Sharif Digital Repository

Drag reduction is one of the most important topics in aerodynamics. Several techniques have been represented to reduce this force, such as surface roughness reduction, blowing, suction, cooling the fluid, etc. Blowing and creating a film of a secondary lower viscosity fluid is the technique used here. In our computations, we used large eddy simulation approach considering viscosity ratio variations effects. Investigations were performed for multiple squared cross sectional jets inclined normally into a turbulent cross flow. Each jet generates a pair of counter rotating vortex pair (CRVP) at its downstream while entering the cross flow. Two horseshoe vortices and a couple of wake vortices... 

Shock control bump (SCB) and suction and blowing are flow control methods used to control the shock wave/boundary layer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. A SCB uses a small local surface deformation to reduce the shock-wave strength, while suction decreases the boundary-layer thickness and blowing delays the flow separation. Here, a single-point, a multi-point, and a robust optimization method are used to find the optimum design of SCB and suction and blowing. The flow control methods are used separately or together on two transonic airfoils i.e.; RAE-2822 and NACA-64A010 for a wide range of off-design transonic Mach numbers. The RANS flow... 

Turbine engines performance is notably dependent on environmental conditions, i.e. pressure and temperature and also on flight speed. Every engine has a specific flight ceiling, i.e. altitude above which engine shuts down. Engine shut down during altitude increase, is because of combustor performance loss and its efficiency and stability decrease. Combustor stability limit can be extended by performing modifications such as replacing fuel injectors and/or improving fuel characteristics, and the combustor can be used for higher altitude whitout any required change in design. In this thesis, influence of combustor various parameters like air flow rate, fuel equivalence ratio, inlet pressure...