Submersion Depth Research Articles

Exciting forces due to interaction of water waves with a submerged sphere in an ice-covered two-layer fluid of finite depth

Abstract Scattering of water waves by a sphere in a two-layer fluid, where the upper layer has an ice-cover modelled as an elastic plate of very small thickness, while the lower one has a rigid horizontal bottom surface, is investigated within the framework of linearized water wave theory. The effects of surface tension at the surface of separation is neglected. There exist two modes of time-harmonic waves – the one with lower wave number propagating along the ice-cover and the one with higher wave number along the interface. Method of multipole expansions is used to find the particular solution for the problem of wave scattering by a submerged sphere placed in either of the layers. The exciting forces for vertical and horizontal directions are derived and plotted against different values of the wave number for different submersion depths of the sphere and flexural rigidity of the ice-cover. When the flexural rigidity and the density of the ice-cover are taken to be zero, the numerical results for the exciting forces for the problem with free surface are recovered as particular cases.

Particle Image Velocimetry Study of Flow Patterns and Mixing Characteristics in Multiple Impeller Stirred Tank

The flow generated in a stirred tank of 0.48 m diameter, agitated by three impellers of 0.19 m diameter, including one half-elliptical blade disc turbine (HEDT) below and two up-pumping wide-blade hydrofoils (WHU), were investigated by using 360° ensemble-averaged particle image velocimetry (PIV) technique. The flow characteristics for seven impeller combinations with different impeller spacings were investigated. Results show that global circulation patterns in the stirred tank are strongly dependent on the impeller spacing. Three types of flow patterns were observed, including five, four, and three circulation loops in the flow field, by changing the spacing between the bottom and the middle impellers (C1), the spacing between the middle and the top impellers (C2), and the submersion depth of the top impeller (C3). While the clearance (ΔC) of the bottom impeller is equal to 0.4T, the five circulation loops flow pattern occurs when C1 = 0.48T, C2 = 0.48T, and C3 = 0.4T, and the four circulation loops flow pattern occurs when C1 = 0.48T, C2 = 0.4T, and C3 = 0.4T, and the three circulation loops flow pattern occurs when C1 = 0.48T, C2 = 0.4T, C3 = 0.32T. The mixing efficiency defined based on the mixing time and the power consumption were also discussed and the results show that less circulation loops could lead to higher mixing efficiency, but the mixing efficiency does not solely increase with the decreasing of the circulation loops.

Electrochemical Impedance Spectroscopy to Assess Vascular Oxidative Stress

Vascular inflammatory responses are intimately linked with oxidative stress, favoring the development of pre-atherosclerotic lesions. We proposed that oxidized low density lipoprotein (oxLDL) and foam cell infiltrates in the subendothelial layer engendered distinct electrochemical properties that could be measured in terms of the electrochemical impedance spectroscopy (EIS). Concentric bipolar microelectrodes were applied to interrogate EIS of aortas isolated from fat-fed New Zealand White (NZW) rabbits and explants of human aortas. Frequency-dependent EIS measurements were assessed between 10 kHz and 100 kHz, and were significantly elevated in the pre-atherosclerotic lesions in which oxLDL and macrophage infiltrates were prevalent (At 100 kHz: aortic arch lesion=26.7±2.7 kΩ vs. control=15.8±2.4 kΩ; at 10 kHz: lesions=49.2±7.3 kΩ vs. control=27.6±2.7 kΩ, n=10, p<0.001). Similarly, EIS measurements were significantly elevated in the human descending aorta where pre-atherosclerotic lesions or fatty streaks were prominent. EIS measurements remained unchanged in spite of various depths of electrode submersion or orientation of the specimens. Hence, the concentric bipolar microelectrodes provided a reliable means to measure endoluminal electrochemical modifications in regions of pro-inflammatory with high spatial resolution and reproducibility albeit uneven lesion topography and non-uniform current distribution.

