A Method of Characteristics Based Coupled Pump/Line Model to Predict Noise Sources of Hydrostatic Transmissions

2009 ◽  
Author(s):  
Richard Klop ◽  
Andrea Vacca ◽  
Monika Ivantysynova
Keyword(s):  
Method Of Characteristics ◽  
Numerical Approach ◽  
Noise Sources ◽  
Line Model ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Pressure Ripple ◽  
Flow Oscillations ◽  
Hydrostatic Transmissions ◽  
Parameter Approach

This study is a part of a larger research project to predict noise sources of hydrostatic transmissions and investigating new methods for designing quieter systems. The aim of this study is to validate the developed model describing pump dynamics coupled with effects of a connecting line, thus validating a coupled pump-motor-line model for hydrostatic transmissions. This paper illustrates a numerical approach for evaluating pressure and flow oscillations generated by a hydraulic pump coupled with a connecting line. The presented model describes pump dynamics using a lumped parameter approach as well as one-dimensional unsteady compressible fluid flow by means of method of characteristics (MOC). Several lumped parameter models have been developed for hydraulic pumps and motors and the method of characteristics has been applied for many applications; however, the presented model uniquely utilizes both approaches and considers influence of pump dynamics and propagating pressure and flow pulsations throughout the line. Measurements of pressure ripple in the line at two different points were carried out at various loading conditions to validate the developed model. Comparisons between measurements, the developed model, and another more simplified model were conducted. Results indicate a reasonable match between the developed model and measurements as well as the importance of considering a line model based on method of characteristics.

Analytical Coupled Modeling and Model Validation of Hydraulic On/Off Valves

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
John Mahrenholz ◽  
John Lumkes
Keyword(s):  
High Speed ◽  
Eddy Currents ◽  
Hydraulic Systems ◽  
Coupled Modeling ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Fluid Transients ◽  
Pressure Ripple ◽  
Valve Dynamics ◽  
Fully Coupled

The goal of this paper is to describe a method for modeling high speed on/off valves. This model focuses on the nonlinearities of the electromagnetic, fluidic, and mechanical domains, specifically within solenoid driven poppet style valves. By including these nonlinearities, the model accurately predicts valve transition time for different driving voltages and valve strokes. The model also predicts fluid transients such as pressure ripple. Unique attributes of the model are the inclusion of the effect of eddy currents and fringing while still being fully coupled with the fluid and mechanical domains. A prototype was constructed and used to experimentally validate the model. By developing accurate lumped parameter models, valve dynamics can be applied to hydraulic systems to accurately capture their dynamics.

scholarly journals Numerical modelling of unsteady turbulent flow in tubes, including the effects of roughness and large changes in Reynolds number

2011 ◽  
Vol 225 (8) ◽  
pp. 1874-1885 ◽  
Author(s):  
D N Johnston
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Effective Viscosity ◽  
Method Of Characteristics ◽  
Turbulence Energy ◽  
Turbulent Friction ◽  
Pipe Flows ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Long Time

A method has been developed for predicting unsteady turbulent friction in smooth, transitional, and rough pipe flows. For transitional and rough pipe flows the effective viscosity at the wall is varied depending on Reynolds number and roughness. An approximation has been made for the transition region using a cubic spline for the friction factor between the smooth and rough regions. This turbulence model can be implemented readily in several types of numerical model for pipe flow, including simple lumped parameter models, finite difference/finite element methods, and the method of characteristics. An approximate method for representing changes in turbulence energy is discussed. Using this, the method is suitable for small and large changes in flow, and for short and long time scales, but further validation is needed.

Dynamic Stability of a Water Brake Dynamometer

1998 ◽  
Vol 120 (1) ◽  
pp. 89-96 ◽  
Author(s):  
R. A. Van den Braembussche ◽  
H. Malys
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Lumped Parameter Model ◽  
Stable Operation ◽  
Pressure Oscillations ◽  
Lumped Parameter ◽  
Flow Oscillations ◽  
Brake Dynamometer ◽  
Low Torque ◽  
Frequency Variations

A lumped parameter model to predict the high frequency pressure oscillations observed in a water brake dynamometer is presented. It explains how the measured low frequency variations of the torque are a consequence of the variation in amplitude of the high frequency flow oscillations. Based on this model, geometrical modifications were defined, aiming to suppress the oscillations while maintaining mechanical integrity of the device. An experimental verification demonstrated the validity of the model and showed a very stable operation of the modified dynamometer even at very low torque.

