Prediction of hydrodynamic performance of pump jet propulsor considering the effect of gap flow model

2009 ◽

Cited By ~ 7

Author(s):

Matteo Pelosi ◽

Monika Ivantysynova

Keyword(s):

Temperature Field ◽

Energy Dissipation ◽

Film Thickness ◽

Elastic Deformation ◽

Flow Model ◽

Piston Cylinder ◽

Gap Flow ◽

First Time ◽

Fully Coupled

The lubricating gaps of piston machines represent the main source of energy dissipation. The lubricating gap in these machines has to fulfill a sealing and bearing function. Therefore the prediction of the gap flow, the load carrying ability and the energy dissipation is necessary. The paper discusses a novel fully coupled model for the determination of piston/cylinder gap behavior considering the contribution of solid parts temperature induced strain. In particular, the non-isothermal gap flow model considers the squeeze film effect due to the micro-motion of the moveable parts and simultaneously the change of fluid film thickness due to the elastic deformation of the solid bodies caused by the fluid pressure field and the parts temperature field. The determination of the temperature field inside the parts, by means of detailed finite volume models, allows for the first time to accurately predict solid parts thermal expansion, which is directly affecting the gap film thickness. Therefore, the novelty of the developed fully coupled fluid-structure-thermal interaction model is the integration of a finite element solver for the determination of surface thermo-elastic deformation in a dynamic non-isothermal fluid flow model. This will allow for the first time to solve the thermo-elastohydrodynamic lubrication problem under changing load conditions, considering the impact of several different physical phenomena.

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Abstract 5808: Assessment of Aortic Bioprostheses is Feasible Applying Cardiovascular Magnetic Resonance - In Vivo and In Vitro Studies

Circulation ◽

10.1161/circ.118.suppl_18.s_107-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Florian von Knobelsdorff ◽

Ralf Wassmuth ◽

Andre Rudolph ◽

Andreas Greiser ◽

Mathias Dieringer ◽

...

Keyword(s):

Cardiovascular Magnetic Resonance ◽

Magnetic Resonance ◽

Flow Model ◽

Close Correlation ◽

Hydrodynamic Performance ◽

Specific Reference ◽

Slice Thickness ◽

Orifice Area

Orifice area is decisive to assess bioprosthetic performance after aortic valve replacement. However, standard calculation by transthoracic echocardiography (TTE) is often limited. This is the first series testing cardiovascular magnetic resonance (CMR) to quantify the orifice area of bioprostheses. Prosthetic orifice visualization was performed in a clinical 1.5T MR system (Siemens Magnetom Avanto) within a stack of prosthesis parallel steady state free precession cines (slice thickness 5mm, no gap). Orifice quantification was done manually by planimetry. In vivo, we compared the orifice area obtained by CMR with TTE (continuity equation) prospectively in 56 patients with aortic bioprostheses (40 stented, 16 stentless). In a subgroup of 23 patients also transesophageal echocardiography (planimetry; TEE) was applied. In vitro, we studied four different bioprostheses in a CMR-compatible pulsatile flow model under standardized conditions. In vivo, CMR planimetry was feasible in 52 patients (92.9%). Atrial fibrillation with rapid heart rate, inability to sustain breath holds and flow-artifacts rendered image-quality non-diagnostic in 3 patients. Three patients had insufficient transthoracic acoustic windows. Correlations of CMR with TTE (n=50; r=0.85; p<0.001) and CMR with TEE (n=21; r=0.97; p<0.001) were highly significant, both for stentless and stented bioprostheses. In Bland-Altman analysis, mean difference between CMR and TTE was −0.06±0.24cm 2 , between CMR and TEE 0.03±0.12cm 2 . In vitro, mean orifice areas obtained by CMR planimetry were 1.60±0.04cm 2 for Hancock 25, 1.59±0.01cm 2 for Perimount 23, 1.29±0.07cm 2 for Perimount 21 and 1.56±0.04cm 2 for Mitroflow 25. The assessment of bioprostheses by CMR is technically feasible and provides orifice areas with close correlation to echocardiography. Thus, CMR is an important non-invasive tool to assess bioprostheses in selected patients. The flow model allows for establishing CMR specific reference orifice areas for various valve types and comparing their hydrodynamic performance under standardized conditions. The concepts and information presented in this abstract are based on research and are not commercially available.