Effects of submersion depth on wave uplift force acting on Biloxi Bay Bridge decks during Hurricane Katrina

A large portion of the Biloxi Bay Bridge was submerged and destroyed by surface waves and storm surge associated with Hurricane Katrina in 2005. In this paper, the time history of wave forces exerted on the Biloxi Bay Bridge during Hurricane Katrina was investigated by a wave-loading model. The Volume of Fluid (VOF) method was adopted in the model to track the variations of water surface levels. In order to obtain wave parameters and storm-surge elevation at the bridge site during Hurricane Katrina, a storm surge model and a wave propagation model were coupled to hindcast the hydrodynamic conditions. Outputs of the coupled wave–surge models were imported to the wave-loading model to simulate the dynamic wave forces acting on the bridge deck. In order to evaluate the maximum uplift wave force, five different bridge deck elevations submerged at different water depths were investigated. The processes of wave–bridge interaction were simulated by the wave-loading model. The wave profiles, velocity field in the vicinity of the bridge, and dynamic wave forces on the decks were analyzed. Results indicate that the uplift force on the submerged bridge deck span exceeded its own weight under the extreme wave and storm surge conditions during Hurricane Katrina. Moreover, the numerical simulations suggest that the maximum uplift wave force occurred when the storm surge water level reached the top of the bridge deck.

Periodic flow characteristics during RH vacuum circulation refining

The circulation period of RH vacuum refining was studied to promote the refining efficiency. The influences of the lift gas flow rate and submersion depth of snorkels on the circulation period, and the relationship between mixing time and circulation flow were discussed. The effects of the lift gas flow rate and submersion depth on the degassing rate in one circulation period were studied by water modeling. The results show that the circulation period is shortened by increasing the lift gas flow rate. The circulation period is the shortest when the submersion depth of snorkels is 560 mm. The whole ladle can be mixed thoroughly after three times of circulation. Increasing the lift gas flow rate can enhance the degassing rate of RH circulation.

ПРОМЫСЛОВЫЕ ИССЛЕДОВАНИЯ ПРОЦЕССА СЕПАРАЦИИ ГАЗА НА ПРИЕМЕ ПОГРУЖНЫХ НАСОСОВ

Introduction The problem of studying the process of gas separation in the design of artificial oil lift is sufficiently relevant. According to data of the separation, we can predict the actual pump flow and calculate the necessary depth of submersion under the dynamic level. Aims and Objectives Determination of the gas separation at the reception of submersible pumps as well as the link between the separation rate and GOR. Methods The method is based on measuring the amount of gas withdrawn from the annulus, and the amount of gas evolved from oil at the wellhead. Results Studies were conducted on the wells of some Lukoil-Komi deposits. It was shown that the coefficient of separation of gas at the pump intake varies widely: from 0,1 to 1,0, depending on the feed pumps and gas-oil ratio of oil. Conclusion The extraction of gas from the annulus directly into the gas line before the gas meter can improve the accuracy of gas-oil ratio by eliminating the pressure drop in the non-return valve and an additional mixing with the liquid to a gas separator.

Preliminary Designing Method of External Pressure Vessels for Sea Subsurface Applications

Preliminary Designing Method of External Pressure Vessels for Sea Subsurface ApplicationsThis paper describes a unique engineering method intended for the preliminary designing of marine echo-location systems. The solved designing problem consists in determining geometrical parameters and selecting structural materials for a vessel of a buoyancy necessary to contain measuring instruments of a given mass, as well as its maximum gabarites and operational submersion depth. The assumed variability range of the system's parameters determines a space of permissible applicability parameters of the method. Stress level related to permissible and critical stresses was assumed to be safety criterion for the vessel. The method may be applied also to solving converse problems consisting in determining maximum permissible submersion depth for a vessel made of assumed structural materials and having given geometrical parameters. The presented description of the method is illustrated by an example of its application.

Submersion time, depth, substrate type and sampling method as variation sources of marine periphyton

Periphyton is an additional food source in African and Asian brackish and freshwater fish ponds. The present study was a preliminary assessment of periphyton development on artificial substrates in temperate marine ponds. The effects of submersion time, substrate type, water depth, and total or partial sampling methods on the quantity and quality of periphyton collected, were evaluated. Four types of substrate (W: wooden poles, S: smooth fiber-glass strips, m: mosquito screen (1 mm-mesh) and M: garden netting (5 mm-mesh)) were deployed in a marine pond, and periphyton was collected 15 and 30 days later. The total amount of periphyton per substrate unit was collected as one sample or as 5 sub-samples. Results showed that (i) periphyton biomass in a marine pond increased between day 15 and day 30, (ii) more periphyton was collected on mosquito screen than on wooden poles, fiberglass strips and garden netting, (iii) periphyton biomass increased with submersion depth, (iv) sub-sampling leads to an underestimate compared to whole unit sampling, and (v) a correction of periphyton weight must be carried out considering the dissolved inorganic salts present in periphyton samples from marine and brackish ponds. Whole substrate unit sampling using a tube and stopper is recommended to avoid underestimation of periphyton development. Finally, the autotrophic fraction in the periphyton communities was very low compared to periphyton developed on biodegradable substrates in fertilized tropical ponds. Studies on fertilization and use of biodegraded substrates (i.e. long-time submerged wood) are recommended to further optimize periphyton development in temperate marine ponds.

