Quasi-Steady Analysis of a Magnetorheological Dashpot Damper

Aerospace ◽  
2004 ◽  
Author(s):  
Young-Tai Choi ◽  
Norman M. Wereley
Keyword(s):  
Mixed Mode ◽  
Shear Flows ◽  
Performance Metrics ◽  
Fluid Velocity ◽  
Flow Mode ◽  
Damping Capacity ◽  
Stress Profile ◽  
Bingham Plastic ◽  
Bingham Number ◽  
Moving Wall

This paper addresses quasi-steady analysis of a magnetorheological (MR) dashpot damper. MR dashpot dampers show mixed fluid mode of flow and shear flows since a dashpot inside dampers works as a piston and a moving wall simultaneously. In this study, quasi-steady analysis of MR dashpot dampers has developed based on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. For the mixed mode MR damper that is the sums of flow and shear flows, fluid velocity profile, shear stress profile, and damping coefficient are theoretically derived. In addition, the preyield thickness equation to characterize the relationship between the Bingham number and the preyield thickness is constructed. Through computer simulation, damping characteristics of the mixed mode MR dashpot damper are evaluated and compared with flow mode case.

NONDIMENSIONAL QUASISTEADY ANALYSIS OF A MAGNETORHEOLOGICAL DASHPOT DAMPER

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1584-1590 ◽  
Author(s):  
YOUNG-TAI CHOI ◽  
NORMAN M. WERELEY
Keyword(s):  
Mixed Mode ◽  
Performance Metrics ◽  
Fluid Velocity ◽  
Hydraulic Cylinder ◽  
Flow Mode ◽  
Damping Capacity ◽  
Shear Mode ◽  
Stress Profile ◽  
Cylinder Wall ◽  
Bingham Plastic

This paper addresses nondimensional analysis of a magnetorheological (MR) dashpot damper. An MR dashpot damper consists of a loosely fitting piston within a hydraulic cylinder or reservoir of MR fluids. The fluid flow within such a damper presents both Poiseuille (flow mode or pressurized flow through the duct) and Couette (shear mode or shear flow due to relative motion between piston and hydraulic cylinder wall) simultaneously. Thus, an MR dashpot damper, which mixes both shear and flow modes of behavior, is called a mixed mode damper. In this study, a quasi-steady analysis of MR dashpot dampers was revisited based on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. For the mixed mode MR damper, key physical quantities are derived: fluid velocity profile, shear stress profile, and damping coefficient. In addition, the plug thickness equation to characterize the relationship between the Bingham number and the plug thickness is constructed. Through computer simulation, damping characteristics of the mixed mode MR dashpot damper are evaluated and compared to the flow mode case.

Quasi-Steady Herschel-Bulkley Analysis of Magnetorheological Dampers With Preyield Viscosity

Aerospace ◽  
2005 ◽  
Author(s):  
Sung-Ryong Hong ◽  
Shaju John ◽  
Norman M. Wereley
Keyword(s):  
Yield Stress ◽  
Power Law ◽  
Performance Metrics ◽  
Dynamic Range ◽  
Fluid Velocity ◽  
Constitutive Behavior ◽  
Flow Mode ◽  
Damping Capacity ◽  
Mr Fluid ◽  
Bingham Plastic

A magnetorheological (MR) fluid, modeled as a Bingham-plastic material, is characterized by a field dependent yield stress, and a (nearly constant) postyield plastic viscosity. Based on viscometric measurements, such a Bingham-plastic model is an idealization to physical magnetorheological behavior, albeit a useful one. A better approximation involves modifying both the preyield and postyield constitutive behavior as follows: (1) assume a high viscosity preyield behavior over a low shear rate range below the yield stress, and (2) assume a power law fluid (i.e., variable viscosity) above the yield stress that accounts for the shear thinning behavior exhibited by MR fluids above the yield stress. Such an idealization to the MR fluid’s constitutive behavior is called a viscous-power law model, or a Herschel-Bulkley model with preyield viscosity. This study develops analytical quasi-steady analysis for such a constitutive MR fluid behavior applied to a flow mode MR damper. Closed form solutions for the fluid velocity, as well as key performance metrics such as damping capacity and dynamic range (ratio of field on to field off force). Also, specializations to existing models such as the Herschel-Bulkley, the Biviscous, and the Bingham-plastic models, are shown to be easily captured by this model when physical constraints (idealizations) are placed on the rheological behavior of the MR fluid.

