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pressure-distribution
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Computational and experimental investigations of boundary layer tripping
, Article Journal of Applied Fluid Mechanics ; Volume 3, Issue 2 , 2010 , Pages 53-63 ; 17353572 (ISSN) ; Soltani, M. R ; Farahani, M ; Taeibi Rahni, M ; Sharif University of Technology
2010
Abstract
Supersonic flow over a tapered body of revolution has been investigated both experimentally and numerically. The experimental study consisted of a series of wind tunnel tests on an ogive-cylinder body. Static pressure distributions on the body surfaces at several longitudinal cross sections, as well as the boundary layer profiles at various angles of attack have been measured. Further, the flow around the model was visualized using Schlieren technique. Tests with a natural development of the boundary layer and with tripping were also carried out. All tests were conducted in the trisonic wind tunnel of Qadr Research Center. Our results show that artificial boundary layer tripping has minor...
Experimental investigation of aerodynamic performance of a wind turbine blade undergoing pure pitch and plunge motions
, Article Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ; Volume 67, Issue 1 , 2020 , Pages 105-118 ; Soltani, M. R ; Davari, A. R ; Sharif University of Technology
Penerbit Akademia Baru
2020
Abstract
In this paper, extensive experimental tests were carried out for an aerodynamic characterization of the airfoil cross-section of a wind turbine blade. The wind turbine blade cross-sections are usually exposed to unsteady pitch and plunge oscillations. One way to increase the power of blade, is to improve it's aerodynamic performance, so it is necessary to study and compare the unsteady aerodynamic behavior of the airfoil. The aerodynamic behavior of turbine blades are dependent on several parameters including initial angle of attack, reduced frequency and oscillation amplitude. In this study, reduced frequency and oscillation amplitude assumed constant and the initial angle of attack of the...
Three dimensional numerical simulation of air flow over domed roofs
, Article NUMERICAL ANALYSIS AND APPLIED MATHEMATICS: International Conference on Numerical Analysis and Applied Mathematics, Corfu, 16 September 2007 through 20 September 2007 ; Volume 936 , 2007 , Pages 191-194 ; 0094243X (ISSN) ; 073540447X (ISBN); 9780735404472 (ISBN) ; Bahadori, M. N ; Sharif University of Technology
2007
Abstract
Using domed roofs to reduce building solar load in hot arid area is one of Iranian mechanical engineering masterworks. The first application of these roofs was to cover large buildings such as mosques, shrines, etc. However their thermal performance made them to be employed in other buildings like bazaars. The aim of this study was to determine the air pressure and velocity distribution over domed roofs, by employing numerical methods. The results of this study will be used as the first step for thermal performance evaluation of domed roofs. © 2007 American Institute of Physics
Calculation of the rolling pressure distribution and force in wire flat rolling process
, Article Journal of Materials Processing Technology ; Volume 171, Issue 2 , 2006 , Pages 253-258 ; 09240136 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2006
Abstract
In this study a slab analysis is developed to predict the rolling pressure distribution and rolling force in the wire flat rolling process. In the slab analysis the variations of width of contact area between the rolls and wire during rolling is considered. Two differential equations are derived and solved using a modified Eulerian numerical method. The effects of friction coefficient, reduction in height and yield stress of wire on the rolling pressure distribution and rolling force are assessed. It is found that in the flat rolling of wire, there exists a maximum in the pressure distribution similar to that of the strip rolling process. Also, the effects of friction coefficient, reduction...
A coupled prescribed wake-Euler solver for efficient computing helicopter rotor flows in hover
, Article 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 3 , 2006 , Pages 1670-1681 ; Mohammadi, M ; Sharif University of Technology
Curran Associates Inc
2006
Abstract
A numerical solution technique is developed to simulate the flowfield of hovering helicopter rotor. The present method uses a coupled prescribed wake-Euler solver to efficiently allow the vortical wake effects. The threedimensional Euler equations written in a rotating coordinate frame are solved by using a cell-centered finite volume scheme that is based on the Roe's flux-difference splitting on unstructured meshes. High-order accuracy is achieved via the reconstruction of flow variables using the MUSCL interpolation technique. Calculations are carried out for an isolated rotor in hover for two operating conditions of subsonic and transonic tip Mach numbers, Mtip = 0.44 and Mtip = 0.877 ,...
