Water Surface Fluctuations Research Articles

Hydrological dynamics of temporary wetlands in the southern Great Plains as a function of surrounding land use

We used remote sensing imagery to characterize the hydrological dynamics of 8404 temporary freshwater wetlands (playas) in Texas (Landsat 5 TM WRS-2 P30/R36) from 2008 to 2011, comparing known wet and dry periods, and related these to land use within 100 m. Hydroperiods were highly variable, and peak water availability occurred in different seasons in different years, varying by as much as two orders of magnitude with date. Land use affected the likelihood and duration of inundation, with playas in urban settings being modified in such a way as to extend hydroperiod, and playas surrounded by cropland experiencing shorter hydroperiods: 3726 playa basins never contained standing water during the four-year period, and many of these were surrounded by cotton, corn, wheat, or sorghum. In contrast, 25 playas never dried, and most of these were surrounded by urban development. Median hydroperiod was 17–109 days, being longer during the relatively wet year of 2010 compared to exceptional drought in 2011. Remote sensing was useful in monitoring playa surface water fluctuations as a function of land use, providing an alternative source of data in the absence of ground-based hydrological records, and granting a temporal perspective that may otherwise not exist for seasonal or ephemeral wetlands.

지하댐 건설로 인한 지하수 증가량 계산 및 유황 분석

지하수 , 지하댐, 유효공극률 , 유황곡선 , 대체 수자원This paper aims to calculate the increase in groundwater quantity following groundwater dam construction, and toassess its impact on surface water. In the study area of Osib-cheon, Yeongdeok, we estimated groundwater quantity,groundwater level, and effective porosity, and examined surface water fluctuations with respect to the increasedgroundwater quantity based on the flow duration. The results reveal that the increased groundwater quantity was atmost 91,746 m

Water level stabilization in open channels using Chebyshev polynomials and teaching–learning-based optimization

Water level fluctuations in open channels can cause serious problems for conveyance systems which lead to economical and performance issues. The problem of water level stabilization in open channels containing two pumping stations at both ends is investigated in this paper. The optimal control that should be imposed at one end of the channel to minimize water surface fluctuations due to sudden increase in water demand at the other end is determined. Chebyshev polynomials are effectively hybridized with a modern teaching–learning-based optimization algorithm for the first time to estimate the optimal control. An efficient shock-capturing model is used to evaluate the value of the objective function. Results are compared with those obtained by the variational approach. The optimal control found by the proposed method shows fewer fluctuations in water level than that found by the variational method. Moreover, the proposed approach is easier to implement and to extend for solving more general problems.

Three-dimensional Computations of Water–Air Flow in a Bottom Spillway During Gate Opening

Undesired entrainment of air in a bottom spillway often leads to problems in both safety and operational functions. A numerical analysis of a transient process of air entrainment into bottom spillway flows when a spillway gate is opened was conducted in this study. The Volume of Fluid (VOF) model was used. The 3D computational domain consisted of a spillway conduit, a moving bulkhead gate, a gate shaft, an upstream reservoir and a downstream outlet. The large number of cells, together with the dynamic mesh modelling of the moving gate, required substantial computational resources, which necessitated parallel computing on a mainframe computer. The simulations captured the changes in the flow patterns and predicted the amount of air entrainment in the gate shaft and the detrainment downstream, which help in the understanding of the system behaviour during opening of the spillway gate. The initial conduit water level and the gate opening procedure affect the degree of air entrainment in the gate shaft. To release the undesired air, a de-aeration chamber with a tube leading to the atmosphere was added to the conduit. Despite the incomplete air release, the de-aeration chamber was found to be effective in reducing water surface fluctuations in the downstream outlet.

The Experimental Research of Stabilize Water Delivery on Varying Water Head and Non Pressure Water Tunnel

The simple and efficient facilities of steady flow and wave elimination-flow-stabilizing plate and wave-eliminating barrier were introduced to study strong water surface fluctuation existing in free flow tunnel in Aan water project, through comparative trial and fluctuation analysis, it could be found that the introduction of steady-flow and wave-elimination facilities could stabilize the flow pattern of free flow tunnel.

