Active Control of Shocks and Sonic Boom Ground Signal

The manipulation of a flow field to obtain a desired change is a much heightened subject. Active flow control has been the subject of the major research areas in fluid mechanics for the past two decades. It offers new solutions for mitigation of shock strength, sonic boom alleviation, drag minimization, reducing blade-vortex interaction noise in helicopters, stall control and the performance maximization of existing designs to meet the increasing requirements of the aircraft industries. Despite the wide variety of the potential applications of active flow control, the majority of studies have been performed at subsonic speeds. The active flow control cases were investigated in transonic speed in this study. Although the active flow control provides significant improvements, the sensibility of aerodynamic performance to design parameters makes it a nontrivial and expensive problem, so the designer has to optimize a number of different parameters. For the purpose of gaining understanding of the active flow control concepts, an automated optimization cycle process was generated. Also, the optimization cycle reduces cost and turnaround time. The mass flow coefficient, location, width and angle were chosen as design parameters to maximize the aerodynamic performance of an aircraft. As the main contribution of this study, a detailed parametric study and optimization process were presented. The second step is to appraise the practicability of weakening the shock wave and thereby reducing the wave drag in transonic flight regime using flow control devices such as two dimensional contour bump, individual jet actuator, and also the hybrid control which includes both control devices together, thereby gaining the desired improvements in aerodynamic performance of the air-vehicle. After this study, to improve the aerodynamic performance, the flow control and shape parameters are optimized separately, combined, and in a serial combination. The remarkable part of all these studies is both gradient and non-gradient optimization techniques were used to find the global optimum point. The second part of this study includes investigation of the possibility of weakening the shock strength and the reduction of far field signature by using off-body energy addition. The main obstacle for flying supersonically over land is the detrimental effects of sonic boom on general public and structures. The shock waves generated from various parts of an aircraft flying at supersonic speed, coalesce to form a classic sonic boom acoustic signature, \u27N\u27 wave associated with the sonic boom on the ground. High pressure was imposed on certain parts of the computational domain to simulate the pulsed laser effects, and then the propagation and interaction of this pulsed shock with shock waves generated from the diamond shaped model were investigated. Optimization of the location and the power of the pulsed shock were achieved using the non-gradient optimization technique. The main contribution of this study is the optimization of the parameters of pulsed shock

Heat Transfer Enhancement in a Straight Channel via a Rotationally Oscillating Adiabatic Cylinder

Heat convection from the uniformly heated walls of a straight channel in presence of a rotationally oscillating cylinder (ROC) is simulated at Re = 100. Heat transfer enhancement due to vortex shedding from the ROC is investigated. Systematic studies are performed to explore the rotation angle and frequency influences on heat transfer by varying the latter in range of the lock-in regime and the former from 0 to 2 π/3. All simulation results are based on the numerical solutions of two-dimensional, unsteady, incompressible Navier-Stokes and energy equations using an h/p type finite element algorithm. Considering time periodicity of the resulting flow and temperature fields, time averaged wall Nusselt number is reported to quantify the heat transfer enhancement for Pr = 0.1, 1.0, 5.0 and 10.0 fluids. Performance analyses of the ROC device based on its total power consumption and heat transfer enhancement are also presented

Heat transfer enhancement in a straight channel via a rotationally oscillating adiabatic cylinder

Heat convection from the uniformly heated walls of a straight channel in presence of a rotationally oscillating cylinder (ROC) is simulated at Re = 100. Heat transfer enhancement due to vortex shedding from the ROC is investigated. Systematic studies are performed to explore the rotation angle and frequency influences on heat transfer by varying the latter in range of the lock-in regime and the former from 0 to 2π/3. All simulation results are based on the numerical solutions of two-dimensional, unsteady, incompressible Navier–Stokes and energy equations using an h/p type finite element algorithm. Considering time periodicity of the resulting flow and temperature fields, time averaged wall Nusselt number is reported to quantify the heat transfer enhancement for Pr = 0.1, 1.0, 5.0 and 10.0 fluids. Performance analyses of the ROC device based on its total power consumption and heat transfer enhancement are also presented