Correlations of Thermodynamic Effects for Developed Cavitation

1981 ◽  
Vol 103 (4) ◽  
pp. 534-542 ◽  
Author(s):  
M. L. Billet ◽  
J. W. Holl ◽  
D. S. Weir
Keyword(s):  
Cavity Length ◽  
Operating Point ◽  
Combined Effects ◽  
Liquid Temperature ◽  
Dimensionless Numbers ◽  
Fluid Properties ◽  
Thermodynamic Effects ◽  
The Difference ◽  
Temperature Depression ◽  
Temperature Correlations

The net positive suction head (NPSH) requirements for a pump are determined by the combined effects of cavitation, fluid properties, pump geometry, and pump operating point. An important part of this determination is the temperature depression (ΔT) defined as the difference between ambient liquid temperature and cavity temperature. Correlations are presented of the temperature depression for various degrees of developed cavitation on venturis and ogives. These correlations, based on a semiempirical entrainment theory, express ΔT in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, Weber, and Pe´cle´t, and dimensionless cavity length (L/D). The ΔT data were obtained in Freon 114, hydrogen, and nitrogen for the venturis and in Freon 113 and water for the ogives.

Thermodynamic Effects on Developed Cavitation

1975 ◽  
Vol 97 (4) ◽  
pp. 507-513 ◽  
Author(s):  
J. W. Holl ◽  
M. L. Billet ◽  
D. S. Weir
Keyword(s):  
Cavity Length ◽  
Cavitation Number ◽  
Measured Temperature ◽  
Cavity Pressure ◽  
Dimensionless Form ◽  
Dimensionless Numbers ◽  
Thermodynamic Effect ◽  
Thermodynamic Effects ◽  
Temperature And Pressure ◽  
Temperature Depression

The results of an investigation of thermodynamic effects are presented. Distributions of temperature and pressure in a developed cavity were measured for zero- and quarter-caliber ogives. A semiempirical entrainment theory was developed to correlate the measured temperature depression, ΔT, in the cavity. This theory correlates ΔTmax expressed in dimensionless form as the Jakob number in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, and Pe´cle´t, and dimensionless cavity length, L/D. The results show that in general ΔT increases with L/D and temperature and the cavitation number based on measured cavity pressure is a function of L/D for a given model contour, independent of the thermodynamic effect.

Thermodynamic Effect on a Cavitating Inducer in Liquid Nitrogen

2006 ◽  
Vol 129 (3) ◽  
pp. 273-278 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Kengo Kikuta ◽  
Satoshi Hasegawa ◽  
Mitsuru Shimagaki ◽  
Takashi Tokumasu
Keyword(s):  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Cavitation Number ◽  
Experimental Investigations ◽  
Thermodynamic Effect ◽  
Blade Tip ◽  
Cryogenic Flow ◽  
The Difference ◽  
Temperature Depression

For experimental investigations of the thermodynamic effect on a cavitating inducer, it is nesessary to observe the cavitation. However, visualizations of the cavitation are not so easy in cryogenic flow. For this reason, we estimated the cavity region in liquid nitrogen based on measurements of the pressure fluctuation near the blade tip. In the present study, we focused on the length of the tip cavitation as a cavitation indicator. Comparison of the tip cavity length in liquid nitrogen (80K) with that in cold water (296K) allowed us to estimate the strength of the thermodynamic effect. The degree of thermodynamic effect was found to increase with an increase of the cavity length. The temperature depression was estimated from the difference of the cavitation number of corresponding cavity condition (i.e., cavity length) between in liquid nitrogen and in cold water. The estimated temperature depression caused by vaporization increased rapidly when the cavity length extended over the throat. In addition, the estimated temperature inside the bubble nearly reached the temperature of the triple point when the pump performance deteriorated.

scholarly journals Machine Learning Model of Dimensionless Numbers to Predict Flow Patterns and Droplet Characteristics for Two-Phase Digital Flows

2021 ◽  
Vol 11 (9) ◽  
pp. 4251
Author(s):  
Jinsong Zhang ◽  
Shuai Zhang ◽  
Jianhua Zhang ◽  
Zhiliang Wang
Keyword(s):  
Machine Learning ◽  
Learning Algorithms ◽  
Digital Microfluidics ◽  
Flow Patterns ◽  
Machine Learning Algorithms ◽  
Dimensionless Numbers ◽  
Two Phase ◽  
The Difference ◽  
Input Variables ◽  
Digital Microfluidic

In the digital microfluidic experiments, the droplet characteristics and flow patterns are generally identified and predicted by the empirical methods, which are difficult to process a large amount of data mining. In addition, due to the existence of inevitable human invention, the inconsistent judgment standards make the comparison between different experiments cumbersome and almost impossible. In this paper, we tried to use machine learning to build algorithms that could automatically identify, judge, and predict flow patterns and droplet characteristics, so that the empirical judgment was transferred to be an intelligent process. The difference on the usual machine learning algorithms, a generalized variable system was introduced to describe the different geometry configurations of the digital microfluidics. Specifically, Buckingham’s theorem had been adopted to obtain multiple groups of dimensionless numbers as the input variables of machine learning algorithms. Through the verification of the algorithms, the SVM and BPNN algorithms had classified and predicted the different flow patterns and droplet characteristics (the length and frequency) successfully. By comparing with the primitive parameters system, the dimensionless numbers system was superior in the predictive capability. The traditional dimensionless numbers selected for the machine learning algorithms should have physical meanings strongly rather than mathematical meanings. The machine learning algorithms applying the dimensionless numbers had declined the dimensionality of the system and the amount of computation and not lose the information of primitive parameters.

