Sharif Digital Repository

In this paper, we study a variation of the equations of a chemotaxis kinetic model and investigate it in one dimension. In fact, we use fractional diffusion for the chemoattractant in the Othmar-Dunbar-Alt system (Othmer in J Math Biol 26(3):263-298, 1988). This version was exhibited in Calvez in Amer Math Soc, pp 45-62, 2007 for the macroscopic well-known Keller-Segel model in all space dimensions. These two macroscopic and kinetic models are related as mentioned in Bournaveas, Ann Inst H Poincaré Anal Non Linéaire, 26(5):1871-1895, 2009, Chalub, Math Models Methods Appl Sci, 16(7 suppl):1173-1197, 2006, Chalub, Monatsh Math, 142(1-2):123-141, 2004, Chalub, Port Math (NS), 63(2):227-250,... 

Bladeless fan is a novel fan type that has no observable impeller, usually used for domestic applications. Numerical investigation of a Bladeless fan via Finite Volume Method was carried out in this study. The fan was placed in center of a 4×2×2m room and 473 Eppler airfoil profile was used as cross section of the fan. Performance and noise level of the fan by solving continuity and momentum equations as well as noise equations of Broadband Noise Source (BNS) and Ffowcs Williams and Hawkings (FW-H) in both steady state and unsteady conditions were studied. Flow increase ratio of the fan was captured. Furthermore, BNS method could find outlet slit of the air as the main source of the noise... 

Using the Yang-Shih low Reynolds k-ε turbulence model, the mean flow field of a turbulent offset jet issuing from a long circular pipe was numerically investigated. The experimental results were used to verify the numerical results such as decay rate of streamwise velocity, locus of maximum streamwise velocity, jet half width in the wall normal and lateral directions, and jet velocity profiles. The present study focused attention on the influence of nozzle geometry on the evolution of a 3D incompressible turbulent offset jet. Circular, square-shaped, and rectangular nozzles were considered here. A comparison between the mean flow characteristics of offset jets issuing from circular and... 

The mixed convection of a three-dimensional square duct with various arrangements of fins in both laminar and turbulent flow is numerically characterized and studied. This study focuses on the ability of fin arrangements to enhance a heat transfer while flow is incompressible and the fluid is air. In our models, the lower duct wall is defined with a constant heat flux condition while the two side walls and upper wall are insulated. The finite volume method with the SIMPLE (Semi Implicit Method for Pressure Linked Equations) algorithm is used for handling the pressure–velocity coupling. The numerical results are validated with experimental data and show good agreement. The computations... 

This paper presents a case study and numerical simulations of a corner of a deep excavation in Tehran supported by soldier piles and ground anchors. This study focuses on the differences between 2D and 3D numerical modelling in estimating the wall deflection at the corner locations of the excavation. Furthermore, the performance of modelling with Mohr–Coulomb constitutive law was compared with the result of a hardening soil model. The modelling procedure was calibrated against a full-scale instrumented tieback wall at Texas A&M University and the monitoring data of the excavation project. The results indicated that the hardening soil model yields reasonable predictions of wall deflection in... 

This paper presents a case study and numerical simulations of a corner of a deep excavation in Tehran supported by soldier piles and ground anchors. This study focuses on the differences between 2D and 3D numerical modelling in estimating the wall deflection at the corner locations of the excavation. Furthermore, the performance of modelling with Mohr–Coulomb constitutive law was compared with the result of a hardening soil model. The modelling procedure was calibrated against a full-scale instrumented tieback wall at Texas A&M University and the monitoring data of the excavation project. The results indicated that the hardening soil model yields reasonable predictions of wall deflection in... 

Abstract: This study investigates and compares the effects of different shot peening treatments including conventional and severe shot peening on microstructure, mechanical properties, fatigue behavior, and residual stress relaxation of AISI 1060 steel. Shot peening treatments were applied with two Almen intensities of 17 and 21 A and a wide ranges of coverage (100%–1500%). Various microstructural observations were carried out to analyze the evolution of microstructure. Microhardness, residual stress and surface roughness measurements and also axial fatigue test were performed. Moreover, the extent of the residual stress relaxation during cyclic loading was investigated by means of XRD... 

