scholarly journals Optimization of a Water Rocket in OpenMDAO/dymos

2020 ◽  
Author(s):  
Bernardo Bahia Monteiro
Keyword(s):  
Optimal Control ◽  
Collocation Methods ◽  
Water Volume ◽  
Bottle Water ◽  
Initial Water

This work presents a model of a soda-bottle water rocket developed with NASA'sOpenMDAO Dymos optimal control multidisciplinary framework. This is an acces-sible example that is able to highlight many of the benfitts and challenges of multi-disciplinary optimization and of collocation methods. Optimization results for flightrange and height at apogee with respect to empty mass, initial water volume andlaunch angle are presented.

The Numerical Modeling of Spherical Explosion in the Foam

2016 ◽  
Vol 11 (1) ◽  
pp. 60-65 ◽  
Author(s):  
R.Kh. Bolotnova ◽  
E.F. Gainullina
Keyword(s):  
Shock Wave ◽  
Numerical Modeling ◽  
Initial Pressure ◽  
Water Volume ◽  
Symmetric Model ◽  
Two Phase ◽  
Experimental Conditions ◽  
Initial Water ◽  
Aqueous Foam ◽  
Spherical Explosion

The spherical explosion propagation process in aqueous foam with the initial water volume content α10=0.0083 corresponding to the experimental conditions is analyzed numerically. The solution method is based on the one-dimensional two-temperature spherically symmetric model for two-phase gas-liquid mixture. The numerical simulation is built by the shock capturing method and movable Lagrangian grids. The amplitude and the width of the initial pressure pulse are found from the amount of experimental explosive energy. The numerical modeling results are compared to the real experiment. It’s shown, that the foam compression in the shock wave leads to the significant decrease in velocity and in amplitude of the shock wave.

THREE-DIMENSIONAL SEEPAGE ANALYSIS OF A COAL REFUSE PILE RECLAMATION

2020 ◽  
Vol 9 (4) ◽  
pp. 44-66
Author(s):  
Iuri Lira Santos ◽  
Keyword(s):  
Mine Drainage ◽  
Characteristic Curve ◽  
Water Volume ◽  
Low Permeability ◽  
Initial Water Content ◽  
Initial Water ◽  
Seepage Analysis ◽  
Cover System ◽  
Coal Refuse ◽  
Refuse Pile

Abstract. A coal refuse pile located in Greenbrier County, West Virginia was studied to restrict generation of acid mine drainage through the use of a cap and cover system. This paper presents results of a finite element method seepage analysis on a proposed reclamation design. The proposed reclamation incorporates a cap and cover system with a 0.3-m thick surface vegetation cap layer over a 0.6-m thick low permeability layer. The low permeability layer is directly above the coal refuse. Unsaturated soil mechanics was utilized, adopting the Fredlund and Xing equation for soil-water characteristic curve (SWCC) estimation. SWCC fitting parameters were calculated using the Zapata and the Hernandez estimation techniques. Different precipitation events were used to evaluate seepage throughout the reclamation area and assess the effectiveness of the cap and cover system. A steep area (>4H:1V) and a flat area were considered. The water balance analysis showed a 50% to 88% reduction in water volume at the coal refuse layer and a reduction in the time for the refuse to return to initial water content due to the cap and cover system implementation. Moisture detainment was observed in the growth layer and is important for supporting vegetation persistence.

scholarly journals Influence of bentonite type and producing method on hydraulic conductivity of sand–bentonite mixture

2020 ◽  
Vol 205 ◽  
pp. 10005
Author(s):  
Tomonori Sakita ◽  
Hideo Komine ◽  
Atsuo Yamada ◽  
Hailong Wang ◽  
Shigeru Goto
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Water Mass ◽  
Water Volume ◽  
Dry Density ◽  
Initial Water Content ◽  
Specimen Preparation ◽  
Initial Water ◽  
Compaction Energy ◽  
Low Level Radioactive Waste

Sand-bentonite mixtures with bentonite content of 10-30% had been planned to handle low-level radioactive waste in Japan, because of its low permeability. Hydraulic conductivity of sand–bentonite mixture depends on the bentonite type, bentonite content, initial water content, and other factors. Given this background, falling head permeability tests were conducted on sand–bentonite mixture by varying the compaction energy for specimen preparation, initial water content (10–20%), and bentonite content (15– 30%). For these tests, the hydraulic gradient of 25-500 was set. Consequently, the hydraulic conductivities were 10-8 – 10-13 m/s for all tested conditions. Correlation between the hydraulic conductivity and the effective montmorillonite dry density (montmorillonite mass divided by the sum of montmorillonite, air, water volume), which is often used to correlate the hydraulic conductivity of bentonite, was found. Correlation was also found between the hydraulic conductivity and a new index designated as the effective montmorillonite wet density (sum of montmorillonite and water mass / sum of montmorillonite, air, water volume). Effective montmorillonite wet density reveals differences in the specimen structural distribution through consideration of the initial water content.

Trajectory Optimization for Nonholonomic Vehicles on Non-Flat Terrains Using Shooting and Collocation Methods

2013 ◽  
Author(s):  
Dimitris M. Chatzigeorgiou
Keyword(s):  
Optimal Control ◽  
Mobile Robots ◽  
Performance Index ◽  
Trajectory Optimization ◽  
Optimization Problem ◽  
Control Policy ◽  
Collocation Methods ◽  
Governing Equations ◽  
Nonholonomic Mobile Robots ◽  
Nonholonomic Vehicles

In this paper we focus on the trajectory optimization problem for a specific family of robots; nonholonomic mobile robots. We study the particular case where such robots operate on smooth, non-flat terrains, i.e. terrains with large differences in elevation. Initially we present the governing equations of such robots and then study the trajectory optimization problem in order to solve for the optimal control policy. We test two different approaches for this problem, namely a shooting and a collocation method, for evaluating and optimizing a performance index.

Time-dependent Tsunami Source Following the 2018 Anak Krakatau Volcano Eruption Inferred from Nearby Tsunami Recordings

2020 ◽  
Author(s):  
Yifan Zhu ◽  
Chao An ◽  
Teng Wang ◽  
Hua Liu
Keyword(s):  
Source Region ◽  
Time Dependent ◽  
Tsunami Source ◽  
Water Volume ◽  
Generation Process ◽  
Tsunami Generation ◽  
Time Duration ◽  
Initial Water ◽  
Volcano Eruption ◽  
Krakatau Volcano

Abstract The eruption of the Anak Krakatau volcano, Indonesia, on 22 December 2018 induced a destructive tsunami (the Sunda Strait tsunami), which was recorded by four nearby tidal gauges. In this study we invert the tsunami records and recover the tsunami generation process. Two tsunami sources are obtained, a static one of instant initial water elevation and a time-dependent one accounting for the continuous evolution of water height. The time-dependent results are found to reproduce the tsunami recordings more satisfactorily. The complete tsunami generation process lasts approximately 9 min and features a two-stage evolution with similar intensity. Each stage lasts about 3.5 min and elevates a water volume of about 0.15 km 3 . The time, duration and volume of the volcano eruption in general agree with seismic records and geomorphological interpretations. We also test different sizes of the potential source region, which lead to different maximum wave height in the source area, but all the results of time-dependent tsunami sources show the robust feature of two stages of wave generation. Our results imply a time-dependent and complex process of tsunami generation during the volcano eruption.

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