Surface pressure variation on an airfoil in plunging and pitching motions
, Article 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 2 , 2006 , Pages 962-971 ; 9781604232271 (ISBN) ; Rasi Marzabadi, F ; Seddighi, M ; Sharif University of Technology
2006
Abstract
Unsteady aerodynamic experiments were conducted on an oscillating airfoil in a subsonic wind tunnel. The model was oscillated in two types of motion, pitch and plunge, at a range of reduced frequencies, k=0.029-0.1. In addition, steady data were acquired and examined to furnish a baseline for analysis and comparison. The unsteady surface pressure is measured along the chord for both upper and lower surfaces of the model. Particular emphases were placed on the effects of different types of motion on the unsteady pressure distribution of the airfoil at pre-stall, near stall, and post stall conditions. It was found that the variations of the pressure distribution with angle of attack have...
Experimental Investigation of Pressure Distribution in the Wind Tunnel Contarection and Preventation of Probable Separation
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Contraction sections are an integral part of all wind tunnels, whether designed for basic fluid flow research or model testing. The location of the contraction, just upstream of the test section, makes it very important to achieve a high quality contraction design. The effect of a contraction on unsteady velocity variations is significant to increase the mean velocity. Furthermore, contraction has a suitable role on the turbulence reduction in a wind tunnel. The contraction itself further reduces the turbulence in terms of percentage of the wind speed. This is due to the increase of the wind speed by a factor equal to the contraction ratio. In this research, to investigation flow quality in...
Investigation of the effects of angle of attack and tail deflection angle on the controlling tail flow field
, Article Aerospace Systems ; Volume 3, Issue 4 , 19 October , 2020 , Pages 309-326 ; Shahrian, A ; Javadpoor Langroodi, P ; Ghodrat, M ; Sharif University of Technology
Springer Science and Business Media B.V
2020
Abstract
In the current study, the flow behavior due to the variation of the tail angle of attack and its deflection has been investigated on a body–tail with a controlling tail. Numerical computations were carried out at a constant velocity of 90 m/s with the tail angle of attack and deflection ranging from 0 to 30 degrees. It provides a deeper understanding of how the aerodynamics of the tail is influenced by the deflection of the tail and the variation of the angle of attack, along with body and nose vortices. The formation of structure and breakdown of vortices along with their effects on the pressure distribution over the tail and the corresponding normal force coefficients derived from the...
A parametric study on residual stresses and forging load in cold radial forging process
, Article International Journal of Advanced Manufacturing Technology ; Volume 33, Issue 1-2 , 2007 , Pages 7-17 ; 02683768 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
2007
Abstract
In this work, a comprehensive study of radial forging process is presented through 2-D axisymmetric and 3-D finite element simulations while considering internal tube profile. The tube used in this investigation has four internal helical grooves along its length. The material is modeled with the elastic-plastic behavior, and sliding-sticking friction model is utilized to model the die-workpiece and mandrel-workpiece contacts. The numerical results in the 2-D case are compared with available experimental data. Residual stresses in the forged product, stress concentration around the grooves, pressure distribution on the hammers and mandrel and maximum forging load are studied. The effects of...
Flow analysis around a pitching airfoil
, Article Collection of Technical Papers - 22nd AIAA Applied Aerodynamics Conference, Providence, RI, 16 August 2004 through 19 August 2004 ; Volume 2 , 2004 , Pages 914-924 ; 10485953 (ISSN) ; Mani, M ; Soltani, M. R ; Boroomand, M ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2004
Abstract
A series of low-speed wind tunnel tests were performed to investigate the unsteady pressure distribution over an airfoil. Dynamic pitching motion was produced by oscillating the model over a range of reduced frequencies, k=0.022 - 0.066. In addition, steady data were acquired and examined to furnish as a baseline for analysis and comparison. The model was oscillated between 0-18° angle of attack. Surface static pressure was measured from x/c=5-80% for both upper and lower surfaces. The pressure coefficients in the low angle of attack range showed little overshoot when compared with the static values, while for the large angle of attack cases the differences were significant. For a constant...
