scholarly journals THE ROLE OF SURFACE TENSION IN BREAKING WAVES

1972 ◽  
Vol 1 (13) ◽  
pp. 22 ◽  
Author(s):  
Robert L. Miller
Keyword(s):  
Surface Tension ◽  
Natural Waters ◽  
Experimental Studies ◽  
Breaking Waves ◽  
Engineering Model ◽  
Constant Depth ◽  
Model Studies ◽  
Limit Form ◽  
Satisfactory Theory

Breaking criteria in the vicinity of the crest, such as limit crest angle and limit form, and larger dimensions such as limit height (H/L) and breaker height (Hb/db)» are found experimentally to be significantly affected by change in surface tension. A number of wave types were examined, including periodic waves, solitary waves, and standing waves, over both constant depth and uniform slopes. Variations in natural waters in some cases were found to be of equivalent magnitude to those induced for the experiments. The conclusion is drawn that surface tension should be taken into account in development of a satisfactory theory of breakers. It is also an important factor in experimental studies, particularly engineering model studies involving breaking waves.

scholarly journals Bubble production by air filament and cavity breakup in plunging breaking wave crests

2021 ◽  
Vol 929 ◽  
Author(s):  
Qiang Gao ◽  
Grant B. Deane ◽  
Lian Shen
Keyword(s):  
Surface Tension ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Interface Instability ◽  
Interface Curvature ◽  
Rayleigh Taylor Instability ◽  
Air Cavities ◽  
Rayleigh Instabilities ◽  
Good Agreement

Air filaments and cavities in plunging breaking waves, generically cylinders, produce bubbles through an interface instability. The effects of gravity, surface tension and surface curvature on cylinder breakup are explored. A generalized dispersion relation is obtained that spans the Rayleigh–Taylor and Plateau–Rayleigh instabilities as cylinder radius varies. The analysis provides insight into the role of surface tension in the formation of bubbles from filaments and cavities. Small filaments break up into bubbles through a Plateau–Rayleigh instability driven through the action of surface tension. Large air cavities produce bubbles through a Rayleigh–Taylor instability driven by gravity and moderated by surface tension, which has a stabilizing effect. Surface tension, interface curvature and gravity are all important for cases between these two extremes. Predicted unstable mode wavenumber and bubble size show good agreement with direct numerical simulations of plunging breaking waves and air cylinders.

Effective Stress Theory of Shrinkage Phenomena

1971 ◽  
Vol 8 (4) ◽  
pp. 503-513 ◽  
Author(s):  
A. Sridharan ◽  
G. Venkatappa Rao
Keyword(s):  
Surface Tension ◽  
Effective Stress ◽  
Void Ratio ◽  
Applied Pressure ◽  
Experimental Studies ◽  
Satisfactory Explanation ◽  
Stress Theory ◽  
Factors Affecting ◽  
Repulsive Forces

Shrinkage is one of the important soil phenomena in which an engineer is interested. The various factors affecting shrinkage phenomena are discussed. The investigation deals with theoretical and experimental studies of the physical mechanism involved in the process of shrinkage of a clay soil. A modified effective stress concept has been made use of for a satisfactory explanation of the phenomena. The relative importance of dielectric constant (in effecting the electrical attractive and repulsive forces) and the surface tension on the shrinkage of a clay has been brought out, using various organic solvents as pore fluids. Kaolinite has been used in the experimental investigation which includes conventional shrinkage limit tests, tests on samples consolidated to 1 ton/ft2 (1.093 kg/cm2) with different fabric as well as the same initial fabric, tests on samples consolidated to different pressures, and finally tests on samples with constant external applied pressure. The experimental results reveal that the modified effective stress concept proposed governs the shrinkage phenomena. Though surface tension is believed to be the cause of shrinkage, it has been shown that the void ratio at the shrinkage limit is governed by the contact stress at particle contact and (or) between particles, as defined by the modified effective stress concept. The role of fabric and externally applied load on shrinkage is discussed.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

Helping when desire is low: The role of Expectancy in helping

2020 ◽  
Author(s):  
Małgorzata Kossowska
Keyword(s):  
Experimental Studies ◽  
Helping Behavior ◽  
Perceived Effectiveness ◽  
Do So

One might assume that the desire to help (here described as Want) is the essential driver of helping declarations and/or behaviors. However, even if desire to help is low, helping behavior may still occur if the expectancy regarding the perceived effectiveness of helping is high. We tested these predictions in a set of three experimental studies. In all three, we measured the desire to help (Want) and the Expectancy that the aid would be impactful for the victim; in addition, we manipulated Expectancy in Study 3. In Studies 1 and 3, we measured the participants’ declaration to help while in Study 2, their helping behavior was examined. In all three studies, we used variations of the same story about a victim. The results supported our hypothesis. Thus, the studies help to tease apart the determinants of helping behavior under conditions of lowered desire to do so, an issue of great importance in public policymaking.

The capacity of short term memory from an evolutionary perspective

2019 ◽  
Author(s):  
Majid Manoochehri
Keyword(s):  
Short Term Memory ◽  
Memory Span ◽  
Critical Role ◽  
Experimental Studies ◽  
Cognitive System ◽  
Evolutionary Approach ◽  
Evolutionary Perspective ◽  
Short Term ◽  
Term Memory

Memory span in humans has been intensely studied for more than a century. In spite of the critical role of memory span in our cognitive system, which intensifies the importance of fundamental determinants of its evolution, few studies have investigated it by taking an evolutionary approach. Overall, we know hardly anything about the evolution of memory components. In the present study, I briefly review the experimental studies of memory span in humans and non-human animals and shortly discuss some of the relevant evolutionary hypotheses.

The methodology of experimental research of the feed components extrusion process in order to improve its energy performance

2020 ◽  
pp. 147-152
Author(s):  
E. M. Ratnikov ◽  
D. O. Milko
Keyword(s):  
Experimental Studies ◽  
Energy Performance ◽  
Extrusion Process ◽  
Mathematical Methods ◽  
Screw Extruder ◽  
Mathematical Planning ◽  
Factors Affecting ◽  
Extrusion Processing ◽  
Definition Of

Annotation Purpose. Development of a program and methods for conducting experimental studies of the extrusion process with the definition of parameters and modes of operation of the extruder to improve its energy performance. Methods. Methods of mathematical statistics, synthesis, analysis, description and modeling were used. Results. The application of mathematical methods, in particular mathematical planning, reduces the number of experiments several times, and allows to evaluate the role of influencing factors, obtain a mathematical model of the process and determine the optimal conditions for its parameters and modes, etc. Conclusions. The methodology for experimental studies of a screw extruder is presented with the necessary equipment and methodology for processing the obtained experimental data. A mathematical method of planning, which reduces the number of experiments several times, allows us to evaluate the role of factors affecting productivity and energy intensity is presented. Keywords: extruder, auger, nutrients, research methodology, extrusion, processing, feed.

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