Analytical study of the water surface fluctuations induced by grid-stirred turbulence

The free surface dynamics excited by grid stirred turbulence is analysed with a Lagrangian approach, with the analytical model calibrated by using experimental results. The Lagrangian model for free surface oscillations has been developed by assuming that coherent structures in the water layer close to the free interface have the shape of blobs and are mobilized by a periodic force. The blobs are assumed to behave like nonlinear oscillators with different spring stiffness in upwelling and downwelling and neglecting viscosity as first approximation. In order to calibrate the model, a set of experiments in a grid stirred tank was used where free surface elevation time series were measured and all the necessary variables were computed.Through calibration and with some working assumptions, the radius of the blobs is shown to be of the order of the integral vertical length scale of turbulence. The forced oscillations are analysed by the method of Rauscher (1938) [1] to predict the amplitude of the oscillations, possible resonances and discontinuities in the amplitude–frequency space. If the forcing term has multiple harmonics, in some cases a blow up of the oscillator is forecast. Some tests including a small damping, in order to evaluate the effects of viscosity, show that a jump is expected in the amplitude–frequency diagram and a range of unstable frequency. The presence of a small damping should also prevent the blow up for multiple harmonics in the forcing term.

Computation of Filling Time of a Ship Lock

In this paper, Steady-flow Integration Approach (SIA) and Volume of Fluid (VOF) method are both used to calculate the filling time of a ship lock. The values of filling time derived from these two different methods have the same order of magnitude. SIA is only used to give a quick but coarse estimation; however in the application of more time-consuming VOF approach, the fluctuations of water surface are additionally considered and computed, It provides a more precise estimation of the filling time and a more realizable details about the filling process. In practical engineering, the geometry of ship lock will be far more complex than here; the SIA is not enough to satisfy the demands for a desired design. The VOF method will be a nice choice and give reasonable predictions of filling time, water fluctuations and velocity fields in the ship lock.

Recombination, Dissociation, and Transport of Ion Pairs across the Liquid/Liquid Interface. Implications for Phase Transfer Catalysis

Molecular dynamics simulations are used to calculate several free energy profiles relevant to the recombination/dissociation and transport of individual ions and ion pairs across the water/chloroform interface. Tetra methyl ammonium (TMA(+)) and tetra butyl ammonium (TBA(+)) (typically used as phase transfer catalysts) and a chloride ion (as an example of a transferred nucleophile) are considered. The free-energy profiles for the transfer of the three ions and the two ion pairs (TMA(+)Cl(-) and TBA(+)Cl(-)) across the interface, as well as the potential of mean force for the dissociation of these two ion pairs at different interface locations, are calculated and correlated with structural and energetic changes at the interface. These equilibrium calculations, together with nonequilibrium trajectory calculations, provide molecular insight into the mechanism of phase transfer catalysis. In particular, water surface fluctuations are strongly coupled to the ion-pair location along the interface normal and the ion-pair bond length.

WAVE HEIGHTS RECOVERY FROM SUBSURFACE PRESSURES UPON A SMALL VERTICAL CYLINDER

In this paper, the fluctuation of water surface has been recovered from subsurface dynamic pressures exerted on a small vertical cylinder of a tripod structure and it finds that the wave heights can be estimated accurately from the pressures measured at θ = 180°. Seven pressure transducers were mounted around the cylinder to get the circumference distribution of the dynamic pressures. The time histories of the water surface fluctuations and the concurrent dynamic pressures upon the cylinder have been analyzed in frequency domain. A part of the linear diffraction theory of MacCamy & Fuchs has been applied to analyze the experimental data. Additionally, the empirical factor, which is the ratio of the measured and recovered wave height, is presented.

浅場表層の間隙水圧変動の影響を考慮した人工浅場の地形変化解析

Topographic change of an artificial shallow is investigated using a fluid-sediment interaction model combined with a sediment transport model considering pore-water pressure in the surface layer of the seabed. From a comparison with hydraulic experiments, it is demonstrated that the model can predict experimental data reasonably well in terms of water surface fluctuation, flow velocity, and pore-water pressure. Numerical results of the topographic change of the shallow show that pore-water pressure has a reducing effect on sediment transport and resulting topographic change from the upper part of the slope to the crown of the shallow, and demonstrate that the predictive capability of the model for the topographic change of the shallow is improved by the consideration of the pore-water pressure in the sediment transport model.

