Volume Flux Research Articles

Cohesive Channel Response to Watershed Urbanization: Insights from the Sand River, Aiken SC

Stream channel degradation is among the most widely documented symptoms of urban stream syndrome arising from watershed urbanization. Nevertheless, our present understanding of space and time scales associated with channel response to urbanization is poorly constrained and largely limited to assessments of non-cohesive systems. The purpose of this study is to assess the evolution of a cohesive, ephemeral river channel in response to watershed urbanization. The assessment of historical images document the stable, pre-urbanized channel conditions from 1870 to 1930. Historical assessments revealed a 131% increase in urbanized watershed area from 1930 to 1992, and a minimal increase in urbanized extent from 1992 to 2012. A 2012 lidar dataset was used to generate the modern long-channel profile, to reconstruct cross-channel profiles observed in 2002, and to estimate the volume flux of sediment removed from the channel from 1930 to 1992, and from 1992 to 2012. The long-channel profile reveals incision of up to 35 m in response to urbanization from 1930 to 1992. Cross-channel profiles reveal incision and widening of 2.5 and 3 m, respectively, from 2002 to 2012. Volume flux estimates indicate erosion rates of 9000 m3/yr during the first 62 years of the study period, and a flux of 4000 m3/yr after installation of stormwater control measures in 1992. Collectively, our findings highlight a cohesive channel that has undergone substantial incision and widening at a rate of ~0.20 m/yr since 1930, and the channel continues to adjust. Hence, we contend that the channel has not yet attained a new equilibrium “shape” at 82 years after peak land use change within the watershed, and that the channel will continue to adjust its shape until this new balance is achieved.

Contrasting Hydrodynamic Responses to Atmospheric Systems with Different Scales: Impact of Cold Fronts vs. That of a Hurricane

In this paper, subtidal responses of Barataria Bay to an atmospheric cold front in 2014 and Hurricane Barry of 2019 are studied. The cold fronts had shorter influencing periods (1 to 3 days), while Hurricane Barry had a much longer influencing period (about 1 week). Wind direction usually changes from southern quadrants to northern quadrants before and after a cold front’s passage. For a hurricane making its landfall at the norther Gulf of Mexico coast, wind variation is dependent on the location relative to the location of landfall. Consequently, water level usually reaches a trough after the maximum cold front wind usually; while after the maximum wind during a hurricane, water level mostly has a surge, especially on the right-hand side of the hurricane. Water level variation induced by Hurricane Barry is about 3 times of that induced by a cold front event. Water volume flux also shows differences under these two weather types: the volume transport during Hurricane Barry was 4 times of that during a cold front. On the other hand, cold front events are much more frequent (30–40 times a year), and they lead to more frequent exchange between Barataria Bay and the coastal ocean.

Vertically distributed wall sources of buoyancy. Part 1. Unconfined

Abstract

The Eutrophication of the Baltic Sea has been Boosted and Perpetuated by a Major Internal Phosphorus Source

The phosphorus (P) concentration c1 in the surface layer of the Baltic proper in winter depends on the land-based P source LPS, and the ocean P source OPS, which are known. It also depends on the internal P source IPS from anoxic bottoms and the sum of internal and external P sinks TPsink, which are estimated in this paper. IPS is parameterized as fs·Aanox, where fs is the specific annual mass flux of P from anoxic sediments and Aanox is the area of anoxic bottoms, and TPsink is parameterized as c1·TRVF, where TRVF is the total removal volume flux. We use a time-dependent P budget model, and 47 years of observational data, and the method of least squares to determine the best estimates of the unknown parameters fs and TRVF. The result is TRVF = 3,000 km3 year−1 and fs = 1.22 tons P km−2 year−1. With these parameter values, the model gives a quite good description of the observed evolution of c1. The observed runaway evolution of c1, with increasing c1 since the 1980s although the land-based supply LPS has been halved, is well-described by the model. It is concluded that the internal P source IPS provides a positive feedback mechanism that has boosted and perpetuated the eutrophication of the Baltic proper and that IPS is the major driver of the Baltic Sea eutrophication since the late 1990s. It is suggested that measures to eliminate IPS should be included in the management strategy to reduce the eutrophication of the Baltic proper.

