Surface motion induced by the interaction of pulsed laser radiation with highly absorbing dielectric fluids

1993 ◽  
Vol 250 ◽  
pp. 385-421 ◽  
Author(s):  
Konstantin A. Naugol'nykh ◽  
Oleg V. Puchenkov ◽  
Victor V. Zosimov ◽  
Alexander E. Pashin
Keyword(s):  
Capillary Waves ◽  
Intense Laser ◽  
Contaminated Water ◽  
Recoil Momentum ◽  
Surface Distribution ◽  
Recoil Pressure ◽  
Surface Motion ◽  
Dielectric Fluids ◽  
Water Surfaces ◽  
The Impact

The disturbances on the free surface of dielectric fluids resulting from intense laser heating of their boundary layer are studied theoretically and experimentally. The heating is accompanied by pronounced evaporation from the surface and thereby leads to a recoil pressure momentum applied to the surface. For small values of total momentum transferred to the fluid, the low-amplitude initially hollow-like displacement of the surface in the impact zone decays to produce linear gravity–capillary waves (GCW) spreading out on the surface. This regime is treated analytically and the results obtained are compared with experiments involving weakly viscous (water, ethanol) and highly viscous (glycerol) liquids. An experimental arrangement for remote generation and subsequent detection of probe GCW-packets is given. The evolution of broadband GCW-disturbances on clean and surfactant-contaminated water surfaces are described. Results of GCW-attenuation spectrum measurements on clean water surfaces and on film-covered surfaces are presented.High total recoil momentum values give rise to substantially nonlinear surface motion: after a short transient stage the surface takes the shape of a hemisphere expanding into the liquid, and later the liquid above the hemisphere closes up to form a cavity and slow down the expansion. For this regime the dynamics of the hemisphere expansion are determined and satisfactory agreement with experimental data obtained with the shadowgraph technique is established. Consistency of theory and experiment allowed the determination of the total recoil pressure momentum and its surface distribution.In the intermediate case of moderate values of recoil momentum, the nonlinear evolution of broadband GCW-packets on clean and surfactant-contaminated water surfaces is investigated experimentally.

The Impact of Surface Contamination on the Flow Beneath Wind-Generated Waves

2007 ◽  
Author(s):  
Kamran Siddiqui ◽  
Mark R. Loewen
Keyword(s):  
Water Surface ◽  
Flow Characteristics ◽  
Streamwise Velocity ◽  
Viscous Sublayer ◽  
Contaminated Water ◽  
Near Surface ◽  
Water Surface Temperature ◽  
Water Surfaces ◽  
The Mean ◽  
The Impact

We report on an experimental study conducted to investigate flow characteristics in the near-surface layer beneath clean and surfactant-contaminated water surfaces in the presence of wind. The two-dimensional velocity field beneath the water surface was measured using particle image velocimetry. The water surface temperature measurements were made simultaneously using infrared imagery. The results show the existence of the viscous sublayer beneath both clean and contaminated water surfaces. Within the viscous sublayer in contaminated water, the mean streamwise velocity is 25–30% larger and the mean streamwise velocity gradients are more than a factor of two larger compared to that beneath clean water surfaces.

Pesticidal Pollution

2019 ◽  
pp. 155-176
Author(s):  
Rizwana Mobin ◽  
Hamida-Tun-Nisa Chisti ◽  
Tauseef Ahmad Rangreez ◽  
Rafia Bashir ◽  
Altaf Ahmad Najar
Keyword(s):  
Broad Spectrum ◽  
Food Chain ◽  
Negative Impact ◽  
Green Revolution ◽  
Synergetic Effect ◽  
Contaminated Water ◽  
Ecology And Environment ◽  
Pesticide Runoff ◽  
The Impact ◽  
Impact Of Pesticides

The development and application of pesticides has contributed in a long way in making the “Green Revolution” possible. These newer pesticides have synergetic effect over the control of pests that otherwise have negative impact on the quality and quantity of food. The toxicity, persistence, and environmental pathway are some important criteria that determine the impacts on ecology and environment. The generalization of the impact of pesticides on different organisms is difficult as these are of broad spectrum chemical nature. However, the major problem that arises due to widespread use of pesticides is the contamination of water by pesticide runoff. The chemically contaminated water in turn leads to the much aggravated problems of bio-concentration and bio-magnification of these chemicals. While the bio-concentration describes the transfer of a chemical from surrounding into the tissue/body of organism, the bio-magnification is related to the increased concentration of such a chemical along a food chain.

