Water Surface Roughness Research Articles

An airborne acoustic method to reconstruct a dynamically rough flow surface.

Currently, there is no airborne in situ method to reconstruct with high fidelity the instantaneous elevation of a dynamically rough surface of a turbulent flow. This work proposes a holographic method that reconstructs the elevation of a one-dimensional rough water surface from airborne acoustic pressure data. This method can be implemented practically using an array of microphones deployed over a dynamically rough surface or using a single microphone which is traversed above the surface at a speed that is much higher than the phase velocity of the roughness pattern. In this work, the theory is validated using synthetic data calculated with the Kirchhoff approximation and a finite difference time domain method over a number of measured surface roughness patterns. The proposed method is able to reconstruct the surface elevation with a sub-millimeter accuracy and over a representatively large area of the surface. Since it has been previously shown that the surface roughness pattern reflects accurately the underlying hydraulic processes in open channel flow [e.g., Horoshenkov, Nichols, Tait, and Maximov, J. Geophys. Res. 118(3), 1864-1876 (2013)], the proposed method paves the way for the development of non-invasive instrumentation for flow mapping and characterization that are based on the acoustic holography principle.

INVESTIGATION ON THE WATER ABSORPTION CHARACTERISTICS OF PLYWOOD MANUFACTURED USING VENEERS FROM OIL PALM STEM

There are four main weaknesses in using Oil Palm Stem (OPS) as a material for plywood manufacturing. High variation in density, moisture contents (MC), high water absorption and surface roughness. This paper report the investigation on the effect of water on physical properties of OPS plywood (PTA) namely water absorption, thickness swelling and delamination. These properties were compared with the properties of another two types of commercial OPS plywood denoted as PTB and PTC which were manufactured using OPS veneer with tropical hardwood veneer for face and back veneer and control plywood denoted as PTD which was manufactured using 100% tropical hardwood veneer. The results showed that PTA has lowest value of water absorption but has highest value of thickness swelling and delaminating.

Direct numerical simulation of a turbulent stably stratified air flow above a wavy water surface

The influence of the roughness of the underlaying water surface on turbulence is studied in a stably stratified boundary layer (SSBL). Direct numerical simulation (DNS) is conducted at various Reynolds (Re) and Richardson (Ri) numbers and the wave steepness ka. It is shown that, at constant Re, the stationary turbulent regime is set in at Ri below the threshold value Ric depending on Re. At Ri > Ric, in the absence of turbulent fluctuations near the wave water surface, three-dimensional quasiperiodical structures are identified and their threshold of origin depends on the steepness of the surface wave on the water surface. This regime is called a wave pumping regime. The formation of three-dimensional structures is explained by the development of parametric instability of the disturbances induced by the surface water in the air flow. The DNS results are quite consistent with prediction of the theoretical model of the SSBL flow, in which solutions for the disturbances of the fields of velocity and temperature in the wave pumping regime are found to be a solution of a two-dimensional linearized system with the heterogeneous boundary condition, which is caused by the presence of the surface wave. In addition to the turbulent fluctuations, the three-dimensional structures in the wave pumping regime provide for the transfer of impulse and heat, i.e., the increase in the roughness of the water–air boundary caused by the presence of waves intensifies the exchange in the SSBL.

Click Grafting of Chitosan onto PVC Surfaces for Biomedical Applications

ABSTRACTIn this study, polyvinyl chloride (PVC) has been modified through click grafting of chitosan onto its surface. This goal has been achieved using three consecutive steps involving amination, activation, and grafting. Both the amination and chitosan grafting steps were confirmed based on the determination of nitrogen content. The chemical structure of the modified PVC membranes was confirmed by FTIR spectroscopy and thermal analysis, and the morphological changes were monitored by scanning electron microscopy. In addition, the induced physicochemical characteristics were investigated by analyzing the water uptake, mechanical properties, surface roughness, and contact angle. Finally, an evaluation of blood compatibility and protein adsorption characteristics for the chitosan‐g‐PVC membranes is presented.

