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Simulation of detonation initiation in straight and baffled channels
, Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 37-49 ; 10263098 (ISSN) ; Hossainpour, S ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
Euler conservation equations, ideal gas state equations and simplified chemical kinetics models were used to simulate two-dimensional straight and baffled shock tubes. In a straight channel, detonation waves were initiated by a strong shock wave and allowed to travel down the channel to reach a CJ wave condition. It has been shown that a two-step reaction, kinetics model with an induction time delay, resulted in a physically plausible transient solution. The one-step kinetics model solution is only valid at the limit of a steady state CJ wave condition and should not be used for transient problems. The two-step kinetics model was then used to simulate a detonation initiation in a baffled...
Erratum: Shock polar investigation in supersonic rarefied gas flows over a circular cylinder (Physics of Fluids (2021) 33 (052006) DOI: 10.1063/5.0050571)
, Article Physics of Fluids ; Volume 33, Issue 6 , 2021 ; 10706631 (ISSN) ; Roohi, E ; Daliri, A ; Soltani, M. R ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
This article was originally published online on 25May 2021 with the third author listed at the wrong affiliation. The affiliations appear correct above. All online versions of the article were corrected on 28 May 2021; the article is correct as it appears in the printed version of the journal. © 2021 American Institute of Physics Inc.. All rights reserved
Detonatlve travelling waves for combustions
, Article Applicable Analysis ; Volume 77, Issue 3-4 , 2001 , Pages 405-418 ; 00036811 (ISSN) ; Razani, A ; Sharif University of Technology
2001
Abstract
The existence of travelling wave solution to equations of a viscous heat conducting combustible fluid is proved. The reactions are assumed to be one step exothermic reactions with a natural discontinuous reaction rate function. The problem is studied for a general gas. Instead of assuming the ideal gas conditions we consider a general thermodynamics which is described by a fairly mild set of hypotheses. Travelling waves for detonations reduce to specific heteroclinic orbits of a discontinuous system of ODE's. The existence proof for heteroclinic orbits corresponding to weak and strong detonation waves is carried out by some general topological arguments in ODE. The uniqueness and...
Shock polar investigation in supersonic rarefied gas flows over a circular cylinder
, Article Physics of Fluids ; Volume 33, Issue 5 , 2021 ; 10706631 (ISSN) ; Roohi, E ; Daliri, A ; Soltani, M. R ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
Well-known polars in classical shock wave theory, that is, flow deflection angle-shock angle (θ-β), hodograph (u*,v*), and pressure deflection (θ-P*) diagrams, are investigated for the rarefied gas flows using a recently proposed shock wave detection technique by Akhlaghi and coworkers. The agreement between the obtained polars with the analytical relations in classical shock wave theory has been shown in the continuum limit for the cases of supersonic flow over the wedge and cylinder geometries. Investigations are performed using the RGS2D direct simulation Monte Carlo solver for supersonic gas flows over a circular cylinder at continuum limit and Kn = 10-4, 10-3, 0.01, 0.03, 0.07, and...
Shock polar investigation in supersonic rarefied gas flows over a circular cylinder
, Article Physics of Fluids ; Volume 33, Issue 5 , 2021 ; 10706631 (ISSN) ; Roohi, E ; Daliri, A ; Soltani, M. R ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
Well-known polars in classical shock wave theory, that is, flow deflection angle-shock angle (θ-β), hodograph (u*,v*), and pressure deflection (θ-P*) diagrams, are investigated for the rarefied gas flows using a recently proposed shock wave detection technique by Akhlaghi and coworkers. The agreement between the obtained polars with the analytical relations in classical shock wave theory has been shown in the continuum limit for the cases of supersonic flow over the wedge and cylinder geometries. Investigations are performed using the RGS2D direct simulation Monte Carlo solver for supersonic gas flows over a circular cylinder at continuum limit and Kn = 10-4, 10-3, 0.01, 0.03, 0.07, and...
