychic health, as any disturbance at this level entails repercussions in psychological and social behavior. Such a disruption is the total edification that seriously alters not only the dental system but the whole organism, putting various biological and psychosocial problems to the practitioner. The total expression represents not only a physical disability but also a psychological one. A special importance in studying psychological changes at total edentulous presents the psychological aspects of senile involution. This is not only a theoretical but also a practical importance due to the increase in the number of elderly people. Through the researches of the present paper we intend to present the reality of the psychological manifestations in the total edentation, which is objectified on different methods of psychodiagnosis in the first part, in order for the second part to be addressed to problems of prosthetic psychotherapy.The study comprises a group of 43 patients, of whom 24 were men and 19 women with total uni or bimaxilar edentation. Total edentation can be and is responsible for somatopsychic alterations, along with other pathogens, general, local, social, which sometimes can take a dramatic form, converting, where the area is also favorable, a pure somatic disease, for those who are not in psychopathy or even psychosis, although these latter cases are extremely rare and especially in youngsters, which would disrupt not only the person�s behavior as an individual, but also their status, function and social integrity. The treatment of dental and psychological complex is mandatory for any patient, but especially for the elderly, where recovery is more difficult, with disease-specific disorders adding to those of senescence.

scholarly journals An approach to the modeling of a virtual thermal manikin

2014 ◽  
Vol 18 (4) ◽  
pp. 1413-1423 ◽  
Author(s):  
Dragan Ruzic ◽  
Sinisa Bikic
Keyword(s):  
Turbulence Models ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Thermal Manikin ◽  
Flow Conditions ◽  
Body Segments ◽  
Nominal Size ◽  
Natural Flow ◽  
Good Agreement ◽  
Made In

The aim of the research described in this paper, is to make a virtual thermal manikin that would be simple, but also robust and reliable. The virtual thermal manikin was made in order to investigate thermal conditions inside vehicle cabins. The main parameters of the presented numerical model that were investigated in this paper are mesh characteristics and turbulence models. Heat fluxes on the manikin's body segments obtained from the simulations were compared with published results, from three different experiments done on physical thermal manikins. The presented virtual thermal manikin, meshed with surface elements of 0.035 m in nominal size (around 13,600 surface elements) and in conjunction with the two-layer RANS Realizable k-? turbulence model, had generally good agreement with experimental data in both forced and natural flow conditions.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

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