Computation of Electromagnetic Fields Scattered From Objects With Uncertain Shapes Using Multilevel Monte Carlo Method

Computational tools for characterizing electromagnetic scattering from objects with uncertain shapes are needed in various applications ranging from remote sensing at microwave frequencies to Raman spectroscopy at optical frequencies. Often, such computational tools use the Monte Carlo (MC) method to sample a parametric space describing geometric uncertainties. For each sample, which corresponds to a realization of the geometry, a deterministic electromagnetic solver computes the scattered fields. However, for an accurate statistical characterization the number of MC samples has to be large. In this work, to address this challenge, the continuation multilevel Monte Carlo (CMLMC) method is used together with a surface integral equation solver. The CMLMC method optimally balances statistical errors due to sampling of the parametric space, and numerical errors due to the discretization of the geometry using a hierarchy of discretizations, from coarse to fine. The number of realizations of finer discretizations can be kept low, with most samples computed on coarser discretizations to minimize computational cost. Consequently, the total execution time is significantly reduced, in comparison to the standard MC scheme.Comment: 25 pages, 10 Figure

Hydro-meteorological processes driving solute transport in Lake Victoria

This study explores by a vertically integrated tracer transport model, hydro-meteorological event characteristics and their influence on solute transport. Changes in Hydro-meteorological processes and increasing frequency of extreme weather events are responsible for changing the lake water balance, influencing streamflow variations, and lake tracer transport. We compare historical data over a long time with model data from a vertically integrated model in Comsol Multiphysics. We consider water balance, sources of data uncertainty, correlations, extreme rain and inflow years, and seasonal variations. The lake transport model has estimated soluble loading and transportation. The results showed that the lake rainfall is seasonal; there are strong correlations between tributary inflows and precipitation, and between lake outflow and water level. It was found that “events” influence lake level fluctuations. The solute transport was shown to vary more in wet periods. Modeled transportations were higher in Kenya and Uganda lake zones than in Tanzanian zones. The major inflow, from the Kagera river, appears to strongly influence lake solute transportation, so the composition of this river must be considered.QCR 20191106</p

Hydro-meteorological processes driving solute transport in Lake Victoria

This study explores by a vertically integrated tracer transport model, hydro-meteorologicalevent characteristics and their influence on solute transport. Changes in Hydro-meteorologicalprocesses and increasing frequency of extreme weather events are responsible for changingthe lake water balance, influencing streamflow variations, and lake tracer transport. Wecompare historical data over a long time with model data from a vertically integrated modelin COMSOL Multiphysics. We consider water balance, sources of data uncertainty, correlations,extreme rain and inflow years, and seasonal variations. The lake transport model has estimatedsoluble loading and transportation. The results showed there are strong correlations betweentributary inflows and precipitation, and between lake outflow and water level. It was found that“events” influence lake level fluctuations. The solute transport was shown to vary more in wetperiods. Modeled transportations were higher in Kenya and Uganda lake zones than inTanzanian zones. The major inflow, from the Kagera river, appears to strongly influence lakesolute transportation, so the composition of this river must be considered.QC 20231101</p

Developed Numerical Simulation of Falling and Moving Objects in Viscous Fluids under the Action of a Reynolds Lubrication Theory and Low Reynolds Numbers

The development work focuses on the numerical simulations of free body movement in viscous fluid. The aim is to make the simulation of very slow motion of the small body in viscous fluid. We developed bodies’ immersed dynamics simulations in viscous fluid by seeking numerical solutions for appropriate field variables. We developed the methods for vertically and spherically cylindrical objects’ motions, the forces on bodies close to a plane stationary wall are computed from the velocity and pressure fields using the Stokes equation through COMSOL Multiphysics finite element software. The Navier-Stokes equation is reduced to Stokes equation there is independence of time which means object will have an effect only on the motion and the slightly compressible flow assumption is made in order to obtain smooth solution numerically. The forces on an object in slightly compressible Stokes flow have been exerted on the falling objects. The resulting forces have compared with analytical results from the Reynolds Lubrication Theory, and achieved significant results from the development method in Matlab and achieved significant numerical simulations in COMSOL. In addition, an investigation has been madeto an object swimming at low Reynolds number. At low Reynolds number moving is possible when object scale is small and flow pattern is slow and sticky. We have developed a system for a thin two-dimensional (2D) worm-like object wiggle that is passing a wave along its centreline and its motion has simulated by the Ordinary Differential Equations (ODE) system and by the Arbitrary Lagrangian-Eulerian (ALE) moving mesh technology. The development method result shows that it is possible for the small object to have a motion from one position to another through small amplitudes and wavelengths in viscous fluid.QC 20231101</p

Hydro-meteorological processes driving solute transport in Lake Victoria

This study explores by a vertically integrated tracer transport model, hydro-meteorological event characteristics and their influence on solute transport. Changes in Hydro-meteorological processes and increasing frequency of extreme weather events are responsible for changing the lake water balance, influencing streamflow variations, and lake tracer transport. We compare historical data over a long time with model data from a vertically integrated model in Comsol Multiphysics. We consider water balance, sources of data uncertainty, correlations, extreme rain and inflow years, and seasonal variations. The lake transport model has estimated soluble loading and transportation. The results showed that the lake rainfall is seasonal; there are strong correlations between tributary inflows and precipitation, and between lake outflow and water level. It was found that “events” influence lake level fluctuations. The solute transport was shown to vary more in wet periods. Modeled transportations were higher in Kenya and Uganda lake zones than in Tanzanian zones. The major inflow, from the Kagera river, appears to strongly influence lake solute transportation, so the composition of this river must be considered.QCR 20191106</p