On the microphysical behaviour of wind-forced water surfaces and consequent re-aeration

2014 ◽  
Vol 743 ◽  
pp. 399-447 ◽  
Author(s):  
William L. Peirson ◽  
James W. Walker ◽  
Michael L. Banner
Keyword(s):  
Measurement Techniques ◽  
Critical Factor ◽  
Capillary Waves ◽  
Heat Fluxes ◽  
Gas Transfer ◽  
Mechanical Coupling ◽  
Diffusion Layers ◽  
Water Surfaces ◽  
Presence And Absence ◽  
Low Solubility

AbstractA detailed laboratory investigation of the mechanical and low-solubility gas coupling between wind and water has been undertaken using a suite of microphysical measurement techniques. Under a variety of wind conditions and in the presence and absence of mechanically generated short waves, approximately fetch-independent surface conditions have been achieved over short laboratory fetches of several metres. The mechanical coupling of the surface is found to be consistent with Banner (J. Fluid Mech. vol. 211, 1990, pp. 463–495) and Banner & Peirson (J. Fluid Mech. vol. 364, 1998, pp. 115–145). Bulk observations of re-aeration are consistent with previous laboratory studies. The surface kinematical behaviour is in accordance with the observations of Peirson & Banner (J. Fluid Mech. vol. 479, 2003, pp. 1–38). Also, their predictions of a strong enhancement of low-solubility gas flux at the onset of microscale breaking is confirmed and direct observations show a concomitant onset of very thin aqueous diffusion sublayers. It is found that the development of strong parasitic capillary waves towards the incipient breaking limit does not noticeably enhance constituent transfer. Across the broad range of conditions investigated during this study, the local instantaneous constituent transfer rate remains approximately log-normally distributed with an approximately constant standard deviation of $0.62\pm 0.15({\mathrm{log}}_e(\mathrm{m}~ {\mathrm{s}}^{-1}))$. Although wind-forced water surfaces are shown to be punctuated by intense tangential stresses and local surface convergence, localized surface convergence does not appear to be the single critical factor determining exchange rate. Larger-scale orbital wave straining is found to be a significant constituent transfer process in contrast to Witting (J. Fluid Mech. vol. 50, 1971, pp. 321–334) findings for heat fluxes, but the measured effects are consistent with his model. By comparing transfer rates in the presence and absence of microscale breaking, low-solubility gas transfer was decomposed into its turbulent/capillary ripple, gravity-wave-related and microscale breaking contributions. It was found that an efficiency factor of approximately $17\, \%$ needs to be applied to Peirson & Banner’s model, which is extended to field conditions. Although bulk thermal effects were observed and thermal diffusion layers are presumed thicker than their mass diffusion counterparts, significant thermal influences were not observed in the results.

CFD Analysis of Thermal Shadowing and Optimization of Heatsinks in 3rd Generation Open Compute Server for Single-Phase Immersion Cooling

2019 ◽  
Author(s):  
Jimil M. Shah ◽  
Ravya Dandamudi ◽  
Chinmay Bhatt ◽  
Pranavi Rachamreddy ◽  
Pratik Bansode ◽  
...  
Keyword(s):  
Thermal Management ◽  
Power Density ◽  
Heat Sink ◽  
Single Phase ◽  
Data Centers ◽  
Air Cooling ◽  
Third Generation ◽  
Dielectric Fluids ◽  
Immersion Cooling ◽  
The Impact