Canopy modeling of aquatic vegetation: A radiative transfer approach

Aquatic vegetation in shallow waters can absorb nitrogen and phosphorus from eutrophic waters, and effectively control water bloom. However, our knowledge of the interaction between solar radiation and aquatic vegetation is limited. This restricts the protection of aquatic vegetation. This paper proposes a radiative transfer approach for homogeneous aquatic vegetation canopy, based on the theories for terrestrial vegetation and Case II water. The effects of rough water surface and bottom reflection are also taken into consideration. Validations against an independent Monte Carlo model and field experiment data exhibit well consistencies on the bidirectional reflectance of homogeneous aquatic vegetation canopy. As expected, the results for sparse canopy degenerate. This model can be used for canopy modeling of emergent, floating or submerged aquatic vegetation. Potential applications include retrieval of biophysical or biochemical parameters based on hyperspectral data and physical process.

Antifouling coatings for dental implants: Polyethylene glycol-like coatings on titanium by plasma polymerization.

Titanium dental implants are commonly used for the replacement of lost teeth, but they present a considerable number of failures due to the infection on surrounding tissues. The aim of this paper is the development of a polyethylene glycol-like (PEG-like) coating on the titanium surface by plasma polymerization to obtain a novel improved surface with suitable low bacterial adhesion and adequate cell response. Surface analysis data of these coatings are presented, in particular, water contact angle, surface roughness, and film chemistry, demonstrating the presence of a PEG-like coating. Streptococcus sanguinis and Lactobacillus salivarius bacterial adhesion assays showed a decreased adhesion on the plasma polymerized samples, while cell adhesion of fibroblasts and osteoblasts on the treated surfaces was similar to control surfaces. Thus, the PEG-like antifouling coating obtained by plasma polymerization on Ti confers this biomaterial's highly suitable properties for dental applications, as they reduce the possibility of infection while allowing the tissue integration around the implant.

Water sorption, solubility and surface roughness of resin surface sealants

Surface sealants have been suggested as final glaze of the surface of composite restorations. However, little is known about bulk and surface properties of these materials aiming the long-term preservation of the surface integrity of these restorations. AIM: To evaluate the water sorption, solubility and surface roughness of commercial surface sealants for restorations. METHODS: Five disc-shaped specimens 15 mm diameter X 1 mm high were made from the surface sealants Natural Glaze DFL and Permaseal Ultradent and were light cured according to the manufacturer's instructions. The specimens were finished with 1500-grit SiC paper. Water sorption WS and solubility SL were assessed as recommended by the ISO 4049/2000 and were expressed in µg/mm3. Surface roughness was evaluated before and after WS and SL, and was expressed in µm as R1 before WS and SL and R2 after WS and SL. It was obtained from three parallel measurements along a 4mm length. Data were analyzed using t-test and paired t-test α=0.05. RESULTS: Water sorption and solubility of Natural Glaze were significantly lower than that of Permaseal p 0.05. CONCLUSIONS: Surface sealants used in composite restorations undergo hydrolytic degradation; however, this degradation seems not to interfere on surface roughness of these materials.

Water sorption, solubility and surface roughness of resin surface sealants

Water sorption, solubility and surface roughness of resin surface sealants

Aluminium Alloy 8011: Surface Characteristics

Aluminium alloys are the predominant materials in modern industries. Increased knowledge about the surface characteristics of bare aluminium can enhance the understanding about how to optimize the working conditions for the equipment involving aluminium parts. This work focusses on the properties of native surface of aluminium alloy 8011, which is the main construction material for the production of air-to-air heat exchanger fins. In this study, we address its water wettability, surface roughness and frost formation in different psychometric parameters. The contact angle measurements revealed that this aluminium alloy exhibits a relatively high contact angle of about 78 degree, i.e. is not wetted completely. AFM measurements revealed significant surface roughness of typical heat exchanger fins. The thickness of formed frost was studied in relation to the wettability, humidity and the cold surface temperature.

