Steady state characteristics of an adjustable hybrid gas bearing – Computational fluid dynamics, modified Reynolds equation and experimental validation

2015 ◽  
Vol 229 (7) ◽  
pp. 807-822 ◽  
Author(s):  
Fabian G Pierart ◽  
Ilmar F Santos
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Experimental Validation ◽  
Reynolds Equation ◽  
Modified Reynolds Equation ◽  
Gas Bearing

Use of computational fluid dynamics in hydrodynamic lubrication

1998 ◽  
Vol 212 (6) ◽  
pp. 427-436 ◽  
Author(s):  
P. Y. P. Chen ◽  
E. J. Hahn
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Negligible Effect ◽  
Squeeze Film ◽  
Inertia Effect ◽  
Squeeze Film Dampers

This paper demonstrates the suitability of using computational fluid dynamics software for solving steady state hydrodynamic lubrication problems pertaining to slider bearings, step bearings, journal bearings and squeeze-film dampers under conditions of constant unidirectional or rotating loading. The relevance of the inertia and viscous terms which are neglected in the derivation of the Reynolds equation are briefly investigated for the above bearing and damper configurations and it is shown that the neglected viscous terms have negligible effect whereas the inertia effect predictions agree reasonably well with those reported in the literature.

An Assessment of the Value of Theory in Predicting Gas-Bearing Performance

1961 ◽  
Vol 83 (2) ◽  
pp. 195-200 ◽  
Author(s):  
S. Cooper
Keyword(s):  
Steady State ◽  
Slip Velocity ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Experimental Methods ◽  
Experimental Results ◽  
Theoretical Investigations ◽  
Gas Bearing ◽  
Theoretical Results

The object of the paper is to indicate the value of theoretical investigations of hydrodynamic finite bearings under steady-state conditions. Methods of solution of Reynolds equation by both desk and digital computing, and methods of stabilizing the processes of solution, are described. The nondimensional data available from the solutions are stated. The outcome of an attempted solution of the energy equation is discussed. A comparison between some theoretical and experimental results is shown. Experimental methods employed and some difficulties encountered are discussed. Some theoretical results are given to indicate the effects of the inclusion of slip velocity, stabilizing slots, and a simple case of whirl.

CFD Leakage Predictions of Unworn and Worn Labyrinth Seals With and Without Tooth Axial Offset

2017 ◽  
Author(s):  
Hasham H. Chougule ◽  
Alexander Mirzamoghadam
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Modeling ◽  
Steady State ◽  
Flow Field ◽  
Labyrinth Seals ◽  
Small Clearance ◽  
Total Leakage ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Deflection

The objective of this study is to develop a Computational Fluid Dynamics (CFD) based methodology for analyzing and predicting leakage of worn or rub-intended labyrinth seals during operation. The simulations include intended tooth axial offset and numerical modeling of the flow field. The purpose is to predict total leakage through the seal when an axial tooth offset is provided after the intended/unintended rub. Results indicate that as expected, the leakage for the in-line worn land case (i.e. tooth under rub) is higher compared to unworn. Furthermore, the intended rotor/teeth forward axial offset/shift with respect to the rubbed land reduces the seal leakage. The overall leakage of a rubbed seal with axial tooth offset is observed to be considerably reduced, and it can become even less than a small clearance seal designed not to rub. The reduced leakage during steady state is due to a targeted smaller running gap because of tooth offset under the intended/worn land groove shape, higher blockages, higher turbulence and flow deflection as compared to worn seal model without axial tooth offset.

scholarly journals Converting a food oven into a thermal sanitizer for Personal Protective Equipment against COVID-19: Computational Fluid Dynamics simulation

2021 ◽  
Author(s):  
Eleonora Bottani ◽  
Roberto Montanari ◽  
Andrea Volpi ◽  
Giulio Di Maria ◽  
Federico Solari ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Temperature Distribution ◽  
Personal Protective Equipment ◽  
Experimental Validation ◽  
Dynamics Simulation ◽  
Protective Equipment ◽  
Computational Fluid Dynamics Simulation ◽  
Food Sector ◽  
Know How

COVID-19 brought several management problems, and among these surely the topic of Personal Protective Equipment (PPE) turned out to be crucial. Indeed, in the light of mandatory measurements adopted by governments both for private individuals and companies, their demand has rapidly increased, thus generating shortages, increased waste and unbalanced prices. In response to that, many industrial fields offered their tools and know-how for trying to partly face this issue, and in this paper part of a solution of this kind is presented. Specifically, it is meant the redesign of a food oven produced by an Italian company operating in the food sector (Nilma S.p.A.) for thermal sanitization against the virus in question. In this paper, the simulation of the temperature distribution inside the chamber is simulated, with subsequent experimental validation at 95°C.

