Porous MHD Convection: Effect of Vadasz Inertia Term

2017 ◽  
Vol 118 (3) ◽  
pp. 519-536 ◽  
Author(s):  
Florinda Capone ◽  
Roberta De Luca
Keyword(s):  
Inertia Term

Development of Control System by Nonlinear Compensation Using Digital Acceleration Control

2010 ◽  
Author(s):  
Takanori Emaru ◽  
Kazuo Imagawa ◽  
Yohei Hoshino ◽  
Yukinori Kobayashi
Keyword(s):  
Control System ◽  
System Identification ◽  
Mechanical System ◽  
Pid Control ◽  
Estimation Method ◽  
Proportional Integral Derivative ◽  
Inertia Term ◽  
Modeling Errors ◽  
Nonlinear Compensation ◽  
Simulation Results

Proportional-Integral-Derivative (PID) control has been most commonly used to operate mechanical systems. In PID control, however, there are limits to the accuracy of the resulting movement because of the influence of gravity, friction, and interaction of joints. We have proposed a digital acceleration control (DAC) that is robust over these modeling errors. One of the most practicable advantages of DAC is robustness against modeling errors. However, it does not always work effectively. If there are modeling errors in the inertia term of the model, the DAC controller cannot control a mechanical system properly. Generally an inertia term is easily modeled in advance, but it has a possibility to change. Therefore, we propose an online estimation method of an inertia term by using a system identification method. By using the proposed method, the robustness of DAC is considerably improved. This paper shows the simulation results of the proposed method using 2-link manipulator.

Non-Darcian Boundary Layer Flow and Forced Convective Heat Transfer Over a Flat Plate in a Fluid-Saturated Porous Medium

1990 ◽  
Vol 112 (1) ◽  
pp. 157-162 ◽  
Author(s):  
A. Nakayama ◽  
T. Kokudai ◽  
H. Koyama
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Porous Medium ◽  
Flat Plate ◽  
Similarity Solution ◽  
Temperature Fields ◽  
Solid Boundary ◽  
Local Similarity ◽  
Viscous Term ◽  
Inertia Term

The local similarity solution procedure was successfully adopted to investigate non-Darcian flow and heat transfer through a boundary layer developed over a horizontal flat plate in a highly porous medium. The full boundary layer equations, which consider the effects of convective inertia, solid boundary, and porous inertia in addition to the Darcy flow resistance, were solved using novel transformed variables deduced from a scale analysis. The results from this local similarity solution are found to be in good agreement with those obtained from a finite difference method. The effects of the convective inertia term, boundary viscous term, and porous inertia term on the velocity and temperature fields were examined in detail. Furthermore, useful asymptotic expressions for the local Nusselt number were derived in consideration of possible physical limiting conditions.

Parametric investigation of twin tube magnetorheological dampers using a new unsteady theoretical analysis

2019 ◽  
Vol 30 (6) ◽  
pp. 878-895
Author(s):  
Mohammad Mehdi Zolfagharian ◽  
Mohammad Hassan Kayhani ◽  
Mahmood Norouzi ◽  
Amir Jalali
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Static Analysis ◽  
Fluid Velocity ◽  
Magnetorheological Fluid ◽  
Magnetorheological Damper ◽  
Parallel Plates ◽  
Fluid Inertia ◽  
Time Duration ◽  
Inertia Term

In the present work, a new unsteady analytical model is developed for magnetorheological fluid flow through the annular gap which is opened on the piston head of twin tube magnetorheological damper, considering fluid inertia term into the momentum equation. This new unsteady model is based on Stokes’ second problem that is extended for magnetorheological fluid flow between finite oscillating parallel plates under the pressure gradient. A quasi-static analysis is also developed for magnetorheological fluid flow in twin tube damper, to compare its results with present unsteady solution and to show the effect of magnetorheological fluid inertia. The obtained results are validated experimentally and then, a parametric study is presented using both unsteady and quasi-static analysis. The effect of fluid inertia term is investigated on force–displacement and force–velocity loops, magnetorheological fluid velocity profile, pressure drop, phase difference between pressure drop and flow rate and change of plug thickness with time duration. According to the obtained results, quasi-static analysis included considerable error respect to new unsteady analysis as the gap height, magnetorheological fluid density, excitation frequencies and amplitudes are increased and yield stress is decreased. It is found that the plug thickness is considerably affected by inertia term of magnetorheological fluid.

