scholarly journals Summary on the Results of Two Computational Fluid Dynamic Benchmarks of Tube and Different Channel Geometries

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Attila Kiss ◽  
Andrey Churkin ◽  
Darwan S. Pilkhwal ◽  
Abhijeet M. Vaidya ◽  
Walter Ambrosini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Computational Fluid Dynamic ◽  
Prediction Accuracy ◽  
Fluid Dynamic ◽  
Annular Channel ◽  
Initial Boundary ◽  
Sensitivity Analyses ◽  
Cfd Models

Two computational fluid dynamic (CFD) benchmarks have been performed to assess the prediction accuracy and sensitivity of CFD codes for heat transfer in different geometries. The first benchmark focused on heat transfer to water in a tube (first benchmark), while the second benchmark covered heat transfer to water in two different channel geometries (second benchmark) at supercritical pressures. In the first round with the experimental data unknown to the participants (i.e., blind calculations), CFD calculations were conducted with initial boundary conditions and simpler CFD models. After assessment against measurements, the calculations were repeated with the refined boundary conditions and material properties in the follow-up calculation phase. Overall, the CFD codes seem to be able to capture the general trend of heat transfer in the tube and the annular channel but further improvements are required in order to enhance the prediction accuracy. Finally, sensitivity analyses on the numerical mesh and the boundary conditions were performed. It was found that the prediction accuracy has not been improved with the introduction of finer meshes and the effect of mass flux on the result is the strongest among various investigated boundary conditions.

Application of Magnetic Resonance (MR) Imaging for the Development and Validation of Computational Fluid Dynamic (CFD) Models of the Rat Respiratory System

2006 ◽  
Vol 18 (10) ◽  
pp. 787-794 ◽  
Author(s):  
Kevin R. Minard ◽  
Daniel R. Einstein ◽  
Richard E. Jacob ◽  
Senthil Kabilan ◽  
Andrew P. Kuprat ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Respiratory System ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Cfd Models ◽  
Development And Validation

Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity With and Without the Trailing-Edge Cooling Holes

2014 ◽  
Author(s):  
Mohammad Taslim ◽  
Joseph S. Halabi
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Flow Direction ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Cfd Models ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides) with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. Realizable k–ε turbulence model in conjunction with enhanced wall treatment approach for the near wall regions, was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

The Effect of the Fuel Injector Internal Geometry Upon the Primary Zone Aerodynamics

1998 ◽  
Author(s):  
R. A. Hicks ◽  
M. Whiteman ◽  
C. W. Wilson
Keyword(s):  
Boundary Conditions ◽  
Fluid Dynamic ◽  
Radial Component ◽  
Fuel Injector ◽  
Air Blast ◽  
Fuel Injectors ◽  
Cfd Models ◽  
Primary Zone ◽  
Flow Through ◽  
Semi Empirical

One of the major aims of research in gas turbine combustor systems is the minimisation of non-desirable emissions. The primary method of reducing pollutants such as soot and NOx has been to run the combustion primary zone lean. Unfortunately, this causes problems when the combustor is run under idle and relight conditions as the primary zone air fuel ratio (AFR) can exceed the flammability limit. Altering this AFR directly affects the primary zone aerodynamics through changes in the spray profile. One method of determining the influence of changes in AFR upon the primary zone is to use Computational Fluid Dynamic (CFD) models. However, to model the flow through an air-blast fuel injector and accurately predict the resulting primary zone aerodynamics requires hundreds of thousands, if not millions, of cells. Therefore, with current computer capabilities simplifications need to be made. One simplification is to model the primary zone as a 2-D case. This reduces the number of cells to a computationally solvable level. However, by reducing the problem to 2-D the ability to accurately model air-blast fuel injectors is lost as they are intrinsically 3-D devices. Therefore, it is necessary to define boundary conditions for the fuel injector. Currently, due to difficulties in obtaining experimental measurements inside a air-blast fuel injector, these boundary conditions are often derived using semi-empirical methods. This paper presents and compares two such models; the model proposed by Crocker et al. in 1996 and one developed at DERA specifically for modelling air-blast fuel injectors. The work also highlights the importance of the often neglected radial component upon the primary zone aerodynamics.

scholarly journals Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity with and without the Trailing-Edge Cooling Holes

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
M. E. Taslim ◽  
J. S. Halabi
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Flow Direction ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Cfd Models ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing-edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross-sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides) with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing-edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs, and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. Realizablek-εturbulence model in conjunction with enhanced wall treatment approach for the near wall regions was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

scholarly journals Analisa Aliran Udara Panas pada Drying Chamber Raw Mill PT. Semen Padang menggunakan Computational Fluid Dynamic (CDF)