Abstract In today’s networking world, utilization of servers and data centers has been increasing significantly. Increasing demand of processing and storage of data causes a corresponding increase in power density of servers. The data center energy efficiency largely depends on thermal management of servers. Currently, air cooling is the most widely used thermal management technology in data centers. However, air cooling has started to reach its limits due to high-powered processors. To overcome these limitations of air cooling in data centers, liquid immersion cooling methods using different dielectric fluids can be a viable option. Thermal shadowing is an effect in which temperature of a cooling medium increases by carrying heat from one source and results in decreasing its heat carrying capacity due to reduction in the temperature difference between the maximum junction temperature of successive heat sink and incoming fluid. Thermal Shadowing is a challenge for both air and low velocity oil flow cooling. In this study, the impact of thermal shadowing in a third-generation open compute server using different dielectric fluids is compared. The heat sink is a critical part for cooling effectiveness at server level. This work also provides an efficient range of heat sinks with computational modelling of third generation open compute server. Optimization of heat sink can allow to cool high-power density servers effectively for single-phase immersion cooling applications. A parametric study is conducted, and significant savings in the volume of a heat sink have been reported.

scholarly journals Hydrodynamics of Two-Phase Gas-Very Viscous Liquid Flow in Heat Exchange Conditions

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5709
Author(s):  
Krystian Czernek ◽  
Stanisław Witczak
Keyword(s):  
Liquid Film ◽  
Viscous Liquid ◽  
Capillary Waves ◽  
Liquid Cooling ◽  
Two Phase ◽  
Flow Parameters ◽  
Smooth Interface ◽  
Viscous Liquid Film ◽  
Vertical Tubes ◽  
The Impact

This paper presents the results of analyses of the impact of heat transfer conditions on the hydrodynamics of downward co-current annular flow in vertical tubes of very viscous liquid and gas. The research was conducted within the range of gas velocities of 0–30.0 m/s and liquid velocities of 0.001–0.254 m/s, while the viscosity was in the unprecedented range of 0.046–3.5 Pas. The research demonstrates that the volume and nature of the liquid waves with various amplitudes and frequencies arising on the surface of the film are relative to the flow rate and viscosity of the gas phase. At the same time, we found that, under the condition of liquid cooling, an increase in viscosity resulted in the formation of a smooth interface whereas, under the conditions where the liquid is heated at the end of the channel section, a greater number of capillary waves were formed. This research resulted in the development of new dependencies which take into account the influence of selected thermal and flow parameters (including mass fraction) on the values of volumes specific to very viscous liquid film flows. These dependencies improve the accuracy of calculation by 8–10% and are fully applicable to the description of the performance of an apparatus with a hydraulically generated liquid film.

Composite Granulated Adsorbents Based on Chitosan and Agricultural Processing Waste for Sewage Treatment

2018 ◽  
Vol 7 (4.3) ◽  
pp. 320
Author(s):  
L. A. Bezdeneznych ◽  
O. V. Kharlamova ◽  
V. M. Shmandiy
Keyword(s):  
Sewage Treatment ◽  
Biological Properties ◽  
Contaminated Water ◽  
Industrial Complex ◽  
Industrial Waste Water ◽  
Industrial Enterprises ◽  
Physico Chemical ◽  
Chitin And Chitosan ◽  
Physical And Chemical ◽  
The Impact

To minimize the impact of industrial enterprises on water objects, a wide variety of adsorbents (based on activated carbon, natural materials, nanomaterials, vegetable waste of agro-industrial complex, etc.) is used. Recently, chitin and chitosan have attracted the attention of scientists due to a number of unique physico-chemical and biological properties (adsorption, antioxidant, radioprotective, immunomodulating, lamina-forming). We have improved the method of obtaining powdered chitosan and established the basic physical and chemical parameters (bulk density, humidity). The method of obtaining chitosan granules and composite materials based on chitosan and modified sunflower husks (MSH) has been further developed by the "drip method". The adsorption properties of powder chitosan, chitosan granules and MSH were studied. It is set that a granular adsorbent has a high adsorbtivity in comparing to the original chitosan. Efficiency of wastewater treatment with the use of chitosan granules and MSH is equally high (up to 98%). The optimum amount of adsorbent for effective cleaning of contaminated water is 1% of its volume. The use of the results of the conducted research allows us to obtain an effective adsorbent for the treatment of industrial waste water. 