Control of pressure gradient in the contraction of a wind tunnel
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 261-266 ; 2010376X (ISSN) ; Mirzaei, M ; Ghorbanian, K ; Sharif University of Technology
2009
Abstract
Subsonic wind tunnel experiments were conducted to study the effect of tripped boundary layer on the pressure distribution in the contraction region of the tunnel. Measurements were performed by installing trip strip at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence and pressure distribution. The reduction in the free stream turbulence and reduction of the wall static pressure distribution deferred signified with the location of the trip strip
Thermal Performance Evaluation of Domed Roofs
,
Ph.D. Dissertation
Sharif University of Technology
;
Bahadori Nezhad, Mehdi
(Supervisor)
Abstract
Domed roofs were commonly used in buildings with large areas. These roofs played an important role in the Iranian architecture and had a great effect on the buildings cooling loads. Solar energy absorption causes the roof temperature to increase in comparison with its ambient atmosphere. Wind flow removes some of the heat from the roof, and the rest goes thorough the roof and enters the building.The eometrical configuration of these domed roofs causes the wind velocity to increase over them, resulting in an increase in the convection heat transfer coefficient. Also, the heat transfer of the roof is accentuated by the fact that the area of a domed configuration is considerably greater than a...
Experimental Investigation of Pressure Distribution on the Surface of a Supercritical Airfoil in Transonic Regime
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Transonic flow study is important due to its vast applications. Supercritical airfoils are designed for transonic flow to postpone drag divergence and reduce the strength of shock. This type of airfoils are chiefly used in modern commercial airplanes because of their low drag in transonic regime and, as a result, reduction in their fuel consumption. Using supercritical airfoils needs accurate investigation of flow field due to several influential factors such as specific geometry, nonlinear nature of flow phenomena, and compressibility effects. However, the availability of experimental and numerical data for supercritical airfoils is less than that of the conventional ones. Thus,...
Experimental Investigation of wake flow of a Supercritical Airfoil in Transonic Regime
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Transonic flow study is important due to its vast applications. Supercritical airfoils are designed for transonic flow to postpone drag divergence and reduce the strength of shock. This type of airfoils are chiefly used in modern commercial airplanes because of their low drag in transonic regime and, as a result, reduction in their fuel consumption. Using supercritical airfoils needs accurate investigation of flow field due to several influential factors such as specific geometry, nonlinear nature of flow phenomena, and compressibility effects. However, the availability of experimental and numerical data for supercritical airfoils is less than that of the conventional ones. Thus,...
Experimental Investigation of Spin on Rotating Body at Supersonic and Transonic Flow
, Ph.D. Dissertation Sharif University of Technology ; Soltani, Mohamd Reaza (Supervisor) ; Farahani, Mohamad (Co-Supervisor)
Abstract
One of the methods for the stability of the projectile is its rotation. The rotational velocity of the body surface induces velocity to the adjacent flow, thus changing the shape of the boundary layer, and due to the change in the thickness distribution of the boundary layer, the effective aerodynamic shape of the body also changes, which causes a force perpendicular to the angle of attack.This effect is called the Magnus effect. Since the force created by the rotation is an undamped force, the possibility of dynamic instability is very likely. There is no comprehensive analytical method that can accurately calculate its value for a wide range of projectiles.Due to the effect of Magnus...