A novel design for a gas-inducing impeller at the lowest critical speed

To disperse the unreacted overhead gas phase into the liquid in an agitated reactor without gas outlet, a gas-inducing impeller is usually employed. To determine the lowest critical rotating speed, the gas-induction mechanism was reconsidered by constituting a mechanical energy conservation equation between the gas inlet orifice in the gas phase and the gas outlet orifice in the liquid phase under a certain rotational speed. According to this model, the critical speed of the gas-inducing impeller could be basically determined by the submersion depth and the radial position of the gas outlet, and a novel design was proposed by introduction of six short pipes stretched radially from the axis of the impeller. The final design of the gas-inducing impeller was obtained by an optimal combination of the gas-inducing pipes, the blades of the impeller and the baffle dimension.

The underwater environment: cardiopulmonary, thermal, and energetic demands

Water covers over 75% of the earth, has a wide variety of depths and temperatures, and holds a great deal of the earth's resources. The challenges of the underwater environment are underappreciated and more short term compared with those of space travel. Immersion in water alters the cardio-endocrine-renal axis as there is an immediate translocation of blood to the heart and a slower autotransfusion of fluid from the cells to the vascular compartment. Both of these changes result in an increase in stroke volume and cardiac output. The stretch of the atrium and transient increase in blood pressure cause both endocrine and autonomic changes, which in the short term return plasma volume to control levels and decrease total peripheral resistance and thus regulate blood pressure. The reduced sympathetic nerve activity has effects on arteriolar resistance, resulting in hyperperfusion of some tissues, which for specific tissues is time dependent. The increased central blood volume results in increased pulmonary artery pressure and a decline in vital capacity. The effect of increased hydrostatic pressure due to the depth of submersion does not affect stroke volume; however, a bradycardia results in decreased cardiac output, which is further reduced during breath holding. Hydrostatic compression, however, leads to elastic loading of the chest wall and negative pressure breathing. The depth-dependent increased work of breathing leads to augmented respiratory muscle blood flow. The blood flow is increased to all lung zones with some improvement in the ventilation-perfusion relationship. The cardiac-renal responses are time dependent; however, the increased stroke volume and cardiac output are, during head-out immersion, sustained for at least hours. Changes in water temperature do not affect resting cardiac output; however, maximal cardiac output is reduced, as is peripheral blood flow, which results in reduced maximal exercise performance. In the cold, maximal cardiac output is reduced and skin and muscle are vasoconstricted, resulting in a further reduction in exercise capacity.

Effects of Flow Amplitudes on Intraprong Pressures During Bubble Versus Ventilator-Generated Nasal Continuous Positive Airway Pressure in Premature Infants

The goal were to characterize the flow dependence of bubble nasal continuous positive airway pressure delivery in a cohort of preterm infants and to compare the actual (delivered) intraprong continuous positive airway pressure with the intended (set) nasal continuous positive airway pressure for both ventilator-generated nasal continuous positive airway pressure and bubble nasal continuous positive airway pressure delivery. A range of set values and constant flow rates were studied in the same preterm infants. For 12 premature infants of <1500 g (birth weight: 1140 +/- 267 g; gestational age: 28.5 +/- 1.9 weeks; study age: 12.9 +/- 8 days; all mean +/- SD), intraprong pressures were measured at 3 increasing flow settings, repeated for set nasal continuous positive airway pressures (or desired immersion depths) of 4 and 6 cm H(2)O. Next, intraprong pressures were measured at bubble nasal continuous positive airway pressure expiratory tubing submersion depths and ventilator-generated nasal continuous positive airway pressure set expiratory pressures of 2, 3, 4, 5, and 7 cm H(2)O while the flow rate was held constant. Actual (delivered) intraprong pressure during bubble nasal continuous positive airway pressure delivery was highly flow dependent and increased as the flow rate increased. During ventilator-generated nasal continuous positive airway pressure delivery, actual pressure at the nasal prongs closely approximated the pressure set at the ventilator. During bubble nasal continuous positive airway pressure delivery at constant flow rate, the average delivered prong pressure was 1.3 cm H(2)O (range: 0.5-2.2 cm H(2)O) higher than that set through submersion of the expiratory tubing, and the relative difference between the set and actual pressures increased at lesser immersion depths. Prong pressure during bubble nasal continuous positive airway pressure delivery is highly variable and depends on the interaction of submersion depth and flow amplitudes.

