Water Surface Conditions Research Articles

Analysis of Image Processing Algorithms for Water Surface Garbage Cleaning Robots

To facilitate the observation of the water surface conditions in front of the water surface garbage cleaning robots during navigation, an image transmission function was designed using cameras and wireless transmission equipment. However, due to the influence of water surface lighting, the transmitted images were unclear. In this paper, five image processing algorithms were written in Python language using the OpenCV library: Histogram Equalization, Gray World Algorithm, Retinex-based Enhancement Algorithm, Automatic White Balance (AWB) Algorithm, and Automatic Color Equalization (ACE) Algorithm. The algorithms were used on both static and dynamic water surface images, and the program results showed that the Automatic Color Equalization (ACE) Algorithm is the most appropriate image processing algorithm for water surface garbage cleaning robots.

Experimental study of frosting characteristics of trace water vapor under cryogenic wind tunnel conditions

In cryogenic wind tunnels, the working fluid mixed with trace amounts of water vapor may form frost on the test model, which could affect the testing results. To investigate the frosting phenomenon under trace water condition, an experimental system is built for visualizing the frosting process on a cryogenic surface. The effects of variable factors on frost formation are analyzed focusing on the growth characteristics of frost layer. Under trace water and cryogenic surface conditions, the water vapor desublimates into crystals without obvious condensation. As the surface temperature increases from −183 ℃ to −123 ℃, the frost becomes thicker and more porous due to the thinner outer boundary layer. When the water vapor content rises from 30 ppm to 500 ppm, the frost morphology transforms from a flat layer to frost clumps with visible dendritic structure. Additionally, the decrease in nitrogen flow temperature and the increases in ambient pressure and surface roughness of the cryogenic surface are conducive to the development of the branches on the frost crystal, which accelerate the growth of the frost layer. Furthermore, a dimensionless correlation is proposed for predicting the frost thickness under cryogenic and trace water conditions, with an overall error within ±20 %.

Numerical study of water entry of vehicle under near free surface caused by underwater explosion

Water entry of a high-speed vehicle with a small angle can easily cause such phenomena as bouncing and unstable trajectory. Underwater explosion near the free surface can provide better wave conditions for vehicle, which may significantly reduce slamming loads and improve trajectory stability. In this paper, numerical models of underwater explosion near free surface and water entry of a high-speed vehicle are established based on Coupled Euler-Lagrange (CEL) method of ABAQUS software. The feasibility of water entry of vehicle with small angle in underwater explosion bubble is verified by CEL numerical method. First, in order to verify the effectively of CEL method for solving problems of water entry and underwater explosion, experiment on water entry of projectile is carried out, a numerical models of a small projectile entering water and free-field underwater explosion are established. The obtained numerical results are compared with those of experiments or empirical formulas. Then, a water entry model of a high-speed vehicle with a small angle under static water surface conditions is established; and its slamming loads and motion trajectory during entry process are analyzed. Finally, numerical model water entry of a vehicle in an underwater explosion bubble is developed. The obtained results for the trajectory and slamming load characteristics are compared with those under static water surface conditions. The results show that underwater explosion near free surface can provide a cavity before water entry can significantly reduce the overload of the vehicle and effectively improve its trajectory stability during entry process. This study provides an innovative approach to reducing loads of a high-speed vehicle with small angle, which has a significant value for solving cross-media entry problems in the field of ships and ocean engineering.

Study on the Polarization Pattern Induced by Wavy Water Surfaces

In nature, the wavy ocean surface is a common polarizer, which can change the polarization state of incident light by refraction and reflection and form a new polarization pattern different from the atmosphere. In this paper, we establish the polarized optical transmission model of wavy ocean surface reflection and refraction and simulate polarization patterns induced by wavy ocean surfaces. We study the polarization patterns reflected by wavy water surfaces and polarization patterns inside and outside Snell’s window under wavy ocean surfaces. The correctness of the simulation results is verified by qualitative and quantitative analysis. The environmental factors affecting the corresponding polarization patterns are discussed. Through contrastive analysis, we find that polarization patterns induced by wavy water surfaces are predictable and regular, which has great potential for human application. This kind of polarization pattern is influenced by the sun’s position and water surface condition. The study will promote the development of remote sensing, target detection, and polarization navigation.