scholarly journals Numerical Investigation to the Effect of Suction-Induced Seepage on the Settlement in the Underwater Vacuum Preloading with Prefabricated Vertical Drains

2021 ◽  
Vol 9 (8) ◽  
pp. 797
Author(s):  
Shu Lin ◽  
Dengfeng Fu ◽  
Zefeng Zhou ◽  
Yue Yan ◽  
Shuwang Yan
Keyword(s):  
Practical Implication ◽  
Soil Surface ◽  
Small Strain ◽  
Seepage Flow ◽  
Excess Pore Pressure ◽  
Combined Effects ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
The Difference

Vacuum preloading combined with prefabricated vertical drains (PVDs) has the potential to improve the soft sediments under water, however, its development is partly limited by the unclear understanding of the mechanism. This paper aims to extend the comprehension of the influential mechanism of overlapping water in the scenario of underwater vacuum preloading with PVDs. The systematic investigations were conducted by small strain finite element drained analyses, with the separated analysis schemes considering suction-induced consolidation, seepage and their combination. The development of settlement in the improved soil region and the evolution of seepage flow from the overlapping water through the non-improved soil region into improved zone are examined in terms of the build-up of excess pore pressure. Based on the results of numerical analyses, a theoretical approach was set out. It was capable to estimate the time-dependent non-uniform settlement along the improved soil surface in response to the combined effects of suction-induced consolidation and seepage. The difference of underwater and onshore vacuum preloading with PVDs is discussed with some practical implication and suggestion provided.

The combined effects of nitrates on multibilayer lipid membranes: Thermodynamic effects

BIOPHYSICS ◽  
2017 ◽  
Vol 62 (2) ◽  
pp. 227-232 ◽  
Author(s):  
O. V. Vashchenko ◽  
A. O. Sadchenko ◽  
L. V. Budianska ◽  
L. N. Lisetski
Keyword(s):  
Lipid Membranes ◽  
Combined Effects ◽  
Thermodynamic Effects

scholarly journals A thermodynamic cavitation model applicable to high temperature flow

2011 ◽  
Vol 15 (suppl. 1) ◽  
pp. 95-101 ◽  
Author(s):  
De-Min Liu ◽  
Shu-Hong Liu ◽  
Yu-Lin Wu ◽  
Hong-Yuan Xu
Keyword(s):  
High Temperature ◽  
Pressure Coefficient ◽  
Internal Flow ◽  
Mass Transfer Equation ◽  
Modified Model ◽  
Cavitation Characteristic ◽  
Different Temperatures ◽  
Thermodynamic Effects ◽  
Temperature Depression ◽  
Latent Heat Of Vaporization

Cavitation is not only related with pressure, but also affected by temperature. Under high temperature, temperature depression of liquids is caused by latent heat of vaporization. The cavitation characteristics under such condition are different from those under room temperature. The paper focuses on thermodynamic cavitation based on the Rayleigh-Plesset equation and modifies the mass transfer equation with fully consideration of the thermodynamic effects and physical properties. To validate the modified model, the external and internal flow fields, such as hydrofoil NACA0015 and nozzle, are calculated, respectively. The hydro-foil NACA0015?s cavitation characteristic is calculated by the modified model at different temperatures. The pressure coefficient is found in accordance with the experimental data. The nozzle cavitation under the thermodynamic condition is calculated and compared with the experiment.

scholarly journals Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 138 ◽  
Author(s):  
Hang Zou ◽  
Haijiang Hu ◽  
Guang Xu ◽  
Ziliu Xiong ◽  
Fangqin Dai
Keyword(s):  
Transformation Temperature ◽  
Bainitic Transformation ◽  
Combined Effects ◽  
Medium Carbon ◽  
Thermomechanical Simulation ◽  
Higher Temperature ◽  
The Difference ◽  
The Individual ◽  
Isothermal Bainitic Transformation ◽  
Kinetics Of

Both ausforming and transformation temperature affect the successive bainitic transformation and microstructure. The individual influence of each case is clear, whereas the combined effects are still unknown. Thermomechanical simulation and metallography were used to investigate the combined effects of ausforming and transformation temperature on bainitic transformation and microstructure. The kinetics of isothermal bainitic transformation in non-deformed and deformed materials was analyzed. A lower transformation temperature can lead to more bainite formation without deformation. However, ausforming with small strains can partially compensate for the decrease of bainite amount caused by the decreased undercooling. The larger the applied strain is, the smaller the difference between the final amounts of bainite with different undercooling. Ausforming at a relatively higher temperature is more favorable to the acceleration of subsequent isothermal bainitic transformation. The results in the present work provide reference for optimizing the fabrication technology of medium-carbon nanobainite steels.