A comparison of waveform processing algorithms for single-wavelength LiDAR bathymetry

Due to the low-cost and lightweight units, single-wavelength LiDAR bathymetric systems are an ideal option for shallow-water (<12m) bathymetry. However, one disadvantage of such systems is the lack of near-infrared and Raman channels, which results in difficulties in extracting the water surface. Therefore, the choice of a suitable waveform processing method is extremely important to guarantee the accuracy of the bathymetric retrieval. In this paper, we test six algorithms for single-wavelength bathymetric waveform processing, i.e. peak detection (PD), the average square difference function (ASDF), Gaussian decomposition (GD), quadrilateral fitting (QF), Richardson–Lucy deconvolution (RLD), and Wiener filter deconvolution (WD). To date, most of these algorithms have previously only been applied in topographic LiDAR waveforms captured over land. A simulated dataset and an Optech Aquarius dataset were used to assess the algorithms, with the focus being on their capability of extracting the depth and the bottom response. The influences of a number of water and equipment parameters were also investigated by the use of a Monte Carlo method. The results showed that the RLD method had a superior performance in terms of a high detection rate and low errors in the retrieved depth and magnitude. The attenuation coefficient, noise level, water depth, and bottom reflectance had significant influences on the measurement error of the retrieved depth, while the effects of scan angle and water surface roughness were not so obvious.

The Distinguishing Quality of Water Droplets on Insulating Surface under AC and DC Electric Field Stress

This paper presents the comparison of water droplets on insulating surface under alternating current (AC) and direct current (DC) electric field. Besides that, it is demonstrated about the insulator deterioration under both electric field stressed due to an ageing and partial discharge (PD) phenomenon. The vital parameters factors are water droplets conductivity, droplet volume, surface roughness and droplet positioning that they cause to occur the electric field intensification. The field is intensified at the interface between the droplet, air and insulating material. Thus, the PD occurred due to electric field intensification increases with the deformed droplet. The deformation of water droplet under AC electric field stress is more intense than DC field. The electrostatic forces change the droplet shapes and spread them along the electric field direction. The local electric field intensification provokes the PD giving way to reduction of hydrophobicity of insulator surfaces. In addition, the PD activity could appear as a trigger for a surface breakdown. And the localized arcs cause damage to insulating material then finally leads to deterioration of insulation materials and the pollutant contamination.

Principles of Designing an “Ideal” System of Imaging Through a Rough Water Surface

We propose new principles for designing a system of imaging through a rough water surface. These principles permit one to reduce the negative impact of the surface roughness and multiple scattering in water on the spatial resolution. The system model in which the image of underwater objects is generated by angular scanning with an illumination beam is considered. Image distortions in such a system are due mainly to random variations in the refraction angle of a laser beam on the surface and can be eliminated if the true direction of entry of the beam into water is known. Information on the beam refraction angle is suggested to be taken from the angular distribution of the radiance of the signal backscattered by the subsurface water layer. Reduced impact of multiple scattering in water is reached by high-frequency modulation of the beam power by a complex signal and matched processing in the reception system. It is shown that a combination of proposed imaging techniques gives an essential gain in the resolution of the airborne imaging system.

Fluid interfacial nanoroughness measurement through the morphological characteristics of graphene.

The interfacial nanoroughness of liquid plays an important role in the reliability of liquid lenses, capillary waves, and mass transfer in biological cells [Grilli et al., Opt. Express 16, 8084 (2008), Wang et al., IEEE Photon. Technol. Lett. 18, 2650 (2006), and T. Fukuma et al., 92, 3603 (2007)]. However, the nanoroughness of liquid is hard to visualize or measure due to the instability and dynamics of the liquid-gas interface. In this study, we blanket a liquid water surface with monolayer graphene to project the nanoroughness of the liquid surface. Monolayer graphene can project the surface roughness because of the extremely high flexibility attributed to its one atomic thickness. The interface of graphene and water is successfully mimicked by the molecular dynamics method. The nanoroughness of graphene and water is defined based on density distribution. The correlation among the roughness of graphene and water is developed within a certain temperature range (298-390 K). The results show that the roughness of water surface is successfully transferred to graphene surface. Surface tension is also calculated with a simple water slab. The rise of temperature increased the roughness and decreased the surface tension. Finally, the relationship between graphene roughness and surface tension is fitted with a second-order polynomial equation.