Quasi-Steady Axisymmetric Bingham-Plastic Model of Magnetorheological Flow Damper Behavior

Aerospace ◽  
2005 ◽  
Author(s):  
Jin-Hyeong Yoo ◽  
Norman M. Wereley
Keyword(s):  
Closed Form ◽  
Yield Stress ◽  
Dynamic Range ◽  
Closed Form Solution ◽  
Form Solution ◽  
Damping Capacity ◽  
Stress Profile ◽  
Mr Fluid ◽  
Bingham Plastic ◽  
Closed Form Solutions

A typical magnetorheological (MR) flow mode damper consists of a piston attached to a shaft that travels in a tightly fitting hydraulic cylinder. The piston motion makes fluid flow through an annular valve in the MR damper. An electro-magnet applies magnetic field to the MR fluid as it flows through the MR valve, and changes its yield stress. An MR fluid, modeled as a Bingham-plastic material, is characterized by a field dependent yield stress, and a (nearly constant) postyield plastic viscosity. Although the analysis of such an annular MR valve is well understood, a closed form solution for the damping capacity of a damper using such an MR valve has proven to be elusive. Closed form solutions for the velocity and shear stress profile across the annular gap are well known. However, the location of the plug must be computed numerically. As a result, closed form solutions for the dynamic range (ratio of field on to field off damper force) cannot be derived. Instead of this conventional theoretic procedure, an approximated closed form solution for a dampers dynamic range, damping capacity and other key performance metrics is derived. And the approximated solution is used to validate a rectangular duct simplified analysis of MR valves for small gap condition. These approximated equations are derived, and the approximation error is also provided.

Nondimensional Damping Analysis of Flow-Mode Magnetorheological and Electrorheological Dampers

Aerospace ◽  
2003 ◽  
Author(s):  
Wei Hu ◽  
Norman M. Wereley
Keyword(s):  
Magnetic Circuit ◽  
Design Method ◽  
Damping Coefficient ◽  
Flow Mode ◽  
Shear Mode ◽  
Number Range ◽  
Bingham Plastic ◽  
Bingham Number ◽  
Er Damper ◽  
The Relationship

In an effort to develop a Magnetorheological (MR) and Electrorheological (ER) damper initial design method, a quasi-steady relationship between force and velocity exhibited by a flow-mode MR/ER damper is developed based on a Bingham plastic model and a parallel plate assumption. A nondimensional damping coefficient is described as a nonlinear explicit function of an independent nondimensional Bingham number. Since the nondimensional damping coefficient is not a simple analytical function of the Bingham number, a uniform rational approximation approaches is used to determine the relationship between nondimensional damping coefficient and Bingham number. Approximate linear relationship is obtained in a certain Bingham number range. Thus, the quasi-steady flow mode damping approximately consists of a controllable damping and a linear viscous or post-yield damping, which is similar to the behavior of a shear mode damper. The effect on the nondimensional damping coefficient due to the magnetic circuit is also considered by introducing a ration of the length of active region to the total flow gap length.

A Preliminary Parametric Study of Electrorheological Dampers

1994 ◽  
Vol 116 (3) ◽  
pp. 570-576 ◽  
Author(s):  
Z. Lou ◽  
R. D. Ervin ◽  
F. E. Filisko
Keyword(s):  
Cross Section ◽  
Mixed Mode ◽  
Flow Mode ◽  
Shear Mode ◽  
Zero Field ◽  
Damping Force ◽  
Bingham Plastic ◽  
Control Effectiveness ◽  
Er Damper ◽  
Er Fluid

In approaching the design of an electrorheology-based, semi-active suspension, the electrorheological component (ER damper) can be built as either a flow-mode, shear-mode, or mixed-mode type of damper. The source of damping force in the flow-mode is exclusively from flow-induced pressure drop across a valve, while that in the shear-mode is purely from the shear stress on a sliding surface. The dynamics of the fluid flow are included in the derivation of the zero-field damping forces. The control effectiveness is found to be strongly related to the dynamic constant (which is proportional to the square root of the vibration frequency) and, for shear-and flow-mode dampers, the ratio of the piston area to the cross-section of the ER control gap. To achieve the same performance, a flow-mode ER damper is not as compact and efficient as a shear-mode ER damper. With the same ER damping force, a mixed-mode damper is more compact than a shear-mode damper. However, the mixed-mode damper does not have as a low zero-field damping force as the shear-mode damper. The analysis is based on the assumption that the ER fluid is Bingham plastic.

Nondimensional Analysis of Electrorheological and Magnetorheological Dampers Using a Herschel-Bulkley Constitutive Model

Aerospace ◽  
2003 ◽  
Author(s):  
Norman M. Wereley
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Constitutive Model ◽  
Yield Stress ◽  
Flow Mode ◽  
Damping Capacity ◽  
Bingham Plastic ◽  
Field Dependent ◽  
Local Shear ◽  
Local Shear Stress

Quasisteady modeling of linear stroke flow mode magnetorheological (MR) and electrorheological (ER) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the yield stress of the fluid, τy, is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a preyield condition where the local shear stress is less than the yield stress, τ < τy, or (2) a postyield condition, where the local shear stress is greater than the yield stress, τ > τy, so that the material flows with a constant postyield viscosity. The objective of this paper is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits postyield shear thinning or thickening behavior, that is, the postyield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results—velocity profile, shear stress profile, and damping coefficient—are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.

