The subgrid scale estimation model, which has been previously studied for large eddy simulations of turbulent channel flow, was extended to convective flows. The estimation procedure involves expanding the temperature and velocities to scales smaller than the grid size using the properties of the top-hat filter, Fourier expansions, and nonlinear interactions among the resolved scales. An expanded field, which contains subgrid scales two times smaller than the grid size, is used to calculate the subgrid scale stresses directly from the definition. In an a priori analysis, the exact quantities computed from the direct numerical simulation data are compared with results from the estimation model and the Smagorinsky model applied without wall functions. The subgrid scale stresses from the estimation model agree well with the exact quantities, but the Smagorinsky model results do not. The same conclusions are reached after both models are implemented in actual large eddy simulations. For both the velocities and temperature, the estimation model produces a more realistic distribution of subgrid scale stresses across the convective layer, does not require wall functions for correct behavior near the boundary, and does not contain any arbitrary constants, in contrast to the Smagorinsky model. Additionally, numerically stable backscatter is inherent in the estimation model.

Abstract. Advances in computers and in computational techniques now allow the calculation of electromagnetic (EM) wave propagation through simulated refractive index turbulence in the lower atmosphere. Such applications call for instantaneous turbulence fields, not turbulence statistics, the traditional focus of the turbulence community. We clarify their important differences and review what is known about key statistics of refractive index turbulence. We discuss the calculation of EM propagation with a parabolic equation model that uses composite refractive index fields, the larger scales being calculated with a dynamical mesoscale model and the smaller scales being calculated through large-eddy simulation. The locally, instantaneously sharp top of the atmospheric boundary layer can have a profound effect on forward scatter of EM waves. This top appears to be even sharper than is revealed by conventional measurements, particularly in the convective boundary layer. IntroductionThree parallel developments over the past few decades now allow a new approach to the calculation of electromagnetic (EM) wave propagation in environmental flows, one that does not require inventing your own refractive index fields. They are (1) is similar to the most advanced operational forecast 643

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Students often experience difficulties in developing an adequate understanding of how to solve engineering graphics problems using traditional teaching methods. Application of an explicit problem-solving technique to graphics problems can help students to understand the solution strategy. This method reinforces the details of the process, enabling students to apply the same techniques to more complicated problems. The problem-solving heuristic involves devising and evaluating a solution plan before it is implemented. Without such a solution plan, students are more likely to rush into an ill-conceived solution design without any meaningful preliminary thought. By considering a detailed solution plan for even simple problems, students should gain an in-depth understanding of the class material. This paper presents and discusses the implementation of a problem-solving approach to engineering graphics, which can be applied to both drafting and computer-aided design (CAD) exercises. Preliminary results indicate that students' skills at solving engineering graphics problems improve as a result of implementing a structured approach towards developing a solution plan.

Many students enter undergraduate engineering programs lacking basic problem solving skills. We have adapted the problem solving heuristics originally used in a computer science environment to an introductory engineering class to help freshman engineering students develop these skills. The introductory Engineering Design and Graphics course at Penn State -Berks Campus exposes students to conventional drafting techniques, computer graphics and engineering design.