Remote sensing technique for near-surface wind by optical images of rough water surface

The study of a new remote-sensing technique for the investigation of near-surface wind fields is an important oceanographic problem. This article is focused on a new method of recording wind fields by the analysis of optical images of sea surface and range–time–intensity images (RTI images) of the sea surface. An RTI image constructed from optical profiles of the sea surface is an optical analogue of a side-looking radar image of the sea surface but has a higher spatial resolution and some possibility for remote sensing of sea roughness. It is possible to form RTI images with a range from some tens of metres to tens of kilometres, depending on the spatial resolution needed. A set of original optical devices for recoding RTI images using linear arrays of CCD-photodiodes was created. An analytical model of sea surface radiance for visible light was developed taking into account the polarization of light and shadowing of surface waves for grazing view geometry. The principle of remote sensing of near-surface winds by its manifestations on a waved surface under grazing angles based on a comparison of measured and modelled surface radiance is discussed. Investigations of near-surface wind field features in internal reservoirs and various regions of the seas during the last few years have been conducted by optical systems. The structure of near-surface wind fields, eddies, wind fronts, and katabatic wind flows for ranges from hundreds of metres to some tens of kilometres was recorded and analysed. Derived data of optical monitoring of water surfaces may serve for future investigations of near-surface wind features.

Relationship between inter-annual variations of microwave land surface emissivity and climate factors over the desert

Microwave land surface emissivity of the Taklimakan Desert was retrieved based on AMSR- E( advanced microwave scanning radiometer-earth observing system) Leval 2A measurements and land surface and atmosphere products from GDAS( global data assimilation system) in 2008 under clear atmospheric conditions.Then,the spectral characteristics of the retrieved emissivity were classified and analyzed with respect to the soil types,and the relationships between desert emissivity annual variability and climate factors were also analyzed. The analyses indicate that the desert microwave emissivity and its annual variability are closely related to soil types.Moreover,there is a significant correlation between soil volume water content as well as land skin temperature and inter- annual variations of emissivity,which decreases with both of the two land surface parameters. Furthermore,vegetation coverage,canopy water content and surface roughness depending on the soil moisture are also the influencing factors of emissivity,and the soil moisture is restricted by both the atmospheric total precipitable water and the underlying soil type. Additionally,the surface emissivity of the desert mostly composed of sand observably decreases with the desert depth.

An autonomous image based approach for detecting glacial lake outburst floods

Abstract. The potential danger caused by glacier margin lakes and the related risk of glacier lake outburst floods (GLOF) increases constantly due to glaciers retreating in many parts of the world. Reasons for this development are on the one hand the new formation and enlargement of glacier margin lakes due to melt water. On the other hand, retreating and thinning glacier tongues lead to a decrease of the back pressure against the dammed glacier lakes. The paper describes the design of a photogrammetric GLOF monitoring system, based on monoscopic image sequence analysis for automatic detection of water level changes. The presented approach for measuring the water line in an image sequence is based on directional edge detection in LoG-filtered image data. After that, the water level is determined by a transformation of image measurements into object space based on orientation parameters of the camera and a geo-referenced lake basin model. The model can for instance be determined by photogrammetric methods after a GLOF; it may also be determined portion-wise by analysing shore lines at various water levels. Camera orientation parameters are determined by a local GPS-supported photogrammetric network. Comparing the determined water level changes with reference data provided by a water gauge, the precision is estimated in the order of one decimetre. A major challenge is the automatic detection of the water line in image sequences under varying light and visibility conditions. The paper will also discuss promising approaches such as multispectral images as well as a statistical analysis of grey value changes over short image sequences to eliminate disturbing reflections on the rough water surface.

Titania nanoparticles prevent development of Pseudomonas fluorescens biofilms on polystyrene surfaces

Direct observation of the influence of titanium oxide (TiO2) nanoparticles on the development of Pseudomonas fluorescens biofilms on the surfaces of TiO2/polystyrene nanocomposite films was performed using scanning electron and atomic force microscopies. Significant reduction in the area covered by the biofilm on the nanocomposite surface was detected, as well as a decrease in the amount of extracellular polymeric substance secreted by the microorganism. The water contact angle values and surface roughness of the thermoplastic films showed negligible changes with the introduction of TiO2 nanoparticles in polystyrene, indicating that the nanostructures inhibit cellular adhesion by affecting the microorganisms directly and not by changing the surface properties of the polymer.