Single Longitudinal Mode Fiber Laser Based on Saturated Absorber

2014 ◽  
Vol 1044-1045 ◽  
pp. 426-431
Author(s):  
Wu Pan ◽  
Hong Lin Zhang ◽  
Zheng Ke Xu ◽  
Hui Zhang
Keyword(s):  
Cavity Length ◽  
Free Spectral Range ◽  
Ring Cavity ◽  
Longitudinal Mode ◽  
Transmission Peak ◽  
Single Longitudinal Mode ◽  
Laser Threshold ◽  
Filter Performance ◽  
Saturated Absorber ◽  
The Difference

In order to realize single longitudinal mode (SLM) output, an erbium-doped fiber (EDF) laser with fiber ring cavity is proposed which uses an un-pumped EDF saturated absorber as a SLM selector. Ring cavity length, coupler ratio and insertion loss which affect ring cavity filter performance are analyzed theoretically and simulated numerically. Un-pumped EDF length and Er3+ concentration are analyzed theoretically and simulated. Research shows that, the bigger coupling output ratio of ring cavity, the greater transmission peak; the greater mode line width; the shorter ring cavity length, the wider free spectral range; the bigger coupling loss, the smaller transmission peak; when the difference between two cavities length is big, cursor effect is not obvious. Laser threshold increases with absorber length increasing; the bigger saturated absorber concentration, the higher laser threshold.

Dimensional Analysis and Scaling of Rotating Seals

2005 ◽  
Author(s):  
J. Denecke ◽  
J. Fa¨rber ◽  
K. Dullenkopf ◽  
H.-J. Bauer
Keyword(s):  
Pressure Ratio ◽  
Numerical Data ◽  
Dimensionless Numbers ◽  
Labyrinth Seals ◽  
Fluid Properties ◽  
Specific Geometry ◽  
Total Temperature ◽  
Discharge Behavior ◽  
Effects Of Rotation ◽  
Numerical Parametric Study

To characterize contactless seals in turbo machinery, their discharge behavior, the development of the circumferential velocity (swirl) and the loss induced total temperature increase (windage heating) are of special interest for the designer. For the discharge behavior of non-rotating labyrinth seals, a well established set of non-dimensional numbers already exists: the discharge coefficient of two seals with different sizes but similar geometry is identical, if pressure ratio, axial Reynolds number, fluid properties and turbulence level are also identical. In this paper, the set of non-dimensional numbers is extended to cover swirl and windage heating using the well established Buckingham-π theorem to derive possible candidates. First, as a proof of concept, the known set of numbers for the non-rotating case was redeveloped and subsequently the influence of rotation was included. To validate the candidates, a comprehensive numerical parametric study was conducted. A variety of convergent and divergent stepped labyrinth seals was scaled from laboratory to typical engine conditions such that the dimensionless numbers stayed constant. Then, simulations at different rotational speeds, radii, and inlet circumferential velocities were performed to investigate the effects of rotation while maintaining nearly constant discharge behavior. The numerical data were used to validate the new non-dimensional numbers and to derive laws for the scaling of labyrinth seals. The non-dimensional numbers can also be applied to other seal types, such as brush or finger seals, because their theoretical deduction does not imply a specific geometry.

Thermodynamic Effects on Pressure Fluctuations of a Liquid Oxygen Turbopump

2021 ◽  
Author(s):  
Deyou Li ◽  
Zhipeng Ren ◽  
Yu Li ◽  
Boxuan Miao ◽  
Ruzhi Gong ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pressure Fluctuations ◽  
Rotational Frequency ◽  
Liquid Oxygen ◽  
Rocket Engines ◽  
Cavitation Flow ◽  
Characteristic Frequencies ◽  
Thermodynamic Effects ◽  
The Difference

Abstract Liquid oxygen turbopumps are an important component of rocket engines. The instability induced by cavitation flow in turbopumps has received considerable attention because of thermodynamic effects. In this study, unsteady numerical simulations of a turbopump with thermodynamic effects were performed. The frequency composition and source of pressure fluctuations in a turbopump were analyzed, and the difference in pressure fluctuations with/without thermodynamic effects was revealed. The results showed that the pressure fluctuations were mainly caused by the interaction between the impeller and diffuser, and the thermodynamic effects slightly increased the amplitudes of the characteristic frequencies. In addition, in the inducer and impeller, three characteristic frequencies (4.089fn, 2.519fn, and 3.238fn, where fn is the rotational frequency) were confirmed. Analyses revealed that the 4.089fn was due to the periodic shedding of cavitation structures on the suction surfaces at the inducer outlet, 2.519fn was induced by the periodic occurrence and collapse of cavitation on the suction surfaces at the impeller inlet; and 3.238fn was from the periodic shedding of cavitation structures on the suction surfaces at the impeller middle blades. The existence of thermodynamic effects decreased the frequency of cavitation shedding and increased the frequency of the periodic occurrence and collapse of cavitation.

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