On the Influence of Piston and Cylinder Density in Tribodynamics of a Radial Piston Digital Fluid Power Displacement Motor

2015 ◽  
Author(s):  
Per Johansen ◽  
Daniel B. Roemer ◽  
Torben O. Andersen ◽  
Henrik C. Pedersen
Keyword(s):  
Fluid Mechanics ◽  
Multibody Dynamics ◽  
Solid Body ◽  
Parametric Analysis ◽  
Solid Mechanics ◽  
Force Balance ◽  
Body Motion ◽  
Fluid Power ◽  
Inertia Term ◽  
Operating Modes

In the past three decades an increasing amount of research has been performed in the field of tribodynamics of fluid power pumps and motors. The main incentives for this research are optimization of reliability and efficiency through the study of loss and wear mechanisms. These mechanisms are very difficult to study experimentally, whereby modeling and simulation are necessary. The modeling of tribodynamics is a multiphysics problem involving multibody dynamics, fluid mechanics, thermodynamics and solid mechanics. Consequently, the simulation durations can easily become impractical for parametric analysis or optimization. The coupling between multibody dynamics and fluid mechanics depend on the formulation of the solid body motion equations, where two approaches have historically been used. One approach is where the external forces on any lubricated joint are balanced by the fluid forces, such that solid body inertia is neglected. The other approach includes the inertia terms in the calculation of microdynamics. The inclusion of inertia terms entails a need for smaller time steps in comparison to the force balance approach, wherefore it is of interest to analyze the influence of the inertia term. In this paper the influence of the inertia term on the lubrication gaps of a radial piston motor are studied by a parametric analysis of the piston and cylinder density in a multibody tribodynamic simulation model. The motor is modeled as a digital fluid power displacement machine and a series of full-stroke displacement simulations are used as basis for the parametric analysis. From the parametric analysis a change, in the minimum film thickness as function of piston and cylinder density, is shown for certain operating modes of the digital fluid power displacement motor. This indicate a need for careful assessment of the applicability, of the force balance condition, if it is used in multibody tribodynamic simulations of radial piston digital fluid power displacement motors.

scholarly journals GEORGE KEITH BATCHELOR 8 March 1920–30 March 2000 Founding Editor, Journal of Fluid Mechanics, 1956

2000 ◽  
Vol 421 ◽  
pp. 1-14 ◽  
Author(s):  
HERBERT E. HUPPERT
Keyword(s):  
Fluid Mechanics ◽  
International Organizations ◽  
Solid Mechanics ◽  
Applied Mathematics ◽  
Fluid Flows ◽  
Theoretical Physics ◽  
Founding Editor ◽  
Number Of Factors ◽  
Quantitative Understanding ◽  
The Subject

George Batchelor was one of the giants of fluid mechanics in the second half of the twentieth century. He had a passion for physical and quantitative understanding of fluid flows and a single-minded determination that fluid mechanics should be pursued as a subject in its own right. He once wrote that he ‘spent a lifetime happily within its boundaries’. Six feet tall, thin and youthful in appearance, George's unchanging attire and demeanour contrasted with his ever-evolving scientific insights and contributions. His strongly held and carefully articulated opinions, coupled with his forthright objectivity, shone through everything he undertook.George's pervasive influence sprang from a number of factors. First, he conducted imaginative, ground-breaking research, which was always based on clear physical thinking. Second, he founded a school of fluid mechanics, inspired by his mentor G. I. Taylor, that became part of the world renowned Department of Applied Mathematics and Theoretical Physics (DAMTP) of which he was the Head from its inception in 1959 until he retired from his Professorship in 1983. Third, he established this Journal in 1956 and actively oversaw all its activities for more than forty years, until he relinquished his editorship at the end of 1998. Fourth, he wrote the monumental textbook An Introduction to Fluid Dynamics, which first appeared in 1967, has been translated into four languages and has been relaunched this year, the year of his death. This book, which describes the fundamentals of the subject and discusses many applications, has been closely studied and frequently cited by generations of students and research workers. It has already sold over 45 000 copies. And fifth, but not finally, he helped initiate a number of international organizations (often European), such as the European Mechanics Committee (now Society) and the biennial Polish Fluid Mechanics Meetings, and contributed extensively to the running of IUTAM, the International Union of Theoretical and Applied Mechanics. The aim of all of these associations is to foster fluid (and to some extent solid) mechanics and to encourage the development of the subject.

scholarly journals Breaking the Barriers

2012 ◽  
Vol 134 (05) ◽  
pp. 32-37
Author(s):  
Lee S. Langston
Keyword(s):  
Fluid Mechanics ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Solid Mechanics ◽  
Commercial Aircraft ◽  
Commercial Aviation ◽  
New Developments ◽  
Exhaust Heat ◽  
Turbine Component ◽  
Made In

