Numerical Simulations of Rocket Solid Motor Engine Ignition and Duct Overpressure Waves at Reduced Scale

This paper and the companion paper (Rateiro et al., 2011) present an illustrative case of the joint application of experimental tests and numerical simulations for the proper analysis of a complex offshore operation (launching of a sub-sea equipment using one or two vessels). The main idea of the whole study is to compare two methodologies and operational procedures for the installation of the equipment in the seabed, using either one vessel (conventional operation) or two vessels in a synchronized operation in a Y-configuration. The experiment was conducted under a simplified configuration, and uses ODF (one degree of freedom) servo-actuator to emulate the vessels induced motion. The hydrodynamic properties of the equipment was then calculated, and some preliminary conclusions about system dynamics could also be drawn. After that, numerical simulations were conducted, considering the coupled dynamics of the vessels, cables and equipments under irregular sea state. Those simulations were used for determining the limiting environmental condition for a safe operation, and are described in the companion paper. This paper describes the reduced scale experimental setup used for evaluating the hydrodynamic properties of the equipment during a subsea installation under waves excitation. The reduced scale model of the equipment was attached to one or two servo-actuator, that emulate the wave-induced motion. The tests were conducted at the physical wave basin of Numerical Offshore Tank (Tanque de Provas Nume´rico – TPN). The experiments enabled the preliminary evaluation of the dynamic behavior of the equipment when submerged by one or two launching cables. In the later case (two launching cables), several tests considering phase shifts between the servo-actuator have been conducted. The reduction in the dynamic amplification of cable traction could also be experimentally verified.

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A two-way approach to adapt reduced-scale laboratory experiments and corresponding numerical simulations of offshore seismic surveys in complex marine environments

The Journal of the Acoustical Society of America ◽

10.1121/1.5137729 ◽

2019 ◽

Vol 146 (4) ◽

pp. 3088-3089

Author(s):

Nathalie Favretto-Cristini ◽

Bence Solymosi ◽

Paul Cristini ◽

Vadim Monteiller ◽

Bjorn Ursin ◽

...

Keyword(s):

Numerical Simulations ◽

Laboratory Experiments ◽

Marine Environments ◽

Seismic Surveys ◽

Reduced Scale

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Uplift Bearing Capacity of Cone-Cylinder Foundation for Transmission Line in Frozen Soil Regions, Using Reduced-Scale Model Tests and Numerical Simulations

Energies ◽

10.3390/en13082066 ◽

2020 ◽

Vol 13 (8) ◽

pp. 2066

Author(s):

Yangchun Han ◽

Jiulong Cheng ◽

Qiang Cui ◽

Qianyun Dong ◽

Wanting Song

Keyword(s):

Transmission Line ◽

Numerical Simulations ◽

Bearing Capacity ◽

Frozen Soil ◽

Scale Model ◽

Three Dimension ◽

Scale Modeling ◽

Bottom Width ◽

The Impact ◽

Reduced Scale

In order to analyze the uplift bearing capacity of cone-cylinder foundation for transmission line in frozen soil regions, a series of reduced-scale modeling tests and numerical simulations are carried out. First, three reduced-scale cone-cylinder foundations with the same sizes, that are five times smaller than the prototype, are made and then loaded under uplift load at −5 °C, −10 °C, and −15 °C, respectively. On this basis, the foundations of nine sizes are modeled and loaded by numerical simulation. The impact of three dimension factors, including the ratio of depth to bottom width ( λ = h t / D t ), the top diameter of the cone-cylinder (d), and the bottom diameter of the cone-cylinder (D), on the uplift bearing capacity of foundations have been investigated. The results reveal that, for cone-cylinder foundation, the uplift bearing capacity is obviously affected by the freezing temperatures and the foundation sizes. The capacity is negatively correlated with the former. Whereas the order of correlation with the latter is as follows: λ, D, and d based on the comprehensive results of range and variance analysis, but none of them are the significant factors, according to the F-test. Furthermore, three failure mechanisms of frozen soil are distinguished and named T-mode, V-mode, and U-mode, respectively. Based on the above results, the bearing mechanism of cone-cylinder foundation in frozen soil is elaborated in detail.

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Behavior of Shipment Casks Under Explosive Loading

Transportation, Storage, and Disposal of Radioactive Materials ◽

10.1115/pvp2004-2774 ◽

2004 ◽

Author(s):

Karine Cheval ◽

Olivier Loiseau ◽

Bruno Autrusson ◽

Jean-Marc Gue´rin ◽

Didier Pre´mont

Keyword(s):

Mechanical Behavior ◽

Numerical Simulations ◽

Numerical Models ◽

Nuclear Material ◽

Explosive Loading ◽

Degree Of Freedom ◽

Computer Codes ◽

Physical Phenomena ◽

Reduced Scale ◽

Complete Program

The behavior of the casks used for the shipment of nuclear material must be assessed for a set of various normal and accidental situations. The security of the casks must also be studied in the case of an explosion. To perform this study, the « Institut de Radioprotection et Suˆrete´ Nucle´aire » (IRSN) led a multi-years program since 1996, including numerical simulations and a set of 9 experimentations on reduced-scale mock-ups. Such a complete program is necessary to validate numerical models used to simulate the mechanical behavior of constitutive materials of the representative mock-up. On a counterpart, since numerous experimentations would be costly prohibitive, numerical simulations are used to find the worse conditions of loading considering the security of the casks. These conditions being established, different points are investigated (check of leaks, effects of surrounding casks, ...). The two last experimentations are devoted to specific aspects which could not be studied, in details, with numerical simulations because of the high number of degree of freedom or because the physical phenomena associated are not correctly modeled with computer codes yet.

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Direct Numerical Simulations of Gas–Liquid Multiphase Flows

10.1017/cbo9780511975264 ◽

2001 ◽

Cited By ~ 151

Author(s):

Grétar Tryggvason ◽

Ruben Scardovelli ◽

Stéphane Zaleski

Keyword(s):

Numerical Simulations ◽

Multiphase Flows ◽

Direct Numerical Simulations

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Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038023 ◽

2020 ◽

Vol 640 ◽

pp. A53

Author(s):

L. Löhnert ◽

S. Krätschmer ◽

A. G. Peeters

Keyword(s):

Growth Rate ◽

Numerical Simulations ◽

Accretion Disks ◽

Gravitational Instability ◽

Turbulent Viscosity ◽

Radial Distance ◽

Maximum Growth ◽

Wave Number ◽

Radiative Cooling ◽

Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

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