A simple constitutive model for predicting the pressure histories developed behind rigid porous media impinged by shock waves

2013 ◽  
Vol 718 ◽  
pp. 507-523 ◽  
Author(s):  
O. Ram ◽  
O. Sadot
Keyword(s):  
Shock Wave ◽  
Porous Medium ◽  
Porous Media ◽  
Shock Waves ◽  
Constitutive Model ◽  
Wave Attenuation ◽  
Front Face ◽  
Viscous Effects ◽  
Pressure History ◽  
Target Wall

AbstractShock wave attenuation by means of rigid porous media is often applied when protective structures are dealt with. The passage of a shock wave through a layer of porous medium is accompanied by diffractions and viscous effects that attenuate and weaken the transmitted shock, thus reducing the load that develops on the target wall that is placed behind the protective layer. In the present study, the parameters governing the pressure build-up on the target wall are experimentally investigated using a shock tube facility. Different porous samples are impinged by normal shock waves of various strengths and the subsequent pressure histories that are developed on the target wall are recorded. In addition, different standoff distances from the target wall are investigated. Assuming that the flow through the porous medium is close to being isentropic enabled us to develop a general constitutive model for predicting the pressure history developed on the target wall. This model can be applied to predict the pressure build-up on the target wall for any pressure history that is imposed on the front face of the porous sample without the need to conduct numerous experiments. Results obtained by other investigators are found to be in very good agreement with the predictions of the presently developed constitutive model.

On Difference Methods for Shock Wave Propagation in Variable Area Ducts Including Wall Friction

1973 ◽  
Vol 95 (2) ◽  
pp. 327-332
Author(s):  
R. H. Fashbaugh ◽  
A. Widawsky
Keyword(s):  
Shock Wave ◽  
Wave Attenuation ◽  
Fluid Dynamic ◽  
Finite Difference Methods ◽  
Wall Friction ◽  
Variable Cross ◽  
Viscous Effects ◽  
Cross Sectional ◽  
Basic Fluid ◽  
Difference Methods

Results are presented of an analytical study concerned with the prediction of the propagation of shock waves through air ducting systems. The solution is one-dimensional but is appropriate for ducts which have a variable cross-sectional area and includes attenuation due to viscous effects at the wall of the duct. Finite-difference methods are utilized to obtain an approximate solution to the basic fluid dynamic equations. Comparisons are given between analytical results and shock tube experimental data which validate the capabilities of the methods used to predict shock wave attenuation and the effect of duct area variation on shock strength.

Analysis of the pressure buildup behind rigid porous media impinged by shock waves in time and frequency domains

2015 ◽  
Vol 779 ◽  
pp. 842-858 ◽  
Author(s):  
O. Ram ◽  
O. Sadot
Keyword(s):  
Porous Medium ◽  
Shock Waves ◽  
Shock Tube ◽  
Pressure Profile ◽  
Air Gap ◽  
Front Face ◽  
Porous Sample ◽  
Rear Face ◽  
Pressure Buildup ◽  
End Wall

The transformation of a time-dependent pressure pulse imposed on the front face of a rigid porous medium sample, mounted in a tunnel, through the sample and a fixed-volume air gap between the rear face of the sample and the end wall of a tunnel is studied both experimentally and analytically. In the experiments, rigid porous samples that are placed at various distances from a shock tube end wall are subjected to the impingement of shock waves. The pressure buildup behind the porous sample is monitored and compared with the pressure imposed at the front face of the porous sample. The shock tube is fitted with a short driver section in order to generate blast-like decaying pressure profiles, which continue to decay after the initial shock impingement. In this scenario, the measured pressure profile at the end wall, which is affected by the properties of the porous medium and the size of the air gap separating its rear face and the shock tube end wall, is significantly different from the pressure profile imposed on the front face of the porous sample. The mechanism governing the pressure transformation provided by the porous medium is attributed to a selective filtration process that attenuates the pressure changes associated with high frequencies. The results of the present study are also analysed in conjunction with previously published analytical and numerical models to achieve a broader understanding of the physical mechanisms affecting the pressure buildup.

scholarly journals 2.5D les simulation of an airfoil shock wave reduction by using porous media

