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Numerical simulation and parametric study of a supersonic intake
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 227, Issue 3 , January , 2013 , Pages 467-479 ; 09544100 (ISSN) ; Younsi, J. S ; Farahani, M ; Masoud, A ; Sharif University of Technology
2013
Abstract
A computational fluid dynamics code was developed to compute the flow inside and around a supersonic external compression axisymmetric intake. The code solves the Reynolds-averaged Navier-Stokes equations using an explicit finite volume method in a structured grid and uses the Baldwin-Lomax algebraic model to compute the turbulent viscosity coefficient. Experiments were performed to validate the predicted results and good agreements are achieved. In the next part of the research, a parametric study was undertaken using the designed base case at a constant Mach number of 2 and at 0° angle of attack. The effects of various important parameters such as free stream Mach number, spike deflection...
Computation on new deformation routes of tube channel pressing considering back pressure and friction effects
, Article Computational Materials Science ; Volume 59 , June , 2012 , Pages 174-181 ; 09270256 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2012
Abstract
Three deformation routes for recently invented severe plastic deformation (SPD) method named tube channel pressing (TCP) have been introduced in this paper. The effects of routes, back pressure and friction have been investigated on deformation behavior of commercially pure (CP) aluminum tubes. Utilizing finite element analysis provides a broader understanding of these effects through different deformation routes. Due to the large values of strains accumulated in TCP, modified Estrin-Tóth-Molinari-Brechet (METMB) constitutive model has been employed in finite element analysis program to consider a realistic flow stress of the material in TCP. Employing experimental procedures confirms the...
Modifications in Commercial Diesel Engines to Perform Under Difficult Respiration Conditions
, M.Sc. Thesis Sharif University of Technology ; Durali, Mohammad (Supervisor)
Abstract
In this project we are about to adopt a method for implementing commercial diesel engines (truck and bus engines) in applications with difficult respiration condition like what happens in a submarine. To this end, working conditions of such engines are introduced and standard constraints are explained. Then the structure of already manufactured submarine engines is presented. At this point an engine from known manufacturers was selected for calculations to be performed on it. Since test and measurement equipments were not yet ready, simulation using computer software (GT-POWER v6.1) was selected as the solving method. First, the engine was modeled in its nominal working conditions. After...
Use of Numerical Simulation to Study the Reduction of Steam Turbine Back Pressure Via Implementing Heat Pipe in Upstream Air Condenser
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
Iran's experience shows that either single or combined power generation cycles, face heavy summer performance deficiencies. The most limitation of power generation in steam cycles is due to their poor condenser performance.The less condenser performance, the more turbine back pressure, and the more turbine back pressure, the less cycle power generation. The main objective of the present study is to reduce steam turbine back pressure in the combined cycle of an organic Rankine-vapor compression refrigeration by installing heat pipes in suitable locations inside the Air cooled condense (ACC). In order to do so, a commercial numerical simulation solver (FLUENT) is used to find the most suitable...
DSMC solution of supersonic scale to choked subsonic flow in micro to nano channels
, Article 6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, Darmstadt, 23 June 2008 through 25 June 2008 ; Issue PART A , 2008 , Pages 985-993 ; 0791848345 (ISBN); 9780791848340 (ISBN) ; Darbandi, M ; Mirjalili, V ; ASME ; Sharif University of Technology
2008
Abstract
In this study, the supersonic and choked subsonic flows through micro/nano channels are investigated using direct simulation Monte Carlo (DSMC) method. The supersonic case is simulated at different Knudsen numbers covering slip to transition flow regimes, while the effects of inlet Mach and back pressure are studied in details. The inlet/outlet pressure boundary conditions are suitably implemented benefiting from the basics of characteristics theory. A behavior similar to the one predicted by the Fanno theory is observed here; i.e., the supersonic flow velocity decelerates up to a choking condition where any further increase in Knudsen number is impossible unless strong normal/oblique shocks...
