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Comparison of the unsteady loads of an airfoil in the pitching and plunging motions
, Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2 FORUMS , 2006 , Pages 977-985 ; 0791847500 (ISBN); 9780791847503 (ISBN) ; Seddighi, M ; Rasi, F ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
A series of experiments were conducted on an oscillating airfoil in subsonic flow. The model was oscillated in two types of motions, pitch and plunge, at different velocities, and reduced frequencies. In addition, steady data were acquired and examined to furnish a baseline for analysis and comparison. The imposed variables of the experiment were reduced frequency, mean incident angle, amplitude of motion, and free stream velocity as well as the surface grit roughness. The unsteady aerodynamic loads were calculated using surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces of the model. Particular emphases were placed on the effects of different type of...
Application of Micro Combustion In Boundary Layer Control
, M.Sc. Thesis Sharif University of Technology ; Javadi, Khodayar (Supervisor) ; Mardani, Amir (Co-Advisor)
Abstract
The present study focus is on finding a new solution to control laminar separation bubble phenomenon by combustion actuators in micro scale, which is investigated in flows with low Reynolds number surface effect and free flows. The main parameters in this problem are classified in three groups of formation location of laminar separation bubble, its length, and transition from laminar to turbulent around airfoil SD8020 in attack angle of 5 and 8 degree. Following that, the new combustion actuators in micro scale method the comparison it with cold (and hot) air jet injection is introduced to control boundary layer flow with separation bubble point of view. Some mechanisms are identified in...
Experimental Study of a Side Intake in Transonic Speed
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
This study aims to evaluate aerodynamic coefficients of an airplane with air breathing engine experimentally. In these experiments, an ejector is used to better simulate flying conditions and aerodynamic interferences generated in inlet and exhaust engine. Therefore, at first, an ejector was designed for simultaneous simulation of exit cold flow and inlet flow of engine. All tests were conducted at QRC Trisonic wind tunnel and at Mach number of 0.5 to 0.85, angles of -4 to 6 deg. and for various amounts of pressure ejector and control surfaces angles. Finally, for the Mach number of 0.5, effect of roughness on the aerodynamic coefficients was examined. The results showed that, drag...
Investigation of the Leading Edge Flap Effects on the Aerodynamic Coefficients of a Cranked Arrow Delta Wing
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
In this study, investigated the simulation flow over a double-delta wing. The flow field was simulated by three dimension grid and RANS flow equation by K-ω-SST model. In order to investigate effect of AOA and leading edge flap simulated variable AOA and leading edge flap angle. The results shows created two vortex in inside and outside the wing. The vortex burst at high AOA and the Lift decrease after vortex bursting. The using leading edge flap effect on the vortex power and postpone vortex bursting and increasing wing lift coefficient in the high AOA. Also the leading edge flap effect on the pitch moment coefficient and change the pitch moment coefficient curve slope. The other effects of...
Adaptive fin failures tolerant integrated guidance and control based on backstepping sliding mode
, Article Transactions of the Institute of Measurement and Control ; Volume 42, Issue 10 , 2020 , Pages 1823-1833 ; Fathi Jegarkandi, M. F ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
An integrated guidance and control (IGC) is designed in this study for a surface-to-air missile considering burned or broken fin as a fault. The IGC model in the pitch plane is developed with various uncertainties in the presence of fin failure. The considered fault may cause a change in the vehicle’s shape that leads to a change in aerodynamic coefficients and consequently in the model. To identify the new model, aerodynamic coefficients are estimated using an estimator and the result is sent to the controller. Then, an adaptive robust controller is designed using the combination of backstepping and sliding mode scheme to compensate fin failure and changes in the dynamic. The simulation...
Determination of Hydrodynamic and Aerodynamic Coefficients and Longitudinal Dynamic Equation of a High Speed Catamaran with Commercial Softwares
, M.Sc. Thesis Sharif University of Technology ; Kazemzadeh Hannani, Siamak (Supervisor) ; Seif, Mohammad Saeed (Co-Advisor)
Abstract
In recent years design and manufacturing of high speed marine vessels has been developed. to estimate and control dynamics of these vessels the dynamic equation is needed.The aim of this research is Determination of hydrodynamic and aerodynamic coefficients and longitudinal dynamic equation of a high speed catamaran wich is a kind of AAMV. There are three ways to determine these coefficients. Analytical method which is usually not applicable for industrial problems, Experimental method which is too expensive and numerical method which have two parts. The first is softwares that analyse the flow with assumption that the fluid is inviscid and second softwares which solve the full Navier-Stokes...
