Mechanical Models of Low-Gravity Sloshing Taking Into Account Viscous Damping

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
M. Utsumi
Keyword(s):  
Surface Tension ◽  
Mechanical Model ◽  
Damping Ratio ◽  
Space Vehicle ◽  
Control Analysis ◽  
Phase Lag ◽  
Low Gravity ◽  
Correction Model ◽  
Mechanical Models ◽  
Modal Equation

Mechanical models of damped low-gravity sloshing are developed using a proposed analytical method for arbitrary axisymmetric tanks. It is shown that (a) the complex amplitudes of the force and moment caused by the conventional mechanical model do not coincide with the complex amplitudes of the force and moment calculated from the modal equation of sloshing and (b) these differences arise not only from the damping ratio but also from the surface tension although the surface tension does not cause energy dissipation. A mechanical model for correcting these differences is developed. The mass of this correction model is found to be equal to the mass of the liquid that fills the domain bounded by the meniscus and the plane that includes the contact line of the meniscus with the tank wall. With decreasing Bond number, the correction model mass as well as the damping ratio increase and, therefore, the correction becomes important. The force and moment caused by the conventional uncorrected mechanical model have phase lag with respect to the force and moment calculated from the modal equation of sloshing near the resonant frequency. Therefore, the correction is important for the dynamics and control analysis of a space vehicle.

Dynamics of Liquid Sloshing in Upright and Inverted Bladdered Tanks

1987 ◽  
Vol 109 (1) ◽  
pp. 58-63 ◽  
Author(s):  
F. T. Dodge ◽  
D. D. Kana
Keyword(s):  
Structural Dynamics ◽  
Mechanical Model ◽  
The Body ◽  
Liquid Sloshing ◽  
Model Parameters ◽  
Test Results ◽  
Governing Equations ◽  
Low Gravity ◽  
Equivalent Mechanical Model ◽  
Mechanical Models

The sloshing of liquids in tanks that use a flexible, inextensible bladder to contain the liquid is investigated experimentally and theoretically. The bladder affects both the configuration of the liquid in the tank and the sloshing frequencies and motion. The governing equations of liquid sloshing coupled to the structural dynamics of the bladder are formulated and examined to determine the interaction between the body forces of the liquid and the stiffness of the bladder and to show that the slosh dynamics can be represented by equivalent mechanical models. Tests are conducted to establish such mechanical models for normal and low-gravity conditions. For an inverted tank (liquid above the bladder), the sloshing is sufficiently different from conventional sloshing that the form of the equivalent mechanical model as well as the numerical values of the model parameters must be derived from the test results.

Study of Sand Production Using Geomechanical and Hydro-Mechanical Models

2018 ◽  
Vol 876 ◽  
pp. 181-186
Author(s):  
Son Tung Pham
Keyword(s):  
Production Rate ◽  
Mechanical Model ◽  
Failure Criteria ◽  
Sand Production ◽  
Geomechanical Model ◽  
Strength Failure ◽  
Rate Versus ◽  
Mechanical Models ◽  
Rock Mechanical Properties ◽  
Bottomhole Pressure

Sand production is a complicated physical process depending on rock mechanical properties and flow of fluid in the reservoir. When it comes to sand production phenomenon, many researchers applied the Geomechanical model to predict the pressure for the onset of sand production in the reservoir. However, the mass of produced sand is difficult to determine due to the complexity of rock behavior as well as fluid behavior in porous media. In order to solve this problem, there are some Hydro – Mechanical models that can evaluate sand production rate. As these models require input parameters obtained by core analysis and use a large empirical correlation, they are still not used popularly because of the diversity of reservoirs behavior in the world. In addition, the reliability of these models is still in question because no comparison between these empirical models has been studied. The onset of sand production is estimated using the bottomhole pressure that makes the maximum effective tangential compressive stress equal or higher than the rock strength (failure criteria), which is usually known as critical bottomhole pressure (CBHP). Combining with Hydro – Mechanical model, the main objective of this work aims to develop a numerical model that can solve the complexity of the governing equations relating to sand production. The outcome of this study depicts sand production rate versus time as well as the change of porosity versus space and time. In this paper, the Geomechanical model coupled with Hydro – Mechanical model is applied to calibrate the empirical parameters.

Some Properties of a Mechanical Model of Plasticity

1948 ◽  
Vol 15 (3) ◽  
pp. 222-225
Author(s):  
H. F. Bohnenblust ◽  
Pol Duwez
Keyword(s):  
Plastic Deformation ◽  
Potential Energy ◽  
Work Hardening ◽  
Mechanical Model ◽  
Strain Curve ◽  
Hysteresis Curve ◽  
Plastic Range ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Mechanical Models

Abstract Various mechanical models explaining the plastic deformation of metals have been proposed. One of the present authors has shown that in some cases an analytical expression for the stress-strain curve and the hysteresis curve of a metal in the plastic range can be deduced from such a model. The present investigation is a further analysis of the model leading to the computation of the change in potential energy of the metal due to work-hardening.