This article explores the new developments in the field of gas turbines and the recent progress that has been made in the industry. The gas turbine industry has had its ups and downs over the past 20 years, but the production of engines for commercial aircraft has become the source for most of its growth of late. Pratt & Whitney’s recent introduction of its new geared turbofan engine is an example of the primacy of engine technology in aviation. Many advances in commercial aviation gas turbine technology are first developed under military contracts, since jet fighters push their engines to the limit. Distributed generation and cogeneration, where the exhaust heat is used directly, are other frontiers for gas turbines. Work in fluid mechanics, heat transfer, and solid mechanics has led to continued advances in compressor and turbine component performance and life. In addition, gas turbine combustion is constantly being improved through chemical and fluid mechanics research.

scholarly journals The fluid mechanics of poohsticks

2020 ◽  
Vol 378 (2179) ◽  
pp. 20190522 ◽  
Author(s):  
Julyan H. E. Cartwright ◽  
Oreste Piro
Keyword(s):  
Fluid Flow ◽  
Fluid Mechanics ◽  
Solid Body ◽  
State Of The Art ◽  
The State ◽  
Theme Issue ◽  
Two Fluids ◽  
Stokes Drag ◽  
Complex Fluid

The year 2019 marked the bicentenary of George Gabriel Stokes, who in 1851 described the drag—Stokes drag—on a body moving immersed in a fluid, and 2020 is the centenary of Christopher Robin Milne, for whom the game of poohsticks was invented; his father A. A. Milne’s The House at Pooh Corner , in which it was first described in print, appeared in 1928. So this is an apt moment to review the state of the art of the fluid mechanics of a solid body in a complex fluid flow, and one floating at the interface between two fluids in motion. Poohsticks pertains to the latter category, when the two fluids are water and air. This article is part of the theme issue ‘Stokes at 200 (part 2)’.

scholarly journals Fluid Mechanics and Fluid Power (FMFP)

Sadhana ◽  
2017 ◽  
Vol 42 (4) ◽  
pp. 447-448
Author(s):  
Amitabh Bhattacharya ◽  
Jyotirmay Banerjee
Keyword(s):  
Fluid Mechanics ◽  
Fluid Power

Flexible Multibody Dynamics Based on a Fully Cartesian System of Support Coordinates

1993 ◽  
Vol 115 (2) ◽  
pp. 294-299 ◽  
Author(s):  
N. Vukasovic ◽  
J. T. Celigu¨eta ◽  
J. Garci´a de Jalo´n ◽  
E. Bayo
Keyword(s):  
Multibody Dynamics ◽  
Reference Frames ◽  
Deformable Body ◽  
Equations Of Motion ◽  
Flexible Multibody Dynamics ◽  
Body Motion ◽  
Cartesian System ◽  
Flexible Multibody ◽  
Local Reference ◽  
Rigid Multibody

In this paper we present an extension to flexible multibody systems of a system of fully cartesian coordinates previously used in rigid multibody dynamics. This method is fully compatible with the previous one, keeping most of its advantages in kinematics and dynamics. The deformation in each deformable body is expressed as a linear combination of Ritz vectors with respect to a local frame whose motion is defined by a series of points and vectors that move according to the rigid body motion. Joint constraint equations are formulated through the points and vectors that define each link. These are chosen so that a minimum use of local reference frames is done. The resulting equations of motion are integrated using the trapezoidal rule combined with fixed point iteration. An illustrative example that corresponds to a satellite deployment is presented.

Dynamics of axisymmetric bodies rising along a zigzag path

2008 ◽  
Vol 606 ◽  
pp. 209-223 ◽  
Author(s):  
PEDRO C. FERNANDES ◽  
PATRICIA ERN ◽  
FRÉDÉRIC RISSO ◽  
JACQUES MAGNAUDET
Keyword(s):  
Aspect Ratio ◽  
Transverse Direction ◽  
Transverse Velocity ◽  
Density Ratio ◽  
Transverse Component ◽  
The Body ◽  
Force Balance ◽  
Body Motion ◽  
Major Influence ◽  
Inertia Force

The forces and torques governing the planar zigzag motion of thick, slightly buoyant disks rising freely in a liquid at rest are determined by applying the generalized Kirchhoff equations to experimental measurements of the body motion performed for a single body-to-fluid density ratio ρs/ρf ≈ 1. The evolution of the amplitude and phase of the various contributions is discussed as a function of the two control parameters, i.e. the body aspect ratio (the diameter-to-thickness ratio χ = d/h ranges from 2 to 10) and the Reynolds number (100 < Re < 330), Re being based on the rise velocity and diameter of the body. The body oscillatory behaviour is found to be governed by the force balance along the transverse direction and the torque balance. In the transverse direction, the wake-induced force is mainly balanced by two forces that depend on the body inclination, i.e. the inertia force generated by the body rotation and the transverse component of the buoyancy force. The torque balance is dominated by the wake-induced torque and the restoring added-mass torque generated by the transverse velocity component. The results show a major influence of the aspect ratio on the relative magnitude and phase of the various contributions to the hydrodynamic loads. The vortical transverse force scales as fo = (ρf − ρs)ghπd2 whereas the vortical torque involves two contributions, one scaling as fod and the other as f1d with f1 = χfo. Using this normalization, the amplitudes and phases of the vortical loads are made independent of the aspect ratio, the amplitudes evolving as (Re/Rec1 − 1)1/2, where Rec1 is the threshold of the first instability of the wake behind the corresponding body held fixed in a uniform stream.

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