Analysis of a swimmer’s hand and forearm in impulsive start from rest using computational fluid dynamics in unsteady flow conditions

The present studies deliver the computational investigations of a 10 MW turbine with a diameter of 205.8 m developed within the framework of the AVATAR (Advanced Aerodynamic Tools for Large Rotors) project. The simulations were carried out using two methods with different fidelity levels, namely the computational fluid dynamics (CFD) and blade element and momentum (BEM) approaches. For this purpose, a new BEM code namely B-GO was developed employing several correction terms and three different polar and spatial interpolation options. Several flow conditions were considered in the simulations, ranging from the design condition to the off-design condition where massive flow separation takes place, challenging the validity of the BEM approach. An excellent agreement is obtained between the BEM computations and the 3D CFD results for all blade regions, even when massive flow separation occurs on the blade inboard area. The results demonstrate that the selection of the polar data can influence the accuracy of the BEM results significantly, where the 3D polar datasets extracted from the CFD simulations are considered the best. The BEM prediction depends on the interpolation order and the blade segment discretization.

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CFD Comparison of Clearance Flow in a Rotor-Casing Assembly Using Asymmetric vs. Symmetric Lobe Rotors

Fluids Engineering ◽

10.1115/imece2003-41714 ◽

2003 ◽

Author(s):

Bassam Abu-Hijleh ◽

Jiyuan Tu ◽

Aleksander Subic ◽

Huafeng Li ◽

Katherine Ilie

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Numerical Analysis ◽

Mesh Generation ◽

Cfd Analysis ◽

Air Leakage ◽

Flow Conditions ◽

Leakage Path ◽

Clearance Flow ◽

Computational Fluid Dynamics Cfd

The performance of a Rotor-Casing Assembly is influenced more by the internal air leakages than by any other thermo-fluid aspect of its behaviour. The pressure difference driving the air along a leakage path varies periodically and does so in a manner that may not be the same for every leakage path. So the distribution of leakage through the various leakage paths within the machine is important for the improvement of its performance. The total volume of air leakage and the distribution of the leakage among the different paths depend on the rotor-rotor and rotor-casing clearances as well as the geometry of the rotors’ lobes. Computational Fluid Dynamics (CFD) analysis was carried out using the FLUENT. Geometry definition, mesh generation, boundary and flow conditions, and solver parameters have all been investigated as the part of the numerical analysis. This analysis was conducted for static rotors at different positions. The results indicate that the size of the clearances as well as the geometry of the rotors’ lobes can have a significant effect on the total volume of the air leakage as well as the distribution of the leakage among the three main leakage paths. The results can be used to ascertain the proper levels of clearances to be used and the best rotor lobes geometry to be used for the practical reduction of air leakage.

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The Design of Refinement Criteria for Dynamic Grid Adaptation Applied to Airfoil Flow Modeling

Emerging Technology in Fluids, Structures, and Fluid Structure Interactions ◽

10.1115/pvp2003-1952 ◽

2003 ◽

Author(s):

Melih Demir ◽

Govert de With ◽

Arne E. Holdo̸

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Flow Field ◽

Unsteady Flow ◽

Mesh Refinement ◽

Research Centre ◽

Shear Stresses ◽

Wall Region ◽

Grid Adaptation ◽

Computational Fluid Dynamics Cfd

At present a large number of fluid dynamics applications are found in aerospace, civil and automotive engineering, as well in medical related fields. In many applications the flow field is turbulent and the computational modelling of such flows remains a difficult task. To resolve all turbulent flow phenomena for flow problems where turbulence is of key interest is a priori not feasible in a Computational Fluid Dynamics (CFD) investigation with a conventional mesh. The use of a Dynamic Grid Adaptation (DGA) algorithm in a turbulent unsteady flow field is an appealing technique which can reduce the computational costs of a CFD investigation. A refinement of the numerical domain with a DGA algorithm requires reliable criteria for mesh refinement which reflect the complex flow processes. At present not much work has been done to obtain reliable refinement criteria for turbulent unsteady flow. The purpose of the work is to implement a new refinement technique for the boundary layer in the vicinity of the wall. It is aimed to model the flow around an airfoil with a LES turbulence model and a new DGA algorithm. In addition to that several simulations have been carried out for parametric studies. In these studies the incompressible solver in REACFLOW has been used. This Computational Fluid Dynamics (CFD) code REACFLOW was developed in collaboration with the joint Research Centre (JRC) in Italy. The following aims are aspired: • A new mesh refinement criteria method suitable for boundary layers; • To carry out LES simulations to establish the performance of the refinement criteria. The new criteria which are created in this work are for the near wall region. This criteria uses the wall shear stresses for the refinement technique. For the main flow stream the refinement criteria proposed by de With et al [6] will be used.

