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Purpose: Unmanned aerial vehicles (UAV) with remote and/or automated flight and mission controls have replaced airplanes with pilots in many important roles. This study aims to deal with computational fluid dynamics (CFD) analysis and development of the aerodynamic configuration of a multi-purpose UAV for low and medium altitudes. The main aerodynamic requirement was the application of the tandem wing (TW) concept, where both wings generate a positive lift and act as primary lifting devices. Design/methodology/approach: Initial design analyses of the UAV’s aerodynamic configuration were performed using ANSYS Fluent. In previous work in Fluent, the authors established a calculation model that has been verified by experiments and, with minor adjustments, could be applied for subsonic, transonic and supersonic flow analyses. Findings: The design evolved through eight development configurations, where the latest V8 satisfied all the posted longitudinal aerodynamic requirements. Both wings generate a substantial amount of positive lift, whereas the initial stall occurs first on the front wing, generating a natural nose-down stall recovery tendency. In the cruising flight regime, this configuration has the desired range of longitudinal static stability and its centre of pressure is in close proximity to the centre of gravity. Practical implications: The intermediate development version V8 with proper longitudinal aerodynamic characteristics presents a good starting point for future development steps that will involve the optimization of lateral-directional aerodynamics. Originality/value: Using contemporary CFD tools, a novel and original TW aerodynamic configuration have evolved within eight development stages, not being based on or derived from any existing designs.

Wind forces can cause huge damage to the building elements due to their inadequate design or material deterioration..., Силе генерисане ветром могу изазвати велика оштећења на зградама услед њиховог неадекватног пројектовања, или недовољне чврстоће примењених материјала...

Wind tunnel tests of wind influence on ground objects require proper experimental modeling of the atmospheric boundary layer (ABL). The authors have performed computational analyses with an aim to establish a reliable computational algorithm that could resemble complex flow patterns in wind tunnels with various obstacles, used to simulate appropriate velocity profiles within the ABL. For experimental verifications, measurements from two experimental facilities were applied, with speeds ranging from 1-4 m/s in the first, and 45 m/s in the second. For all considered cases, good agreements between the measured and computed speed profiles for operational engineering purposes have been achieved. In the sense of qualitative analyses, calculated contours of velocity magnitude and eddy viscosity inside the wind tunnel test sections have verified that good homogeneity of the simulated ABL in both wind tunnels had been established in the domains where velocity profiles were measured. Presented results have shown the capability of here established calculation model to resemble a number of costly wind tunnel test hours during preparations of proper obstacle arrangements for experimental ABL modeling in a wide wind speed range, and thus reduce the overall project costs. Also, presented CFD algorithm can readily be calibrated and used for engineering research of wind effects on different ground objects, as a virtual wind tunnel.

Maass cusp forms of the Fuchsian group are eigenfunctions of the hyperbolic Laplacian representing bound states. It is known that the Maass cusp forms can only be solved numerically. The aim of this paper is to ex-tend Hejhal's algorithm to compute Maass cusp form on the modular group SL(2, R)\H using Mathematica with the intent of exploiting its graphical and symbolic capabilities. We compute the eigenvalues of the Maass cusp forms em-ploying a graphical scheme to locate the approximate value of the eigenvalue. We also plotted Maass cusp forms corresponding to selected eigenvalues.

The topic of this study is the computation of Maass cusp form, i.e. the eigenfunctions of the hyperbolic Laplace-Beltrami operator on punctured surfaces namely singly punctured two-torus and triply punctured two-sphere. Punctured surfaces are surfaces with points removed or located infinitely far away and they have complex topological and geometrical properties. The presence of the punctures or cusps means that there is a continuous spectrum as well as the discrete one. This work focuses on the discrete part of computational nature. Hejhal developed an algorithm to compute Maass cusp form on triangle groups. The algorithm of Hejhal is based on automorphy condition and also applies to the computation of the Maass cusp forms on Fuchsian group whose the fundamental domain has exactly one cusp. In this work the method due to Hejhal was recalled and extended for computation of Maass cusp on singly punctured two-torus which still has one cusp but a nonzero genus. The algorithm was modified further to carry out the computation for the surfaces with three cusps i.e. triply punctured two-sphere. All the computations were implemented in Mathematica and built in a way accessible to any one with an introductory knowledge in Mathematica. The results of the study are the first low-lying eigenvalues, examples of Fourier coefficients and graphic plots of Maass cusp forms each for modular group, singly punctured two-torus and triply punctured two-sphere. The eigenvalues and the Fourier coefficients were computed with the desired accuracy. Some comparisons between singly punctured two-torus and triply punctured two-sphere are also presented.

The determination of eigenvalues and their related eigenfunctions is one of the central problems of quantum mechanics. In this work, the problem of finding energy eigenvalues and eigenfunctions are aptly demonstrated with one dimensional systems of infinite double square well potential, finite double square well potential, rectangular potential hole between two walls and asymmetric square well potential. We develop Mathematica packages for which the Schrodinger equations are solved for each model. The solutions are obtained by graphical and numerical methods in these packages. The packages are easy to use; the user does not need to know the details of the packages in order to use them but the user has a direct control over parameters of the models. Eigenvalues and eigenfunctions have been obtained for various well depths and widths as well as various barrier widths. They are shown to have appropriate limiting solutions. The packages are stable, fast, efficient and can serve as useful tools for teaching systems of one dimensional rectangular potential, in quantum mechanics.