Experimental investigation of shock-buffet criteria on a pitching airfoil
, Article Chinese Journal of Aeronautics ; Volume 35, Issue 7 , 2022 , Pages 179-191 ; 10009361 (ISSN) ; Zeinalzadeh, A ; Abdi, M. A ; Soltani, M. R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
An experimental investigation of the shock-buffet phenomenon subject to unsteady pitching supercritical airfoil around its quarter chord has been conducted in a transonic wind tunnel. The model was equipped with pressure taps connected to the fast response pressure-transducers. Measurements were conducted at different free-stream Mach number from 0.61 to 0.76. The principle goal of this investigation was to experimentally discuss the shock-buffet criterion over a SC(2)-0410 supercritical pitching related to the hysteresis loops of total drag and trailing edge pressure, the behaviour of the shock wave foot location, the pressure distribution over the upper surface, and by implementing the...
Performance Optimization of an Axisymmetric Supersonic Inlet
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
The main aim of this study is to propose a new structure of compression surfaces of a supersonic inlet in order to improve target performance parameter i.e. total pressure recovery ratio. This idea resulted in developing a new type of supersonic inlet, utilizing four ramps and a cone as compression surfaces simultaneously.A prototype of this type of inlet has been designed for Mach 3 and its performance has been studied via numerical simulation in design point and off design conditions. Eventually the new inlet compared to experimental performance survey data from two cases of two-cone inlets and also analytical calculations of ideal performance of some types of supersonic inlets. Results of...
Modeling and Optimization of Supersonic Separators
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor)
Abstract
Supersonic separation is a modern technology which is used in petroleum’s industry. Supersonic flow is obtained by converging-diverging nozzle in which by decreasing pressure and increasing fluid’s velocity, we can reach low temperature which is required for separation. After separation in low temperature, pressure is recovered via normal shockwave or a second nozzle. In the case of using second nozzle, fluid’s velocity is decreased and its pressure is increased. In these separators, we have two important issues: Separation efficiency and Pressure recovery . On the other hand, nozzle’s performance depends on two sets of factors: Factors related to nozzle’s geometry and Factors related to...
Molecular dynamics simulation of orientation dependency in the shock-induced phase transition of C60 fullerene single crystals into amorphous diamond
, Article Phase Transitions ; Vol. 87, Issue. 3 , 2014 , Pages 271-285 ; ISSN: 01411594 ; Naghdabadi, R ; Sharif University of Technology
Abstract
A molecular dynamics simulation of the shock-wave propagation in the face-centered cubic (FCC) structured C60 fullerene along the <100>, <110> and <111> crystallographic directions is performed. For this purpose, the response of the material under different shock-wave loadings is studied through Hugoniot curves. Three regimes of the material behavior have been observed from fully elastic to elastic-plastic to plastic. The Hugoniot elastic limit and the phase transition are also investigated along different crystallographic directions. It is shown that the shock wave travels faster along the <110> and <111> directions than in the <100> direction in the material. Comparing the results with the...
Analytical Solution for Isothermal Flow in a Shock Tube Containing Rigid Granular Material
, Article Transport in Porous Media ; Volume 93, Issue 1 , 2012 , Pages 13-27 ; 01693913 (ISSN) ; Ahmadi, M. M ; Mohammadi, S ; Sharif University of Technology
2012
Abstract
Analytical solution of shock wave propagation in pure gas in a shock tube is usually addressed in gas dynamics. However, such a solution for granular media is complex due to the inclusion of parameters relating to particles configuration within the medium, which affect the balance equations. In this article, an analytical solution for isothermal shock wave propagation in an isotropic homogenous rigid granular material is presented, and a closed-form solution is obtained for the case of weak shock waves. Fluid mass and momentum equations are first written in wave and (mathematical) non-conservation forms. Afterwards by redefining the sound speed of the gas flowing inside the pores, an...