Sound Field Properties of Non-Cavitating Marine Propellers

The sound field properties of non-cavitating marine propellers are investigated using a hybrid method, in which the FWH (Ffowcs William-Hawkings) analogy is coupled with the BEM (Boundary Element Method) approach. The investigations include both the uniform and non-uniform inflow conditions. For both conditions, the dominant sound source terms and the decay rate of the noise with regard to the distance to propeller centre are investigated. The influence of the permeable surface dimensions in the permeable FWH approach on the hydroacoustic result is also investigated. To carry out the investigations, the formulation to calculate acoustic pressure generated by the propeller wake sheet is proposed for the first time. The issues associated to coupling permeable FWH approach and BEM are also discussed, including the fictitious volume flux problem and the consideration of the ship wake field. It was found that the influence of the permeable surface dimension is little for the 1st BPF (Blade Passage Frequency), but cannot be ignored for the 3rd BPF. In the uniform inflow situation the thickness terms are found to be dominant, while in the non-uniform inflow situation the loading terms are dominant.

Laser diagnostics of atomization and combustion of kerosene in a model combustion chamber

The experimental results are presented of implementation of a built-up laser-based diagnostic system at a test rig for investigations of the flame tube heads of aircraft gas turbine engines, both existing and being under development. At this test rig the processes of liquid fuel atomization and mixing with air by flame tube heads of model combustion chambers equipped with newly-developed atomizers, and of combustion of the fuel–air mixture formed in the flow have been studied. These studies enable development and optimization of advanced low-emission engines satisfying the established environmental requirements for the levels of polluting species in the exhaust gases. By using the particle shadow velocimetry technique with a pair of 10 μs delayed 5 ns laser pulses the transverse spatial distributions of average kerosene droplet dimensions, the axial components of their average velocity, and of the average volume flux of the fuel have been measured in the mixture flow axial cross-section. By employing coherent anti-Stokes Raman scattering with 10 ns pump laser pulses at 10 Hz repetition rate during combustion of the produced kerosene–air mixture the statistical characteristics of local ‘instantaneous’ gas temperature fluctuations in the flame, slow variations of these temperatures in time during the combustion process, and transverse distributions of average temperatures in the flame axial cross-section have been measured.

Experimental air/particle flow characteristics of an 80,000 Nm3/h fly ash entrained-flow gasifier with different multi-burner arrangements

A novel burner arrangement for entrained-flow pulverized coal gasifier with multiple low-set burners, which burners are arranged to be counter-biased, is proposed aimed at mitigating high-temperature corrosion to the wall. To verify the characteristics of this improvement in an 80,000 Nm3/h fly ash entrained-flow gasifier, experiments were conducted on the model to investigate the impact of six burners being co-biased, opposed and counter-biased on the air/particle flow field by using a particle dynamics anemometer. The results show that, on the horizontal cross-section passing through burner centerlines with co-biased burners, opposed burners and counter-biased burners, the radius of mixing zone is 0.196, 0.16 and 0.174; the ratio of total particle volume flux in the near-wall region to the total particle volume flux in the measurement zone was 76.5%, 26.1% and 57.8%, respectively. On the vertical cross-section above burner outlet, the radius of central recirculation zone with co-biased burners remains to expand to 0.88 while that of counter-biased burners gradually shrinks to 0.33. There is no central recirculation zone under opposed burners; air and particle swirl numbers are close to zero. This study shows that new burner arrangement could ease high-temperature corrosion to gasifier wall and strengthens mixing of burner jets.

Numerical Simulation of Thawing Process in Frozen Soil

Permafrost has been thawing faster due to climate change which would release greenhouse gases, change the hydrological regimes, affect buildings above, and so on. It is necessary to study the thawing process of frozen soil. A water-heat coupling model for frozen soil thawing is established on Darcy’s law and Heat Transfer in Porous Media interfaces in Comsol Multiphysics 5.5. Three curves of total liquid water volume, minimum temperature, and total heat flux in the thawing process are obtained from a numerical simulation. The distributions of liquid water, temperature, and pressure based on time are simulated too. The liquid water distribution is consistent with the total liquid water volume curve. The temperature distribution is confirmed by the minimum temperature and total heat flux curve. The pressure distribution represents ice in the frozen soil that generates negative pressure during the melting process. The numerical simulation research in this article deepens the understanding of the internal evolution in the process of frozen soil thawing and has a certain reference value for subsequent experimental research and related applications.