Performance calculations within the conceptual design process of hand-launched aircraft
, Article Applied Mechanics and Materials ; Vol. 629, issue , October , 2014 , p. 145-151 ; Banazadeh, A ; Sharif University of Technology
Abstract
Matching diagram is a key part of the conceptual design process to determine the wing area and the required power. However, it requires drag polar estimation and the assumption of maximum lift coefficient. In case of conventional manned aircraft, early estimation techniques are based on statistical data that are not suitable for hand-launched aircraft. In this study, it has been attempted to present the performance calculations and a proper conceptual design model by acquiring sound values for the aerodynamic coefficients in low Reynolds number, using statistical wetted area as well as a raw design of fuselage, wing and tails. The process is applied to a sample scenario and the results are...
Performance analysis of elliptic-profile airfoil cascade for designing reversible axial flow fans
, Article AIAA Journal ; Volume 57, Issue 4 , 2019 , Pages 1492-1501 ; 00011452 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2019
Abstract
Because reversible fans must be able to provide similar performance in either rotation direction, they need to have completely symmetrical blades. In the present study, an elliptic profile with itsmaximum thickness of 8%chord length at themiddle of the chord line is studied. For verification, theNACA0012 airfoilwas once analyzed two-dimensionally in the isolatedformationandonce in cascade formation with0.55 and 0.83 solidities, andthe obtainedresultswere comparedwith numerical and experimental results. Three well-known Reynolds-averaged Navier-Stokes turbulence models including Spalart-Allmaras, realizable κ-ϵ, and shear-stress transport κ-ω were used to find the suitable turbulence method....
Performance analysis of elliptic-profile airfoil cascade for designing reversible axial flow fans
, Article AIAA Journal ; Volume 57, Issue 4 , 2019 , Pages 1492-1501 ; 00011452 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2019
Abstract
Because reversible fans must be able to provide similar performance in either rotation direction, they need to have completely symmetrical blades. In the present study, an elliptic profile with itsmaximum thickness of 8%chord length at themiddle of the chord line is studied. For verification, theNACA0012 airfoilwas once analyzed two-dimensionally in the isolatedformationandonce in cascade formation with0.55 and 0.83 solidities, andthe obtainedresultswere comparedwith numerical and experimental results. Three well-known Reynolds-averaged Navier-Stokes turbulence models including Spalart-Allmaras, realizable κ-ϵ, and shear-stress transport κ-ω were used to find the suitable turbulence method....
Optimization of Actuators Position of a Low Aspect Ratio Variable-camber Wing and Derivation of Its Aerodynamic
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firouzabadi, Rouhollah (Supervisor) ; Haddadpour, Hassan (Supervisor)
Abstract
Morphing concepts can potentially improve the performance and fuel consumption of modern aircrafts. Smart materials can reduce the weight and complexity, and also are of the best choices to improve efficiency and reliability for realizing morphing wings. Developing of a simple model and optimization of smart piezocomposite actuators position of a thin wing with variable camber is considered. The goal is to gain desired properties in incompressible subsonic regime. Lifting surfaces of a composite wing are simplified using shell model. Keeping the problem simple, a piezocomposite patch is used to change the shell curvature. Basic modes are extracted from FEM software and behavior of bimorph...
Continuous-time state-space unsteady aerodynamic modeling based on boundary element method
, Article Engineering Analysis with Boundary Elements ; Volume 36, Issue 5 , 2012 , Pages 789-798 ; 09557997 (ISSN) ; Ghadiri, B ; Abdalla, M. M ; Haddadpour, H ; De Breuker, R ; Sharif University of Technology
2012
Abstract
In this paper a continuous-time state-space aerodynamic model is developed based on the boundary element method. Boundary integral equations governing the unsteady potential flow around lifting bodies are presented and modified for thin wing configurations. Next, the BEM discretized problem of unsteady flow around flat wing equivalent to the original geometry is recast into the standard form of a continuous-time state-space model considering some auxiliary assumptions. The system inputs are time derivative of the instantaneous effective angle of attack and thickness/camber correction terms while the outputs are unsteady aerodynamic coefficients. To validate the model, its predictions for...
Experimental study of stall control over an airfoil with dual excitation of separated shear layers
, Article Aerospace Science and Technology ; Volume 82-83 , 2018 , Pages 402-411 ; 12709638 (ISSN) ; Hajipour, M ; Ghamkhar, K ; Sharif University of Technology
Abstract
This paper investigates the stall control over an airfoil employing dual excitation of separated shear layers with dielectric barrier discharge plasma actuators. This novel approach is studied experimentally on the NACA 0015 airfoil at the angle of attack and Reynolds number of 14° and 0.3×106, respectively. To analyze the baseline flow, Time-averaged pressure distributions on the airfoil surfaces are evaluated with 40 pressure taps. Further, the dominant natural frequencies associated with flow structures in the airfoil wake are examined utilizing a hot-wire anemometer. Two plasma actuators, one on the suction side just upstream the separation point and the other on the pressure side at the...