Dinocyst assemblages and water surface conditions in the Sea of Marmara during MIS 6 and 5 from two long cores

The Sea of Marmara is the connection between the vast Black Sea-Caspian Sea basin (Pontocaspian) and the Global Ocean via the Mediterranean Sea. Its water levels and water conditions has widely varied over times. Combining two cores in the Sea of Marmara (Turkey) and using organic-walled dinoflagellate cyst assemblages as the main proxy (combined with alkenones, diatoms and benthic foraminifera), allow qualitatively reconstructing water conditions during Marine Isotopic Stage (MIS) 6 and 5, such as salinity and oxygen level. A clear main marine phase is illustrated in MIS 5e. A minor marine incursion occurred during MIS 5c, mostly supported by alkenone data. The rest of the record indicates brackish Pontocaspian conditions, with more Spiniferites inaequalis in MIS 6 and more S. cruciformis in the non-marine parts of MIS 5.At the MIS 6/MIS 5 transition, an earlier initial marine flooding in the Sea of Marmara (dinocyst assemblages) in comparison to the Black Sea was highlighted. The marine reconnection occurred at different moments as seen in the terrestrial vegetation reconstructed from pollen analysis linking the two seas.The sapropels of the Sea of Marmara form when marine water penetrates at depth from the Aegean Sea beneath a layer of lower salinity water. Variations of the residence time of the marine deep water in a stratified Sea of Marmara are potentially an important factor underlying hypoxia/anoxia and sapropel deposition. When combining surface water proxies with benthic foraminifera (test assemblages and presence of inner organic lining), it appears that the successive MIS 5 sapropels formed under decreasing salinity and oxygen availability conditions as the marine inflow was increasingly restricted. Understanding the hydrologic evolution of the Sea of Marmara during MIS 5 implies taking into account that the Bosphorus and Dardanelle straits are hydrodynamically coupled and may not be simplified as on/off switches based on present day sill depths.

Investigation on the cavitation and atomization characteristics of multiphase fluids in underwater explosion near a free surface

The characteristics of cavitation and atomization induced by underwater explosion near a free surface have been investigated by the multiphase fluid model based on two-fluid phase transition. This numerical method can provide the phase transition between liquid and its vapor phases during shock wave and rarefaction wave propagation at any time in underwater explosion. The detailed density, pressure, vapor, and liquid phases of volume fraction contours in cavitation and atomization zones can be obtained. The phase transition model was first used to quantitatively research the phenomenon of vapor liquefaction after shock wave propagation in initial water containing different trace amounts of vapor. Then the contribution of phase transition to the formation of cavitation and atomization in underwater explosion was investigated through a shock tube test and two typical underwater explosion cases. It is found that the phase transition effect between the vapor and liquid phases contributes more than 60% to the formation of the cavitation zone. Two charges under two different water surface conditions have been investigated by comparison with the case of a single charge. We can conclude that it is very necessary to introduce the phase transition model into the simulation of underwater explosion, which can provide details of the flow field in the cavitation and atomization zones that cannot be obtained by the one-fluid cavitation model.

Study on vertical line source Green's function for hydrodynamic calculations of ocean structures in water with ice cover

The numerical calculation of panel integrals associated with the Green's function satisfying water surface condition with ice cover is the basis for the boundary element method (BEM) to solve hydrodynamic problems of ocean structures in ice regions. In order to simplify the calculation process and reduce the time consuming, the vertical line source representing the analytical integral of ice-covered Green's function over vertical line segment is firstly derived in this paper. Then a semi-analytical quadrature, which accumulates a series of vertical line sources distributing along the horizontal direction, can be derived for the panel integral. In the numerical implementation, the asymptotic analysis method is employed to eliminate the singularity at zero point of the denominator, variable substitution is performed to treat the integral at infinite and approximate polynomials are introduced to evaluate the Bessel functions. Through the calculations of vertical line and panel integrals of Green's function and its derivatives, the analytical expression of vertical line source is proved to be accurate and more efficient than the normal numerical quadrature. Based on this, a BEM program is developed and applied in the hydrodynamic calculations of submerged structures with ice cover. The computed results are found to be in excellent agreement those of the validated BEM based on point source, which further verifies the reliability and practicability of utilization of vertical line source.

