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Influence Of Initial Turbulence Intensity On The Heat And Moisture Transfer Through A Recirculated Air Curtain, Nguyen Quang Van

Doctoral Dissertations

"An air curtain is a directed jet of air separating a controlled space from an environment of different temperature and humidity. This investigation describes the development and verification of an eddy viscosity model which accounts for the influence of the initial turbulence intensity on the transfer of heat and moisture across a recirculated air curtain. The control of the turbulence intensity at the nozzle exit of an air curtain permits control of heat and moisture transfer and therefore the energy required to operate the air curtain.

Both theoretical and experimental studies were made of the recirculated air curtain. An explicit …

Bit Penetration Into Rock - A Finite Element Study, Jaw-Kuang Wang

Doctoral Dissertations

"A finite element approach has been developed to simulate bit penetration from bit-rock interaction to chip formation. A mathematical rock failure model, based on a review of the existing literature on rock tests, has been proposed to represent post-failure rock behavior and applied in the penetration simulations. The finite element program has been developed for two dimensional plane strain problems with non-linear material properties, geometrical nonlinearities and fracture. An anisotropic element as well as variable stiffness and stress release methods have been used. An iteration method, using an incremental approach, has been applied for continuous penetration and modifications of material …

Development Of Helicopter Flight Path Models Utilizing Modern Control Techniques, Alfred Fermelia

Doctoral Dissertations

"The nonlinear set of equations which represents helicopter motion are linearized about a prescribed nominal state. Once the linearized system is obtained it is validated by comparing the output of the nonlinear system to that of its linearized counterpart. Having obtained a linear model, linear system theory may then be applied in order to investigate the stability and control characteristics of the aircraft.

General techniques for simulating helicopter pilot response for inclusion in a flight path simulation program have been devised. To provide the desired flight goal, a nominal flight trajectory is obtained from an existing nonlinear model. With this …