An investigation into the interaction of a grazing angle broadband spherical audio signal with the dynamically rough air–water interface of shallow flows in rivers and channels

Laboratory measurements were made of a broadband audio signal transmitted and received at grazing angles over a range of shallow water flow regimes. Synchronous measurements of local surface fluctuation were taken using a thin-wire wave gauge positioned at the point of specular reflection. The first and second statistical moments of the acoustic intensity at the receiver are shown to be directly related to the second statistical moment of the water surface fluctuations. It was hypothesized that this relationship was due to the path-length of the dominant signal fluctuating in direct relation to the interface fluctuations at the specular reflection point. This hypothesis is corroborated by analysis of the second statistical moment of the “time-of-flight” of the surface-reflected signal, and by direct analysis of the instantaneous water surface position.

WATER SURFACE FLUCTUATION AND ITS ADVECTION FEATURE OF TURBULENT FLOW WITH HEMISPHERIC ROUGHNESS ELEMENTS ANALYZED BY LES WITH IMMERSED BOUNDARY METHOD

In non-intrusive river flow measurements such as imaging or radar techniques, water surface irregularities in turbulent flow condition is assumed advected with the surface flow. The surface irregularities are usually considered to be induced by turbulence originated from boil vortices generated near the rough bed. However, the relationship between bottom roughness and water surface fluctuation is not well understood so far. Therefore, we conducted experimental and numerical investigations with relatively simple bed roughness composed of hemispheres. Particle tracing velocimetry (PTV) technique is applied in the experiment and the large eddy simulation (LES) with immersed boundary method (IBM) is used in the simulation. It was made clear that the numerical simulation reproduces the water surface fluctuation fairly well and advection speed of surface pattern can represent the surface flow velocity.

Feasibility of curtain weir installation for water quality management in Daecheong Reservoir

The study was aimed to determine the optimal location of a vertically moveable curtain weir in Daecheong Reservoir (Korea) and to assess its effectiveness for the control of algal bloom in the reservoir. A laterally averaged two-dimensional hydrodynamic and eutrophication model (CE-QUAL-W2) was used to simulate water quality variables and the effect of curtain weir. The original model was modified to accommodate vertical displacement of the weir according to the water surface fluctuation. The model calibrated in a previous study was validated for different hydrological conditions representing drought year (2008) and normal year (2006) for the study, and adequately reproduced the temporal and spatial variations of temperature, nutrients and phytoplankton concentrations. The performance of curtain weir on the control of algal bloom was assessed by applying the validated model to 2001 when an abnormal mono-specific bloom of the Microcystis aeruginosa had developed and 2006 based on 9 different installation s...

Field investigations on port non-tranquility caused by infra-gravity water waves

Field investigations have been carried out in two 60-day stages on the surf beat low frequency waves in Anzali port, one of the main commercial ports in Iran, located in southwest coast of the Caspian Sea. The characteristics of significant water waves were measured at three metering stations in the sea, one at the entrance of the port and three in the basin. The measured data were inspected to investigate the surf beat negative effects on the tranquility of the port. Using field measurements and complementary numerical modeling, the response of the basin to the infra-gravity long waves was inspected for a range of wave frequencies. It was concluded that the water surface fluctuations in the port is strongly related to the incident wave period. The long waves with periods of about 45s were recognized as the worst cases for water surfaceperturbation in the port. For wave periods higher than the mentioned range, the order of fluctuation was generally low.

Field investigations on port non-tranquility caused by infra-gravity water waves

Field investigations have been carried out in two 60-day stages on the surf beat low frequency waves in Anzali port, one of the main commercial ports in Iran, located in southwest coast of the Caspian Sea. The characteristics of significant water waves were measured at three metering stations in the sea, one at the entrance of the port and three in the basin. The measured data were inspected to investigate the surf beat negative effects on the tranquility of the port. Using field measurements and complementary numerical modeling, the response of the basin to the infra-gravity long waves was inspected for a range of wave frequencies. It was concluded that the water surface fluctuations in the port is strongly related to the incident wave period. The long waves with periods of about 45s were recognized as the worst cases for water surfaceperturbation in the port. For wave periods higher than the mentioned range, the order of fluctuation was generally low.

