Recent Unmanned Combat Air Vehicle (UCAV) configurations have not-so-slender wings with moderate leading-edge sweepangles of 45◦ to 60◦. Planforms vary from pure delta to diamond and even lambda more or less blended wing bodies with a relatively small thickness ratio at the inner wing/fuselage region. The performance and low-observable signature considerations require a compromise between a small radar cross-section and lifting surface shapes for long range and sufficient agility. The airflow is governed largely by the progression of vortices shed from the wing leading edge which interact and produce non-linear aerodynamics. Like early swept wing fighters like the Saab 32 the UCAV may exhibit undesirable flying characteristics over part of the envelope with tip stall and pitch-up. Such problems were mitigated by vortex control "devices" like leading edge fences and notches which violate the low observable requirement. The AVT-181 SACCON is a well studied case. We attempt to improve its stalling characteristics by mimicking the leading edge fence action by a configuration of very small vortex generators and study their effect by CFD.

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.

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.

This study explored two-dimensional (2D) numerical hydrodynamic model simulations of Lake Victoria. Several methods were developed in Matlab to build the lake topography. Old depth soundings taken in smaller parts of the lake were combined with more recent extensive data to produce a smooth topographical model. The lake free surface numerical model in the COMSOL Multiphysics (CM) software was implemented using bathymetry and vertically integrated 2D shallow water equations. Validated by measurements of mean lake water level, the model predicted very low mean flow speeds and was thus close to being linear and time invariant, allowing long-time simulations with low-pass filtered inflow data. An outflow boundary condition allowed an accurate simulation to achieve the lake’s steady state level. The numerical accuracy of the linear measurement of lake water level was excellent.

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 paper, 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.

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 & 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. 

In this article, we present a sub-critical two-dimensional shallow water flow regulation. From the energy estimate of a set of one-dimensional boundary stabilization problems, we obtain a set of polynomial equations with respect to the boundary values as a requirement for the energy decrease. Using the Riemann invariant analysis, we build stabilizing local boundary conditions that guarantee the stability of the hydrodynamical state around a given steady state. Numerical results for the controller applied to the nonlinear problem demonstrate the performance of the method.

Lake Victoria is the largest tropical lake in the world and is very important for environment andeconomy in East Africa. The hydrodynamic processes in the shallow (40-80 m deep) watersystem are unique due to its location at the equator which makes Coriolis effects noticeable alsofor vertical transport. The limited river inflow, and the large surface area compared to its volumemake Lake Victoria vulnerable to climate changes. A model of the circulation patterns, mixing,dispersion and stratification will be necessary to devise strategies for management of the naturalresources. The goal of this project is to improved water quality of Lake Victoria.COMSOL Multiphysics® software supports models for the different processes to be included,and we are developing interfaces used by the geo-hydrodynamical community, such as theDigital Elevation Map (DEM) file format. However, much data remains to collect and coordinatebefore the goal is reached. It turns out that modern depth soundings covering the whole lake maynot be available so scarce and old data have to be used initially. To assess the data collected, amodeling approach can be employed. Data for river in- and outflow as well as evaporation andrainfall have been collected for many years and can be correlated with data series for lake waterlevels in the simulation model.As a first step we have built a vertically integrated St. Venant shallow water model to look at theeffects of bottom topography on large-scale flow patterns and the water level variation. TheCOMSOL® coefficient form PDE represents streamline artificial viscosity, Coriolis forces, andbottom friction, with boundary conditions representing river in- and outflow. The topographymodel must have continuous gradients, and a combination of Kriging with Delaunay triangulationis used to produce the surface model. Results of the long-time simulations will be presented aswell as numerical experiments with other approximate flow models to represent the moving watersurface.

Local explicit feedback boundary conditions are given for the stabilization in L2-norm of the 2-D shallow water model. The proposed method is based on symmetrization of the flux matrices of the linearized model and analysis of the Riemann invariants. The non-conservative 2-D shallow water equations are linearized around the target steady state sub-critical flow. The established feedback control laws guarantee a decay of the energy of the perturbation model. We present numerical simulations to demonstrate how the proposed controller works for the linearized as well as nonlinear shallow water problem.

This paper describes a framework for control allocation problem using Computational Fluid Dynamics (CFD) aerodata, which is represented by a multidimensional array of dimensionless coefficients of aerodynamic forces and moments, stored as a function of the state vector and control-surface deflections. The challenges addressed are, first, the control surface treatment for the automated generation of aerodata using CFD and, second, sampling and data fusion to allow the timely calculation of large data tables. In this framework, the generation of aerodynamic tables is described based on an efficient sampling/data fusion approach. Also, the treatment of aerodynamics of control surfaces is being addressed for three flow solvers: TORNADO, a vortex-lattice method, and two CFD codes, EDGE from the Swedis Defence Agency and PMB from the University of Liverpool. In TORNADO, the vortex points located at the trailing edge of the flaps are rotated around the hinge line to simulate the deflected surfaces. The transpiration boundary conditions approach is used for modeling moving flaps in EDGE, whereas, the surface deflection is achieved using mode shapes in PMB. The test cases used to illustrate the approaches is the Ranger 2000 fighter trainer and a reduced geometry description of Boeing 747-100. Data tables are then generated for the state vector and multiple control surface deflections. The look-up table aerodata are then used to resolve the control allocation problem under the constraint that each surface has an upper and lower limit of deflection angle.