Hydro-meteorological processes driving solute transport in Lake Victoria

This study explores by a vertically integrated tracer transport model, hydro-meteorological event characteristics and their influence on solute transport. Changes in Hydro-meteorological processes and increasing frequency of extreme weather events are responsible for changing the lake water balance, influencing streamflow variations, and lake tracer transport. We compare historical data over a long time with model data from a vertically integrated model in Comsol Multiphysics. We consider water balance, sources of data uncertainty, correlations, extreme rain and inflow years, and seasonal variations. The lake transport model has estimated soluble loading and transportation. The results showed that the lake rainfall is seasonal; there are strong correlations between tributary inflows and precipitation, and between lake outflow and water level. It was found that “events” influence lake level fluctuations. The solute transport was shown to vary more in wet periods. Modeled transportations were higher in Kenya and Uganda lake zones than in Tanzanian zones. The major inflow, from the Kagera river, appears to strongly influence lake solute transportation, so the composition of this river must be considered.QCR 20191106</p

Hydrodynamic wind induce model influencing inner Murchison Bay flow circulation

Wind stress is exerted by the wind on the lake surface may be important for lake flow analysis and the Inner Murchison Bay is strongly influenced by urban pollution from Uganda Capital Kampala and bay is highly eutrophic cause of back and forth nutrient movement. The rapid population growth, growing commercial activities and industrialization in Kampala, Uganda coupled with inadequate provision of waste management services which have led to increase volume of urban waste entering the North-Western part of Lake Victoria. The Murchison Bay (MB) is in the Northern part of Lake Victoria in Uganda which has for decades received a daily wastewater load of 0.2 % of its volume from Kampala City of Uganda, through the Nakivubo channel [1]. Kampala City people habitants 1.7 million. The uncontrolled solid waste seen along roadsides and storm water drains enter the Nakivubo Channel. The Nakivubo channel is ended in a papyrus swamp in Uganda that retained a large portion of water pollution before it reached in the inner Murchison Bay [2]. In addition, the channel is widened in 2001-2003 to improve the city drainage which has increased the potential loading of nutrients to the bay. The partially treated effluent from treatment plants are mixed with the water in channel and it contribute a high significant pollution load, and is the most polluted system by organic matter in solid waste and wastewater discharged from slums and un-sewered areas, Luzira Prison and small &amp; large scale industries [3]. There are urgent need to resolve the problem. Nowadays, the inner Murchison Bay (MB) water quality are destroying by several complex mixture processes, Ex.: pollution and nutrients loading, river inflows, un-sewered water, wetland management and flora and fauna populations. Present study is focusing on inner Murchison Bay (MB) water pollution behaviour by using wind speed hydrodynamic model. The model processes are determining the fate and transport of pollutant that are vertically mixing (wind force) and horizontal flow (advection-dispersion) analysis. Vertically transport of wind flow that is forcing on the lake water surface are analysed by the vertically integrated Shallow Water Equation model. Horizontally transport of pollution of water and its flow and speed are analyzing by advectiondispersion and diffusion model. Result shows that the horizontal mixing is continuing with lake nutrients and the vertically wind flow from MB into lake is also determine the mixing of lake water which is not much affecting the lake nutrients. QC 20231101</p

Hydrodynamic wind induce model influencing inner Murchison Bay flow circulation

Wind stress is exerted by the wind on the lake surface may be important for lake flow analysis and the Inner Murchison Bay is strongly influenced by urban pollution from Uganda Capital Kampala and bay is highly eutrophic cause of back and forth nutrient movement. The rapid population growth, growing commercial activities and industrialization in Kampala, Uganda coupled with inadequate provision of waste management services which have led to increase volume of urban waste entering the North-Western part of Lake Victoria. The Murchison Bay (MB) is in the Northern part of Lake Victoria in Uganda which has for decades received a daily wastewater load of 0.2 % of its volume from Kampala City of Uganda, through the Nakivubo channel [1]. Kampala City people habitants 1.7 million. The uncontrolled solid waste seen along roadsides and storm water drains enter the Nakivubo Channel. The Nakivubo channel is ended in a papyrus swamp in Uganda that retained a large portion of water pollution before it reached in the inner Murchison Bay [2]. In addition, the channel is widened in 2001-2003 to improve the city drainage which has increased the potential loading of nutrients to the bay. The partially treated effluent from treatment plants are mixed with the water in channel and it contribute a high significant pollution load, and is the most polluted system by organic matter in solid waste and wastewater discharged from slums and un-sewered areas, Luzira Prison and small &amp; large scale industries [3]. There are urgent need to resolve the problem. Nowadays, the inner Murchison Bay (MB) water quality are destroying by several complex mixture processes, Ex.: pollution and nutrients loading, river inflows, un-sewered water, wetland management and flora and fauna populations. Present study is focusing on inner Murchison Bay (MB) water pollution behaviour by using wind speed hydrodynamic model. The model processes are determining the fate and transport of pollutant that are vertically mixing (wind force) and horizontal flow (advection-dispersion) analysis. Vertically transport of wind flow that is forcing on the lake water surface are analysed by the vertically integrated Shallow Water Equation model. Horizontally transport of pollution of water and its flow and speed are analyzing by advectiondispersion and diffusion model. Result shows that the horizontal mixing is continuing with lake nutrients and the vertically wind flow from MB into lake is also determine the mixing of lake water which is not much affecting the lake nutrients. QC 20231101</p