Experimental and numerical investigation of cavitation regimes and its effects on drag characteristics of wedge shaped bodies
, Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 2 FORA, Issue PART A , August , 2007 , Pages 377-384 ; 0791842886 (ISBN); 9780791842881 (ISBN) ; Razmi, A. M ; Mansouri, H ; Amini, M. A ; Sharif University of Technology
2007
Abstract
Cavitation phenomenon is defined as the process of rupturing any liquid by a decrease in pressure at nearly constant temperature. The cavities driven by the flow in a region of high pressure will implode and generate high pressure pulses leading eventually to erosion and vibration. But in supercavitation the bubbles produced by cavitation combine to form a large, stable bubble region around the supercavitating object. This phenomenon decreases the drag on the supercavitating body. Experimental testsware performed at 2-D unsteady flow for two wedge shaped bodies made before in laboratory and cavitation inception and its development were captured by a high speed camera. Then this cavitation...
Torsional buckling of carbon nanopeapods
, Article Carbon ; Volume 45, Issue 5 , 2007 , Pages 952-957 ; 00086223 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2007
Abstract
Torsional buckling of carbon nanopeapods (carbon nanotubes filled with fullerenes) is studied using a continuum-based multi-layered shell model. The model takes into account non-bonded van der Waals interactions between nested fullerenes and the innermost layer of host nanotube. For nanopeapods with linearly arranged nested fullerenes, equivalent pressure distribution is proposed to model these interactions. Deriving explicit equations governing the torsional stability, it is concluded that the critical torsional load of a carbon nanopeapod is less than that of a carbon nanotube under otherwise identical geometric and mechanical conditions. Performing numerical calculations, it is also shown...
Effects of reduced frequency on the performance of a wind turbine blade in the low and high turbulent unsteady flow
, Article 25th AIAA Applied Aerodynamics Conference, 2007, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 2 , 2007 , Pages 877-882 ; 10485953 (ISSN); 1563478986 (ISBN); 9781563478987 (ISBN) ; Amiralaei, M. R ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2007
Abstract
An extensive experimental study is conducted to investigate the effects of reduced frequency on a harmonically pitching wing where its cross section is used in a 660 kW wind turbine under construction in Iran. The corresponding lift coefficient and real time pressure signatures at three sections of the model at various reduced frequencies are examined. The test covers a wide range of angles of attack at prestall, stall, and deep stall regions. Pressure distributions at tip, middle, and root sections of the wing were recorded and from these distributions the lift coefficients are computed. The results show great role of the reduced frequency in altering the maximum lift coefficients, lift...
Inverse design of supersonic diffuser with flexible walls using a Genetic Algorithm
, Article Journal of Fluids and Structures ; Volume 22, Issue 4 , 2006 , Pages 529-540 ; 08899746 (ISSN) ; Ziaei-Rad, M ; Sharif University of Technology
2006
Abstract
An efficient algorithm for the design optimization of the compressible fluid flow problem through a flexible structure is presented. The methodology has three essential parts: first the behavior of compressible flow in a supersonic diffuser was studied numerically in quasi-one-dimensional form using a flux splitting method. Second, a fully coupled sequential iterative procedure was used to solve the steady state aeroelastic problem of a flexible wall diffuser. Finally, a robust Genetic Algorithm was implemented and used to calculate the optimum shape of the flexible wall diffuser for a prescribed pressure distribution. © 2006 Elsevier Ltd. All rights reserved
Separation control of aero boundary layer in supercavitating bodies and its effect on pressure drag reduction
, Article 2005 ASME Fluids Engineering Division Summer Meeting, FEDSM2005, Houston, TX, 19 June 2005 through 23 June 2005 ; Volume 2005 , 2005 , Pages 19-27 ; 0791837602 (ISBN); 9780791837603 (ISBN) ; Yazdani, M ; Sharif University of Technology
2005
Abstract
Supercavitation is known as the way of viscous drag reduction for the projectiles, moving in the liquid phase. In recent works, there is distinct investigation between cavitation flow and momentum transfer far away from the cavity surface. In fact such methodologies consider cavitation flow statically, rather than taking dynamic effects of overall flow into account. However, it seems that there is strong connection between overall flow and what takes place in the sheet cavity where a constant pressure distribution is assumed. Thereby, in order to configure the system conditions which may be cause of cavity perturbation and so system oscillation, we need to use proper methodologies in which...