A Nonlinear Model for Short Length, Cylindrical Squeeze Films With Large Planar Motions

1992 ◽  
Vol 114 (1) ◽  
pp. 192-198 ◽  
Author(s):  
Yong Lu ◽  
R. J. Rogers
Keyword(s):  
Heat Exchanger ◽  
Short Length ◽  
Squeeze Film ◽  
Inertia Force ◽  
Flow Induced Vibration ◽  
Damping Force ◽  
Rotating Shaft ◽  
Viscous Term ◽  
Inertia Term ◽  
Planar Motions

A rotating shaft vibrating in a squeeze film bearing and a tube in a heat exchanger oscillating with fluid-filled cylindrical supports both involve cylindrical squeeze films. Many theoretical and experimental results show that the squeeze film force consists of both a damping force and an inertia force. For relatively large amplitude motions or when the initial eccentricity is large, the time waveform of the squeeze force is significantly nonlinear. In order to predict the transient response of a rotor with squeeze film bearings or a heat exchanger tube subject to flow induced vibration, the nonlinear instantaneous squeeze force must be calculated. This paper presents a model for the instantaneous cylindrical squeeze film force for planar motion. The squeeze film model for a two-dimensional plate shows that there are three nonlinear terms included in the squeeze force. Based on this model, an equation for the short length, cylindrical squeeze film force for moderately large eccentricities is developed. The equation includes the three nonlinear terms: the viscous term, the unsteady inertia term, and the convective inertia term. All three terms are functions of instantaneous eccentricity. The equation predicts the nonlinear multi-harmonic and unsymmetrical time waveforms of the instantaneous squeeze film force for planar motions with both in-line and out-of-line initial eccentricities. The results are compared with experimentally measured squeeze force waveforms obtained with a length to diameter ratio of 0.75 and instantaneous eccentricities less than 0.75. The squeeze force waveforms for this finite length geometry can be reasonably predicted if correction coefficients, which account for the circumferential flow, are applied to the three nonlinear force terms. These coefficients are themselves functions of frequency, initial eccentricity and amplitude.

Inclusion of an Aerobic Inertia Term in the Critical Velocity Model Applied to Kayaking

2006 ◽  
Vol 38 (Supplement) ◽  
pp. S235
Author(s):  
Fábio Y. Nakamura ◽  
Thiago O. Borges ◽  
Eduardo Kokubun
Keyword(s):  
Critical Velocity ◽  
Velocity Model ◽  
Inertia Term

Influence of Bed Size on the Flow Characteristics and Porosity of Randomly Packed Beds of Spheres

1973 ◽  
Vol 40 (3) ◽  
pp. 655-660 ◽  
Author(s):  
G. S. Beavers ◽  
E. M. Sparrow ◽  
D. E. Rodenz
Keyword(s):  
Rectangular Cross Section ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Darcy Law ◽  
Equivalent Diameter ◽  
Packed Beds ◽  
Sphere Diameter ◽  
Number Range ◽  
Inertia Term ◽  
Bed Porosity

Experiments were performed to investigate the flow characteristics and porosity of randomly packed beds of glass spheres for conditions where the bed size cannot be regarded as infinitely large compared with the sphere size. The operating conditions of the flow experiments extended over a Reynolds number range for which the flow was governed by the Forchheimer extension of the linear Darcy law. The influence of the bed bounding walls on the permeability, on the coefficient of the Forchheimer inertia term, and on the porosity, was studied by using beds of rectangular cross section. It was found that the permeability was not apparently influenced by the bounding walls when the equivalent diameter of the bed was greater than 12 times the sphere diameter, whereas the coefficient of the inertia term was affected by the presence of the walls for bed equivalent diameters as high as 40 sphere diameters. The porosity of the beds was not influenced by the bed size for values of the bed equivalent diameter greater than 15 sphere diameters. When the large-bed porosity value was used with the Carman-Kozeny relationship for the permeability as a function of sphere diameter, an excellent representation of accumulated experimental data was attained.

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