Sharif Digital Repository

A three-dimensional numerical study has been performed to investigate the influence of angle of shock waves on sonic transverse Hydrogen micro-jets subjected to a supersonic crossflow. This study focuses on mixing of the Hydrogen jet in a Mach 4.0 crossflow with a global equivalence ratio of 0.5. Flow structure and fuel/air mixing mechanism were investigated numerically. Parametric studies were conducted on the angle of shock wave by using the Reynolds-averaged Navier-Stokes equations with Menter's Shear Stress Transport turbulence model. Complex jet interactions were found in the downstream region with a variety of flow features depending upon the angle of shock incident. These flow... 

Space environments have a significant influence on advanced composite structures and adhesive joints. Degradation in the mechanical properties of aerospace materials changes the dynamic behavior of the structures and adhesive joints. In this paper, a typical tubular adhesive joint with material degradation due to geostationary orbit (GEO) thermal cycles has been studied numerically with Python scripts. Adhesive joint geometry and boundary conditions are the main parametric study parameters. The results show that the first non–zero natural frequencies of the clamped-free tubular adhesive joint decreased due to mechanical property degradation. A dynamic behavior comparison of the degradation... 

In this paper, numerical simulation is performed to investigate the effects of micro air jets on mixing of the micro hydrogen jet in a transverse supersonic flow. The fundamental flow feature of the interaction between an array of fuel and air jets is investigated in a Mach 4.0 crossflow with a fuel global equivalence ratio of 0.5. Parametric studies were conducted on the various air jet conditions by using the Reynolds-averaged Navier–Stokes equations with Menter's Shear Stress Transport (SST) turbulence model. Numerical study of eight streamwise transverse sonic fuel and air jets in a fully turbulent supersonic flow revealed an extremely complex feature of fuel and air jet interaction. The... 

In this study, the effects of the mesh barrier on the free dispersion of ammonia were numerically investigated under different atmospheric conditions. This study presents the detail and flow feature of the dispersion of ammonia through the mesh barrier on various free stream conditions to decline and limit the toxic danger of the ammonia. It is assumed that the dispersion of the ammonia occurred through the leakage in the pipeline. Parametric studies were conducted on the performance of the mesh barrier by using the Reynolds-averaged Navier-Stokes equations with realizable κ-ε turbulence model. Numerical simulations of ammonia dispersion in the presence of mesh barrier revealed significant... 

In this study, a numerical study on failure assessment and stress distribution on the adhesive region in a composite T-joint under bending load case is investigated using cohesive zone method (CZM). The Finite Element Model (FEM) has been verified with experimental results. To study the load transfer capability of the T-joint, five different adhesives are considered in the adhesive region and the effect of geometrical parameters such as stringer thickness, corner radius, and adherend thickness as well as micromechanical properties of reinforced fiber composite adherends are investigated. Effective properties of two composite adherends including Carbon-Epoxy (IM7/8552) and Glass-Epoxy... 

A new method for the shape reconstruction of conducting cylinders from the measured data based on the cubic uniform B-splines was discussed. B-Spline was defined by an ordered set of control points which determined the shape of the curve. A direct problem was formulated using standard integral equations that were solved using method of moments. Principal polarization were treated separately. The method was found less sensitive to noise than those using Fourier expansions  

This research investigated the forced convection heat transfer by using the swirling impinging jets. This study focused on nozzles, which equipped with twisted tapes via a numerical approach. The computational domain created by utilizing the fully structured meshes, which had very high quality from the viewpoint of aspect ratio and skewness. The numerical simulations were performed at four different jet-to-plate distances (L/D) of 2, 4, 6 and 8, four Reynolds numbers of 4000, 8000, 12,000 and 16,000, and also four different twist ratios (y/w) of 3, 4, 5 and 6. The mesh-independent tests were conducted based upon the average Nusselt number. The obtained results revealed good agreement with... 

In this article, a three-dimensional numerical investigation is performed to study the effect of a magnetic field on a ferrofluid inside a tube. This study comprehensively analyzes the influence of a non-uniform magnetic field in the heat transfer of a tube while a ferrofluid (water with 0.86 vol% nanoparticles (Fe3O4) is let flow. The SIMPLEC algorithm is used for obtaining the flow and heat transfer inside the tube. The influence of various parameters, such as concentration of nanoparticles, intensity of the magnetic field, wire distance and Reynolds number, on the heat transfer is investigated. According to the obtained results, the presence of a non-uniform magnetic field significantly... 

Virtual Reality (VR) technology is a growing technology that has been used in various fields of psychology, education, and therapy. One group of potential users of VR are children with autism who need education and have poor social interactions; this technology could help them improve their social skills through real-world simulation. In this study, we evaluated the feasibility of conducting virtual music education programs with automatic assessment system for children with autism at treatment/research centers without the need to purchase a robot, resulting in the possibility of offering schedules on a larger scale and at a lower cost. Intervention sessions were conducted for five children... 

Virtual Reality (VR) technology is a growing technology that has been used in various fields of psychology, education, and therapy. One group of potential users of VR are children with autism who need education and have poor social interactions; this technology could help them improve their social skills through real-world simulation. In this study, we evaluated the feasibility of conducting virtual music education programs with automatic assessment system for children with autism at treatment/research centers without the need to purchase a robot, resulting in the possibility of offering schedules on a larger scale and at a lower cost. Intervention sessions were conducted for five children... 

In this paper, we have presented a novel virtual reality setup with the ability to teach music to children with autism as well as perform automatic assessment of their behaviors. This setup contains Social Virtual Reality Robots (V2Rs) and virtual musical instruments (i.e. xylophone and drum). After conducting a game-session pilot study, we observed that the acceptance rate of the virtual reality headset is about 65% among children with autism, while all of the typically developing children attending the session used the headset. Furthermore, using statistical analysis, it is indicated that the performance of children with autism in music assignments was significantly weaker than their... 

We propose a novel method for analyzing precursory seismic data before an earthquake that treats them as a Markov process and distinguishes the background noise from real fluctuations due to an earthquake. A short time (on the order of several hours) before an earthquake the Markov time scale tM increases sharply, hence providing an alarm for an impending earthquake. To distinguish a false alarm from a reliable one, we compute a second quantity, T1, based on the concept of extended self-similarity of the data. T1 also changes strongly before an earthquake occurs. An alarm is accepted if both tM and T1 indicate it simultaneously. Calibrating the method with the data for one region provides a...