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boundary-layer-control
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Jet-into-crossflow boundary-layer control: Innovation in gas turbine blade cooling
, Article AIAA Journal ; Volume 45, Issue 12 , May , 2007 , Pages 2910-2925 ; 00011452 (ISSN) ; Taeibi Rahni, M ; Darbandi, M ; Sharif University of Technology
2007
Abstract
Jet into crossflow has numerous technological applications, such as in film cooling of gas turbine blades. It has been more than half a century that people have been studying this problem and research is still underway due to its importance and its complexities. This paper is a computational study concerned with film cooling of gas turbine blades. A novel near-wall flow control technique of using staggered arrangement of small injection ports near a film-cooling hole (combined triple jet) is introduced. The fluid injected from the small ports changes the flow pattern downstream, resulting in a considerable enhancement of cooling efficiency. The flowfield computations, governed by the...
Effects of boundary layer control method on hydrodynamic characteristics and tip vortex creation of a hydrofoil
, Article Polish Maritime Research ; Volume 24, Issue 2 , 2017 , Pages 27-39 ; 12332585 (ISSN) ; Tanha, A ; Kourabbasloo, N. N ; Tavakoli, S ; Sharif University of Technology
De Gruyter Open Ltd
2017
Abstract
There is currently a significant focus on using boundary layer control (BLC) approach for controlling the flow around bodies, especially the foil sections. In marine engineering this is done with the hope of increasing the lift - to - drag ratio and efficiency of the hydrofoils. In this paper, effects of the method on hydrodynamic characteristics and tip vortex formation of a hydrofoil are studied. Steady water injection at the tip of the hydrofoil is simulated in different conditions by using ANSYS-CFX commercial software. Validity of the proposed simulations is verified by comparing the obtained results against available experimental data. Effects of the injection on the lift, drag, and...
Standard and boundary layer perturbation approaches to predict nonlinear axisymmetric behavior of cylindrical shells
, Article Composite Structures ; Volume 204 , 2018 , Pages 855-881 ; 02638223 (ISSN) ; Taati, E ; Asghari, M ; Reddy, J. N ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The feasibility and performance of standard and boundary layer perturbation techniques in nonlinear analyses of cylindrical shells are investigated. To this end, the nonlinear axisymmetric behavior of short and long functionally graded (FG) cylindrical shells is considered. The nonlinear governing equations of shell theory with first-order approximation and the von Karman nonlinearity are decoupled. This uncoupling makes it possible to present an analytical solution. A new boundary layer perturbation solution is presented by reducing the governing equations to a normalized form of boundary-layer type. Also, the uncoupled governing equations are solved using standard one-, two-, and...
Theoretical study of diffusional release of a dispersed solute from a hollow cylindrical polymeric matrix
, Article Scientia Iranica ; Volume 28, Issue 3 , 2021 , Pages 1428-1435 ; 10263098 (ISSN) ; Tajsoleiman, T ; Abdekhodaie, M. J ; Sharif University of Technology
Sharif University of Technology
2021
Abstract
The present study proposes an exact solution for the release kinetic of a solute from inside a hollow cylindrical polymeric matrix into an infinite medium when the initial concentration of the solute (A) is greater than the solubility limit (Cs). A combination of analytical and numerical methods was used to calculate the solute concentration profile and the release rate. The model was developed for two different conditions including: (1) The release medium was flowing through the hollow cylinder in which the boundary layer may be neglected, and (2) The release medium inside the hollow cylinder was stagnant where the boundary layer needed to be considered. The results indicated that the...
Numerical study on boundary layer control using CH4[sbnd]H2[sbnd]air Micro-reacting jet
, Article International Journal of Hydrogen Energy ; Volume 41, Issue 47 , 2016 , Pages 22433-22452 ; 03603199 (ISSN) ; Yahyavi Koochaksarai, M ; Javadi, K ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
The focus of present numerical study is on assessment of control of laminar separation bubble phenomenon using Micro-scale combustion actuators in an airfoil with low Reynolds number under surface effect and free flows. In this way, the characteristics of laminar separation bubble such as its formation, geometry, and transition from laminar to turbulent around airfoil SD8020 in attack angles of 5 and 8° are investigated. Following that, the new combustion actuators in Micro-scale, cold, and hot air-jet injection are introduced to control boundary layer flow in terms of eliminating the separation bubble. Some mechanisms are identified for improvement of methane-air premixed flame...
Boundary Layer Control of an Incompressible Turbulent Flow over an Airfoil, Using Quasi-spherical Surface Structures
, M.Sc. Thesis Sharif University of Technology ; Javadi, Khodayar (Supervisor) ; Taeibi Rahni, Mohammad (Supervisor)
Abstract
Boundary layer control has long been and still is considered to reduce drag. In this research, the effect of quasi-spherical structures on the control of boundary layer is investigated. First, flow over a NACA0015 airfoil was investigated. Then, flow over the same airfoil with quasi-spherical bumps on its upper surface was numerically simulated and the result of these two situations were compared. The dimensions and numbers of the bumps in longitudinal and lateral directions (different case studies) were chosen using trial and error. The three-dimensional, incompressible, and turbulent flow governing equations were numerically solved, using FVM and the OpenFOAM software. To get preliminary...
Spreading Control of Coolant Jet at the Trailing Edge of Gas Turbine Blade with Arc-jet Exhaust Buffling
, M.Sc. Thesis Sharif University of Technology ; Javadi, Khodayar (Supervisor)
Abstract
This research investigates the use of baffles in sector jets for film cooling of turbine blades. The goal of this study is to compare the cooling performance in three conditions: sector jet without baffles (one 90-degree arc), with one baffle (two 45-degree arcs), and with two baffles (three 30-degree arcs). The effect of using this type of cooling is also compared to the crossflow jet, which is the simplest type of cooling jet. In all conditions, the mass flow ratio is constant and equal to 1. The problem is solved for a turbine blade with the “AGTB-B1” airfoil. The problem is first solved with the Transition SST turbulence model, and the results are used as the initial conditions for the...
Numerical/Experimental Investigation of Semi-Spherical Bumps on Separation Control and Lift Enhancement
, M.Sc. Thesis Sharif University of Technology ; Javadi, Khodayar (Supervisor)
Abstract
The main purpose of the current study is to control the boundary layer of the flow passing over the wing and the lift force enhancement. In this research has been tried to introduce a new generation of passive flow control and use bumpy surface structures to control the separated flow and increase the aerodynamic efficiency. Therefore, the wing with the hawk bird’s airfoil section has been designated. Then, assuming a viscous, incompressible flow and a low Reynolds number range (about 2 × 105), the flow formation and boundary layer development on this wing has been investigated. Subsequently, bump structures have been settled on the upper surface of this wing. The numerical simulations have...
The application of suction and blowing in performance improvement of transonic airfoils with shock control bump
, Article Scientia Iranica ; Volume 24, Issue 1 , 2017 , Pages 274-292 ; 10263098 (ISSN) ; Nejati, A ; Charlang Kiani, K. C ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
Shock Control Bump (SCB) reduces the wave drag in transonic ight. To control the boundary layer separation and to reduce the wave drag for two transonic airfoils, RAE-2822 and NACA-64A010, we investigate the application of two flow control methods, i.e. suction and blowing, to add them to the SCB. An adjoint gradient-based optimization algorithm is used to find the optimum shape and location of SCB. The performance of both Hybrid Suction/SCB (HSS) and Hybrid Blowing/SCB (HBS) is a function of the sucked or injected mass flow rate and their position. A parametric study is performed to find the near optimum values of the aerodynamic coefficients and efficiency. A RANS solver is validated and...