A 3D conjugate heat transfer simulation of a gas turbine vane is performed using Fluent and the t... more A 3D conjugate heat transfer simulation of a gas turbine vane is performed using Fluent and the temperature and heat transfer coefficient distribution over its surface are obtained. The study focused on the linear NASA-C3X cascade, for which experimental data are available. Three full turbulence models and two transitional models are studied, namely, SpalartAllmaras (SA) model, Shear stress transport k − ω (sstkw) model, v2 − f (V2F) model, Transition SST (trans-sst) model and k− kl −ω (k-kl-w) model. Unstructured prism meshes generated with y+ of less than 1 for all of turbulence models. Two turbulence intensities of 0.5% and 20% are studied to see the turbulence models performance at both high and low turbulence intensities. For low turbulence intensity, theV2F model can predict heat transfer coefficient distribution very well while for high turbulence intensity, the trans-sst turbulence model is working better. Comparing the results of both high and low turbulence intensities show that V2F model can be used as a reliable model for simulation of gas turbine vane.
Journal of the Taiwan Institute of Chemical Engineers, 2015
ABSTRACT The turbulent heat transfer to nanofluid flow over double forward-facing steps was inves... more ABSTRACT The turbulent heat transfer to nanofluid flow over double forward-facing steps was investigated numerically. The duct geometry and computational mesh were developed with ANSYS 14 ICEM. Two-dimensional governing equations were discretized and integrated using finite volume technique. The k-epsilon turbulence model was used in the analysis. Al2O3 and CuO nanoparticles at volume fractions varying from 1% to 4% with water as the base fluid were employed for turbulent flow in a passage with a double forward-facing step. The effects of volume fraction and step height were compared with the base fluid thermal performance. The obtained results showed an increase in the Nusselt number with the increase in volume fraction of nanofluid, Reynolds number, and step height. A higher local Nusselt number value was found at the second step compared to the first step for all cases. Velocity contours were developed to visualize the recirculation regions before and after the first and second steps. The results also demonstrated enhanced heat transfer with the increase of nanoparticle concentration, and the largest thermal enhancement factor occurred for the highest nanoparticle volume fraction (4%) of Al2O3 considered in this investigation.
In this paper, reducing the Strouhal number of a circular cylinder is studied numerically. Two-di... more In this paper, reducing the Strouhal number of a circular cylinder is studied numerically. Two-dimensional numerical simulations of flow over a normal circular cylinder and various modified circular cylinders are carried out using FLUENT® soft ware. Two small blades are attached to a circular cylinder and the effects of variation of the blades length and the blade angle are studied numerically. The blade angle is chosen 2α = 0°, 30°, 90°, 120° and 150°. The blades length is chosen l/d = 0.125, 0.25, 0.375. Effects of blade angles and blade lengths were studied for both 2α = 0° and 150°. Results show that increasing in blade lengths decreases the Strouhal number. Moreover, as the blade angle was increased from zero to 90°, the percentage reduction in Strouhal number decreased; however, as the blade angle was further increased from 90° to 150°, the percentage reduction in Strouhal number increased. Although the modifications studied here decrease the vortex shedding frequency they make the vortices shed from the cylinder farther and stronger hence increasing the magnitude of the fluctuating forces.
... AND REMOVAL Goodarz Ahmadi Department of Mechanical and Aeronautical Engineering ... A partic... more ... AND REMOVAL Goodarz Ahmadi Department of Mechanical and Aeronautical Engineering ... A particle suspended in a fluid is subjected to hydrodynamic forces. For low Reynolds' number, the Stokes drag force on a spherical particle is given by FD = 3πµUd, (1) ...
The conditions for energy stability of steady and unsteady motions of two temperature heat conduc... more The conditions for energy stability of steady and unsteady motions of two temperature heat conducting fluid are presented. The model of fluid is essentially the one proposed by Chen, Gurtin and Williams. Certain uniqueness theorems for the unsteady and steady flows are also established. The theorems established are universal in the sense that they may be applied to any geometry of bounded domains and any distribution of the basic flow variables. The paper was concluded by presenting a scheme for improving the stability limits.