scholarly journals Evaluation of passive autocatalytic recombiners operation efficiency by means of the lumped parameter approach

Nukleonika ◽  
2015 ◽  
Vol 60 (2) ◽  
pp. 339-345 ◽  
Author(s):  
Tomasz Bury
Keyword(s):  
Hydrogen Generation ◽  
Cooling System ◽  
Component Mixture ◽  
Pressurized Water ◽  
Water Reactor ◽  
Safety Issues ◽  
Loss Of Coolant Accident ◽  
Lumped Parameter ◽  
Core Cooling ◽  
Parameter Approach

Abstract The problem of hydrogen behavior in containment buildings of nuclear reactors belongs to thermal-hydraulic area. Taking into account the size of systems under consideration and, first of all, safety issues, such type of analyses cannot be done by means of full-scale experiments. Therefore, mathematical modeling and numerical simulations are widely used for these purposes. A lumped parameter approach based code HEPCAL has been elaborated in the Institute of Thermal Technology of the Silesian University of Technology for simulations of pressurized water reactor containment transient response. The VVER-440/213 and European pressurised water reactor (EPR) reactors containments are the subjects of analysis within the framework of this paper. Simulations have been realized for the loss-of-coolant accident scenarios with emergency core cooling system failure. These scenarios include core overheating and hydrogen generation. Passive autocatalytic recombiners installed for removal of hydrogen has been taken into account. The operational efficiency of the hydrogen removal system has been evaluated by comparing with an actual hydrogen concentration and flammability limit. This limit has been determined for the three-component mixture of air, steam and hydrogen. Some problems related to the lumped parameter approach application have been also identified.

Interaction Between Coriolis Forces and Mistuning on a Cyclic Symmetric Structure With Geometrical Nonlinearity

2020 ◽  
Author(s):  
Anthony Tacher ◽  
Fabrice Thouverez ◽  
Jason Armand
Keyword(s):  
Standing Wave ◽  
Geometrical Nonlinearity ◽  
Numerical Approach ◽  
Travelling Wave ◽  
Lumped Parameter Model ◽  
Coriolis Forces ◽  
High Speeds ◽  
Symmetric Structure ◽  
Lumped Parameter ◽  
Cyclic Symmetric

Abstract An investigation of the interaction between Coriolis forces and mistuning on a cyclic symmetric structure is presented in this paper. The sensitivity of the eigenvalues and eigenvectors to mistuning is first studied with the perturbation method. A lumped parameter model is used to perform a modal analysis using a numerical approach after which geometrical nonlinearity is added to compare behavior with the linear case. Two different modes are thoroughly investigated for different rotational speeds, the first with an eigenvalue isolated from the others and the second presenting a frequency veering zone. The evolution from a standing wave domination at low speeds to a travelling wave domination at high speeds is observed for the isolated mode, whereas a standing wave domination remains around the veering zone for the second mode studied. It is also shown that the geometrical nonlinearity reinforces the mistuning effect versus the Coriolis forces.

Lumped parameter models for two-ventricle and healthy and failing extracardiac Fontan circulations

2021 ◽  
Author(s):  
Matthew G Doyle ◽  
Marina Chugunova ◽  
S Lucy Roche ◽  
James P Keener
Keyword(s):  
Single Ventricle ◽  
Left Ventricular ◽  
Sensitivity Analyses ◽  
Surgical Strategies ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Fontan Failure ◽  
Existence Of Periodic Solutions ◽  
Mathematical Definitions ◽  
Extracardiac Fontan

Abstract Fontan circulations are surgical strategies to treat infants born with single ventricle physiology. Clinical and mathematical definitions of Fontan failure are lacking, and understanding is needed of parameters indicative of declining physiologies. Our objective is to develop lumped parameter models of two-ventricle and single-ventricle circulations. These models, their mathematical formulations and a proof of existence of periodic solutions are presented. Sensitivity analyses are performed to identify key parameters. Systemic venous and systolic left ventricular compliances and systemic capillary and pulmonary venous resistances are identified as key parameters. Our models serve as a framework to study the differences between two-ventricle and single-ventricle physiologies and healthy and failing Fontan circulations.

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