scholarly journals Numerical simulation of centrifuge tests to evaluate the performance of desaturation by air injection on liquefiable foundation soil of light structures

2015 ◽  
Vol 55 (6) ◽  
pp. 1388-1399 ◽  
Author(s):  
Narayan Prasad Marasini ◽  
Mitsu Okamura
Keyword(s):  
Numerical Simulation ◽  
Air Injection ◽  
Foundation Soil ◽  
Centrifuge Tests

The Effect of Using Ramps with Trench Cylindrical Holes on Film Cooling Effectiveness

2015 ◽  
Vol 3 (2) ◽  
pp. 15-27
Author(s):  
Ahmed A. Imram ◽  
Humam K. Jalghef ◽  
Falah F. Hatem
Keyword(s):  
Numerical Simulation ◽  
Film Cooling ◽  
Air Injection ◽  
Baseline Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hot Air ◽  
Test Study ◽  
Cylindrical Holes

     The effect of introducing ramp with a cylindrical slot hole on the film cooling effectiveness has been investigated experimentally and numerically. The film cooling effectiveness measurements are obtained experimentally. A test study was performed at a single mainstream with Reynolds number 76600 at three different coolant to mainstream blowing ratios 1.5, 2, and 3. Numerical simulation is introduced to primarily estimate the best ramp configurations and to predict the behavior of the transport phenomena in the region linked closely to the interaction between the coolant air injection and the hot air mainstram flow. The results showed that using ramps with trench cylindrical holes would enhanced the overall film cooling effectiveness by 83.33% compared with baseline model at blowing ratio of 1.5, also  the best overall flim cooling effectevness was obtained at blowing ratio of 2 while it is reduced at blowing ratio of 3.

Stability Enhancement of Supercavitating Projectiles by Unsteady Air Injection

2005 ◽  
Author(s):  
Yasmin Khakpour ◽  
Miad Yazdani
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
High Speed ◽  
The Body ◽  
Air Injection ◽  
Cavity Surface ◽  
The Stability ◽  
Stability Enhancement

In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating hydrofoils. Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile’s motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is injecting of the air into the cavity unsteadily which varies through the projectile’s surface. This approach is provided by arrays of slots distributed on the projectile’s surface and unsteady injection is modeled over the surface. Furthermore, the position of ventilation, dramatically affects the stability like those in aerodynamics. In all approaches it is assumed that the supercavity covers the whole of the body, however the forces caused by the wakes, formed behind the body are taken into account. The calculation is performed at three cavitation numbers with respective velocities of 40 m/s, 50 m/s, 60 m/s.

Frictional Drag Reduction: Review and Numerical Simulation of Microbubble Drag Reduction in a Channel Flow

2018 ◽  
Vol Vol 160 (A2) ◽  
Author(s):  
S Sindagi ◽  
R Vijayakumar ◽  
B K Saxena
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Channel Flow ◽  
Void Fraction ◽  
Rectangular Channel ◽  
Air Injection ◽  
Spanwise Direction ◽  
Flat Plates ◽  
Frictional Drag ◽  
Injection Point

The reduction of ship’s resistance is one of the most effective way to reduce emissions, operating costs and to improve EEDI. It is reported that, for slow moving vessels, the frictional drag accounts for as much as 80% of the total drag, thus there is a strong demand for the reduction in the frictional drag. The use of air as a lubricant, known as Micro Bubble Drag Reduction, to reduce that frictional drag is an active research topic. The main focus of authors is to present the current scenario of research carried out worldwide along with numerical simulation of air injection in a rectangular channel. Latest developments in this field suggests that, there is a potential reduction of 80% & 30% reduction in frictional drag in case of flat plates and ships respectively. Review suggests that, MBDR depends on Gas or Air Diffusion which depends on, Bubble size distributions and coalescence and surface tension of liquid, which in turn depends on salinity of water, void fraction, location of injection points, depth of water in which bubbles are injected. Authors are of opinion that, Microbubbles affect the performance of Propeller, which in turn decides net savings in power considering power required to inject Microbubbles. Moreover, 3D numerical investigations into frictional drag reduction by microbubbles were carried out in Star CCM+ on a channel for different flow velocities, different void fraction and for different cross sections of flow at the injection point. This study is the first of its kind in which, variation of coefficient of friction both in longitudinal as well as spanwise direction were studied along with actual localised variation of void fraction at these points. From the study, it is concluded that, since it is a channel flow and as the flow is restricted in confined region, effect of air injection is limited to smaller area in spanwise direction as bubbles were not escaping in spanwise direction.