2020 ◽  
Vol 32 ◽  
pp. 122-133
Author(s):  
Ion Malael ◽  
Ioana Octavia Bucur ◽  
Valeriu Dragan
Keyword(s):  
Shock Wave ◽  
Porous Media ◽  
Shock Waves ◽  
High Speed ◽  
Aerodynamic Coefficients ◽  
Qualitative Comparison ◽  
Ansys Fluent ◽  
Motion Equations ◽  
Practical Reality ◽  
Naca 0012

Supersonic flight has become a practical reality since the 1950s. One of the first ways to study high speed effects of the shock waves is to evaluate the aerodynamic coefficients of an airfoil. The work described herein refers to a series of 2.5D LES numeric simulations, to investigate the behavior of the shock wave on the airfoil. To reduce the unwanted effects, a porous surface is placed on 80% of suction and pressure side of a NACA 0012 airfoil. Solving the motion equations was carried out with Ansys Fluent. Qualitative comparison consists in the pressure contours visualization for different angles of attack, showing how shock waves form on the airfoil surfaces. After plotting the polar diagrams, CL=f(AoA) and CL=f(CD), a quantitative comparison was made between the baseline airfoil and the same airfoil but with porous media on each surface side.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

Conservative solute transport with periodic velocity and sinusoidal source concentration in semi-infinite porous media: An analytical solution

2014 ◽  
Vol 6 (1) ◽  
pp. 1024-1031
Author(s):  
R R Yadav ◽  
Gulrana Gulrana ◽  
Dilip Kumar Jaiswal
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Laplace Transformation ◽  
Seepage Velocity ◽  
Transformation Technique ◽  
Numerical Examples ◽  
One Dimensional ◽  
Porous Domain ◽  
Conservative Solute Transport ◽  
Source Concentration

The present paper has been focused mainly towards understanding of the various parameters affecting the transport of conservative solutes in horizontally semi-infinite porous media. A model is presented for simulating one-dimensional transport of solute considering the porous medium to be homogeneous, isotropic and adsorbing nature under the influence of periodic seepage velocity. Initially the porous domain is not solute free. The solute is initially introduced from a sinusoidal point source. The transport equation is solved analytically by using Laplace Transformation Technique. Alternate as an illustration; solutions for the present problem are illustrated by numerical examples and graphs.

Features of spatial shock-wave flows in vapor-gas-liquid mixtures

2014 ◽  
Vol 10 ◽  
pp. 27-31
Author(s):  
R.Kh. Bolotnova ◽  
U.O. Agisheva ◽  
V.A. Buzina
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Shock Waves ◽  
Liquid Mixture ◽  
Liquid Mixtures ◽  
Pressure Vessels ◽  
Water Mixture ◽  
Two Dimensional ◽  
Nonstationary Processes ◽  
Two Phase

The two-phase model of vapor-gas-liquid medium in axisymmetric two-dimensional formulation, taking into account vaporization is constructed. The nonstationary processes of boiling vapor-water mixture outflow from high-pressure vessels as a result of depressurization are studied. The problems of shock waves action on filled by gas-liquid mixture volumes are solved.

Capillary Imbibition Dynamics in Porous Media

2014 ◽  
Author(s):  
Swayamdipta Bhaduri ◽  
Pankaj Sahu ◽  
Siddhartha Das ◽  
Aloke Kumar ◽  
Sushanta K. Mitra
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Paper Strip ◽  
Capillary Imbibition ◽  
Flow Physics ◽  
Fundamental Understanding ◽  
Paper Based Microfluidics ◽  
To Come

The phenomenon of capillary imbibition through porous media is important both due to its applications in several disciplines as well as the involved fundamental flow physics in micro-nanoscales. In the present study, where a simple paper strip plays the role of a porous medium, we observe an extremely interesting and non-intuitive wicking or imbibition dynamics, through which we can separate water and dye particles by allowing the paper strip to come in contact with a dye solution. This result is extremely significant in the context of understanding paper-based microfluidics, and the manner in which the fundamental understanding of the capillary imbibition phenomenon in a porous medium can be used to devise a paper-based microfluidic separator.

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