Sensitivity Analysis on Relations Between Earthquake Source Rupture Parameters and Far-Field Tsunami Waves: Case Studies in the Eastern Mediterranean Region

We present several sensitivity tests, that were applied to exhibit the effects of earthquake source rupture characteristics on amplitudes, frequency contents and arrival times of earthquake generated tsunami waves in the far field, as case studies in the eastern Mediterranean. The investigated earthquake parameters are principally epicentral location, focal mechanism parameters (strike, dip and rake angles), faulting area dimensions, maximum displacement and focal (centroid) depth. We have implemented a numerical method of TUNAMI-N2 based on non-linear shallow-water theory to obtain synthetic water surface fluctuations at selected pseudo tide gauge locations in the eastern Mediterranean. It has been observed that the most important source parameters that effect tsunami wave characteristics in the far field are: [1] magnitude and seismic moment (Mo= m × A × D) of earthquake that is a measure of the energy release radiated at the centroid depth. We have observed that wave amplitudes and shapes change considerably with variation of magnitude and seismic moment since tsunami waves develop in direct proportional relation to them; [2] another parameter is the accurate estimation of tsunamigenic earthquake epicentre. Variation of the earthquake location does not significantly affect the initial tsunami wave heights, but final tsunami wave characteristics and their arrival times have been slightly changed due to the variation of distance between the epicentre and coastal plains along the path. Especially, wave spreading causes tsunami waves to decrease in amplitude as they move away from earthquake source; [3] variation in focal mechanism solutions modify the tsunami wave propagation directions, wave amplitudes, shapes and arrival times of tsunami waves observed at the coastal plains; [4] in addition, due to the linearity between the amount of vertical co-seismic displacement and initial tsunami wave, very different tsunami amplitudes were obtained at each pseudo tide gauge stations in case of the variation in maximum displacement; [5] details of local bathymetry (e.g., extended sedimentary shelf area) and the sea bottom irregularities (e.g., sea-mounts, volcanoes, accretionary prisms, trenches, pressure ridges) clearly have crucial effects on tsunami wave characteristics in the far field. Historical records confirm that the eastern Mediterranean region is at risk from tsunamigenic sources located on the Hellenic-Cyprus arcs. Thus, higher resolution near-shore bathymetry data as well as a detailed study of potential tsunami sources in segments of subduction zones are necessary to verify our simulation results.

Water Level Sensor based on a New Design Structure for Irrigation Water Measurement

The objective of this study was to design a new water level sensor for irrigation water measurement to reduce the investment of water measuring equipment required for agriculture management. Based on ultrasonic pulse-echo technology, a new hardware structure including an ultrasonic transmission circuit, echo receiver circuit, data output circuit and micro control unit (MCU) were described in this paper. A specially designed pulse transformer and a drive circuit based on the NEC555 were used to improve the driving capability for ultrasonic transducers. A low cost but has a high quality for accepting circuit was adopted based on Sony Corporation's infrared demodulator, CX20106A. Output circuit which based on the RS232 interface using multichannel RS-232 Drivers-Receivers MAX232 was used to output the dates, this circuit is simple and easy to extend. In addition, an IC card (corn is 64K SPI Bus Serial EEPROM, AT24C64) based correction parameters input circuit was adopted. Furthermore, some factors, such as temperature, water surface fluctuation and process response time etc. which influence accuracy were discussed. Then, the corresponding corrections methods not only include hardware methods but also include software methods were proposed. A temperature detection module which based on a digital sensor, the Dallas Semiconductor™ DS18B20, was added to the hardware systems. At the same time, in order to reduce the process response time of program written in C51 language in the MCU control system, the integration programming technology using C51 language and assembler language was used. Besides, voltage conversion and power supply circuits based on three-port voltage regulator circuit LM7805 and LM7808 was designed. The test result shows that this design has a high accuracy and stability. It is possible to get water level data with small errors, and this design reduces the production cost.

