Interacting turbulent boundary layer over a wavy wall

The two dimensional supersonic flow of a thick turbulent boundary layer over a train of relatively small wave-like protuberances is considered. The flow conditions and the geometry are such that there exists a strong interaction between the viscous and inviscid flow. The problem cannot be solved without inclusion of interaction effects due to the occurrence of the separation singularity in classical boundary layer methods. The interacting boundary layer equations are solved numerically using a time-like relaxation method with turbulence effects represented by the inclusion of the eddy viscosity model. Results are presented for flow over a train of up to six waves for Mach numbers of 10 and 32 million/meter, and wall temperature rations (T sub w/T sub 0) of 0.4 and 0.8. Limited comparisons with independent experimental and analytical results are also given. Detailed results on the influence of small protuberances on surface heating by boundary layers are presented

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

The separated turbulent boundary layer over a wavy wall

A study and application of the fourth order spline collocation procedure, numerical solution of boundary layer like differential equations, is presented. A simple inversion algorithm for the simultaneous solution of the resulting difference equations is given. Particular attention is focused on the boundary condition representation for the spline second derivative approximations. Solutions using the spline procedure, as well as the three point finite difference method, are presented for several model problems in order to assess and improve the spline numerical scheme. Application of the resulting algorithm to the incompressible laminar self similar boundary layer equations is presented

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