Computer assisted video analysis of swimming performance in a forced swim test: Simultaneous assessment of duration of immobility and swimming style in mice selected for high and low swim-stress induced analgesia

In behavioral pharmacology, two problems are encountered when quantifying animal behavior: 1) reproducibility of the results across laboratories, especially in the case of manual scoring of animal behavior; 2) presence of different behavioral idiosyncrasies, common in genetically different animals, that mask or mimic the effects of the experimental treatments. This study aimed to develop an automated method enabling simultaneous assessment of the duration of immobility in mice and the depth of body submersion during swimming by means of computer assisted video analysis system (EthoVision from Noldus). We tested and compared parameters of immobility based either on the speed of an object (animal) movement or based on the percentage change in the object's area between the consecutive video frames. We also examined the effects of an erosion–dilation filtering procedure on the results obtained with both parameters of immobility. Finally, we proposed an automated method enabling assessment of depth of body submersion that reflects swimming performance. It was found that both parameters of immobility were sensitive to the effect of an antidepressant, desipramine, and that they yielded similar results when applied to mice that are good swimmers. The speed parameter was, however, more sensitive and more reliable because it depended less on random noise of the video image. Also, it was established that applying the erosion–dilation filtering procedure increased the reliability of both parameters of immobility. In case of mice that were poor swimmers, the assessed duration of immobility differed depending on a chosen parameter, thus resulting in the presence or lack of differences between two lines of mice that differed in swimming performance. These results substantiate the need for assessing swimming performance when the duration of immobility in the FST is compared in lines that differ in their swimming “styles”. Testing swimming performance can also be important in the studies investigating the effects of swim stress on other behavioral or physiological parameters because poor swimming abilities displayed by some lines can increase severity of swim stress, masking the between-line differences or the main treatment effects.

동해안 사질지반에 시설된 인공어초 3종의 매몰 특성

Using multi beam echo sounder, side scan sonar and scuba diving equipment, ceramic type, uneven type and semicircle-ramus type reefs into sandy bottom were ascertained, the depth of submersion in 7.2-10.3m on the coast of Gangneung, East of Korea, forty uneven type artificial reefs(AR) were totally buried into the sandy bottom. Two of five semicircle-ramus type ARs had only of their top area exposed. For most of the 45 ceramic reefs, only the upper 25-150cm of ARs were visible. The burial pattern is different in west and east side of the reefs, where the east side is deeply buried compared to the west side. From these results. it is recommended that sufficient analysis of bottom structure and materials especially in the sandy sea area should be undertaken in order to determine the best type of artificial reefs to be deployed and the best location for depoloyment.

Análise morfológica de Sagittaria montevidensis desenvolvida em diferentes condições de inundação

O cultivo de arroz irrigado em sistema pré-germinado tem permitido o desenvolvimento de plantas daninhas aquáticas, como as da espécie Sagittaria montevidensis (sagitária), a qual desenvolveu biótipos resistentes a herbicidas inibidores de ALS, no Estado de Santa Catarina. No presente trabalho, objetivou-se examinar as respostas morfológicas de sagitária quanto à variação da lâmina d'água, crescendo sob condições ambientais controladas. Os tratamentos foram representados pelas seguintes condições de inundação: solo saturado, 5, 10 e 20 cm de submersão, em delineamento experimental completamente casualizado, com cinco repetições. A presença de lâmina d'água favoreceu a germinação das sementes de sagitária. O aumento da profundidade de submersão incrementou a estatura da planta por meio do alongamento dos pecíolos das folhas espatuladas e sagitadas. Variação na profundidade da lâmina d'água não modificou o número de plantas, a massa seca, o número de folhas e de raízes, o tamanho da folha linear, o tamanho da lâmina foliar espatulada e sagitada e do escapo floral das plantas de S. montevidensis. As folhas de sagitária de mesmo tipo morfológico, quando desenvolvidas nas profundidades de água testadas, não diferiram histologicamente.

Water modeling of mold powder entrapment in slab continuous casting mold

The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the shearing flow near the narrow face of mold, the entrapment caused by vortexes around the submerged entry nozzle (SEN), and the entrapment caused by the Ar bubbling. Both the velocity of the surface flow and the level fluctuation of the liquids are enlarged with increasing the casting speed, reducing the submersion depth of SEN, decreasing the downward angles of the nozzle outlets, and increasing the Ar flowrate, all of which increase the tendency of mold powder entrapment. Among the four above-mentioned factors, casting speed has the largest effect.

