On the Use of Atmospheric Boundary Conditions for Axial-Flow Compressor Stall Simulations

2004 ◽  
Vol 127 (2) ◽  
pp. 349-351 ◽  
Author(s):  
M. Vahdati ◽  
A. I. Sayma ◽  
C. Freeman ◽  
M. Imregun
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Hysteresis Loop ◽  
Axial Flow ◽  
Computational Domain ◽  
Computational Fluid Dynamics Cfd ◽  
Fan Blade ◽  
Flow Compressor ◽  
Speed Characteristic

This paper describes a novel way of prescribing computational fluid dynamics (CFD) boundary conditions for axial-flow compressors. The approach is based on extending the standard single passage computational domain by adding an intake upstream and a variable nozzle downstream. Such a route allows us to consider any point on a given speed characteristic by simply modifying the nozzle area, the actual boundary conditions being set to atmospheric ones in all cases. Using a fan blade, it is shown that the method not only allows going past the stall point but also captures the typical hysteresis loop behavior of compressors.

Uncertainty in Computational Fluid Dynamics

1996 ◽  
Vol 210 (1) ◽  
pp. 91-94 ◽  
Author(s):  
E H Fisher ◽  
N Rhodes
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Quality Assurance ◽  
Boundary Conditions ◽  
Error Estimation ◽  
Validation Studies ◽  
Postgraduate Training ◽  
Sources Of Uncertainty ◽  
Expert Meeting ◽  
Computational Fluid Dynamics Cfd

The Annual EPSRC/IMechE Expert Meeting brought together some 44 experts to consider sources of uncertainty in computational fluid dynamics (CFD). Presentations and discussions covered modelling, numerical solution techniques, boundary conditions, evaluation protocols and QA (quality assurance) procedures. The principal conclusions to emerge were: (a) the need for additional collaborative validation studies; (b) the desirability of introducing appropriate QA procedures, possibly based on the CFD Community Club initiative; (c) the need for additional postgraduate training, possibly based on the IGDS principle; (d) the value of continuing work in modelling and error estimation techniques for numerical schemes.

scholarly journals Numerical Investigation on Multiphase Flows in Various Configurations of Microchannels Using Computational Fluid Dynamics

2019 ◽  
Vol 17 (1) ◽  
pp. 82
Author(s):  
Mohd Fadhil Majnis ◽  
Mohamad Rawad Jalwan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Flows ◽  
Chaotic Advection ◽  
Computational Domain ◽  
Mixing Performance ◽  
Vof Model ◽  
Computational Fluid Dynamics Cfd ◽  
Miscible Liquids ◽  
Grid Independence

A two-dimensional domain of multiphase flow analyses in this study using the Volume of Fluid (VOF) model was carried out in order to simulate and predict the fluid flows and mixing performance of two miscible liquids in various microchannel configurations. The various microchannels configurations were designed accordingly and the simulation was carried out based on the justified conditions, assumptions and considerations by using the commercial computational fluid dynamics (CFD) software, FLUENT. The grid type and size of the computational domain were verified in terms of stability by performing the grid independence analysis. The result showed that static mixing would be possible to achieve in various configurations of microchannels, however, the simulation results predicted that it appeared to be more efficient in complex and retrofitted microchannels. It showed the potential to promote and enhance chaotic advection, compositions distribution, and diffusivity as compared to basic microchannels that are mostly dependent only on the injection focus. Furthermore, the Reynolds number appeared to be a significant factor to enhance the mixing performance in microchannel beside the configurations.

Numerical Simulation of the Fixed Barge Barge Interaction Under Irregular Wave Using HOS-StarCCM+ Coupling Tool With Experiment Validation

2021 ◽  
Author(s):  
Yali Zhang ◽  
Haihua Xu ◽  
Harrif Santo ◽  
Kie Hian Chua ◽  
Yun Zhi Law ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Free Surface ◽  
Potential Flow ◽  
Computational Domain ◽  
Cfd Model ◽  
Flow Models ◽  
Irregular Wave ◽  
Computational Fluid Dynamics Cfd ◽  
Wave Conditions

Abstract The interaction between two side-by-side floating vessels has been a subject of interest in recent years due floating liquefied natural gas (FLNG) developments. The safety and operability of these facilities are affected by the free-surface elevation in the narrow gap between the two vessels as well as the relative motions between the vessels. It is common practice in the industry to use potential flow models to estimate the free-surface responses in the gap under various wave conditions. However, it is well-known that any potential flow models require calibration of viscous damping, and model tests are carried out to provide a platform to calibrate the potential flow models. To improve beyond the potential flow models, Computational Fluid Dynamics (CFD) models will be required. However, the large computational efforts required render the conventional CFD approaches impractical for simulations of wave-structure interactions over a long duration. In this paper, a developed coupled solver between potential flow and Computational Fluid Dynamics (CFD) model is presented. The potential flow model is based on High-Order Spectral method (HOS), while the CFD model is based on fully nonlinear, viscous and two phase StarCCM+ solver. The coupling is achieved using a forcing zone to blend the outputs from the HOS into the StarCCM+ solver. Thus, the efficient nonlinear long time simulation of arbitrary input wave spectrum by HOS can be transferred to the CFD domain, which can reduce the computational domain and simulation time. In this paper, we make reference to the model experiments conducted by Chua et al. (2018), which consist of two identical side-by-side barges of 280 m (length) × 46 m (breadth) × 16.5 m (draught) tested in regular and irregular wave conditions. Our intention is to numerically reproduce the irregular wave conditions and the resulting barge-barge interactions. We first simulate the actual irregular wave conditions based on wave elevations measured by the wave probes using the HOS solver. The outputs are subsequently transferred to the CFD solver through a forcing zone in a 2D computational domain for comparison of the irregular wave conditions without the barges present. Subsequently, a 3D computational domain is set up in the CFD with fixed side-by-side barges modelled, and the interaction under irregular waves is simulated and compared with the experiments. We will demonstrate the applicability of the HOS-StarCCM+ coupling tool in terms of accuracy, efficiency as well as verification and validation of the results.

