The Effect of Nuclei on the Inception of Bubble and Sheet Cavitation on Axisymmetric Bodies

1981 ◽  
Vol 103 (4) ◽  
pp. 557-563 ◽  
Author(s):  
Y. Kodama ◽  
N. Take ◽  
S. Tamiya ◽  
H. Kato
Keyword(s):  
Size Distribution ◽  
Cavitation Number ◽  
Experimental Results ◽  
Sheet Cavitation ◽  
Upper Limit ◽  
Hydrogen Bubbles ◽  
Cavitation Nuclei ◽  
Axisymmetric Bodies ◽  
Measured Size Distribution

Hydrogen bubbles were generated as cavitation nuclei and their distributions were measured. The number and size distribution of bubble cavities generated on axisymmetric bodies was calculated and compared with experimental results. The measured size distribution of bubble cavities agreed qualitatively with the calculated value, but the total number of cavities was about one half of the calculation. The role of stream nuclei on the inception of sheet cavity was investigated experimentally. Without added nuclei, the value of the incipient cavitation number σi showed a large scattering, whereas with added nuclei the scattering became fairly small and σi converged to the upper limit of that when no nuclei were added. σi with added nuclei also coincided with the desinent cavitation number σd, and σd remained unchanged by adding nuclei.

Cavitation in an Extremely Limited Flow Through Very Small Orifices

1982 ◽  
Vol 104 (1) ◽  
pp. 94-98 ◽  
Author(s):  
R. Oba ◽  
T. Ikohagi ◽  
K. T. Kim
Keyword(s):  
Turbulent Flows ◽  
Water Flow ◽  
Cavitation Number ◽  
Orifice Diameter ◽  
Flow Through ◽  
Cavitation Nuclei ◽  
Technical Interest

In order to clarify the role of cavitation nuclei upon inception, the behavior of inception was carefully investigated in an extremely limited water flow through very small orifices less than 1.0 mm in diameter under a prescribed nuclei condition. The following facts of technical interest were determined: a) The desinent cavitation number (σd) decreased rapidly and exponentially with the orifice diameter d, up to one hundredth in magnitude; and b) the cavitation appearance in such limited flows was quite different from that in fully turbulent flows through larger orifices.

A Limited Role of Separation Bubble in Desinent Cavitation

1985 ◽  
Vol 107 (1) ◽  
pp. 121-125 ◽  
Author(s):  
Y. Ito ◽  
R. Oba
Keyword(s):  
Separation Bubble ◽  
Marked Change ◽  
Cavitation Number ◽  
Hydrodynamic Conditions ◽  
Internal Flows ◽  
Backward Facing Step ◽  
Bubble Cloud ◽  
Limited Role ◽  
Cavitation Nuclei

In order to clarify whether a separation bubble always plays an important role, the desinence of streamer-cavitation, a kind of attached-cavitation, was carefully investigated in typical internal flows through venturies with and without a 40 μm thin backward facing step under a prescribed cavitation nuclei as well as various hydrodynamic conditions. The following facts have been found: (i) the separation bubble can play an important role in the desinence only when the separation bubble thickness H is larger than the diameter of nucleus dnp that may grow up to a critical one [18], (ii) a marked change takes place in the desinent cavitation number σd due to the step, i.e., σd ≅ |Cps| for H > dnp but σd < |Cps| for H ≦ dnp, (iii) for the cavitation there are two geneses, i.e., the nuclei floating within the separation bubble and the bubble-cloud occurring in the reattachment-region.

Transport and fluctuations in nonlinear-dissipative systems: role of interparticle collisions

1999 ◽  
Vol 4 ◽  
pp. 31-86 ◽  
Author(s):  
R. Katilius ◽  
A. Matulionis ◽  
R. Raguotis ◽  
I. Matulionienė
Keyword(s):  
Electric Fields ◽  
Carrier Density ◽  
Experimental Results ◽  
Dissipative Systems ◽  
Doped Semiconductors ◽  
Electron Diffusion ◽  
Electron Collisions ◽  
Electric Noise ◽  
Diffusion Phenomena

The goal of the paper is to overview contemporary theoretical and experimental research of the microwave electric noise and fluctuations of hot carriers in semiconductors, revealing sensitivity of the noise spectra to non-linearity in the applied electric field strength and, especially, in the carrier density. During the last years, investigation of electronic noise and electron diffusion phenomena in doped semiconductors was in a rapid progress. By combining analytic and Monte Carlo methods as well as the available experimental results on noise, it became possible to obtain the electron diffusion coefficients in the range of electric fields where inter-electron collisions are important and Price’s relation is not necessarily valid. Correspondingly, a special attention to the role of inter-electron collisions and of the non-linearity in the carrier density while shaping electric noise and diffusion phenomena in the non-equilibrium states will be paid. The basic and up-to-date information will be presented on methods and advances in this contemporary field - the field in which methods of non-linear analytic and computational analysis are indispensable while seeking coherent understanding and interpretation of experimental results.

