Prediction of Hydraulic Inductance

2002 ◽  
Author(s):  
D. Nigel Johnston
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Calculation ◽  
Dynamic Response ◽  
Complex Geometry ◽  
Fluid Power ◽  
Poppet Valve ◽  
Noise Characteristics ◽  
Spool Valve

The dynamic response, stability and fluid-borne noise characteristics of fluid power components and systems can be strongly influenced by the inertia or ‘hydraulic inductance’ of the fluid in passageways, which are often of complex geometry. The hydraulic inductance is a parameter that has often proved to be very difficult to quantify accurately, either theoretically or experimentally. This paper presents a method of numerical calculation of the hydraulic inductance in a passageway. The method is simple to apply and can be applied to geometries of arbitrary complexity. A simple way of using a Computational Fluid Dynamics package for calculating hydraulic inductance is also demonstrated. Results are presented for a simple cylindrical orifice, a simple spool valve and a conical poppet valve. The effect of the inductance on the response of a poppet valve is demonstrated.

Prediction of Fluid Inertance in Nonuniform Passageways

2006 ◽  
Vol 128 (2) ◽  
pp. 266-275 ◽  
Author(s):  
D. Nigel Johnston
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Finite Element ◽  
Numerical Calculation ◽  
Incompressible Flow ◽  
Complex Geometry ◽  
Mean Flow ◽  
Poppet Valve ◽  
Noise Characteristics ◽  
Spool Valve

The dynamic response, stability, and noise characteristics of fluid components and systems can be strongly influenced by the inertance of the fluid in passageways, which are often of complex geometry. The inertance is a parameter that has often proved to be very difficult to accurately quantify, either theoretically or experimentally. This paper presents a method of numerical calculation of the inertance in a passageway, assuming inviscid, incompressible flow and zero mean flow. The method is simple to apply and can be applied to geometries of arbitrary complexity. Two simple but unorthodox ways of calculating inertance using a computational fluid dynamics and a finite element solid-modeling package are also demonstrated. Results are presented for a simple cylindrical orifice, a simple spool valve, and a conical poppet valve. The effect of the inertance on the response of a poppet valve is demonstrated.

Three-Dimensional Thermo-Elasto-Hydrodynamic Computational Fluid Dynamics Model of a Tilting Pad Journal Bearing—Part II: Dynamic Response

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jongin Yang ◽  
Alan Palazzolo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Dynamic Response ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Static Response ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

Part II presents a novel approach for predicting dynamic coefficients for a tilting pad journal bearing (TPJB) using computational fluid dynamics (CFD) and finite element method (FEM), including fully coupled elastic deflection, heat transfer, and fluid dynamics. Part I presented a similarly novel, high fidelity approach for TPJB static response prediction which is a prerequisite for the dynamic characteristic determination. The static response establishes the equilibrium operating point values for eccentricity, attitude angle, deflections, temperatures, pressures, etc. The stiffness and damping coefficients are obtained by perturbing the pad and journal motions about this operating point to determine changes in forces and moments. The stiffness and damping coefficients are presented in “synchronously reduced form” as required by American Petroleum Institute (API) vibration standards. Similar to Part I, an advanced three-dimensional thermal—Reynolds equation code validates the CFD code for the special case when flow Between Pad (BP) regions is ignored, and the CFD and Reynolds pad boundary conditions are made identical. The results show excellent agreement for this validation case. Similar to the static response case, the dynamic characteristics from the Reynolds model show large discrepancies compared with the CFD results, depending on the Reynolds mixing coefficient (MC). The discrepancies are a concern given the key role that stiffness and damping coefficients serve instability and response predictions in rotordynamics software. The uncertainty of the MC and its significant influence on static and dynamic response predictions emphasizes a need to utilize the CFD approach for TPJB simulation in critical machines.

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.

