Effect of Finite Diaphragm Rupture Process on Microshock Tube Flows

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Arun K. R ◽  
H. D. Kim ◽  
T. Setoguchi
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Shock Front ◽  
Supersonic Nozzle ◽  
Propagation Speed ◽  
Propagation Distance ◽  
Rupture Process ◽  
Shock Propagation ◽  
Diaphragm Rupture ◽  
Contact Distance

The study of flow physics in microshock tubes is of growing importance with the recent development of microscale technology. The flow characteristics in a microshock tube is considerably different from that of the conventional macroshock tube due to the boundary layer effects and high Knudsen number effects. In the present study an axisymmetric computational fluid dynamics (CFD) method was employed to simulate the microshock tube flow field with Maxwell's slip velocity and temperature jump boundary conditions, to accommodate the rarefaction effects. The effects of finite diaphragm rupture process and partial diaphragm rupture on the flow field and the wave propagations were investigated, in detail. The results show that the shock propagation distance attenuates rapidly for a microshock tube compared to a macroshock tube. For microshock tubes, the contact surface comes closer to the shock front compared to the analytical macroshock tube case. Due to the finite diaphragm rupture process the moving shock front will be generated after a certain distance ahead of the diaphragm and get attenuated rapidly as it propagates compared to the sudden rupture case. The shock-contact distance reduces considerably for the finite diaphragm rupture case compared to the sudden diaphragm rupture process. A partially burst diaphragm within a microshock tube initiates a supersonic flow in the vicinity of the diaphragm similar to that of a supersonic nozzle flow. The supersonic flow expansion leads to the formation of oblique shock cells ahead of the diaphragm and significantly attenuates the moving shock propagation speed.

Effect of finite width cavity in axisymmetric supersonic flow field

2016 ◽  
Vol 232 (1) ◽  
pp. 180-184 ◽  
Author(s):  
S Jeyakumar ◽  
K Jayaraman
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Test Section ◽  
Pressure Loss ◽  
Supersonic Nozzle ◽  
Stagnation Pressure ◽  
Test Facility ◽  
Main Stream ◽  
Finite Width ◽  
Constant Length

In this research, the effect of finite width cavities in supersonic flow field is experimentally investigated. The test facility consists of a supersonic nozzle, which provides flow Mach number of 1.9. A circular cross-sectional test section is fastened at the exit of the nozzle. Cavities are incorporated in the test section at a distance of 20 mm from the inlet. Cavities of constant length and width, and varying depth are used for the study. Entrainment of flow in the main stream is observed immediate downstream of the cavity aft edge due to three dimensional effect. As the depth of the cavity is increased, residence time of the fluid as well as the mixing characteristics are enhanced and stagnation pressure loss also increased. Twin cavities are also arranged symmetrically, which further leads to an improvement in mixing with marginal rise in stagnation pressure loss.

Effect of Axisymmetric Aft Wall Angle Cavity in Supersonic Flow Field

2018 ◽  
Vol 35 (1) ◽  
pp. 29-34 ◽  
Author(s):  
S. Jeyakumar ◽  
Shan M. Assis ◽  
K. Jayaraman
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Supersonic Nozzle ◽  
Stagnation Pressure ◽  
Wall Angle ◽  
Blow Down ◽  
Cross Sectional ◽  
Axisymmetric Cavity ◽  
Scramjet Combustors ◽  
Stable Flow

AbstractCavity plays a significant role in scramjet combustors to enhance mixing and flame holding of supersonic streams. In this study, the characteristics of axisymmetric cavity with varying aft wall angles in a non-reacting supersonic flow field are experimentally investigated. The experiments are conducted in a blow-down type supersonic flow facility. The facility consists of a supersonic nozzle followed by a circular cross sectional duct. The axisymmetric cavity is incorporated inside the duct. Cavity aft wall is inclined with two consecutive angles. The performance of the aft wall cavities are compared with rectangular cavity. Decreasing aft wall angle reduces the cavity drag due to the stable flow field which is vital for flame holding in supersonic combustor. Uniform mixing and gradual decrease in stagnation pressure loss can be achieved by decreasing the cavity aft wall angle.

scholarly journals Effects of Barriers on Fault Rupture Process and Strong Ground Motion Based on Various Friction Laws

2020 ◽  
Vol 10 (5) ◽  
pp. 1687
Author(s):  
Jie Yuan ◽  
Jinting Wang ◽  
Shoubiao Zhu
Keyword(s):  
Total Duration ◽  
Propagation Speed ◽  
Propagation Distance ◽  
Rupture Process ◽  
Fault Rupture ◽  
Ground Acceleration ◽  
Fault Surface ◽  
Friction Laws ◽  
Simulation Results ◽  
Rupture Speed

A barrier may induce a supershear rupture on a fault. This paper focuses on two questions: One is whether the existence of a barrier accelerates the propagation speed of a whole fault rupture, and the other is what are the effects of friction laws and strength of a barrier on the rupture propagation process. For these purposes, classical slip-weakening, rate-state, and modified slip-weakening friction laws are employed to simulate the effect of a barrier on the fault rupture process. The simulation results showed that the rupture speed of the fault obviously decreases when the rupture front propagates to the barriers, and the rupture speed obviously increases when the rupture front leaves barriers. It was also found that a barrier on a fault may induce a supershear rupture via the rate-state friction law. The simulation results also showed that with the increase of barrier strength, the rupture speed near barriers fluctuates more and more; when the barrier strength exceeds a certain level, a supershear rupture area appears on the fault; with the increase of barrier strength, the propagation distance of the rupture at supershear wave velocity correspondingly increases. In addition, with the increase of barrier strength, the overall rupture duration of the fault slightly increases. This indicates that a barrier cannot shorten the total duration of a fault rupture. Though a barrier will lead to a supershear rupture, it just regulates the distribution of the rupture speed on the fault surface. Moreover, with the increase of barrier strength, the peak ground acceleration caused by rupture through the barrier also increases, indicating that the existence of a barrier may lead to the intensification of seismic hazards.

