Numerical Studies of Dynamic Compaction of Inert and Energetic Granular Materials

1988 ◽  
Vol 55 (1) ◽  
pp. 36-43 ◽  
Author(s):  
M. R. Baer
Keyword(s):  
Granular Materials ◽  
Mixture Model ◽  
Numerical Study ◽  
Transient Behavior ◽  
Dynamic Compaction ◽  
Two Phase ◽  
Numerical Studies ◽  
Multiphase Mixture ◽  
Impact Experiment ◽  
Compaction Waves

In this paper a numerical study of dynamic compaction of granular materials is presented. A multiphase mixture model treating two-phase nonequilibrium flow is applied to describe dynamic compaction experiments. Compaction is modeled using a description of grain distortion driven by pressure differences. Various energetic and inert granular materials including HMX, Fluid A (Nitrocellulose), Melamine, and Teflon are studied for various piston-impact conditions and compared to existing data. Numerical analysis of a ramp-wave piston-impact experiment is also examined. The multiphase mixture model predicts reasonably well the observed steady compaction wave characteristics. Dynamic compaction experiments with detailed resolution are needed to better address the transient behavior of compaction waves in granular materials.

Numerical Analysis of Combined VIV and Slug Flow in Time Domain

2016 ◽  
Author(s):  
Tor Huse Knudsen ◽  
Svein Sævik ◽  
Mats Jørgen Thorsen
Keyword(s):  
Multiphase Flow ◽  
Time Domain ◽  
Slug Flow ◽  
Structural Model ◽  
Numerical Study ◽  
Two Phase ◽  
Marine Risers ◽  
Numerical Studies ◽  
Vortex Induced Vibrations ◽  
Internal Velocity

Vortex induced vibrations (VIV) and slug flow are two important aspects for marine risers conveying a multiphase flow, and should be carefully examined due to the influence on the fatigue life of the structure. This article examines a truncated riser exposed to VIV with an internal two-phase slug flow. The main focus of the article was to examine the effect of internal slug flow on the VIV of a riser. The VIV were simulated in time domain with a linear structural model with constant pretension. Approximately 150 vortex shedding periods were simulated after the response reached steady state. An internal two-fluid flow was introduced, with constant internal velocity, pressure and uniform slug lengths. From the numerical study it was apparent that the slug velocity and slug length had an influence on the response pattern, amplitude and frequency. An analytical model that predicts additional response frequencies due to slug flow was also compared to the numerical studies. The analytical study produced similar additional response frequencies as the numerical study. The slug length and internal velocity can influence the response of the riser, and should be considered for marine risers conveying multiphase flow.

Pressure Surge During Cryogenic Feedline Chilldown Process

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Gagan Agrawal ◽  
S. Sunil Kumar ◽  
Deepak Kumar Agarwal
Keyword(s):  
Numerical Study ◽  
Rocket Engine ◽  
Inlet Pressure ◽  
Working Fluid ◽  
Flash Evaporation ◽  
Two Phase ◽  
Numerical Studies ◽  
Start Up ◽  
Flow Through ◽  
Pressure Surge

Cryogenic fluid entering a warm feedline absorbs heat and undergoes rapid flash evaporation leading to pressure surges, which can retard the flow inside the feedline. It may have serious repercussion in operation of the rocket engine during start up. Experimental and numerical studies are carried out to examine the effect of inlet pressure and initial feedline temperature on pressure surges. An analytical model using sinda/fluint software is developed to investigate this complex two-phase flow phenomenon including the various boiling regimes that exist during line chilling. The numerical study is carried out considering 1D flow through a cryogenic feedline of 2.47 m long and 0.01 m inner diameter with liquid nitrogen at 77.3 K as working fluid. Predictions are made for the inlet pressure in the range of 0.28–0.76 MPa and initial wall temperature of 200 K and 300 K. Subsequently, an experimental test rig is setup and the model is validated with the experimental data. The studies show that within the range of parameter considered, the magnitude of pressure surge increases exponentially with increase in inlet pressure and decreases with the prechilling of feedline.

A droplet size dependent multiphase mixture model for two phase flow in PEMFCs

2009 ◽  
Vol 194 (1) ◽  
pp. 190-198 ◽  
Author(s):  
Guangli He ◽  
Yohtaro Yamazaki ◽  
Abuliti Abudula
Keyword(s):  
Mixture Model ◽  
Droplet Size ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Size Dependent ◽  
Multiphase Mixture
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