Nondimensional Analysis of Electrorheological and Magnetorheological Dampers Using a Herschel-Bulkley Constitutive Model

2003 ◽  
Author(s):  
Norman M. Wereley
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Constitutive Model ◽  
Yield Stress ◽  
Flow Mode ◽  
Damping Capacity ◽  
Bingham Plastic ◽  
Field Dependent ◽  
Local Shear ◽  
Local Shear Stress

Quasisteady modeling of linear stroke flow mode magnetorheological (MR) and electrorheological (ER) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the yield stress of the fluid, τy, is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a preyield condition where the local shear stress is less than the yield stress, τ < τy, or (2) a postyield condition, where the local shear stress is greater than the yield stress, τ > τy, so that the material flows with a constant postyield viscosity. The objective of this paper is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits postyield shear thinning or thickening behavior, that is, the postyield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results — velocity profile, shear stress profile, and damping coefficient — are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.

scholarly journals Flow Mode Magnetorheological Dampers with an Eccentric Gap

2014 ◽  
Vol 6 ◽  
pp. 931683 ◽  
Author(s):  
Young-Tai Choi ◽  
Norman M. Wereley
Keyword(s):  
Constitutive Model ◽  
Mr Damper ◽  
Flow Mode ◽  
Rectangular Duct ◽  
Damping Force ◽  
Bingham Plastic ◽  
Mr Dampers ◽  
Annular Gap ◽  
Field Dependent ◽  
Viscous Field

This paper analyzes flow mode magnetorheological (MR) dampers with an eccentric annular gap (i.e., a nonuniform annular gap). To this end, an MR damper analysis for an eccentric annular gap is constructed based on approximating the eccentric annular gap using a rectangular duct with a variable gap, as well as a Bingham-plastic constitutive model of the MR fluid. Performance of flow mode MR dampers with an eccentric gap was assessed analytically using both field-dependent damping force and damping coefficient, which is the ratio of equivalent viscous field-on damping to field-off damping. In addition, damper capabilities of flow mode MR dampers with an eccentric gap were compared to a concentric gap (i.e., uniform annular gap).

scholarly journals Laminar Free Convection From a Heated Square Cylinder in Bingham Plastic Fluids

2021 ◽  
Author(s):  
Bairi Levi Rakshith
Keyword(s):  
Nusselt Number ◽  
Free Convection ◽  
Cylinder Surface ◽  
Square Cylinder ◽  
Governing Equations ◽  
Bingham Plastic ◽  
Bingham Number ◽  
Wide Range ◽  
Nusselt Number Distribution ◽  
Plastic Fluids

The free convection phenomenon from a heated square cylinder submerged in Bingham Plastic fluids is numerically investigated. The governing equations are solved for a wide range of physical dimensionless parameters, such as Rayleigh number (10^2 ≤ Ra ≤ 10^5), Prandtl number (10 ≤ Pr ≤ 100) and Bingham number (0 ≤ Bn ≤ 10^7). The heat transfer characteristics are investigated in terms of local Nusselt number distribution over the surface of the cylinder surface average Nusselt number. Streamlines, isothermal contours, yielded and unyielded regions are visualized in detail.

Effect of Sinusoidally Varying Flow of Yield Stress Fluid On Heat Transfer From a Cylinder

2021 ◽  
Author(s):  
Sanjay Gupta ◽  
Swati Patel ◽  
Raj P. Chhabra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Yield Stress ◽  
Process Intensification ◽  
Simple Expression ◽  
Pulsation Frequency ◽  
Mean Velocity ◽  
Bingham Plastic ◽  
Bingham Number

Abstract The effect of pulsating laminar flow of a Bingham plastic fluid on heat transfer from a constant temperaturre cylinder is studied numerically over wide ranges of conditions as: Reynolds number (0.1 = Re = 40) and Bingham number (0.01 = Bn = 50) based the on mean velocity, Prandtl number (10 = Pr = 100), pulsation frequency (0 = w* = Pi) and amplitude (0 = A = 0.8). Results are visualized in terms of instantaneous streamlines, isotherms, apparent yield surfaces at different instants of time during a pulsation cycle. The overall behavior is discussed in terms of the instantaneous and time averaged values of the drag coefficient and Nusselt number. The size of the yielded zone is nearly in phase with the pulsating velocity whereas the phase shift has been observed in both drag coefficient and Nusselt number. The maximum augmentation ( ~30 %) in Nusselt number occurs at Bn = 1, Re = 40, Pr = 100, w* = Pi and A = 0.8 with respect to that for uniform flow. However, the increasing yield stress tends to suppress the potential for heat transfer enhancement. Conversely, this technique of process intensification is best suited for Newtonian fluids in the limit of Bn ~ 0. Finally, a simple expression consolidates the numerical values of the time-average of the Nusselt number as a function of the pertinent dimensionless parameters which is consistent with the widely accepted scaling of the Nusselt number with ~Pe1/3 under these conditions.

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