Key Role of Diabatic Processes in Regulating Warm Water Volume Variability over ENSO Events

AbstractThe equatorial Pacific warm water volume (WWV), defined as the volume of water warmer than 20°C near the equator, is a key predictor for El Niño–Southern Oscillation (ENSO), and yet much about the individual processes that influence it remains unknown. In this study, we conduct idealized ENSO simulations forced with symmetric El Niño– and La Niña–associated atmospheric anomalies as well as a historical 1979–2016 hindcast simulation. We use the water mass transformation framework to examine the individual contributions of diabatic and adiabatic processes to changes in WWV. We find that in both sets of simulations, El Niño’s discharge and La Niña’s recharge periods are initiated by diabatic fluxes of volume across the 20°C isotherm associated with changes in surface forcing and vertical mixing. Changes in adiabatic horizontal volume transport above 20°C between the equator and subtropical latitudes dominate at a later stage. While surface forcing and vertical mixing deplete WWV during El Niño, surface forcing during La Niña drives a large increase partially compensated for by a decrease driven by vertical mixing. On average, the ratio of diabatic to adiabatic contributions to changes in WWV during El Niño is about 40% to 60%; during La Niña this ratio changes to 75% to 25%. The increased importance of the diabatic processes during La Niña, especially the surface heat fluxes, is linked to the shoaling of the 20°C isotherm in the eastern equatorial Pacific and is a major source of asymmetry between the two ENSO phases, even in the idealized simulations where the wind forcing and adiabatic fluxes are symmetric.

Tidal Modulation of Buoyant Flow and Basal Melt Beneath Petermann Gletscher Ice Shelf, Greenland.

A set of collocated, in situ oceanographic and glaciological measurements from Petermann Gletscher Ice Shelf, Greenland, provides insights into the dynamics of under‐ice flow driving basal melting. At a site 16 km seaward of the grounding line within a longitudinal basal channel, two conductivity‐temperature (CT) sensors beneath the ice base and a phase‐sensitive radar on the ice surface were used to monitor the coupled ice shelf‐ocean system. A 6 month time series spanning 23 August 2015 to 12 February 2016 exhibited two distinct periods of ice‐ocean interactions. Between August and December, radar‐derived basal melt rates featured fortnightly peaks of 15 m yr which preceded the arrival of cold and fresh pulses in the ocean that had high concentrations of subglacial runoff and glacial meltwater. Estimated current speeds reached 0.20 – 0.40 m s during these pulses, consistent with a strengthened meltwater plume from freshwater enrichment. Such signals did not occur between December and February, when ice‐ocean interactions instead varied at principal diurnal and semidiurnal tidal frequencies, and lower melt rates and current speeds prevailed. A combination of estimated current speeds and meltwater concentrations from the two CT sensors yields estimates of subglacial runoff and glacial meltwater volume fluxes that vary between 10 and 80 m s during the ocean pulses. Area‐average upstream ice shelf melt rates from these fluxes are up to 170 m yr, revealing that these strengthened plumes had already driven their most intense melting before arriving at the study site.

Note on de Sitter vacua from perturbative and non-perturbative dynamics in type IIB/F-theory compactifications

The properties of the effective scalar potential are studied in the framework of type IIB string theory, taking into account perturbative and non-perturbative corrections. The former modify the Kähler potential and include α′ and logarithmic corrections generated when intersecting D7 branes are part of the internal geometric configuration. The latter add exponentially suppressed Kähler moduli dependent terms to the fluxed superpotential. The possibility of partial elimination of such terms which may happen for particular choices of world volume fluxes is also taken into account. That being the case, a simple set up of three Kähler moduli is considered in the large volume regime, where only one of them is assumed to induce non-perturbative corrections. It is found that the shape of the F-term potential crucially depends on the parametric space associated with the perturbative sector and the volume modulus. De Sitter vacua can be obtained by implementing one of the standard mechanisms, i.e., either relying on D-terms related to U(1) symmetries associated with the D7 branes, or introducing D3‾ branes. In general it is observed that the combined effects of non-perturbative dynamics and the recently introduced logarithmic corrections lead to an effective scalar potential displaying interesting cosmological and phenomenological properties.