The entrainment of bubbles by drop impacts

1990 ◽  
Vol 220 ◽  
pp. 539-567 ◽  
Author(s):  
Hugh C. Pumphrey ◽  
Paul A. Elmore
Keyword(s):  
Water Surface ◽  
Capillary Waves ◽  
Experimental Results ◽  
Single Bubble ◽  
Underwater Sound ◽  
The Third ◽  
Entrainment Process ◽  
Drop Impacts ◽  
The Impact ◽  
Small Bubbles

Various processes are described by which a drop of water, impacting on a water surface, may entrain a bubble. There are: (i) irregular entrainment, in which the complex details of a splash entrain bubbles; (ii) regular entrainment, in which the crater formed by the drop impact develops in a predictable way to form a single bubble; (iii) entrainment of large bubbles, in which most of the volume of the crater is trapped as a bubble; and (iv) Mesler entrainment, in which many very small bubbles are trapped in the very early stages of the impact process; possibly between wave crests of capillary waves which develop on the drop and on the water surface. This last process is different from the preceding three in that it produces very little sound. All of the processes except the third one have been described individually in the literature; here we present them together for comparison. The regular entrainment process is discussed in the greatest detail and some new experimental results are presented which concern the size and nature of the entrained bubbles. The significance of the regular and irregular entrainment processes to the generation of underwater sound by rain is discussed.

scholarly journals DYNAMICS OF METAL CLUSTERS IN RARE GAS CLUSTERS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2439-2448
Author(s):  
M. BAER ◽  
G. BOUSQUET ◽  
P. M. DINH ◽  
F. FEHRER ◽  
P.-G. REINHARD ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Metal Clusters ◽  
Intense Laser ◽  
Rare Gas ◽  
Pump Probe ◽  
Realistic Case ◽  
The Matrix ◽  
Pauli Repulsion ◽  
Gas Clusters ◽  
The Impact

We investigate the dynamics of Na clusters embedded in Ar matrices. We use a hierarchical approach, accounting microscopically for the cluster's degrees of freedom and more coarsely for the matrix. The dynamical polarizability of the Ar atoms and the strong Pauli-repulsion exerted by the Ar -electrons are taken into account. We discuss the impact of the matrix on the cluster gross properties and on its optical response. We then consider a realistic case of irradiation by a moderately intense laser and discuss the impact of the matrix on the hindrance of the explosion, as well as a possible pump probe scenario for analyzing dynamical responses.

scholarly journals The Simultaneous Analysis of Droplets’ Impacts and Heat Transfer during Water Spray Cooling Using a Transparent Heater

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2730
Author(s):  
Vladimir Serdyukov ◽  
Nikolay Miskiv ◽  
Anton Surtaev
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Spray Cooling ◽  
Capillary Waves ◽  
Heat Fluxes ◽  
Small Scale ◽  
Unsteady Temperature ◽  
The Impact

This paper demonstrates the advantages and prospects of transparent design of the heating surface for the simultaneous study of the hydrodynamic and thermal characteristics of spray cooling. It was shown that the high-speed recording from the reverse side of such heater allows to identify individual droplets before their impact on the forming liquid film, which makes it possible to measure their sizes with high spatial resolution. In addition, such format enables one to estimate the number of droplets falling onto the impact surface and to study the features of the interface evolution during the droplets’ impacts. In particular, the experiments showed various possible scenarios for this interaction, such as the formation of small-scale capillary waves during impacts of small droplets, as well as the appearance of “craters” and splashing crowns in the case of large ones. Moreover, the unsteady temperature field during spray cooling in regimes without boiling was investigated using high-speed infrared thermography. Based on the obtained data, the intensity of heat transfer during spray cooling for various liquid flow rates and heat fluxes was analyzed. It was shown that, for the studied regimes, the heat transfer coefficient weakly depends on the heat flux density and is primarily determined by the flow rate. In addition, the comparison of the processes of spray cooling and nucleate boiling was made, and an analogy was shown in the mechanisms that determine their intensity of heat transfer.

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