Shock-wave-detection technique for high-speed rarefied-gas flows
, Article AIAA Journal ; Volume 55, Issue 11 , 2017 , Pages 3747-3756 ; 00011452 (ISSN) ; Daliri, A ; Soltani, M. R ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2017
Abstract
This paper introduces a shock-wave-detection technique based on the schlieren imaging for continuum and rarefied-gas flows. The scheme is applicable for any existing two-dimensional flowfields obtained by experimental or numerical approaches. A Gaussian distribution for a schlieren function within the shock-wave region is considered. This enables the authors to access any desired locations through the shock (e.g., shock center, or leading- and trailing-edge locations). The bow shock-wave profile is described via a rational function, which could be employed for the estimation of shock angle. The relation between pre- and postshock flow properties along the shock wave with a high resolution...
Effect of sinusoidal splitter on mixing performance of co-flow jets of hydrogen and air inside dual-combustor ramjet
, Article Acta Astronautica ; Volume 180 , 2021 , Pages 211-217 ; 00945765 (ISSN) ; Sharifi Rayeni, N ; Moghimihanjani, M ; Moradi, R ; Li, Z ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this study, the existence of a sinusoidal splitter on the formation and distribution of hydrogen and air co-jets are investigated in a dual-combustion ramjet engine. The main scope of this research is to analyze the comprehensive flow structure and flame features directly downstream of the sinusoidal splitter. In this work, shockwave/shear-layer interactions behind the sinusoidal splitter are thoroughly studied through a computational fluid dynamic approach. Two different splitter profiles are compared with a simple splitter to demonstrate the main effects of multi shock wave interactions on fuel distribution and penetrations. To simulate co-air jet, Reynolds Average Navier-Stocks...
Numerical Simulation of Combustion and Pressure Waves are Induced by Gas Detonation in High Pressure Pipelines
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
In general, a combustible mixture can support two modes of combustion: deflagration and deto-nation. In the deflagration regime, in the limit it can burn as a laminar flame at a typical velocity of the order of about 0.5 m/s, or it may accelerate to a turbulent flame where velocity can be or-ders of magnitude higher. The other extreme is the detonation mode, in which a detonation wave propagates at about 2000 m/s amplifying the pressure by a factor of 20 across the wave. Detona-tion is defined as a combustion supported shock wave with significant pressure and density rise across the wave. The main characteristic of detonation waves is the coupled motion of the shock front and the reaction...
On the existence of fast strong and fast weak ionizing detonation waves in magnetohydrodynamics
, Article Chaos, Solitons and Fractals ; Volume 40, Issue 1 , 2009 , Pages 298-308 ; 09600779 (ISSN) ; Farjami, Y ; Hesaaraki, M ; Sharif University of Technology
2009
Abstract
The existence of structure for ionizing fast-strong and fast-weak detonation waves in magnetohydrodynamics are proved. The reactions are assumed to be one step exothermic reactions with a natural discontinuous reaction rate function. The problem is studied for a general gas, considering some general thermodynamics rules which described by a fairly mild set of hypotheses. The uniqueness and nonuniqueness of structure are also considered. © 2007 Elsevier Ltd. All rights reserved
Shock wave sintering of Al/SiC metal matrix nano-composites: A molecular dynamics study
, Article Computational Materials Science ; Volume 125 , 2016 , Pages 255-262 ; 09270256 (ISSN) ; Mahnama, M ; Naghdabadi, R ; Sharif University of Technology
Elsevier
2016
Abstract
Mechanical properties of nano-composites produced by shock wave sintering of aluminum and silicon carbide nano-powders are investigated using Molecular Dynamics (MD) simulations. In this regard, the shock wave response of aluminum and silicon carbide nano-particles, arranged in a BCC super-lattice, is studied via the NPHug Hugoniostat method. Moreover, the effect of the initial hydrostatic compaction of powders as well as the cooling rate of the shocked material on the mechanical properties of the shock-sintered nano-composites is investigated. Employing the Hugoniot curves corresponding to the powders, it is concluded that an initial hydrostatic pressure, leads to a less temperature rise...