Effects of photomultiplier tube voltage setting on phase-Doppler measurements

ABSTRACT Phase Doppler measurement devices have established themselves as an alternative to laser diffraction-based measurements for recording spray drop size distributions. In addition, phase Doppler devices also provide droplet velocities and volume flux. One limitation of the phase Doppler systems that is not discussed often in the literature is their sensitivity to the amplification voltage used on the photo-multiplier tube (PMT) detector. The correct value of voltage to use depends on the spray density, and so a calibration must be made for each spray by mechanically measuring the flux at a point in the spray. Phase Doppler output parameters (drop sizes, velocities, validation rate, and derived parameters) were measured as a function of voltage in a fixed location in a water spray. The measurements of volume median diameter were not as sensitive to the voltage setting as the volume flux measurements, which may be why the issue of voltage sensitivity is not discussed much in the literature. The contributions of the current work are: for the first time, measurements of sensitivity of DV 05 and LWC to PMT voltage settings in PDI are reported, as well as the details of the different validation parameters instead of only the overall validation rate.

Performance Analysis of a Roundabout and a 3 leg Intersection Under Heterogeneous Traffic

This paper addresses the analysis of the operational performance of a roundabout and a 3-legged intersection located in quite a busy area of the Aligarh city. The city has an urban population of around 0.9 million people. The roundabout and 3-legged intersection are located in the close proximity of busy commercial areas and schools. Roundabout that has been taken under consideration is un-signalized and 3-legged intersection is priority controlled. The Current study has been undertaken analyze the operational execution of the two intersections and to pave the way for forthcoming investigations related to improvement of the intersections in the Aligarh District region. Traffic data was accumulated on weekdays during peak periods (5:30 pm to 6:30 pm). Video recording was taken in consideration to accomplish this task. The traffic was categorized in 3 classes; light vehicles, heavy vehicles and bicycles. To execute the evaluation of functioning performance of both intersections, SIDRA INTERSECTION software has been used. Results have shown that both the roundabout and 3-legged intersection are operating nearly at their maximum capacities and Level of Service (LOS) is not adequate for such amount of traffic influx into both the intersections. Volume to capacity (v/c) ratio has revealed that both the roundabout and 3-legged intersection are in an unstable state and roundabout condition is worse than the 3-legged intersection as the heavy vehicle volume influx is quite higher for the roundabout.

Analytical and experimental study of stress sensitivity effect on matrix / fracture transfer in fractured tight reservoir

In fractured tight reservoirs, the stress sensitivity effect has important impacts on the law of pressure diffusion as well as the matrix/fracture transfer flow, which is the main fluid migration way. In this paper, the stress sensitivity effect is considered to establish the matrix/fracture transfer flow model, and the transfer shape factor and transfer function are deduced. According to the characteristics of the simplified model, the 1D and 2D matrix/fracture transfer flow experiments considering the stress sensitivity effect are designed, and the theoretical model is verified. Then, the stress sensitivity tests and transfer flow experiments are carried out, the influences of stress sensitivity factors (lithology, initial permeability and effective stress) on transfer flow are studied. The experiment results show that the average errors of matrix average pressure, transient transfer flow and cumulative transfer volume flux are 3.6%, 4.8% and 5.2% respectively, and the calculation accuracy is high. The stress sensitivity of the Glutenite is the strongest, the Turbidite the middle and the Beach bar sand the weakest; the smaller the initial value of permeability is, the stronger the stress sensitivity is; the bigger the effective stress is, the more the permeability loss is. Due to the differences of stress sensitivity effect, the stronger the stress sensitivity is, the faster the transient transfer flow rate drops, and the fewer the cumulative transfer volume flux is. The new transfer flow model is applied to the well test interpretation theory, and the fitting results of the real pressure build-up data show that the new well test type curve has better fitting effect on the unsteady matrix/fracture transfer stage with an error of 4.2%, which is 25.6% lower than that of the classic theory.

Comparative Study of Plane Poiseuille Flow of Non-isothermal Couple Stress Fluid of Reynold Viscosity Model using Optimal Homotopy Asymptotic Method and New Iterative Method

In this paper, we have explored the steady Poiseuille flow of couple stress fluid between two parallel plates under ‎the influence of non-isothermal effects of Reynold viscosity model, using Optimal Homotopy Asymptotic Method ‎‎(OHAM) and New Iterative Method (NIM). We obtained expressions for velocity profile, temperature distribution, ‎average velocity, volume flux and shear stress. The solutions obtained using these methods are in the form of ‎infinite series; therefore, they can be easily computed. Comparative results of solutions obtained by both methods ‎are given using different tables and graphs.