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A physics-based gap-flow model for potential flow solvers

Ocean Engineering ◽

10.1016/j.oceaneng.2014.03.025 ◽

2014 ◽

Vol 88 ◽

pp. 578-587 ◽

Cited By ~ 8

Author(s):

C.M. Harwood ◽

Y.L. Young

Keyword(s):

Potential Flow ◽

Flow Model ◽

Gap Flow

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Morphing Hydrofoil Model Driven by Compliant Composite Structure and Internal Pressure

Journal of Marine Science and Engineering ◽

10.3390/jmse7120423 ◽

2019 ◽

Vol 7 (12) ◽

pp. 423 ◽

Cited By ~ 1

Author(s):

Fatiha Mohammed Arab ◽

Benoît Augier ◽

François Deniset ◽

Pascal Casari ◽

Jacques André Astolfi

Keyword(s):

Internal Pressure ◽

Composite Structure ◽

Composite Structures ◽

Flow Model ◽

Hydrodynamic Forces ◽

Hydrodynamic Performance ◽

Naval Academy ◽

Cavitation Inception ◽

Model Driven ◽

Cavitation Tunnel

In this work, a collaborative experimental study has been conducted to assess the effect an imposed internal pressure has on the controlling the hydrodynamic performance of a compliant composite hydrofoil. It was expected that the internal pressure together with composite structures be suitable to control the hydrodynamic forces as well as cavitation inception and development. A new concept of morphing hydrofoil was developed and tested in the cavitation tunnel at the French Naval Academy Research Institute. The experiments were based on the measurements of hydrodynamic forces and hydrofoil deformations under various conditions of internal pressure. The effect on cavitation inception was studied too. In parallel to this experiment, a 2D numerical tool was developed in order to assist the design of the compliant hydrofoil shape. Numerically, the fluid-structure coupling is based on an iterative method under a small perturbation hypothesis. The flow model is based on a panel method and a boundary layer formulation and was coupled with a finite-element method for the structure. It is shown that pressure driven compliant composite structure is suitable to some extent to control the hydrodynamic forces, allowing the operational domain of the compliant hydrofoil to be extended according to the angle of attack and the internal pressure. In addition, the effect on the cavitation inception is pointed out.

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Determination of Gap Surface Temperature Distribution in Axial Piston Machines

Fluid Power Systems and Technology ◽

10.1115/imece2006-15249 ◽

2006 ◽

Cited By ~ 5

Author(s):

Monika Ivantysynova ◽

Changchun Huang ◽

Andreas J. Japing

Keyword(s):

Temperature Distribution ◽

Energy Dissipation ◽

Surface Temperature ◽

Thermal Model ◽

Flow Model ◽

Simulation Software ◽

Surface Temperature Distribution ◽

Gap Flow ◽

Axial Piston

The paper presents a new method for determination of gap surface temperature distribution in axial piston machine. A special thermal model has been developed to consider the energy dissipation in the lubricating gap, the heat convection of the fluid and the heat conduction through the rotating group assuming constant case and port temperatures. The energy dissipation in the gap is calculated using gap flow model considering non-isothermal flow, surface deformation and micro motion of parts. The calculated surface temperatures are further used as boundary parameters for the 3D non-isothermal gap flow model. The developed thermal model has been implemented in a new module of the CASPAR simulation software. The program CASPAR has been developed in the research group of the authors (Wieczorek and Ivantysynova 2002, Huang and Ivantysynova 2003). The model will be explained and simulation results will be discussed and compared with measurements. A special single piston test pump has been designed and implemented on a special test rig allowing to measure surface temperature distribution, dynamic pressure field in the gap between piston and cylinder and leakage. The paper will present a comparison of calculated and measured surface temperature fields.

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Siphon Flows in Stratified Coronal Loops

International Astronomical Union Colloquium ◽

10.1017/s0252921100025288 ◽

1994 ◽

Vol 144 ◽

pp. 185-187

Author(s):

S. Orlando ◽

G. Peres ◽

S. Serio

Keyword(s):

Heat Flux ◽

Scaling Laws ◽

Flow Model ◽

Supersonic Flows ◽

Coronal Loops ◽

Characteristic Parameters

AbstractWe have developed a detailed siphon flow model for coronal loops. We find scaling laws relating the characteristic parameters of the loop, explore systematically the space of solutions and show that supersonic flows are impossible for realistic values of heat flux at the base of the upflowing leg.

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