Application of artificial neural network for the prediction of pressure distribution of a plunging airfoil
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 237-242 ; 2010376X (ISSN) ; Masdari, M ; Soltani, M. R ; Sharif University of Technology
2009
Abstract
Series of experimental tests were conducted on a section of a 660 kW wind turbine blade to measure the pressure distribution of this model oscillating in plunging motion. In order to minimize the amount of data required to predict aerodynamic loads of the airfoil, a General Regression Neural Network, GRNN, was trained using the measured experimental data. The network once proved to be accurate enough, was used to predict the flow behavior of the airfoil for the desired conditions. Results showed that with using a few of the acquired data, the trained neural network was able to predict accurate results with minimal errors when compared with the corresponding measured values. Therefore with...
An experimental investigation of the reduced frequency effects into pressure coefficients of a plunging airfoil
, Article 7th International Conference on Advances in Fluid Mechanics, AFM'08, The New Forest, 21 May 2008 through 23 May 2008 ; Volume 59 , 2008 , Pages 153-161 ; 17433533 (ISSN); 9781845641092 (ISBN) ; Ajalli, F ; Soltani, M. R ; WIT Transactions on Engineering Sciences ; Sharif University of Technology
2008
Abstract
Aerodynamic coefficients on a two dimensional plunging airfoil, in a low-speed wind tunnel are presented. Dynamic motion was produced by plunging the model over a range of reduced frequencies, and mean angles of attack. The Reynolds number in the present test was held fixed (Re = 1.5×10 5), and the reduced frequency was varied in an almost wide range. Surface static pressure distribution was measured on the upper and lower sides of the model, during the oscillating motion. It was found that reduced frequency had strong effects on the pressure distribution, near the leading edge of the airfoil. For mean equivalent angles of attack of 0, 5 degrees, hysteresis loops on the upper surface of the...
Pore-scale simulation of fluid flow passing over a porously covered square cylinder located at the middle of a channel, using a hybrid MRT-LBM–FVM approach
, Article Theoretical and Computational Fluid Dynamics ; Volume 29, Issue 3 , 2015 , Pages 171-191 ; 09354964 (ISSN) ; Taeibi Rahni, M ; Jam, F ; Sharif University of Technology
Springer New York LLC
2015
Abstract
A comprehensive study was performed to analyze the unsteady laminar flow characteristics around a porously covered, a fully porous, and a solid squared section cylinder located in the middle of a plane channel. In order to simulate fluid flow inside porous media and porous–fluid interface accurately (minimizing modeling error), the porous region was analyzed in pore scale, using LBM. Additionally, to minimize the LBM-related compressibility error through the porous region, a multi-block multiple relaxation time lattice Boltzmann method (MRT-LBM) was used. Also, to decrease CPU time, a Navier–Stokes flow solver, based on finite volume method and SIMPLE algorithm, was coupled with MRT-LBM to...
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...
Unsteady flow over offshore wind turbine airfoils and aerodynamic loads with computational fluid dynamic simulations
, Article International Journal of Environmental Science and Technology ; Volume 13, Issue 6 , 2016 , Pages 1525-1540 ; 17351472 (ISSN) ; Radmanesh, A. R ; Soltani, M. R ; Sharif University of Technology
Center for Environmental and Energy Research and Studies
Abstract
The first notable megawatt class wind turbine, which was the pioneer of improvement in the blade performance in large wind turbines, appeared in Vermont. Nowadays, modern wind turbines are using blades with multi-airfoils at different sections. In this study, in order to indicate the best airfoil profile for the optimum performance in different sections of a blade, five popular airfoils, including S8xx, FFA and AH series, were studied. On the large-scale profile, shear stress transport K–ω model was applied for the simulation of horizontal axis wind turbines for different wind speeds. The aerodynamic simulation was accomplished using computational fluid dynamic method, which in turn is based...
Aeroelasticity consideration of supersonic vehicle using closed form analytical aerodynamic model
, Article Aircraft Engineering and Aerospace Technology ; Volume 81, Issue 2 , 2009 , Pages 128-136 ; 00022667 (ISSN) ; Salezadeh Nobari, A ; Mahdi, S ; Hassan, H ; Farhad, T ; Sharif University of Technology
2009
Abstract
Purpose - The purpose of this paper is to investigate the aeroelastic behavior of a supersonic flight vehicle flying at moderate angles of attack using global analytic nonlinear aerodynamic model. Design/methodology/approach - Aeroelastic behavior of a supersonic flight vehicle flying at moderate angles of attack is considered, using nonlinear aerodynamics and linear elastodynamics and structural models. Normal force distribution coefficient over the length of the vehicle and pitching moment coefficient are the main aerodynamic parameters used in the aeroelastic modeling. It is very important to have closed form analytical relations for these coefficients in the model. They are generated...