A 3D conjugate heat transfer simulation of a gas turbine vane is performed using Fluent and the t... more A 3D conjugate heat transfer simulation of a gas turbine vane is performed using Fluent and the temperature and heat transfer coefficient distribution over its surface are obtained. The study focused on the linear NASA-C3X cascade, for which experimental data are available. Three full turbulence models and two transitional models are studied, namely, SpalartAllmaras (SA) model, Shear stress transport k − ω (sstkw) model, v2 − f (V2F) model, Transition SST (trans-sst) model and k− kl −ω (k-kl-w) model. Unstructured prism meshes generated with y+ of less than 1 for all of turbulence models. Two turbulence intensities of 0.5% and 20% are studied to see the turbulence models performance at both high and low turbulence intensities. For low turbulence intensity, theV2F model can predict heat transfer coefficient distribution very well while for high turbulence intensity, the trans-sst turbulence model is working better. Comparing the results of both high and low turbulence intensities show that V2F model can be used as a reliable model for simulation of gas turbine vane.
Journal of the Taiwan Institute of Chemical Engineers, 2015
ABSTRACT The turbulent heat transfer to nanofluid flow over double forward-facing steps was inves... more ABSTRACT The turbulent heat transfer to nanofluid flow over double forward-facing steps was investigated numerically. The duct geometry and computational mesh were developed with ANSYS 14 ICEM. Two-dimensional governing equations were discretized and integrated using finite volume technique. The k-epsilon turbulence model was used in the analysis. Al2O3 and CuO nanoparticles at volume fractions varying from 1% to 4% with water as the base fluid were employed for turbulent flow in a passage with a double forward-facing step. The effects of volume fraction and step height were compared with the base fluid thermal performance. The obtained results showed an increase in the Nusselt number with the increase in volume fraction of nanofluid, Reynolds number, and step height. A higher local Nusselt number value was found at the second step compared to the first step for all cases. Velocity contours were developed to visualize the recirculation regions before and after the first and second steps. The results also demonstrated enhanced heat transfer with the increase of nanoparticle concentration, and the largest thermal enhancement factor occurred for the highest nanoparticle volume fraction (4%) of Al2O3 considered in this investigation.
In this paper, reducing the Strouhal number of a circular cylinder is studied numerically. Two-di... more In this paper, reducing the Strouhal number of a circular cylinder is studied numerically. Two-dimensional numerical simulations of flow over a normal circular cylinder and various modified circular cylinders are carried out using FLUENT® soft ware. Two small blades are attached to a circular cylinder and the effects of variation of the blades length and the blade angle are studied numerically. The blade angle is chosen 2α = 0°, 30°, 90°, 120° and 150°. The blades length is chosen l/d = 0.125, 0.25, 0.375. Effects of blade angles and blade lengths were studied for both 2α = 0° and 150°. Results show that increasing in blade lengths decreases the Strouhal number. Moreover, as the blade angle was increased from zero to 90°, the percentage reduction in Strouhal number decreased; however, as the blade angle was further increased from 90° to 150°, the percentage reduction in Strouhal number increased. Although the modifications studied here decrease the vortex shedding frequency they make the vortices shed from the cylinder farther and stronger hence increasing the magnitude of the fluctuating forces.
... AND REMOVAL Goodarz Ahmadi Department of Mechanical and Aeronautical Engineering ... A partic... more ... AND REMOVAL Goodarz Ahmadi Department of Mechanical and Aeronautical Engineering ... A particle suspended in a fluid is subjected to hydrodynamic forces. For low Reynolds' number, the Stokes drag force on a spherical particle is given by FD = 3πµUd, (1) ...
The conditions for energy stability of steady and unsteady motions of two temperature heat conduc... more The conditions for energy stability of steady and unsteady motions of two temperature heat conducting fluid are presented. The model of fluid is essentially the one proposed by Chen, Gurtin and Williams. Certain uniqueness theorems for the unsteady and steady flows are also established. The theorems established are universal in the sense that they may be applied to any geometry of bounded domains and any distribution of the basic flow variables. The paper was concluded by presenting a scheme for improving the stability limits.
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