Simulation of the detection of underwater objects from air

Simulation modelling of the detection through a water-air boundary of underwater objects by means of a CCD camera is performed. The situation using active illumination by pulses of laser radiation is considered. Calculation is performed for the special case of the minimum size of an object detected at a prescribed depth of submersion in relation to its reflection factor.

Unpredictability of Delivered Bubble Nasal Continuous Positive Airway Pressure: Role of Bias Flow Magnitude and Nares-Prong Air Leaks

Nasal continuous-positive-airway-pressure (NCPAP) is popular for infant respiratory support. We compared delivered to intended intra-prong, proximal-airway, and distal-airway pressures using ventilator (V-NCPAP) and bubble (B-NCPAP) devices. Measurements were repeated at five flows (4, 6, 8, 10, and 12 L/min) and three NCPAP (4, 6, and 8 cm H2O) under no, small, and large nares-prong interface leak conditions. With no-leak, delivered B-NCPAP was systematically greater than intended levels at all pressure sites. The corresponding V-NCPAP flow-dependence was none-to-minimal. Prong and intra-airway B-NCPAP overshoots were also observed with small-leak, while only prong B-NCPAP showed a flow-dependent overshoot for large-leak. Leaks did not affect intra-prong V-NCPAP but resulted in progressively lower than desired, flow-independent intra-airway V-NCPAP. We conclude that the self-adjusting capability of ventilators allows closely matched actual versus intended V-NCPAP. Alternatively, for the range of flows used clinically, intra-prong and intra-airway B-NCPAP are systematically higher at increasing flows than operator-intended levels, even when appreciable nares-prong leak is present. Additionally, the oscillations (noise) characterizing B-NCPAP are substantially attenuated between the proximal and distal airways; therefore, it is unlikely that B-NCPAP engenders ventilation or lung recruitment via this phenomenon. Tubing submersion depth for setting the level of B-NCPAP is highly inaccurate, and operators should instead rely on intra-prong pressure measurement.

Polarization-degree imaging contrast in turbid media: a quantitative study

Scattering in biological tissue can degrade imaging contrast and reduce the probe depth. Polarization-based measurement has shown its advantages in overcoming such drawbacks. Here, linear and circular polarization degree imaging is applied to a comblike metal target submerged in Intralipid solutions. Contrasts of the metal bars are measured quantitatively as functions of the Intralipid concentration and the submersion depths. Different behaviors in contrast for linear and circular polarizations are compared. Contributions to the background of circular polarization degree images by backscattering, snake, and diffusive photons are examined carefully.

Flood-damage curves: Methodological development for the Brazilian context

The present paper describes the main results of an on-going research aiming to develop standard flood damage data in the form of generic flood-damage curves. This type of curve allows estimating flood damages from the depth of inundation. Although the research project encompasses flood damages on different urban land use activities (residential, commercial, services and industrial land uses), the paper focus on residential flood damage information. The empirical data used on this research was obtained from systematic surveys performed in the city of Itajubá, a town with 85.000 inhabitants located in the Sapucaí river valley in the South-eastern region of Brazil, during the year of 2002. The survey consisted in interviewing residents in the Itajubá flood prone urban area in order to develop a data base characterizing the social class, the building fabric, the contents (inventory items) and the damages caused to dwellings by a reference flood event, the 2000 flood event. During this event, the town had more than 70% of its urban area flooded for three days and, in some densely urbanised areas, the depth of water was superior to three meters. The FDC curves obtained show relatively high damage according to the submersion depth considering the Brazilian context. This issue suggests that inhabitants can rarely recover, in the short time, from all the harm caused by flooding.

Electrodynamics of microwave near-field probing: Application to medical diagnostics

A theory for the near-field (NF) microwave diagnostics of planar-stratified media is developed based on the design of an equivalent NF probe circuit and the solution of the electrodynamical problem for the electromagnetic field of antenna in an inhomogeneous ambient medium. The theory has been verified experimentally by probing into water with controllable dielectric permittivity. A theoretical and experimental study into a possibility to locate contrast structures (malignant growths) within biological media by means of NF probing has been carried out. Detectable contrasts of a growth have been calculated depending on its dimensions and depth of occurrence. Two-dimensional images of a tumorlike contrast object have been obtained for different depths of the object submersion in water. A measurement technique reducing the masking effect of background fluctuations arising by probe contact with a pliant surface is proposed.