A Computational Fluid Dynamics (CFD) Study of Material Transport and Deposition in Aerosol Jet Printing (AJP) Process

2018 ◽  
Author(s):  
Roozbeh (Ross) Salary ◽  
Jack P. Lombardi ◽  
Darshana L. Weerawarne ◽  
Prahalada K. Rao ◽  
Mark D. Poliks
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Flow ◽  
Complex Geometry ◽  
Sensor Data ◽  
Cfd Model ◽  
Material Transport ◽  
Jet Printing ◽  
Computational Fluid Dynamics Cfd ◽  
Aerosol Jet Printing

The objective of this work is to forward a 3D computational fluid dynamics (CFD) model to explain the aerodynamics behind aerosol transport and deposition in aerosol jet printing (AJP). The CFD model allows for: (i) mapping of velocity fields as well as particle trajectories; and (ii) investigation of post-deposition phenomena of sticking, rebounding, spreading, and splashing. The complex geometry of the deposition head was modeled in the ANSYS-Fluent environment, based on a patented design as well as accurate measurements, obtained from 3D X-ray CT imaging. The entire volume of the geometry was subsequently meshed, using a mixture of smooth and soft quadrilateral elements, with consideration of layers of inflation to obtain an accurate solution near the walls. A combined approach — based on the density-based and pressure-based Navier-Stokes formation — was adopted to obtain steady-state solutions and to bring the conservation imbalances below a specified linearization tolerance (10−6). Turbulence was modeled, using the realizable k-ε viscose model with scalable wall functions. A coupled two-phase flow model was set up to track a large number of injected particles. The boundary conditions were defined based on experimental sensor data. A single-factor factorial experiment was conducted to investigate the influence of sheath gas flow rate (ShGFR) on line morphology, and also validate the CFD model.

Nonlinear spectral dynamic analysis of guyed towers. Part II: Manitoba towers case study

2004 ◽  
Vol 31 (6) ◽  
pp. 1061-1076 ◽  
Author(s):  
A M Horr ◽  
A Yibulayin ◽  
P Disney
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Complex Geometry ◽  
Spectral Element ◽  
Wind Loading ◽  
Space Structures ◽  
Loading Test ◽  
Large Space ◽  
Post Buckling ◽  
Guyed Towers

Dynamic response of large complex space structures under wind loading is important in terms of performance and safety. Conventional method of wind loading calculation has been used successfully in codes to analyze large space structures. The method can be applied by approximating the air pressure, induced by wind, on the surfaces of structures. Although this replaces a wind loading test using complicated wind tunnel tests for any structural systems, the accuracy of the method, in the case of complex geometry guyed tower structures, is a matter of consideration. Hence, it is desirable to search for a procedure with more accuracy and reliability. In this respect, attention is paid to the advanced spectral element method and the computational fluid dynamics. Using the proposed formulation, a material and geometric nonlinear dynamic analyses have been performed to simulate post-buckling behaviours and also collapse modes for series of Manitoba Hydro's guyed towers under extreme wind loading conditions. Key words: computational fluid dynamics, wind loading, collapse mode, nonlinear analysis, post-buckling.

scholarly journals Computational Fluid Dynamics Analysis of Particle Deposition Induced by a Showerhead Electrode in a Capacitively Coupled Plasma Reactor

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1004
Author(s):  
Ho Jun Kim ◽  
Jung Hwan Yoon
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Deposition ◽  
Complex Geometry ◽  
Plasma Reactor ◽  
Electrode Spacing ◽  
Plasma Discharges ◽  
Capacitively Coupled ◽  
Computational Fluid Dynamics Analysis ◽  
Capacitively Coupled Plasma