2019 ◽  
Vol 7 (2) ◽  
pp. 126
Author(s):  
Fajrida Afrina
Keyword(s):  
Heat Transfer ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Exhaust Gas ◽  
Transfer Velocity ◽  
Drying Chamber

Drying  chamber  adalah alat  pengering  bahan  baku  semen  yang  akan  digiling dalam raw  mill.  Keefektifan  kerja raw  mill sangat  dipengaruhi  oleh  sistem pengeringan  pada  bahan  baku  yang  akan  digiliing.  Pengeringan  di  dalam drying chamber ini menggunakan udara panas dari kiln exhaust gas aliran ducting string B. Semakin kering bahan akan semakin mudah proses penggilingan. Heat transfer dari  fluida  ke  bahan  yang  akan  dkeringkan sangat  penting  agar  diperoleh pengeringan  yang  optimum.  Penelitian  ini  dilakukan  dengan  tujuan  untuk mengetahui  sacara  teknis faktor  yang  mempemharuhi heat  transfer dari  udara pengering  ke  bahan  yang  dikeringkan  dengan  bantuan  aplikasi computational fluid  dynamic (CFD).  Hasil  simulasi  yang  dilakukan  menggunakan CFD adalah heat transfer berbanding lurus dengan temperature dan velocity udara pengering, namun  berbanding  terbalik  dengan waktu  tinggal  udara  dalam drying  chamber.Heat transfer optimum  yang diperoleh pada penelitian ini adalah pada perlakuan velocity15 mm/s, temperature 300 0C yaitu 901.480 Btu/s. Kata kunci: CFD, drying chamber, heat transfer, velocity, temperatur

Computational fluid dynamic-derived wall shear stress of non-significant left main bifurcation disease may predict acute vessel thrombosis at 3-year follow-up

2019 ◽  
Vol 35 (3) ◽  
pp. 297-306 ◽  
Author(s):  
Marco Zuin ◽  
Gianluca Rigatelli ◽  
Dobrin Vassilev ◽  
Federico Ronco ◽  
Alberto Rigatelli ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Left Main ◽  
Wall Shear ◽  
Vessel Thrombosis

Angular Remodeling in Single Stent-Assisted Coiling Displaces and Attenuates the Flow Impingement Zone at the Neck of Intracranial Bifurcation Aneurysms

Neurosurgery ◽  
2013 ◽  
Vol 72 (5) ◽  
pp. 739-748 ◽  
Author(s):  
Bulang Gao ◽  
Merih I. Baharoglu ◽  
Adel M. Malek
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Bifurcation Angle ◽  
Impingement Zone ◽  
Wall Shear ◽  
And Migration ◽  
The Impact

Abstract BACKGROUND: Self-expanding intracranial stent-assisted coiling of bifurcation aneurysms has recently been shown to straighten target cerebral vessels, a phenomenon with unknown hemodynamic effect. OBJECTIVE: To investigate the impact of angular remodeling in aneurysms treated with single stent-assisted coiling with the use of computational fluid dynamic techniques. METHODS: Fourteen patients (7 women, mean age 55) who underwent stent coiling of 14 wide-necked bifurcation aneurysms were included based on the availability of high-resolution 3-dimensional rotational angiography. Pretreatment data sets underwent virtual aneurysm removal to isolate the effect of stenting. Wall shear stress and pressure profiles obtained from constant flow input computational fluid dynamic analysis were analyzed for apical hemodynamic changes. RESULTS: Stenting increased the bifurcation angle with significant straightening immediately after treatment and at follow-up (107.3° vs 144.9°, P < .001). The increased stented angle at follow-up led to decreased pressure drop at the bifurcation apex (12.2 vs 9.9 Pa, P < .003) and migration of the flow impingement zone (FIZ) toward the contralateral nonstented daughter branch by a mean of 1.48 ± 0.2 mm. Stent-induced angular remodeling decreased FIZ width separating peak apical wall shear stress (3.4 vs 2.5 mm, P < .004). Analysis of FIZ distance measured from the parent vessel centerline showed it to be linearly (r = .58, P < .002) and FIZ width inversely correlated (r = .46, P < .02) to vessel bifurcation angle. CONCLUSION: Stent-induced angular remodeling significantly altered bifurcation apex hemodynamics in a favorable direction by blunting apical pressure and inducing the narrowing and migration of the FIZ, a novel response to intracranial stenting that should be added to intimal hyperplasia and flow diversion.

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