Ece Ayli

Investigation of the Effects of Length to Depth Ratio on Open Supersonic Cavities Using CFD and Proper Orthogonal Decomposition

Simulations of supersonic turbulent flow over an open rectangular cavity are performed to observe the effects of length to depth ratio (L/D) of the cavity on the flow structure. Two-dimensional compressible time-dependent Reynolds-averaged Navier-Stokes equations with k-ω turbulence model are solved. A reduced order modeling approach, Proper Orthogonal Decomposition (POD) method, is used to further analyze the flow. Results are obtained for cavities with several L/D ratios at a Mach number of 1.5. Mostly, sound pressure levels (SPL) are used for comparison. After a reduced order modeling approach, the number of modes necessary to represent the systems is observed for each case. The necessary minimum number of modes to define the system increases as the flow becomes more complex with the increase in the L/D ratio. This study provides a basis for the control of flow over supersonic open cavities by providing a reduced order model for flow control, and it also gives an insight to cavity flow physics by comparing several simulation results with different length to depth ratios.

A Review of Control Methods for Cavity Flows and Feasibility of Laser Energy Deposition as an Actuator

Studies related to supersonic cavity flow are very important for aeronautics applications. Understanding the physics of cavity flows is crucial for both fluid mechanics and engineering applications. Supersonic cavity flow and control techniques for this type of flow have been studied for many decades. A review of literature on numerical and experimental cavity flow is provided and the flow mechanism inside the cavity is explained using example studies from literature. It is necessary to understand the complex nature of the flow before developing control methods for the cavity flow oscillations. The literature on the development of methods to control the flow oscillations in cavities which are harmful for aircraft is also reviewed. Feasibility of laser energy deposition as an actuator for flow control is investigated demonstrating examples from literature.

4.2 Heat Exchangers

This chapter aims to provide information on classification, types, design methodology, and selection of heat exchangers (HEX), focusing on plate HEX. The details of a software developed based on correlations obtained using experimental data are presented. Plate HEX literature is explained in detail and the correlations in literature are used in the developed HEX selection software for comparison with the new correlations. The analysis shows that specific correlations based on experimental data are necessary to be used with plates utilized in HEX selection, since the plate geometries are unique and need specific correlations to reflect their properties correctly.

DESIGN AND CONSTRUCTION OF AN EXPERIMENTAL TEST RIG FOR HYDRAULIC TURBINES

ABSTRACT Dynamics) is widely usedEvery turbine for every hydroelectric power plant is unique; therefore its model has to be designed using state of the art design techniques and tested before the actual prototype which is costly, is manufactured. In this study, the details of the design and construction of a hydroturbine test facility at TOBB University of Economics and Technology are explained. The facility will be used to test hydroturbine models up 2MWs of power simulating turbine prototypes. The performance and cavitation tests of the turbines will be performed utilizing this facility according to International Electrical Commission (IEC) standards. Thetest facility is 19 meters long with a base area of around 600 meter squares. The hydraulic analysis of the designed set-up is performed using a system where valves, pipes, structures, water records and connections form an intelligent system, same with the experimental facility. According to the results, system performance is checked, alternative designs are evaluated and operating strategies are defined by minimizing the losses.