A Complex Modal Analysis Method for Damped Vibration Systems (The Representation in the Second Order Differential Form of a Modal Equation and its Use for Practical Application)

1985 ◽  
Vol 107 (1) ◽  
pp. 13-18
Author(s):  
Y. Inoue ◽  
T. Fujikawa
Keyword(s):  
Modal Analysis ◽  
Damping Ratio ◽  
Second Order ◽  
Response Analysis ◽  
Modal Damping Ratio ◽  
Vibration Problems ◽  
Modal Mass ◽  
Modal Equation ◽  
Damped Vibration Systems ◽  
Complex Modal

Second order uncoupled differential equations for the general damped vibration systems are derived theoretically. The equations are written in a form similar to the classical real modal equations by using the natural frequency, the modal damping ratio, and the newly defined complex modal mass. Introducing supplementary variables, the response analysis is carried out in a similar manner to the real modal analysis. By comparing these equations to the classical ones, physical meanings of the derived equations are clarified. For the vibration problems near the resonant point, approximate complex modal equations are derived which have almost the same form as the classical one. Some applications of the proposed method to vibration problems are discussed.

Experimental and Theoretical Studies of Liquid Sloshing at Simulated Low Gravity

1967 ◽  
Vol 34 (3) ◽  
pp. 555-562 ◽  
Author(s):  
F. T. Dodge ◽  
L. R. Garza
Keyword(s):  
Natural Frequency ◽  
Mechanical Model ◽  
Small Diameter ◽  
Bond Number ◽  
Liquid Sloshing ◽  
Theoretical Studies ◽  
Low Gravity ◽  
Equivalent Mechanical Model ◽  
Experimental And Theoretical Studies ◽  
Experimental Comparisons

Analyses and experimental comparisons are given for liquid sloshing in a rigid cylindrical tank under conditions of moderately small axial accelerations; in particular, the theory is valid for Bond numbers larger than 10. The analytical results are put in the form of an equivalent mechanical model, and it is shown that the sloshing mass and the natural frequency of the first mode, for a liquid having a 0 deg contact angle at the tank walls, are smaller than for high-g conditions. The experimental data, obtained by using several small-diameter tanks and three different liquids, are compared to the predictions of the mechanical model; good correlation is found in most cases for the sloshing forces and natural frequency as a function of Bond number.

scholarly journals COUPLED SIMULATION FOR FIRE-EXPOSED STRUCTURES USING CFD AND THERMO-MECHANICAL MODELS

2017 ◽  
Vol 13 ◽  
pp. 121
Author(s):  
Stanislav Šulc ◽  
Vít Šmilauer ◽  
František Wald
Keyword(s):  
Fluid Dynamics ◽  
Temperature Field ◽  
Mechanical Model ◽  
Data Transfer ◽  
Thermal Strain ◽  
Dynamics Simulation ◽  
Coupled Simulation ◽  
Fire Dynamics ◽  
Mechanical Models ◽  
Fire Loading

Fire resistance of buildings is based on fire tests in furnaces with gas burners. However, the tests are very expensive and time consuming. This article presents a coupled simulation of an element loaded by a force and a fire loading. The simulation solves a weakly-coupled problem, consisting of fluid dynamics, heat transfer and mechanical model. The temperature field from the computational fluid dynamics simulation (CFD) creates Cauchy and radiative boundary conditions for the thermal model. Then, the temperature field from element is passed to the mechanical model, which induces thermal strain and modifies material parameters. The fluid dynamics is computed with Fire Dynamics Simulator and the thermo-mechanical task is solved in OOFEM. Both softwares are interconnected with MuPIF python library, which allows smooth data transfer across the different meshes, orchestrating simulations in particular codes, exporting results to the VTK formats and distributed computing.

scholarly journals A Sequential Approach to the Biodynamic Modeling of a Human Finger

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Luka Knez ◽  
Janko Slavič ◽  
Miha Boltežar
Keyword(s):  
Mechanical Model ◽  
Index Finger ◽  
Simulated Data ◽  
Body Parts ◽  
Sequential Approach ◽  
Novel Device ◽  
Single Finger ◽  
Mechanical Models ◽  
Human Finger ◽  
Finger Model