Examination on Influence Caused by Air Injection Manners Changing in Aerobic-Anaerobic Landfill Method

2015 ◽  
Vol 768 ◽  
pp. 310-317
Author(s):  
Gang Zhen Jiao ◽  
Lei Zhang ◽  
Xiong Shi ◽  
Gui Fu
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Organic Carbon ◽  
Simulation Model ◽  
Solid Phase ◽  
Landfill Gas ◽  
Air Injection ◽  
Carbon And Nitrogen ◽  
Speed Up ◽  
Leachate Quality

In this study, aerobic-anaerobic landfill method (AANM) is focused on as a new way to speed up landfill stabilization, inhibit landfill gas flux, and ameliorate on leachate quality. Numerical simulation model is developed to guide the air injection craftwork and study its effect on achieving above goals. On basis of work finished in last period (0~310 days), air was injected into Lysimeters A (Lys.A) at 0.5 m, and at 2.5 m in Lys.B with the same rate of 1 L/min. In Lys.C there is no air injected. In order to interview the influence by air injection manners changing, from 310 days till 360 days, air injection manners are changed from Mono-site into Double-site in Lys.A and in Lys. B it will be changed from bottom-site (2.5m) into middle-site (1.5m). In Lys.C there will be no changing. By interviewing the comparisons on simulated results in 50 days with and without air injection manners changing, it was found that air injection manners changing in Lys.A causes TOC discharging amount increase more than 6 times, but T-N and GHE resulted from landfill gas decrease 24.1% and 71 % respectively. Air injection manners changing in Lys.B resulted in discharged TOC and T-N increase 108.1 % and 53.5 % respectively, while T-N decreases 3.7 %. On basis of mechanism assumption, mathematical model was developed and according to the simulated results for 5 years, air injected at 2.5 m achieved improvements on stabilization of solid phase organic carbon and nitrogen for 34 % and 13 %, amelioration on leachate quality for 35 % and 62 % of TOC and T-N, and the restraint of GHE for 14 times compared with no air injection case.

scholarly journals Discriminant Method of Sand Liquefaction

2021 ◽  
Vol 248 ◽  
pp. 01013
Author(s):  
Xiaodong Peng
Keyword(s):  
Numerical Simulation ◽  
Land Reclamation ◽  
Surface Cracks ◽  
National Defense ◽  
Cultivated Land ◽  
Foundation Soil ◽  
Sand Liquefaction ◽  
Dynamic Triaxial Test ◽  
Liquefaction Analysis ◽  
Made In

With the proposal of 1.8 billion mus of cultivated land red line and the rise of land reclamation in China, more and more national defense and civil projects are built on poor geological soil, such as reclamation reefs in the South China Sea. The liquefaction damage caused by earthquake, such as water spraying, grouting and surface cracks, has a great impact on such buildings, and poses a threat to people's lives and property. Therefore, it is of great significance to study the liquefaction of sand in foundation soil. Since Academician Huang Wen-xi first proposed to use indoor dynamic triaxial test to study liquefaction, a series of achievements have been made in the liquefaction of foundation soil. The research methods of sand liquefaction have developed from simple single sample of numerical simulation, numerical simulation and test. Referring to the literature at home and abroad, this paper sorted out the discriminant method of sand liquefaction, experimental study of sand liquefaction and post-liquefaction analysis.

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