A molecular dynamics study of fluid flows through slit-like nanochannels using two different driving systems
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010 ; Issue PARTS A AND B , 2010 , Pages 1029-1033 ; Khaledi Alidusti, R ; Sabouri, M ; Abbasi, H. R ; Sharif University of Technology
Abstract
The Poiseuille flow through slit-like nanochannels is investigated using the nonequilibrium molecular dynamics simulations. To drive a dense flow through the channel, we use two self-adjusting vertical plates strategy. These plates force the liquid to flow through the nanochannel under adjustable inlet and outlet boundary conditions. Comparing with the dual-control-volume grand-canonical molecular dynamics method, the current strategy provides many advantages. The current strategy does not need particle insertion and deletion, therefore, the system dynamics would not be affected at all. Moreover, the number of particles in the simulation system is fixed due to inserting the two...
New visions in experimental investigations of a supersonic under-expanded jet into a high subsonic crossflow
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 224, Issue 10 , 2010 , Pages 1069-1080 ; 09544100 (ISSN) ; Soltani, M. R ; Taeibi Rahni, M ; Sharif University of Technology
2010
Abstract
A series of experiments was performed to investigate the interaction of an under-expanded axisymmetric supersonic jet exhausted from a flat plate with a high subsonic crossflow. The goal was to study the effect of boundary layer thickness (δ) and jet to freestream dynamic pressure ratio (J) on flow field pressure distributions. The resulting measurements upstream of the jet showed that with increasing boundary layer thickness, the magnitude of the pressure coefficient decreases, whereas downstream of the jet, the recovery of the back-pressure moved closer to the nozzle exit. Flow field measurements indicated that with increasing boundary layer thickness, the jet plume dissipation rate...
Study of gas flow in micronozzles using an unstructured dsmc method
, Article Proceedings of the 7th International Conference on Nanochannels, Microchannels, and Minichannels 2009, ICNMM2009, 22 June 2009 through 24 June 2009, Pohang ; Issue PART A , 2009 , Pages 417-424 ; 9780791843499 (ISBN) ; Darbandi, M ; Mirjalili, V ; ASME ; Sharif University of Technology
Abstract
The current research uses an unstructured direct simulation Monte Carlo (DSMC) method to numerically investigate supersonic and subsonic flow behavior in micro convergent-divergent nozzle over a wide range of rarefied regimes. The current unstructured DSMC solver has been suitably modified via using uniform distribution of particles, employing proper subcell geometry, and benefiting from an advanced molecular tracking algorithm. Using this solver, we study the effects of back pressure, gas/surface interactions (diffuse/specular reflections), and Knudsen number, on the flow field in micronozzles. We show that high viscous force manifesting in boundary layers prevents supersonic flow formation...
Physical aspects of rarefied gas flow in micro to nano scale geometries using DSMC
, Article 39th AIAA Fluid Dynamics Conference, 22 June 2009 through 25 June 2009, San Antonio, TX ; 2009 ; 9781563479755 (ISBN) ; Darbandi, M ; Mirjalili, V ; Schneider, G. E ; Sharif University of Technology
Abstract
Rarefied gas flow in micro/nano electro mechanical systems (MEMS/NEMS) does not perform exactly as that in macro-scale devices. The main goal in this study is to investigate mixed subsonic-supersonic flows in micro/nano channels and nozzles and to provide physical descriptions on their behaviors. We use DSMC method as a reliable numerical tool to extend our simulation. It is because the DSMC provides accurate solution for the Boltzmann equations over the entire range of rarefied flow regime or Knudsen numbers. As is known, the appearance of oblique/normal shocks at the inlet of a channel or a nozzle adds to the complexity of internal flow field analyses. We found some very unique physical...
Experimental analysis of cavitaion effects on drag force and back pressure of circular cylinder with free turbulence
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 344-353 ; 10263098 (ISSN) ; Rad, M ; Sharif University of Technology
2009
Abstract
The characteristics of a cavitation water tunnel test setup and the experiments of cavitation around a circular cylinder with free stream turbulence are presented in this paper. The Reynolds number of flow is limited in the range of 1.26 × 105 to 3 × 105 and the far upstream flow has free turbulence. Drag force, back pressure, location of cavitation inception, length of cavity and appearance of cavitation are measured or observed and their results are presented here. It was found that the cavitation effects on the boundary layer and separation of flow over the cylinder and drag force become minimum at the cavitation number of 1.94. The cavitation inception occurs in the sub-layer and at an...