Visualization of Different Flashback Mechanisms for H2/CH4 Mixtures in a Variable-Swirl Burner

2014 ◽  
Author(s):  
Parisa Sayad ◽  
Alessandro Schönborn ◽  
Mao Li ◽  
Jens Klingmann
Keyword(s):  
Flow Field ◽  
Mass Flow ◽  
High Speed ◽  
Vortex Breakdown ◽  
Propagation Speed ◽  
Swirl Burner ◽  
Air Mass ◽  
Spatial Propagation ◽  
Fuel Mixtures ◽  
Flame Flashback

Flame flashback from the combustion chamber to the premixing section is a major operability issue when using high H2 content fuels in lean premixed combustors. Depending on the flow-field in the combustor, flashback can be triggered by different mechanisms. In this work, three flashback mechanisms of H2/CH4 mixtures were visualized in an atmospheric variable swirl burner using high speed OH* chemiluminescence imaging. The H2 mole fraction of the tested fuel mixtures varied between 0.1 and 0.9. The flow-field in the combustor was varied by changing the swirl number from 0.0 to 0.66 and the total air mass-flow rate from 75 to 200 SLPM (standard liters per minute). The following three types of flashback mechanism were observed: Flashback caused by combustion induced vortex breakdown occurred at swirl numbers ≥ 0.53 for all of the tested fuel mixtures. Flashback in the boundary layer and flashback due to autoignition were observed at low swirl numbers and low total air mass-flow rates. The temporal and spatial propagation of the flame in the optical section of the premixing tube during flashback was studied and flashback speed for different mechanisms was estimated. The flame propagation speed during flashback was significantly different for the different mechanisms.

The Supersonic Flow Field Associated with a Conical Flame Sheet

1970 ◽  
Vol 21 (4) ◽  
pp. 368-378 ◽  
Author(s):  
J. F. Clarke ◽  
D. G. Petty
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Base Flow ◽  
Slender Body ◽  
Conical Flow ◽  
Slender Body Theory ◽  
Deflagration Wave ◽  
Flame Sheet ◽  
Base Drag ◽  
Body Theory

SummaryIt is shown that a pair of supersonic inviscid conical flow fields can exist on either side of a conical deflagration wave. The configuration is relevant to the base flow question and indicates how base drag may be alleviated by burning. Results of exact computations are presented as well as those derived from a slender-body theory.

Correction: Computational Simulation of Axis Symmetric Aft Wall Angle Cavity in Supersonic Flow Field

2020 ◽  
Author(s):  
Naresh Relangi ◽  
Divyasri Garimella ◽  
K Jayaraman ◽  
Jayakumar Venkatesan ◽  
S Jeyakumar ◽  
...  
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Computational Simulation ◽  
Wall Angle

Shock waves in a liquid containing gas bubbles

1958 ◽  
Vol 243 (1235) ◽  
pp. 534-545 ◽  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Rarefaction Wave ◽  
Temperature Rise ◽  
Compression Wave ◽  
Liquid Mixture ◽  
Propagation Speed ◽  
Plane Wall ◽  
Shock Propagation ◽  
Wide Range

Considerations of continuity, momentum and energy together with an equation of state are applied to the propagation of plane shock waves in a gas + liquid mixture. The shock-wave relations assume a particularly simple form when the temperature rise across a shock, which is shown to be small for a very wide range of conditions, is neglected. In particular, a simple relation emerges between the shock propagation speed and the pressure on the high-pressure side of the shock, the density of the liquid and the relative proportions, by mass and volume, of gas and liquid in the mixture. It is shown from entropy considerations that a rarefaction wave cannot propagate itself without change of form, and it is argued that a compression wave can be expected to steepen into a shock wave. Consideration of the collision between two normal shock waves, moving in opposite directions, suggests that the strengths of the two shocks are unaltered by the interaction between them. This implies, in particular, that, when a shock impinges normally on a plane wall, the pressure ratio across the reflected shock is equal to that across the incident shock. When the mass ratio of gas to liquid in the mixture is allowed to tend to infinity, the various shock-wave relations for a mixture, derived with the temperature rise across the shock neglected, assume the same limiting form as the corresponding relations for a perfect gas when the ratio of specific heats tends to unity. The theoretical discussion has been illustrated by experiments with a small gas + liquid mixture shock tube. Samples of the records, obtained when the passage of a shock changes the amount of light transmitted through the mixture to a photoelectric cell, illustrate the steepening of a compression wave and the flattening of a rarefaction wave. Measurements confirm the theoretical relation for the propagation speed of shock waves. Reasonably good experi­mental confirmation is also reported of the theoretical predictions for the pressure which arises following the normal impact of a shock wave on a plane wall.

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