Effects of shock wave/boundary-layer interaction on performance and stability of a mixed-compression inlet
, Article Scientia Iranica ; Volume 23, Issue 4 , 2016 , Pages 1811-1825 ; 10263098 (ISSN) ; Daliri, A ; Sepahi Younsi, J ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
Experiments were conducted to study various kinds of Shock wave/Boundary Layer Interaction (SBLI) in an axisymmetric mixed-compression inlet. Experimental findings were compared and verified by numerical solutions where possible. Different types of SBLI relevant to the mixed-compression inlets are classified. Interactions of normal shock wave/boundary-layer at subcritical condition and in buzz condition are investigated using Schlieren and shadowgraph flow visualization as well as unsteady pressure recordings. The data is compared with the CFD predictions. Interactions of cowl lip reflected oblique shock and the terminal normal shock with the spike boundary-layer at both critical and...
The multi-point optimization of shock control bump with constant-lift constraint enhanced with suction and blowing for a supercritical airfoil
, Article Flow, Turbulence and Combustion ; Volume 96, Issue 3 , 2016 , Pages 639-666 ; 13866184 (ISSN) ; Nejati, A ; Sharif University of Technology
Abstract
Both shock control bump (SCB) and suction and blowing are flow control methods used to control the shock wave/boundary layer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. A SCB uses a small local surface deformation to reduce the shock-wave strength, while suction decreases the boundary-layer thickness and blowing delays the flow separation. Here a multi-point optimization method under a constant-lift-coefficient constraint is used to find the optimum design of SCB and suction and blowing. These flow control methods are used separately or together on a RAE-2822 supercritical airfoil for a wide range of off-design transonic Mach numbers. The RANS flow...
Experimental investigation of shock wave oscillation on a thin supercritical airfoil
, Article Scientia Iranica ; Volume 27, Issue 2 , 2021 , Pages 795-805 ; 10263098 (ISSN) ; Talebi, M ; Zeinalzadeh, A ; Abdi, M. A ; Soltani, M. R ; Sharif University of Technology
Sharif University of Technology
2021
Abstract
Experimental results of surface pressure distribution over a thin supercritical airfoil and its wake are presented. All tests were conducted at free stream Mach numbers ranging from 0.27 to 0.85 and at di erent angles of attacks in a transonic wind tunnel. The model was equipped with static pressure ori ces connected to high-frequency pressure transducers. The present paper evaluates variations of shock wave location with both Mach number and angle of attack variation, as well as its interaction with the boundary layer, leading to the bu et phenomenon. Note that, for this thin supercritical airfoil, there exist only a few experimental results regarding surface pressure distributions,...
Application of Compressible SPH Method for Simulation of Impulsive Waves
, M.Sc. Thesis Sharif University of Technology ; Ataei Ashtialni, Behzad (Supervisor)
Abstract
Impulsive waves generated by landslides and slamming on horizontal cylindrical members of a jacket are examples of phenomena which cause damage on structures and endanger human life. Importance of wave generated by land slide was a motivation for a large number of analytical, experimental and numerical studies. Recently, numerical methods that do not use a grid have been used in order simulation and prediction of damage in these sophisticated hydrodynamic problems. One of these modern methods is Smoothed Particle Hydrodynamics (SPH). A general model based on Smoothed Particle Hydrodynamics, “SPHysics”, was developed jointly by researchers to promote the development and use of SPH within the...
Evaluation and Modeling of Queue Length Resulting from Shock Waves in Freeway Work Zone Areas
, M.Sc. Thesis Sharif University of Technology ; Nassiri, Habibollah (Supervisor)
Abstract
Highway work zone is one of the important factors that create long queues and Delays, increase air population, fuel consumption, and road accident. Since in this zones, one and two or sometimes three lanes may be closed, more careful evaluation of the causes of queue formation seems necessary. The purpose of this research was to develop a method to estimate queue length at work zone in rural freeways, based on its traffic flow characteristics. In this study, traffic data from three work zone locations in Karaj-Qazvin freeway was collected. Results of different modeling show that platooning arrival of vehicles at work zone, increase in percentage of heavy vehicles, high variation of speed and...