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Experimental Investigation of Reduced Frequency Effects on the Wake of an Airfoil in Plunging Motion
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Wake aerodynamic of plunging airfoils have received less attention than the other unsteady phenomena. An experimental investigation was carried out to study the unsteady characteristics of flow field behind a model of a plunging airfoil in various conditions. The model has 0.25cm chord and is the 16m section of a 660kW wind turbine blade. All tests were conducted in the subsonic closed circuit wind tunnel in Iran. Invariable parameters were plunging amplitude, mean angle of attack and plunging frequency. The Wakes of plunging airfoil can be characterized as drag-producing, neutral, or thrust-producing .Our preliminary results show that the structure of vortex in the wake for the plunging...
Experimental Study of the Wake behind an MAV using Hot-Wire Anemometer
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor) ; Khoshnevis, Amir (Co-Advisor)
Abstract
In present thesis, experimental study of flow around a two-wing MAV using hot-wire anemometer will be performed which is divided to wake and boundary layer study. This leads to suitable understanding of various parameters affecting its wake and boundary layer. First, effects of upper wing, which has horizontal stabilizer's role, on the main wing's wake will be studied in which effects of angle of attack and distance between the two wings at its cruise velocity will be investigated. Then, effects of angle of attack, velocity and distance between wings on boundary layer of the MAV will be analyzed. Also, experiments are performed at three velocities as 10, 15 and 20 m/s, and three angles of...
Experimental Investigation of Acoustic Excitation on NACA 0012 Airfoil Wake Development
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor) ; Masdari, Mehran (Supervisor)
Abstract
Acoustic excitation frequency effect on NACA 0012 airfoil boundary layer and on its wake development was investigated experimentally in two wind tunnels. Airfoils chord lentgh were 100 and 152 mm. Flow Reynolds numbers was 60000 and 160000 in the first wind tunnel and 100000 and 250000 in the second one. Excitation frequency range was chosen between 300 and 2400 Hz. Airfoil flow and sound characteristics was measured using a 1-D hot-wire sensor and two microphones, one mounted on the wind tunnel wall and the other flash mounted on the model at 10 percent of chord length, respectively. Airfoil angle of attack was set at zero degree in the first wind tunnel and at three angles of zero, five...
Design and Fabrication of an Optimized Wake Equalizing Duct in Order to Improve Propulsion System Operation
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad S (Supervisor) ; Rad, Manouchehr ($item.subfieldsMap.e)
Abstract
Special geometrical sections, known as “duct”, which can be installed on merchant vessels stern in order to improve propulsion system and propeller performance, today have evolved considerably. The force which produces by the propeller depends on efficiency of propulsion system. In the way of improving the efficiency of propulsion systems, by using these special geometrical sections, to much research have been done from the mid-twentieth century. The Wake Equalizing Ducts (WEDs) in addition to conduct the more uniform fluid flow to the propeller disk (which causes to improve the propeller operation), affect on flow separation in ship stern zone and will decrease the separated flow zone....
The Effect of Performance of Ships Propeller on its Maneuvering in Shallow and Deep Water
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
In this thesis ship propeller performance in maneuvering conditions have been investigated which means an oblique flow condition for working propeller. Then results of these investigations have been put to use to simulate maneuvering using MMG equations. These calculations have been done to investigate nominal wake variations in different drift angles and depth conditions. In this project displacement vessel KVLCC2 and propeller POTSDAM VP1304 have been studied due to the abundance of experimental data. Calculations in this study have been carried in three steps: 1, calculation of nominal wake of the vessel in different drift angles and depths via CFD. 2, Using the results of previous...
Experimental Investigation of Geometric Parameters Effect on Energy Harvesting from FIV in Bluff Bodies
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor)
Abstract
The purpose of this research is to design and construct a test stand for the study of the kinematic and flow pattern of bluff bodies oscillating motion due to the induction of wake vortices. An experimental investigation was conducted to explore the effect of bluff bodies cross section to optimize the amount of electrical energy withdraw by electromagnetic harvester. The tests are carried out on cylinders with square section and rectangular sections with a length to width ratio of 1/2 and 2/1 and height of 50 cm, at speeds of 5 to 35 m/s in eiffel type wind tunnel. The effect of cylinder cross-section on the amount of energy harvested showed that the amplitude of oscillation in square-shaped...