Defect formation in the deposition of thin films for semiconductors is not yet sufficiently understood. In a showerhead-type capacitively coupled plasma (CCP) deposition reactor, the showerhead acts as both the gas distributor and the electrode. We used computational fluid dynamics to investigate ways to enhance cleanliness by analyzing the particle deposition induced by the showerhead electrode in a CCP reactor. We analyzed particle transport phenomena using a three-dimensional complex geometry, whereas SiH4/He discharges were simulated in a two-dimensional simplified geometry. The process volume was located between the RF-powered showerhead and the grounded heater. We demonstrated that the efficient transportation of particles with a radius exceeding 1 μm onto the heater is facilitated by acceleration inside the showerhead holes. Because the available space in which to flow inside the showerhead is constricted, high gas velocities within the showerhead holes can accelerate particles and lead to inertia-enhanced particle deposition. The effect of the electrode spacing on the deposition of particles generated in plasma discharges was also investigated. Smaller electrode spacing promoted the deposition of particles fed from the showerhead on the heater, whereas larger electrode spacing facilitated the deposition of particles generated in plasma discharges on the heater.

Analysis of flow field and hemolysis index in axial flow blood pump by computational fluid dynamics–discrete element method

2020 ◽  
Vol 44 (1) ◽  
pp. 46-54
Author(s):  
Lizhi Cheng ◽  
Jianping Tan ◽  
Zhong Yun ◽  
Shuai Wang ◽  
Zheqin Yu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Calculation ◽  
Flow Field ◽  
Discrete Element Method ◽  
Axial Flow ◽  
Discrete Element ◽  
Blood Pump ◽  
Axial Flow Blood Pump ◽  
Element Method

To fully study the relationship between the internal flow field and hemolysis index in an axial flow blood pump, a computational fluid dynamics–discrete element method coupled calculation method was used. Through numerical analysis under conditions of 6000, 8000, and 10,000 r/min, it was found that there was flow separation of blood cell particles in the tip of the impeller and the guide vane behind the impeller. The flow field has a larger pressure gradient distribution, which reduces the lift ratio of the blood pump and easily causes blood cell damage. The study shows that the hemolysis index obtained by the computational fluid dynamics—discrete element method is 4.75% higher than that from the traditional computational fluid dynamics method, which indicates the impact of microcollision between erythrocyte particles and walls on hemolysis index and also further verifies the validity of the computational fluid dynamics–discrete element coupling method. Through the hydraulic and particle image velocimetry experiments of the blood pump, the coincidence between numerical calculation and experiment is analyzed from macro and micro aspects, which shows that the numerical calculation method is feasible.

Computational Fluid Dynamics Investigation of Supercritical Water Flow and Heat Transfer in a Rod Bundle With Grid Spacers

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Malwina Gradecka ◽  
Roman Thiele ◽  
Henryk Anglart
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Flow ◽  
Supercritical Water ◽  
Complex Geometry ◽  
Inlet Section ◽  
Fluid Temperature ◽  
Rod Bundle ◽  
Flow And Heat Transfer

This paper presents a steady-state computational fluid dynamics approach to supercritical water flow and heat transfer in a rod bundle with grid spacers. The current model was developed using the ANSYS Workbench 15.0 software (CFX solver) and was first applied to supercritical water flow and heat transfer in circular tubes. The predicted wall temperature was in good agreement with the measured data. Next, a similar approach was used to investigate three-dimensional (3D) vertical upward flow of water at supercritical pressure of about 25 MPa in a rod bundle with grid spacers. This work aimed at understanding thermo- and hydrodynamic behavior of fluid flow in a complex geometry at specified boundary conditions. The modeled geometry consisted of a 1.5-m heated section in the rod bundle, a 0.2-m nonheated inlet section, and five grid spacers. The computational mesh was prepared using two cell types. The sections of the rods with spacers were meshed using tetrahedral cells due to the complex geometry of the spacer, whereas sections without spacers were meshed with hexahedral cells resulting in a total of 28 million cells. Three different sets of experimental conditions were investigated in this study: a nonheated case and two heated cases. The nonheated case, A1, is calculated to extract the pressure drop across the rod bundle. For cases B1 and B2, a heat flux is applied on the surface of the rods causing a rise in fluid temperature along the bundle. While the temperature of the fluid increases along with the flow, heat deterioration effects can be present near the heated surface. Outputs from both B cases are temperatures at preselected locations on the rods surfaces.

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