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Computations of Unsteady Multistage Compressor Flows in a Workstation Environment

Volume 1: Turbomachinery ◽

10.1115/91-gt-336 ◽

1991 ◽

Cited By ~ 1

Author(s):

Karen L. Gundy-Burlet

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Standard Deviation ◽

Unsteady Flow ◽

Computing Time ◽

Floating Point ◽

Computational Fluid Dynamics Cfd ◽

Multistage Compressor ◽

Gap Spacing

High-end graphics workstations are becoming a necessary tool in the Computational Fluid Dynamics (CFD) environment. In addition to their graphics capabilities, the latest generation of workstations have powerful floating point operation capabilities. As workstations become common, they could provide valuable computing time for applications, such as turbomachinery flow calculations. This paper discusses the issues involved in implementing an unsteady, viscous multistage turbomachinery code (STAGE-2) on workstations. The workstation version of STAGE-2 has then been used to study the effects of axial-gap spacing on the time-averaged and unsteady flow within a 2 1/2-stage compressor. Results include force polar plots, time-averaged pressure contours, standard deviation of pressure contours, time-averaged surface pressures and pressure amplitudes.

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Multilaboratory Particle Image Velocimetry Analysis of the FDA Benchmark Nozzle Model to Support Validation of Computational Fluid Dynamics Simulations

Journal of Biomechanical Engineering ◽

10.1115/1.4003440 ◽

2011 ◽

Vol 133 (4) ◽

Cited By ~ 58

Author(s):

Prasanna Hariharan ◽

Matthew Giarra ◽

Varun Reddy ◽

Steven W. Day ◽

Keefe B. Manning ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Particle Image Velocimetry ◽

Turbulent Flow ◽

Medical Device ◽

Particle Image ◽

Transitional Flow ◽

Flow Conditions ◽

Image Velocimetry ◽

Flow Case

This study is part of a FDA-sponsored project to evaluate the use and limitations of computational fluid dynamics (CFD) in assessing blood flow parameters related to medical device safety. In an interlaboratory study, fluid velocities and pressures were measured in a nozzle model to provide experimental validation for a companion round-robin CFD study. The simple benchmark nozzle model, which mimicked the flow fields in several medical devices, consisted of a gradual flow constriction, a narrow throat region, and a sudden expansion region where a fluid jet exited the center of the nozzle with recirculation zones near the model walls. Measurements of mean velocity and turbulent flow quantities were made in the benchmark device at three independent laboratories using particle image velocimetry (PIV). Flow measurements were performed over a range of nozzle throat Reynolds numbers (Rethroat) from 500 to 6500, covering the laminar, transitional, and turbulent flow regimes. A standard operating procedure was developed for performing experiments under controlled temperature and flow conditions and for minimizing systematic errors during PIV image acquisition and processing. For laminar (Rethroat=500) and turbulent flow conditions (Rethroat≥3500), the velocities measured by the three laboratories were similar with an interlaboratory uncertainty of ∼10% at most of the locations. However, for the transitional flow case (Rethroat=2000), the uncertainty in the size and the velocity of the jet at the nozzle exit increased to ∼60% and was very sensitive to the flow conditions. An error analysis showed that by minimizing the variability in the experimental parameters such as flow rate and fluid viscosity to less than 5% and by matching the inlet turbulence level between the laboratories, the uncertainties in the velocities of the transitional flow case could be reduced to ∼15%. The experimental procedure and flow results from this interlaboratory study (available at http://fdacfd.nci.nih.gov) will be useful in validating CFD simulations of the benchmark nozzle model and in performing PIV studies on other medical device models.

