Compact International Experiences: Expanding Student International Awareness Through Short-Term Study Abroad Courses With Substantial Engineering Technical Content

Compact International Experience (CIE) courses are investigated as a suitable tool to raise student international awareness while retaining substantial engineering technical content. These courses were developed due to a strong student desire for engineering international studies as well as a drive by the home institution for internationalization of the curriculum. The efficacy of such courses is described through experiences gained from delivering two distinct three-semester-unit engineering elective courses in a three-week time frame in France and Australia. While each of these courses, Topics in Fluid Mechanics and Advanced Electronic Circuit Design, focused on its technical content, the desire for student understanding of the cultural environment and the impact of engineering solutions from a global and societal viewpoint were strong driving factors for each. Assessment validates the hypothesis that CIE courses can successfully deliver substantial engineering technical content while providing an enriching international experience to students

Energy- and flux-budget (EFB) turbulence closure model for the stably stratified flows. Part I: Steady-state, homogeneous regimes

We propose a new turbulence closure model based on the budget equations for the key second moments: turbulent kinetic and potential energies: TKE and TPE (comprising the turbulent total energy: TTE = TKE + TPE) and vertical turbulent fluxes of momentum and buoyancy (proportional to potential temperature). Besides the concept of TTE, we take into account the non-gradient correction to the traditional buoyancy flux formulation. The proposed model grants the existence of turbulence at any gradient Richardson number, Ri. Instead of its critical value separating - as usually assumed - the turbulent and the laminar regimes, it reveals a transition interval, 0.1< Ri <1, which separates two regimes of essentially different nature but both turbulent: strong turbulence at Ri<<1; and weak turbulence, capable of transporting momentum but much less efficient in transporting heat, at Ri>1. Predictions from this model are consistent with available data from atmospheric and lab experiments, direct numerical simulation (DNS) and large-eddy simulation (LES).Comment: 40 pages, 6 figures, Boundary-layer Meteorology, resubmitted, revised versio

Energy- and flux-budget turbulence closure model for stably stratified flows. Part II: the role of internal gravity waves

We advance our prior energy- and flux-budget turbulence closure model (Zilitinkevich et al., 2007, 2008) for the stably stratified atmospheric flows and extend it accounting for additional vertical flux of momentum and additional productions of turbulent kinetic energy, turbulent potential energy (TPE) and turbulent flux of potential temperature due to large-scale internal gravity waves (IGW). Main effects of IGW are following: the maximal value of the flux Richardson number (universal constant 0.2-0.25 in the no-IGW regime) becomes strongly variable. In the vertically homogeneous stratification, it increases with increasing wave energy and can even exceed 1. In the heterogeneous stratification, when IGW propagate towards stronger stratification, the maximal flux Richardson number decreases with increasing wave energy, reaches zero and then becomes negative. In other words, the vertical flux of potential temperature becomes counter-gradient. IGW also reduce anisotropy of turbulence and increase the share of TPE in the turbulent total energy. Depending on the direction (downward or upward), IGW either strengthen or weaken the total vertical flux of momentum. Predictions from the proposed model are consistent with available data from atmospheric and laboratory experiments, direct numerical simulations and large-eddy simulations.Comment: 37 pages, 5 figures, revised versio

Global Intermittency and Collapsing Turbulence in the Stratified Planetary Boundary Layer

Direct numerical simulation of the turbulent Ekman layer over a smooth wall is used to investigate bulk properties of a planetary boundary layer under stable stratification. Our simplified configuration depends on two non-dimensional parameters: a Richardson number characterizing the stratification and a Reynolds number characterizing the turbulence scale separation. This simplified configuration is sufficient to reproduce global intermittency, a turbulence collapse, and the decoupling of the surface from the outer region of the boundary layer. Global intermittency appears even in the absence of local perturbations at the surface; the only requirement is that large-scale structures several times wider than the boundary-layer height have enough space to develop. Analysis of the mean velocity, turbulence kinetic energy, and external intermittency is used to investigate the large-scale structures and corresponding differences between stably stratified Ekman flow and channel flow. Both configurations show a similar transition to the turbulence collapse, overshoot of turbulence kinetic energy, and spectral properties. Differences in the outer region resulting from the rotation of the system lead, however, to the generation of enstrophy in the non-turbulent patches of the Ekman flow. The coefficient of the stability correction function from Monin-Obukhov similarity theory is estimated as (Formula presented.) in agreement with atmospheric observations, theoretical considerations, and results from stably stratified channel flows. Our results demonstrate the applicability of this set-up to atmospheric problems despite the intermediate Reynolds number achieved in our simulations. © 2014 The Author(s)

Multiscale statistics of Lagrangian and Eulerian acceleration in turbulent stratified shear flows

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On Acceleration Statistics in Turbulent Stratified Shear Flows

International audienceno abstrac

Student Perceptions and Learning of the Engineering Design Process: An Assessment at the Freshman Level

An investigation into the impact of a single laboratory session team-based design experience early in the freshman year on student learning of the engineering design process is described. Assessment of the experience focused not only on gains in student perceptions of knowledge of and confidence in applying the engineering design process, but also on actual gains in knowledge, as judged by the investigators based on student written responses. The assessment data showed a significant overall increase in both student knowledge and confidence scores as well as significant individual incremental increases. The gains proved to be in particular significant when compared to those for the entire semester-long course. Design-step logs were used to monitor how students navigated through the engineering design process. While the students were exposed to a simplified linear design process in the lecture component of the class, the design logs indicated a more complex reality. Paths for instructional improvement on the topic of the engineering design process should include a discussion of the potentially complex nature of engineering design and a precise definition of terminology

Scale-dependent statistics of Lagrangian and Eulerian acceleration in rotating and sheared homogeneous turbulence

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