View from below: experimental manipulation of water surfaces to evaluate visual integrity of heron-like models through Snell’s window

Abstract The water–air interface is a globally widespread habitat for interactions between prey and predators. We experimentally manipulated water surface conditions (flat, smooth waves, three levels of current-induced turbulence) and digitally quantified the visual integrity of above-surface models from a subsurface perspective. Progressive fragmentation was present in each of the models (upright heron, crouched heron, vertical block, horizontal block) with increased departure from flat surface conditions. Smooth directional waves produced multiple horizontal bands (shadows) that moved across the models while surface currents distorted the profile, including progressive disintegration of the models appearance into multiple fragments of different sizes. This fragmentation is caused by scattered surface irregularities interacting with waves and is accentuated at the broken periphery of the optical window, reducing recognition of the models. Unexpectedly, we found that bands and fragments emerging from different surface conditions resemble common frontal plumage patterns on some Ardeidae and shorebirds (Charadriiformes). While these natural plumages are widely recognized to reflect a diversity of adaptations, including camouflage in terrestrial habitats, we suggest that their resemblance to water surface-induced fragmentation might also reflect foraging adaptations of predators though the water–air interface.

무인 수상정의 경로점 추종을 위한 선형 시스템 및 적분 오차 변수 기반 LQR 제어기 설계

An unmanned surface vessel (USV) experiences many uncertainties generated by variations in the water surface condition, wind, and other external factors. Because those uncertainties degrade the controller performance of the USV, the controller should be carefully designed. A nonlinear control method can compensate for those uncertainties appropriately. However, the design procedure of a nonlinear controller is not only highly complex but also very time-consuming. This study proposes a linear-quadratic-regulator (LQR) control method to address these problems simultaneously by integrating a linear system and integral error variables. Because the proposed method is developed with the LQR control method, the complexity and effort of the controller design can be reduced significantly. Moreover, the integral error terms composed of longitudinal velocity/yawrate commands and responses are incorporated into the existing linear systems. By handling the augmented linear system, the obtained LQR controller results in zero values for both state and integral error variables simultaneously. A simulator is developed using MATLAB Simulink, Gazebo, and robot operating system (ROS) to validate the performance of the proposed method. Then, several waypoints following simulations are conducted, and the performance is analyzed with a result based on a nonlinear control method.

An experimental study on the hydrodynamic performance of the twin vertical baffles underflow breakwater

Recently, with the enhancement of marine environmental protection, the permeable breakwater, which has the advantages of a simple structure, good water permeability, and environment-friendly, has been paid more and more attention. This study experimentally investigated the hydrodynamic characteristics of a twin vertical baffles underflow breakwater in a wave flume. Different parameters including the relative submergence, relative blockage, breakwater width, and water surface condition between baffles have been considered. Their influences on the transmission coefficient, reflection coefficient, relative wave run-up on the front baffle, and energy loss rate of the twin vertical baffles underflow breakwater have been analyzed. Furthermore, the wave resonance phenomenon could occur for the cases with free water surface between the two baffles, which had a significant influence on the hydrodynamic characteristics of the breakwater. Finally, an empirical formula for calculating the transmission coefficient has been given based on the experimental data.

Laboratory Study of the Impact of the Surface Solitary Waves Created by the Internal Solitary Waves on Optical Imaging

AbstractThe effects of Surface Solitary Waves (SSWs), which are created by Internal Solitary Waves (ISWs), on optical imaging were investigated in this paper. We explored the connection between SSWs and optical images using simulations and experiments with calm water surface conditions. An experimental platform was built in a controlled laboratory environment where optical images and in‐situ wave data could be gathered simultaneously. SSWs created by different ISWs were successfully observed. The optical images revealed inverse bright and dark patterns for different ISW types (depression or elevation type). Based on theories and experimental results, simulation models of the ISWs and SSWs were built in Unigraphics NX. Using the illumination simulation function of Light Tools, the reason underlying the reversed patterns was explained by the irradiance distribution. Both the experiment and simulation indicated that the SSWs created by the ISWs affected the characteristics of optical images. To further explore how SSWs affect imaging, 16 experiments were designed to investigate the effects of ISW type, amplitude, and water density ratio. It is found that the relationship among the SSW amplitude, ISW amplitude, and density ratio was consistent with earlier studies. The relationships between imaging characteristics (grayscale differences and pattern widths) and the two types of SSWs were consistent.