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A Numerical and Experimental Investigation of Low-conductivity Unglazed, Transpired Solar Air Heaters

Journal of Solar Energy Engineering ◽

10.1115/1.1823494 ◽

2005 ◽

Vol 127 (1) ◽

pp. 153-155 ◽

Cited By ~ 32

Author(s):

Keith Gawlik ◽

Craig Christensen ◽

Charles Kutscher

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Experimental Investigation ◽

Experimental Work ◽

Experimental Results ◽

Flow Conditions ◽

Numerical Work ◽

Plate Geometry ◽

Modeling Flow ◽

Good Agreement

The performance of low-conductivity unglazed, transpired solar collectors was determined numerically and experimentally. The numerical work consisted of modeling flow conditions, plate geometries, and plate conductivities with modified commercial computational fluid dynamics software, and the experimental work compared the performance of two plate geometries made with high and low conductivity materials under a variety of flow conditions. Good agreement was found between the numerical and experimental results. The results showed that for practical low-conductivity materials, performance differed little from the equivalent plate geometry in high-conductivity material.

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A STUDY ON THE ENGINE COMPARTMENT AIRFLOW OF A LIGHT AIRCRAFT USING COMPUTATIONAL FLUID DYNAMICS

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2013-0052 ◽

2013 ◽

Vol 37 (3) ◽

pp. 641-653

Author(s):

Hsu-jeng Liu ◽

Chih-chun Su ◽

Sheng-liang Huang

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Guide Vane ◽

Flow Characteristics ◽

Prototype Model ◽

Engine Compartment ◽

Flow Conditions ◽

Airflow Velocity ◽

Air Inlet

This study applies FLUENT to simulate and analyze the flow characteristics in the engine compartment of a light aircraft. The air inlet, air duct, guide vane, and air outlet are designed to improve the flow conditions according to the drawbacks of the prototype model. The results show that the air duct and guide vane lead the airflow to the certain position of cylinders, and the air outlet reduces the pressure in the engine compartment. Moreover, combining these designs significantly increases the overall airflow velocity in the engine compartment.

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Determining the spill flow discharge of combined sewer overflows using rating curves based on computational fluid dynamics instead of the standard weir equation

Water Science & Technology ◽

10.2166/wst.2009.752 ◽

2009 ◽

Vol 60 (12) ◽

pp. 3035-3043 ◽

Cited By ~ 12

Author(s):

S. Fach ◽

R. Sitzenfrei ◽

W. Rauch

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Cfd Simulation ◽

Water Levels ◽

Wide Spread ◽

Flow Conditions ◽

Flow Discharge ◽

Combined Sewer ◽

Rating Curves ◽

Simulation Results

It is state of the art to evaluate and optimise sewer systems with urban drainage models. Since spill flow data is essential in the calibration process of conceptual models it is important to enhance the quality of such data. A wide spread approach is to calculate the spill flow volume by using standard weir equations together with measured water levels. However, these equations are only applicable to combined sewer overflow (CSO) structures, whose weir constructions correspond with the standard weir layout. The objective of this work is to outline an alternative approach to obtain spill flow discharge data based on measurements with a sonic depth finder. The idea is to determine the relation between water level and rate of spill flow by running a detailed 3D computational fluid dynamics (CFD) model. Two real world CSO structures have been chosen due to their complex structure, especially with respect to the weir construction. In a first step the simulation results were analysed to identify flow conditions for discrete steady states. It will be shown that the flow conditions in the CSO structure change after the spill flow pipe acts as a controlled outflow and therefore the spill flow discharge cannot be described with a standard weir equation. In a second step the CFD results will be used to derive rating curves which can be easily applied in everyday practice. Therefore the rating curves are developed on basis of the standard weir equation and the equation for orifice-type outlets. Because the intersection of both equations is not known, the coefficients of discharge are regressed from CFD simulation results. Furthermore, the regression of the CFD simulation results are compared with the one of the standard weir equation by using historic water levels and hydrographs generated with a hydrodynamic model. The uncertainties resulting of the wide spread use of the standard weir equation are demonstrated.

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