Lava Discharge Rate of Sinabung Volcano Obtained from Modis Hot Spot Data

DOI:10.17014/ijog.7.3.241-252To find out the long term data of Sinabung magma discharge rate and how long a series of eruption will be ended, time series of the volume of magma discharge is required. The dominant eruption product is pyroclastic flow that begins with the growth of the lava dome, so it is important to determine the volume of the lava dome over time. The method of determining the volume of magma issued is carried out by using hotspot data to resolve the problem of prevented visual observations and ground measurements. The heat and volume flux data expressed within a long period for a better view of variations in the Sinabung volcanic activity are based on thermal satellite data. Related lava dome volume and seismic data are also displayed to be compared with the heat and volume flux data. The numbers of thermally anomalous pixels and sum of radiance for all detected pixels at Sinabung during an overpass in the period of 2014 to 2018 have a downward trend. The discharge rates in the period of January 2014 to April 2015, Mei 2015 to March 2016, April 2016 to March 2017, and June 2017 to February 2018 are 0.86 m3/sec, 0.59 m3/sec, 0.36 m3/sec, and 0.25 m3/sec, respectively. Assuming no new intrusion or deformation rate changes, the lava discharge will be in the lowest rate in the early 2020s.

Field observations of sea spray under Tropical Cyclone Olwyn

Sea spray comprises liquid droplets that cover a broad range of radii, from 0.01 to 1000 μm. For field observations, it is difficult to measure the sea spray size distribution over the full range of radii, particularly as spray production is associated with extreme weather conditions. As a result, differences in magnitude of the sea spray production estimates reach 6 orders. In this study, the sea spray volume flux (SSVF) was measured by laser altimeters under Tropical Cyclone Olwyn in the Indian Ocean. The results show that the SSVF increases gradually with the wind speed and is approximately 2 orders of magnitude larger than the results of two laboratory experiments and existing sea spray generation functions. The SSVF is also influenced by the sea state. When the nondimensional significant wave height is factored in a new parameter $$ {R}_B{\left({u}_{\ast}^2/{gH}_s\right)}^{1/3} $$ , the correlation coefficients are improved, increasing to 0.85 and 0.88. Finally, a new parameterization for SSVF generation function is proposed in terms of the nondimensional wave height and windsea Reynolds number RB.

Influence of mass air flow ratio on gas-particle flow characteristics of a swirl burner in a 29 MW pulverized coal boiler

In a gas/particle two-phase test facility, a three-component particle-dynamics anemometer was used to measure the characteristics of gas/particle two-phase flows in a 29 megawatt (MW) pulverized coal industrial boiler equipped with a new type of swirling pulverized coal burner. The distributions of three-dimensional gas/particle velocity, particle volume flux, and particle size distribution were measured under different working conditions. The mean axial velocity and the particle volume flux in the central region of the burner outlet were found to be negative. This indicated that a central recirculation zone was formed in the center of the burner. In the central recirculation zone, the absolute value of the mean axial velocity and the particle volume flux increased when the external secondary air volume increased. The size of the central reflux zone remained stable when the air volume ratio changed. Along the direction of the jet, the peak value formed by the tertiary air gradually moved toward the center of the burner. This tertiary air was mixed with the peak value formed by the air in the adiabatic combustion chamber after the cross-section of x/d = 0.7. Large particles were concentrated near the wall area, and the particle size in the recirculation zone was small.

Isolated buoyant convection in a two-layered porous medium with an inclined permeability jump

Abstract

Preferential flow at the darcy scale: Parameters from water content time series

AbstractIn soils, fast preferential flow is limited to infiltration and to small fractions of pore volumes. The viscous flow approach to preferential flow combines these features. The approach is based on thin films whose two parameters—thickness and specific contact area per unit volume of the permeable medium—are deducible from time series of volumetric water contents. Such a time series is the response of the permeable system to an input pulse of known duration and volume flux density. This chapter summarizes the theory, offers a step‐by‐step protocol for determining the two parameters, and applies the approach to water content time series recorded at five depths in a profile of a Mollic Cambisol.