Verification Benchmarks to Assess the Implementation of Computational Fluid Dynamics Based Hemolysis Prediction Models

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Prasanna Hariharan ◽  
Gavin D’Souza ◽  
Marc Horner ◽  
Richard A. Malinauskas ◽  
Matthew R. Myers
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Power Law ◽  
Analytical Solutions ◽  
Experimental Validation ◽  
Cfd Simulations ◽  
Flow Models ◽  
Flow Acceleration ◽  
Blood Damage ◽  
Eulerian Models

As part of an ongoing effort to develop verification and validation (V&V) standards for using computational fluid dynamics (CFD) in the evaluation of medical devices, we have developed idealized flow-based verification benchmarks to assess the implementation of commonly cited power-law based hemolysis models in CFD. The verification process ensures that all governing equations are solved correctly and the model is free of user and numerical errors. To perform verification for power-law based hemolysis modeling, analytical solutions for the Eulerian power-law blood damage model (which estimates hemolysis index (HI) as a function of shear stress and exposure time) were obtained for Couette and inclined Couette flow models, and for Newtonian and non-Newtonian pipe flow models. Subsequently, CFD simulations of fluid flow and HI were performed using Eulerian and three different Lagrangian-based hemolysis models and compared with the analytical solutions. For all the geometries, the blood damage results from the Eulerian-based CFD simulations matched the Eulerian analytical solutions within ∼1%, which indicates successful implementation of the Eulerian hemolysis model. Agreement between the Lagrangian and Eulerian models depended upon the choice of the hemolysis power-law constants. For the commonly used values of power-law constants (α  = 1.9–2.42 and β  = 0.65–0.80), in the absence of flow acceleration, most of the Lagrangian models matched the Eulerian results within 5%. In the presence of flow acceleration (inclined Couette flow), moderate differences (∼10%) were observed between the Lagrangian and Eulerian models. This difference increased to greater than 100% as the beta exponent decreased. These simplified flow problems can be used as standard benchmarks for verifying the implementation of blood damage predictive models in commercial and open-source CFD codes. The current study used only a power-law model as an illustrative example to emphasize the need for model verification. Similar verification problems could be developed for other types of hemolysis models (such as strain-based and energy dissipation-based methods). And since the current study did not include experimental validation, the results from the verified models do not guarantee accurate hemolysis predictions. This verification step must be followed by experimental validation before the hemolysis models can be used for actual device safety evaluations.

scholarly journals Computational Fluid Dynamics Modeling of the Human Pulmonary Arteries with Experimental Validation

2018 ◽  
Vol 46 (9) ◽  
pp. 1309-1324 ◽  
Author(s):  
Alifer D. Bordones ◽  
Matthew Leroux ◽  
Vitaly O. Kheyfets ◽  
Yu-An Wu ◽  
Chia-Yuan Chen ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Experimental Validation ◽  
Pulmonary Arteries ◽  
Dynamics Modeling ◽  
Computational Fluid Dynamics Modeling

Computational Fluid Dynamics Modelling of a Load Sensing Proportional Valve

2019 ◽  
Author(s):  
Alessandro Corvaglia ◽  
Giorgio Altare ◽  
Roberto Finesso ◽  
Massimo Rundo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Complex Geometry ◽  
Ansys Fluent ◽  
Proportional Valve ◽  
Fluid Forces ◽  
Load Sensing ◽  
Cfd Models ◽  
Dynamics Modelling

Abstract In this paper, two 3D CFD models of a load sensing proportional valve are contrasted. The models were developed with two different software, Simerics PumpLinx® and ANSYS Fluent®. In both cases the mesh was dynamically modified based on the fluid forces acting on the local compensator. In the former, a specific template for valves was used, in the latter a user-defined function was implemented. The models were validated in terms of flow rate and pressure drop for different positions of the main spool by means of specific tests. Two configurations were tested: with the local compensator blocked and free to regulate. The study has brought to evidence the reliability of the CFD models in evaluating the steady-state characteristics of valves with complex geometry.

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