Modelling the effect of Pliocene–Quaternary changes in sea level on stable and tectonically active land masses

ABSTRACTA mathematical model was used to examine the effect of Pliocene and Quaternary changes in sea level on the development of tectonically active and inactive rock coasts. The model calculated rates of mechanical wave erosion according to such factors as the deep water wave regime, bottom topography and surface roughness, and the resistance of the rocks. Subaerial terraces were truncated or eliminated by subsequent terrace formation at lower elevations, especially on steeply sloping landmasses experiencing slow rates of uplift. Submarine terraces formed during glacial stillstands were best preserved when rapid subsidence quickly carried them below the level of wave action. On slowly subsiding landmasses, submarine terraces formed during interglacials and glacial periods experienced repeated erosional modification during subsequent periods of rising and falling sea level and were generally less distinctive. On rapidly rising or subsiding (&gt;5 mm yr‐1) landmasses, terraces that formed during interglacial stages alternated, above and below present sea level, with terraces formed during glacial stages. Despite some differences in terrace occurrence and elevational distribution, it may be difficult to distinguish profiles cut during accelerating or decelerating uplift. The amount of erosion during sea level oscillations increases with oscillation amplitude and the larger oscillations in the middle to late Quaternary were therefore more conducive to erosion than the smaller oscillations of the Pliocene and early Quaternary. The effect of oscillation amplitude may have been countered during the earlier stages of profile development, however, by steeper submarine gradients and reduced rates of wave attenuation. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Effects of water absorption and surface roughness on the bioreceptivity of ETICS compared to clay bricks

External thermal insulation composite systems (ETICS) have been used in European buildings since the 70's due to the optimal protection from thermal loss, the low cost and the ease of application. The progressive thickening of ETICS used for either thermal insulation in new buildings or energy requalification of ancient buildings has facilitated the growth of microalgae on façades, due to limitation of outgoing heat flux, and hence to condensation of atmospheric moisture on building façade external layer.This study was aimed to comparatively evaluating the growth of two selected microalgal strains on ETICS and fired clay bricks; to this end, the influence of water absorption, porosity and surface roughness of these building materials was investigated. Biodeterioration of building materials was induced through a laboratory-accelerated growth test. Results from colorimetric and confocal laser scanning microscopy (CLSM) analyses clearly demonstrated that bioreceptivity of the building materials assayed is strongly affected by surface roughness and total porosity.

Measuring the Morphology and Dynamics of the Snake River by Remote Sensing

The Snake River is a prominent, central feature of Grand Teton National Park, and this dynamic fluvial system maintains diverse habitats while actively shaping the landscape. Although the riparian corridor is relatively pristine, the Snake River is by no means free from anthropogenic influences: streamflows have been regulated since 1907 by Jackson Lake Dam. Among dam-controlled rivers in the western U.S., the Snake River is unique in that tributaries entering below the dam supply sufficient coarse bed material to produce a braided morphology. As a result of tributary inputs, sediment flux along the Snake River has been relatively unaffected by Jackson Lake Dam, but flow regulation has reduced the magnitude and altered the timing of streamflows. In this study we are coupling an annual image time series with extensive field surveys to document channel changes occurring on the Snake River. Our objective is to quantify how snowmelt runoff events and flow management strategies influence patterns of sediment transfer and storage throughout the river system, with a particular focus on tributary junctions. More specifically, we are using the image sequence to identify areas of erosion and deposition and hence infer the sediment flux associated with the observed changes in channel morphology. This analysis will improve our understanding of the river’s response to flow management and enable us to generate hypotheses as to how the system might adapt to future anthropogenic and/or climate-driven alterations in streamflow and sediment supply. In addition, our research on the Snake River involves an ongoing assessment of the potential to measure the morphology and dynamics of large, complex rivers via remote sensing. A new aspect of this investigation involves estimating flow velocities from hyperspectral images that capture the texture of the water surface. Extensive field measurements of velocity and water surface roughness are being used to develop this innovative approach and thus increase the amount of river information that can be inferred via remote sensing.