In an effort to understand the vibration-induced injuries incurred by manual workers, mechanical models are developed and used to predict the biodynamic responses of human body parts that are exposed to vibration. Researchers have traditionally focused on the arms and hands, but there has been only limited research on finger modeling. To simulate the accurate response of a single finger, a detailed mechanical model based on biodynamic finger measurements is necessary. However, the development of such models may prove difficult using the traditional one-point coupling method; therefore, this study proposes a new approach. A novel device for single-finger measurements is presented and used to expose the finger to a single-axial broadband excitation. The sequentially measured responses of the different finger parts are then used to identify the parameters of a multibody mechanical model of the index finger. Very good agreement between the measured and the simulated data was achieved, and the study also confirmed that the obtained index-finger model is acceptable for further biodynamic studies.

Model-Based Estimation of Mechanical Characters of Arterial Vessels Using Experimental Dynamic Response Data

2011 ◽  
Author(s):  
Rahil Vali ◽  
Takashi Saito
Keyword(s):  
Mechanical Model ◽  
Damping Ratio ◽  
Elastic Shell ◽  
Measurement Data ◽  
Circulatory System ◽  
Stiffness Index ◽  
Working Fluid ◽  
Model Based ◽  
Ring Model ◽  
Downhill Simplex

As both the geometric and stiffness changes may occur in atherosclerosis, it is necessary to estimate respective contribution from structural and material characteristics in the stiffness index. In this study, we employ the primary mechanical model based on one of elastic shell theory, Love’s theory and look upon a blood vessel as a ring model. Furthermore in order to confirm validity of the model, the experiments were carried out on artificial tubes. The circulating circuit is applied as the circulatory system of human body including tubes, and water is designated as the working fluid of the circulating circuit. Experimental data are applied for mechanical model and mechanical parameters are identified using Downhill simplex method as the inverse problem. In this study stiffness index and damping ratio were identified and the result of Love’ theory was compared with measurement data and Donnell’s theory. The result shows that present study can confirm the measurement data with the fine approximation.

Mechanical models and the mobility of robots and mechanisms

Robotica ◽  
2014 ◽  
Vol 33 (1) ◽  
pp. 181-193 ◽  
Author(s):  
Doru Talabă
Keyword(s):  
Mechanical Model ◽  
Dynamic Models ◽  
Dynamic Properties ◽  
Qualitative Assessment ◽  
Fundamental Parameter ◽  
Natural Coordinates ◽  
Closed Loops ◽  
Mechanical Models ◽  
Overconstrained Mechanisms

SUMMARYMobility is a fundamental parameter of mechanisms expressing in a qualitative manner their kinematic and dynamic properties. The mobility formulae presented in literature take into consideration some of the structural entities, such as bodies, joints, constraints, closed loops, and space characteristics; however, the specific mechanical model that has traditionally been at the origin of the mobility criteria themselves is incompletely specified and, even then, only implicitly. In this paper, we propose a classification of the mobility criteria based on the known dynamic models. While all known mobility criteria have been associated with a specific dynamic model, some particular, less used dynamic models (like natural coordinates and multi-particle models) suggested new mobility criteria models. The associated mechanical model for each category of mobility criteria allows a qualitative assessment of the kinematic and dynamic sets of equations to be formulated in later stages of analysis. A simple multi-loop mechanism is taken as an example just to illustrate the mobility calculation and qualitative assessment of the kinematic and dynamic models in each case. Based on the proposed classification of the mobility formulae, an assessment is made with particular regard to their applicability to overconstrained mechanisms.

Low-Gravity Sloshing in an Axisymmetrical Container Excited in the Axial Direction

2000 ◽  
Vol 67 (2) ◽  
pp. 344-354 ◽  
Author(s):  
M. Utsumi
Keyword(s):  
Liquid Surface ◽  
Characteristic Root ◽  
Axial Direction ◽  
Bond Number ◽  
Characteristic Functions ◽  
Surface Oscillation ◽  
Low Gravity ◽  
The Past ◽  
Axial Excitation ◽  
Modal Equation

The response of low-gravity propellant sloshing is analyzed for the case where an axisymmetrical container is exposed to axial excitation. Spherical coordinates are used to analytically derive the characteristic functions for an arbitrary axisymmetrical convex container, for which time-consuming and expensive numerical methods have been used in the past. Numerical results show that neglecting the surface tension results in the underestimation of the magnitude of the liquid surface oscillation. The reason for this is explained by the influences of the Bond number and the liquid filling level on the critical value of the coefficient of the excitation term in the modal equation, above which the oscillation is destabilized, and on the characteristic root of the destabilized system. [S0021-8936(00)01502-6]

Sign in / Sign up

Export Citation Format

Share Document