Comparison of Particle-Wall Interaction Boundary Conditions in the Prediction of Cyclone Collection Efficiency in Computational Fluid Dynamics (CFD) Modeling

2010 ◽  
Vol 660-661 ◽  
pp. 158-163
Author(s):  
M.Ramirez Valverde ◽  
José Renato Coury ◽  
José Antônio Silveira Gonçalves
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Boundary Conditions ◽  
Collection Efficiency ◽  
Cfd Modeling ◽  
Wall Boundary Conditions ◽  
Computational Fluid Dynamics Cfd ◽  
Wall Interaction

In recent years, many computational fluid dynamics (CFD) studies have appeared attempting to predict cyclone pressure drop and collection efficiency. While these studies have been able to predict pressure drop well, they have been only moderately successful in predicting collection efficiency. Part of the reason for this failure has been attributed to the relatively simple wall boundary conditions implemented in the commercially available CFD software, which are not capable of accurately describing the complex particle-wall interaction present in a cyclone. According, researches have proposed a number of different boundary conditions in order to improve the model performance. This work implemented the critical velocity boundary condition through a user defined function (UDF) in the Fluent software and compared its predictions both with experimental data and with the predictions obtained when using Fluent’s built-in boundary conditions. Experimental data was obtained from eight laboratory scale cyclones with varying geometric ratios. The CFD simulations were made using the software Fluent 6.3.26.

scholarly journals An Examination of the Relationship between Flow Parameters and Symptoms According to Fire Phase in a Mine Model

2017 ◽  
Vol 6 (2) ◽  
pp. 58
Author(s):  
Selçuk Keçel
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Ventilation System ◽  
Underground Mine ◽  
Computational Fluid Dynamics Cfd ◽  
The Relationship

This study examines the relationship between temperature, CO dispersions, symptoms, and COHb% levels accumulated in the blood on available ventilation conditions in cases of fire at point in an underground mine model. Based on operating parameters (air velocity and direction) of the ventilation system in the underground mine model, fast growing phase fire analyses were conducted according to the heat release rate (HRR) value in the range of 0-61.34MW. In fire scenarios prepared according to the hydrocarbon fuel type (C2.3H4.2O1.3), boundary conditions were calculated depending on the combustion equation considering fuel lower heating value (Qc). CO dispersions inside the tunnel were examined by transferring the time-dependent boundary conditions to the computational fluid dynamics (CFD) program.  yCO, COHb%, and COHb%/∆t changes were calculated according to the HRR value.  Findings regarding the effects of CO emission (acute and chronic poisoning), were expressed according to the HRR value. Keywords Combustion Model Design, Heat Release Rate (HRR), Carbon Monoxide emission, Symptoms and Survival Time, Computational Fluid Dynamics (CFD);

Use of Computational Fluid Dynamics for the Replication of Clinical Blood Flow and Pressure Measurements and Characterization of Hemodynamics in the Normal Ascending and Thoracic Aorta

2007 ◽  
Author(s):  
John F. LaDisa ◽  
C. Alberto Figueroa ◽  
Irene E. Vignon-Clementel ◽  
Frandics P. Chan ◽  
Jeffrey A. Feinstein ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Thoracic Aorta ◽  
Vascular Anatomy ◽  
Data Set ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd

Complications associated with abnormalities of the ascending and thoracic aorta are directly influenced by mechanical forces. To understand hemodynamic alterations associated with diseases in this region, however, we must first characterize related indices during normal conditions. Computational fluid dynamics (CFD) models of the ascending and thoracic aorta to date have only provided descriptions of the velocity field using idealized representations of the vasculature, a single patient data set, and outlet boundary conditions that do not replicate physiologic blood flow and pressure. Importantly, the complexity of aortic flow patterns, limited availability of methods for implementing appropriate boundary conditions, and ability to replicate vascular anatomy all contribute to the difficulty of the problem and, likely, the scarcity of more detailed studies.

Effect of Inlet Boundary Conditions on Computational Fluid Dynamics (CFD) Simulations of Gas–Solid Flows in Risers

2011 ◽  
Vol 51 (4) ◽  
pp. 1721-1728 ◽  
Author(s):  
Milinkumar T. Shah ◽  
Ranjeet P. Utikar ◽  
Geoffrey M. Evans ◽  
Moses O. Tade ◽  
Vishnu K. Pareek
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd

scholarly journals Mixing Performance of Counter-Axial Flow Impeller using Computational Fluid Dynamics

2018 ◽  
Vol 8 (02) ◽  
Author(s):  
Ian Torotwa ◽  
Changying Ji
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Axial Flow ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Rushton Turbine ◽  
Mixing Performance ◽  
Computational Fluid Dynamics Cfd

In this study, turbulent flow fields in a baffled vessel stirred by counter-axial flow impeller have been investigated in comparison to the Rushton turbine. The resultant turbulence was numerically predicted using computational fluid dynamics (CFD). Turbulence models were developed in ANSYS Fluent 18.1 solver using the Navier-Stokes equation with the standard k-ε turbulence model. The Multiple Reference Frame (MRF) approach was used to simulate the impeller action in the vertical and horizontal planes of the stirred fluid volume. Velocity profiles generated from the simulations were used to predict and compare the performance of the two designs. To validate the CFD model, the simulation results were compared with experimental results from existing work and a satisfactory agreement was established. It was concluded that the counter-axial flow impeller could provide better turbulence characteristics that would improve the quality of mixing systems.

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