Design of android based Unmanned Surface Vehicles (USV) for oil spill monitoring

In this research, a USV will be developed that can detect oil spills on the waters, so in the future it can overcome the problem of water pollution. To be able to determine the thickness of the oil on the water surface, TEMT6000 and LED sensors are used. The light intensity will be converted into ADC value by the TEMT6000 sensor. Furthermore, on this system USV will be controlled by Android and can monitor water surface conditions. Android applications will be connected to Wemos via wifi. Then Wemos is connected serially with a RF915 and another RF915 will be connected to the microcontroller of the USV. From the results of the USV test, the USV can be controlled via Android by moving forward, backward, turning left and right. The maximum range of RF915 is 493.3 meters. Then the oil spill detection average error is 5.45% and the the average of the success rate is 94.55%.

Preliminary Characterization of Coverage for Water-to-Air Visible Light Communication Through Wavy Water Surface

In this paper, we establish a water-to-air (W2A) visible light communication (VLC) link using green light emitting diode (LED), and investigate the coverage characteristics of the designed W2A-VLC link under calm and wavy water conditions. By transmitting a high-frequency sinusoid signal, we extract the variation of link gain. Based on the received signals of an experimental W2A-VLC system, we obtain the real link gains at different receiver points and analyze the channel temporal properties in good link conditions (called link “on” state). It is seen that the mean channel gain under wavy water surface condition can be larger than that under calm water surface condition, especially when the transmitter and receiver are not perfectly aligned, due to the random spatial modulation effect of wavy water surface. Moreover, the “on” state duration and interval can be well fitted by a shifted exponential distribution and a shifted lognormal distribution, respectively. Bit error rate (BER) results reveal the effect of expanded link gain variation under wavy water surface condition. This work provides significant guidance for future works on the communication protocol design and related performance analysis.

Splash erosion affected by initial soil moisture and surface conditions under simulated rainfall

Soil erosion by water is one of the most severe soil degradation processes. Splash erosion is the initial stage of soil erosion by water, resulting from the destructive force of rain drops acting on soil surface aggregates. Apart from rainfall properties, constant soil physical properties (texture and soil organic matter) are crucial in understanding the splash erosion. However, there is lack of information about the effect of variable soil properties such as soil initial water content and surface condition (seal formation) on splash erosion. The objective of the present study was to determine how initial water content and surface condition affected soil splash erosion under simulated rainfall. The changes in soil surface condition were characterized by hydraulic variability (saturated hydraulic conductivity) due to surface seal formation. Slit loam and loamy sand soil textures were used in the experiment. The soil samples were collected from the top layer; air dried, and filled into modified Morgan splash cups for splash erosion measurements. Rainfall was created in the laboratory using two types of rainfall simulators covering intensity range from 28 to 54 mm h−1 and from 35 to 81 mm h−1. The soil samples were exposed to three consecutive rainfall simulations with different time intervals between simulations and different initial water content and surface conditions (air-dried, wet-sealed, and dry-crusted). Wet-sealed soil samples had up to 70% lower splash erosion rate compared to air-dried samples, due to surface ponding followed by seal formation. A significant decrease in soil saturated hydraulic conductivity indicated the formation of surface seal for silt loam soils. A non-significant decrease in saturated hydraulic conductivity for loamy sand soil was attributed to earlier formation of stable seals. Two different rainfall simulators produced different amount of splash erosion rates; however, the splash erosion development for increasing rainfall intensity was almost equal considering same initial surface condition. These results provide insight into dynamic changes of individual soil parameters affected by rainfall, and could find wider application for more complex soil erosion prediction models.

