Supersonic separated turbulent boundary - layer over a wavy wall

A prediction method is developed for calculating distributions of surface heating rates, pressure and skin friction over a wavy wall in a two-dimensional supersonic flow. Of particular interest is the flow of thick turbulent boundary layers. The surface geometry and the flow conditions considered are such that there exists a strong interaction between the viscous and inviscid flow. First, using the interacting turbulent boundary layer equations, the problem is formulated in physical coordinates and then a reformulation of the governing equations in terms of Levy-Lees variables is given. Next, a numerical scheme for solving interacting boundary layer equations is adapted. A number of modifications which led to the improvement of the numerical algorithm are discussed. Finally, results are presented for flow over a train of up to six waves at various flow conditions

Numerical study of supersonic turbulent flow over small protuberances

Supersonic turbulent boundary layers over two-dimensional protuberances are investigated, using the numerical finite difference alternating direction implicit (ADI) method. The turbulence is modeled mathematically. The turbulence is represented here by the eddy viscosity approach. The turbulent boundary layer structure as well as an interest in thick boundary layers and much larger protuberance heights than in the laminar case lead to new difficulties. The problems encountered and the means to remove them are discussed

Modeling and Testing of a Solar Energy Intensifier System

Widespread adoption of solar energy as an alternate energy source is dependent upon careful engineering design. Mathematical models are among the best engineering design tools, because design alternatives can be evaluated without extensive testing and solar systems can be sized and oriented to suit each particular application. Research has been conducted at South Dakota State University since 1976 to develop, through design and testing, a portable, low cost, concentrating solar system for agricultural applications. Solar energy can readily be substituted for other energy sources in agriculture because many such applications do not require a continuous, uninterrupted energy supply and may efficiently utilize the low-quality heat produced by simple, inexpensive solar systems G Farm operators traditionally possess the technical and mechanical skills and equipment to install and maintain solar systems. Usually sites adequate in area and orientation are available near agricultural applications. Concentrators, which intercept solar radiation and concentrate it into a smaller area on a receiver, can be used to increase the solar radiation striking a flat plate collector. This results in higher temperature rises and increased thermal efficiency because there is less collector surface area per Unit of effective intercepted sun area. Solar concentrators are particularly adaptable to situations where, as in the SDSU reflector, the collector or absorber cost is higher than the reflector cost. By designing the flat plate collector large enough relative to the reflector surface, the need for expensive tracking equipment can be eliminated, while the cost advantage of minimizing collector area and maximizing reflector area can be retained. Precise solar system and component evaluation and redesign of solar systems are vital and are needed to further improve the potential of solar energy as an alternate energy resource. A mathematical prediction model based on fundamental laws of heat transfer and thermodynamics. can be used to evaluate design considerations and sizing of collector components for specific applications. Although the concept of solar collection is relatively simple, no existing model is available which can predict the performance of the solar energy intensifier system. Therefore, research was initiated with the following objectives: 1. Redesign the multipurpose solar energy intensifier system. 2. Test the solar energy intensifier collector system for grain drying under actual operating conditions. 3. Evaluate the performance and economic feasibility of the solar energy intensifier system. 4. Develop a generalized computer program for predicting the energy collected from the solar energy intensifier collector system. 5. Validate the performance of this computer simulation using measured data gathered from the corn drying studies

Testing QoE in Different 3D HDTV Technologies

The three dimensional (3D) display technology has started flooding the consumer television market. There is a number of different systems available with different marketing strategies and different advertised advantages. The main goal of the experiment described in this paper is to compare the systems in terms of achievable Quality of Experience (QoE) in different situations. The display systems considered are the liquid crystal display using polarized light and passive lightweight glasses for the separation of the left- and right-eye images, a plasma display with time multiplexed images and active shutter glasses and a projection system with time multiplexed images and active shutter glasses. As no standardized test methodology has been defined for testing of stereoscopic systems, we develop our own approach to testing different aspects of QoE on different systems without reference using semantic differential scales. We present an analysis of scores with respect to different phenomena under study and define which of the tested aspects can really express a difference in the performance of the considered display technologies