Role of Ce2Zr3O10 Phase on the Microstructure and Fracture Toughness of ZTA Composites

2016 ◽  
Vol 840 ◽  
pp. 57-60 ◽  
Author(s):  
Nik Akmar Rejab ◽  
Zhwan Dilshad Ibrahim Sktani ◽  
Afifah Mohd Ali ◽  
Zainal Arifin Ahmad
Keyword(s):  
Fracture Toughness ◽  
Experimental Results ◽  
Mixing Process ◽  
Transformation Toughening ◽  
Simple Route ◽  
Zirconia Toughened Alumina

Despite the impressive development in understanding transformation toughening, tailoring the toughness of zirconia toughened alumina (ZTA) ceramics remained a major challenge. In our research, a simple route based on the powders mixing process of ZTA powders with varying CeO2 additions (0 - 10 wt.%) is developed to investigate this issue. The experimental results clearly reveal that the fracture toughness of ZTA ceramics can be tailored by mixing of ZTA starting powders.

scholarly journals Libet’s experiments and the problem of free will

2016 ◽  
Vol 59 (4) ◽  
pp. 23-29
Author(s):  
Andrea Berber
Keyword(s):  
Free Will ◽  
Experimental Results ◽  
Readiness Potential ◽  
Real Effect

The purpose of this paper is to give an answer to the question of the extent to which Libet?s experiments are helping to solve the problem of free will. Relevance of Libet?s experimental results for the problem of free will is contested by the multitude of complaints. These complaints can be divided into three categories: methodological objections, conceptual objections and complaints regarding the interpretation of the role of readiness potential. I am trying to show that only objections that belong to the last group have a real effect. I conclude that Libet?s experiments while providing significant incentives and suggestions for further research did not contribute to solving the problem of free will.

scholarly journals One, No One, and One Hundred Thousand: The Paradigm of the Z–R Relationship

2020 ◽  
Vol 21 (6) ◽  
pp. 1161-1169
Author(s):  
Massimiliano Ignaccolo ◽  
Carlo De Michele
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Rain Rate ◽  
Scaling Law ◽  
Drop Size Distribution ◽  
Physical Relationship ◽  
Simple Realization ◽  
Linear Fit ◽  
State Of Affairs

AbstractThe Z–R relationship is a scaling-law formulation, Z = ARb, connecting the radar reflectivity Z to the rain rate R. However, more than 100 Z–R relationships, with different values of the parameters, have been reported in literature. This abundance of relationships is in itself a strong indication that no one “physical” relationship exists, a state of affairs that we find similar to that of the protagonist of Luigi Pirandello’s novel One, No One and One Hundred Thousand. Nevertheless the “elevation” of a simple linear fit in the (logR, logZ) space to the role of “scaling law” is such a widespread tenet in literature that it eclipses the simple realization that the abundance of different intercepts and slopes reflects the inhomogeneous nature of rain, and, in ultimate analysis, the statistical variability existing between the number of drops and drop size distribution. Here, we “eliminate” the contribution of the number of drops by rescaling both reflectivity and rainfall rate to per unit drop variables, (Z, R) → (z, r), so that the remaining variability is due only to the variability of the drop size distribution. We use a worldwide database of disdrometer data to show that for the rescaled variables (z, r) only “one,” albeit approximate, scaling law exists.

scholarly journals Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1

2021 ◽  
Vol 647 ◽  
pp. L3 ◽  
Author(s):  
J. Cernicharo ◽  
C. Cabezas ◽  
M. Agúndez ◽  
B. Tercero ◽  
N. Marcelino ◽  
...  
Keyword(s):  
Column Density ◽  
State Of The Art ◽  
Rotational Temperature ◽  
Signal To Noise Ratio ◽  
Laboratory Data ◽  
The Other ◽  
Signal To Noise ◽  
Chemical Models ◽  
Upper Limit

We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ∼4–15. For this species, we derived a rotational temperature of 7 ± 1 K and a column density of 1.2 ± 0.2 × 1013 cm−2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Tr = 7.0 ± 0.3 K, and a column density for its two states (A and E) of 6.5 ± 0.3 × 1012 cm−2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-Pentadiyne), but only a 3σ upper limit of 2.5 × 1012 cm−2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.

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