ЭФФЕКТИВНАЯ «ЗЕЛЕНАЯ» ТЕХНОЛОГИЯ (SWEM) – ПРОИЗВОДСТВО ЭЛЕКТРОЭНЕРГИИ И ВОДЫ ИЗ АТМОСФЕРЫ

Thermal energy created by heating the Earth and the atmospheric air by sunlight exists in the Earth’s atmosphere in quantities many times greater than humanity’s energy needs. The authors formulated and patented the basic principles of concentration and use of this low-potential thermal energy scattered in the atmosphere. The SWEM technology proposed in the article is a way to convert this natural energy into usable electrical energy, in calculated quantities. SWEMtechnology isbasedonmechanisms that canbeobservedinsuchanaturalphenomenon as a hurricane. The SWEM module replicates the chain of transitions of aggregate states of atmospheric moisture, starting with heating the surface of the world’s oceans and evaporating water that saturates the air. The energy accumulated in the water of the sun, as a result of the chain of conversions, is converted into electricity. At the same time, as a by-product of enthalpy of cross-aggregation, fresh water is released, falling out of the air in the form of precipitation. Fresh water, like energy, is the most valuable and vital product for many people on the planet. TheSWEM water-electric module is versatile, lightweight, operationaland portable. The energy generation providing for energy or water consumption can be scaled up in the form of a synchronized battery of basic size SWEM modules or a mega-installation. SWEM modules can be placed on the ground or on the water surface, in steppe or urban landscape conditions. The technology does not require external energy sources and is absolutely green. The fundamental principles of concentration and management of the earth’s low-potential thermal energy, on which SWEM technology is based, can form the basis of a new, clean energy industry that exceeds current and future energy and water needs

Innovative Feasibility Study for the Reclamation of the Cascajo Wetlands in Peru Utilizing Sustainable Technologies

Wetlands are an important feature for our society that provides versatile benefits, such as habitat for diverse wildlife, shoreline erosion protection, flood control, and mitigation of climate change through capture and storage of carbon. The aim of this work was to assess the application of nanotechnologies for the restoration of the water quality in the Cascajo Wetlands, Peru, where the water quality was deteriorated. Ceramic-based bio-filters (CBBFs) were used to reduce and buffer the contamination rates of pollutants, whereas micro-nano bubbles (MNBs) were applied to increase the dissolved oxygen and release free radicals in water. Additionally, bio-fence was implemented to prevent water intrusion from the ocean. Remote sensing data through the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) was used to monitor the water surface condition. With treatment of CBBFs and MNBs for 13 months, we observed reduction in the chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), and total phosphate (TP) in the water body, showing removal percentages of 98.5%, 97.5%, 98.1%, 98.5%, and 94.6%, respectively, in comparison with values before starting the implementation. The trends of NDVI and EVI over seasons are not completely aligned with the results taken from the wetlands treated with MNBs, CBBFs and bio-fence. While TN was highly correlated with the empirical value of TN based on remote sensing, no correlation was observed between COD and empirical COD. The use of eco-friendly techniques has performed efficiently to remove the pollutant.

Five-channel fiber-based laser Doppler vibrometer for underwater acoustic field measurement.

In this paper, a 1550 nm five-channel all-fiber homodyne laser Doppler vibrometer with high sensitivity and good signal probing probability is presented. Under the anechoic tank, standing on an airborne platform above the water surface 3 m away, the calibration experiments of the designed system are conducted. The minimum detectable sound pressure level is up to 101.73 dB re 1 µPa at 10 kHz under the hydrostatic water surface condition, and the time distribution of the final outputs are consistent with that of the underwater sound transducer. For the hydrodynamic detection capability, with the help of a 1064 nm high-pulse-energy laser whose pulse energy is 6J, pulse duration is about 8 ns, and repetition rate is 1 Hz, the system performance is tested in Qiandao Lake. And the signal probing probability of the whole sensing system is up to 59.77%.