Sensitivity Analysis on Relations Between Earthquake Source Rupture Parameters and Far-Field Tsunami Waves: Case Studies in the Eastern Mediterranean Region

We present several sensitivity tests, that were applied to exhibit the effects of earthquake source rupture characteristics on amplitudes, frequency contents and arrival times of earthquake generated tsunami waves in the far field, as case studies in the eastern Mediterranean. The investigated earthquake parameters are principally epicentral location, focal mechanism parameters (strike, dip and rake angles), faulting area dimensions, maximum displacement and focal (centroid) depth. We have implemented a numerical method of TUNAMI-N2 based on non-linear shallow-water theory to obtain synthetic water surface fluctuations at selected pseudo tide gauge locations in the eastern Mediterranean. It has been observed that the most important source parameters that effect tsunami wave characteristics in the far field are: [1] magnitude and seismic moment (M_o= \mu × A × D) of earthquake that is a measure of the energy release radiated at the centroid depth. We have observed that wave amplitudes and shapes change considerably with variation of magnitude and seismic moment since tsunami waves develop in direct proportional relation to them; [2] another parameter is the accurate estimation of tsunamigenic earthquake epicentre. Variation of the earthquake location does not significantly affect the initial tsunami wave heights, but final tsunami wave characteristics and their arrival times have been slightly changed due to the variation of distance between the epicentre and coastal plains along the path. Especially, wave spreading causes tsunami waves to decrease in amplitude as they move away from earthquake source; [3] variation in focal mechanism solutions modify the tsunami wave propagation directions, wave amplitudes, shapes and arrival times of tsunami waves observed at the coastal plains; [4] in addition, due to the linearity between the amount of vertical co-seismic displacement and initial tsunami wave, very different tsunami amplitudes were obtained at each pseudo tide gauge stations in case of the variation in maximum displacement; [5] details of local bathymetry (e.g., extended sedimentary shelf area) and the sea bottom irregularities (e.g., sea-mounts, volcanoes, accretionary prisms, trenches, pressure ridges) clearly have crucial effects on tsunami wave characteristics in the far field. Historical records confirm that the eastern Mediterranean region is at risk from tsunamigenic sources located on the Hellenic-Cyprus arcs. Thus, higher resolution near-shore bathymetry data as well as a detailed study of potential tsunami sources in segments of subduction zones are necessary to verify our simulation results.

Hydrodynamics of a Concentric Twin Perforated Circular Cylinder System

An experimental investigations was carried out on a perforated circular cylinder (0.50m diameter) encircling an impermeable cylinder (0.05m diameter) at a constant water depth of 0.7m for both regular and random waves in the wave flume at the Department of Ocean Engineering, Indian Institute of Technology, Madras, India. The porosity of the outer cylinder was varied from 4.54 to 19.15% to study the influence of porosity on wave forces on and water surface fluctuations in and around the twin cylinder system. A numerical method is developed based on the boundary integral equation method along with a porous body boundary condition, where the porosity is modeled using the resistance coefficient f and added mass coefficient Ca for regular waves. The resistance coefficient increases with the increase in porosity and wave heights except for a porosity of 4.54%, whereas the added mass coefficient is almost zero. Porosity in the range of 10–15% can be recommended for the perforated cylinder based on the experimental results of wave forces and the water surface fluctuations inside the perforated cylinder.

STUDY ON THE UNSTEADY DISCHARGE CHARACTERISTICS OF THE SPILLWAY CREST GATES

The hysteresis phemena which can occur in transition between gated flow and free flow are experimentally clarified, and the profile and the fluctuation of water surface and the velocity profile under the relationship among the water hight, the gate opening and the discharge is described as the discontinuous condition in transition. And then, the unsteady discharge characteristics in transition are experimentally analyzed, and the validiity of the propose equation is confirmed though the comparision with the discharge based on the velocity. In addition, it appears that the numerical simulation model using the incompressible fluid analysis and VOF can simulate the hysteresis phenomena in transition.