The consistent behavior of non-dimensional parameters on the formation and break up of large cylindrical droplets has been studied by direct numerical simulations (DNS). A one-fluid model with a finite difference method and an advanced front tracking scheme was employed to solve unsteady, incompressible, viscous, immiscible, multi-fluid, twodimensional Navier-Stokes equations. This time dependent study allows investigation of evolution of the droplets in different cases. For moderate values of Atwood number (AT), increasing Eotvos number (Eo) explicitly increases the deformation rate in both phenomena. Otherwise, raising the Ohnesorge number (Oh) basically amplifies the viscous effects.... 

In this paper, results of DNAPL spreading experiments carried out in a geocentrifuge are analysed. The experiments are performed in the GeoDelft geocentrifuge. The experiments investigate the intrusion of a known amount of PCE into a water-saturated soil sample. They are carried out under 12, 15, and 30g conditions. The objectives of these experiments were to assess the potential of geocentrifuge tests for the study of environmental problems, to investigate the effect of acceleration on the spreading of DNAPL, and to determine whether capillary pressure-saturation (Pc-S) curves of soils measured in a geocentrifuge are applicable under 1g conditions. In the present paper, numerical simulation... 

In this paper, we report on 2D numerical simulation of spectral response for InGaN dual-band photodetector operating at near ultraviolet and visible wavelengths. The back-to-back p–i–n/n–i–p integrated structure enables independent and simultaneous detection of two bands under back-side illumination. The effect of indium content and absorption layer thickness of the two sub-detectors on external quantum efficiency and optical crosstalk between two sub-detectors have been investigated. The optimum values for indium content and thickness of absorption layer in sub-detectors are determined  

Two-dimensional numerical simulations have been performed to study natural convection in right-angled triangular enclosures filled with water considering different aspect ratios. Continuity, momentum and energy equations are solved assuming Boussinesq approximation utilizing COMSOL. Effect of Rayleigh number, Ra, on heat transfer rate is investigated by showing Nusselt number, Nu, for a range from 1 × 104 to 1 × 107 . It is shown that increasing aspect ratio of the cavity increases averaged Nusselt number in a cavity heated from below. Finally, a correlation for heat transfer rate is developed considering the effect of aspect ratio using simulation results  

Two-dimensional numerical simulations have been performed to study natural convection in circular enclosures filled with water considering different central angles. Continuity, momentum and energy equations are solved assuming Boussinesq approximation utilizing COMSOL. Effect of Rayleigh number, Ra, on heat transfer rate is investigated by showing Nusselt number, Nu, for a range from 1×103 to 1×107. It is shown that decreasing central angle of the cavity increases averaged Nusselt number in a cavity heated from below. Finally, a correlation for heat transfer rate is developed considering the effect of the angle between two sides of the cavity and Ra number using simulation results  

Lab-on-a-chip (LOC) systems have been widely used in chemical and medical analyses. In this study, a novel T-shaped electroosmotic micromixer was simulated and the effects of different parameters on the mixing process were examined. These parameters include; inlet angle, number of conducting hurdles, arrangements of the hurdles, geometry of hurdles and chambers, aspect ratios of the channel cross-sectional profile, hurdle radius, and depth. It was found that the inlet angle has a direct influence on mixing index (σ). The effect of various number of hurdles (one, two, three and four hurdles) and their orientations was investigated. Simulations revealed that using two conducting hurdles is the... 

In this study, a fully coupled dynamic finite element model was employed for numerical simulation of the response of level to gently sloping saturated sand layers subjected to cyclic loading. This model utilized a critical state two-surface-plasticity constitutive model to simulate the cyclic behavior of sandy soil. Moreover, a recently proposed variable permeability function was implemented in the numerical model to reflect the effects of soil permeability variations during the liquefaction phenomenon. The numerical model was validated by simulating a number of well-documented geotechnical centrifuge tests with different relative density of sand, base acceleration time history, and surface... 

Two-dimensional (2D) and three-dimensional (3D) numerical simulations of an external compression supersonic ramped inlet are presented for a free stream Mach number of 2. A comparison made between numerical results and experimental data showed that multi-block structured gird using standard k - " turbulence model gives acceptable results. The shape of present inlet diffuser was transformed gradually into a circular one to encompass the Aerodynamic Interface Plane (AIP). It was observed that the 3D simulation predicted a more accurate static pressure distribution during the length of supersonic inlet and total pressure distribution at the AIP in comparison with the 2D one. Further, a better...