Landscape Change and Vegetation-Channel Interactions in an Estuarine System

We examine the extent of land cover change and sedimentation within the Tijuana River Estuary due to the significant development within Mexico that has increased sedimentation that could alter estuary elevation. We examined aerial imagery to determine major changes in estuary land cover over time (1995–2016), examined sedimentation patterns by calculating vegetation roughness of two dominant lower marsh species: Salicornia pacifica and Spartina foliosa and directly measured sediment deposition within plant stands at multiple elevations and determined how vegetation may be interrupting flow and affecting deposition. Upper elevation scrub has increased slightly through time while marsh area has decreased. Plant roughness for S. foliosa was significantly higher and, based on modeling, each species creates different water surface and channel velocity conditions that could alter deposition patterns. Vegetation inventories and sediment size deposition analysis within vegetation patches show that S. foliosa occupies those areas closest to the channel, is most frequently inundated, and has the smallest sediment sizes present. Sediment size increases with distance from the channel and where it becomes more commonly dominated by S. pacifica. These areas, typically 0.5-1 m above channel bottom elevation, experience the highest volume of sediment deposition. Modeling and direct measurements of deposition indicate that water velocity is impacted by plant stands and deposition is occurring in areas close to the channel. Because these deposition patterns may eventually result in changes in estuary elevation, continual monitoring should be carried out to determine how vegetation-induced sediment behavior, combined with anthropogenic land-use change and sea level rise, influence estuary elevation and land cover.

Analysis of Water Quality Conditions of Lake Hachiroko Using Fuzzy C-Means

Lake Hachiroko, Japan, has many water quality issues, evident from phenomena such as green algae blooms. Understanding the details of the surface water quality of the lake, and the effect of seasons on the quality, is important. In our previous studies, we conducted fuzzy regression analysis of remote sensing data and direct measurements of water quality. The results showed that estimation maps of water quality were well created, using only five data points of the water quality parameters. To obtain maps that are in good agreement with the experimental data, remote sensing data and water quality values should be acquired simultaneously. However, performing such simultaneous observations can affect the preparation of the water quality estimation maps. We overcame this obstacle by using fuzzy c-means clustering (FCM), and considered the effect of specific disturbances and uncertainties on the remote sensing data. Furthermore, FCM using only remote sensing data creates estimation maps in which relative water surface conditions are classified. Therefore, determining the relationship between FCM results and water quality facilitates the creation of low-cost, high-frequency water quality estimation maps. Our results indicated that FCM was particularly effective in determining the presence of suspended solids (SS) during water quality analysis. However, the relationship between FCM results and water quality has not been determined in detail. In this study, we analyzed the water quality conditions of Lake Hachiroko with FCM using the data collected by the Advanced Space-borne Thermal Emission and Reflection Radiometer on Terra and, the Operational Land Imager on Landsat-8. In addition, FCM results were compared with the maps created by fuzzy regression analysis and the actual conditions of water pollution. The results indicated that (i) the maps created using FCM are effective in determining the water surface conditions, (ii) the FCM maps using data obtained during August and September have a strong relationship with biochemical oxygen demand (BOD) and SS, and (iii) the FCM maps using data obtained during May and June have a strong relationship with chemical oxygen demand (COD), SS, and total nitrogen (T-N).

Habitat usage of Daubenton's bat (Myotis daubentonii), common pipistrelle (Pipistrellus pipistrellus), and soprano pipistrelle (Pipistrellus pygmaeus) in a North Wales upland river catchment.

Distributions of Daubenton's bat (Myotis daubentonii), common pipistrelle, (Pipistrellus pipistrellus), and soprano pipistrelle (Pipistrellus pygmaeus) were investigated along and altitudinal gradient of the Lledr River, Conwy, North Wales, and presence assessed in relation to the water surface condition, presence/absence of bank‐side trees, and elevation. Ultrasound recordings of bats made on timed transects in summer 1999 were used to quantify habitat usage. All species significantly preferred smooth water sections of the river with trees on either one or both banks; P. pygmaeus also preferred smooth water with no trees. Bats avoided rough and cluttered water areas, as rapids may generate high‐frequency echolocation‐interfering noise and cluttered areas present obstacles to flight. In lower river regions, detections of bats reflected the proportion of suitable habitat available. At higher elevations, sufficient habitat was available; however, bats were likely restricted due to other factors such as a less predictable food source. This study emphasizes the importance of riparian habitat, bank‐side trees, and smooth water as foraging habitat for bats in marginal upland areas until a certain elevation, beyond which bats in these areas likely cease to forage. These small‐scale altitudinal differences in habitat selection should be factored in when designing future bat distribution studies and taken into consideration by conservation planners when reviewing habitat requirements of these species in Welsh river valleys, and elsewhere within the United Kingdom.