Writing to learn engineering: Identifying effective fechniques for the integration of written communication into engineering classes and curricula (NSF RIGEE project)

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The inclusion of writing-based exercises in technical courses has multiple learning benefits to students. Writing exercises not only serve to improve students’ written communication skills (i.e., “learn to write”), but can also be leveraged to develop critical thinking skills and promote deeper understanding of technical concepts (i.e., “write to learn”). Nevertheless, while writing-intensive assignments are relatively common in upper-level technical courses, especially in the form of laboratory and project reports, writing is often absent in the larger, required core courses that are taken by large numbers of engineering students. This is a missed opportunity to both enhance student learning of technical content as well as missed chance for students to have more writing practice. This NSF RIGEE project aims to investigate, support, and promote the inclusion of writing in technical courses, particularly introductory and core courses. Analysis of an engineering instructor survey carried out as part of the project revealed concerns about assessment and feedback on students’ written work. Additionally, writing instructors were interested in the creation of guides designed to aid instructors in the creation and tailoring of writing prompts for use in their existing technical courses. This paper introduces preliminary resources we have created in response to these stated needs, in order to help instructors develop, implement, and assess writing assignments in their courses. Current resources include a decision tree to help instructors create writing assignments within their classrooms and assessment rubrics that can easily be adapted to specific writing assignment needs. Resources will continue to be developed during the remainder of the project, culminating in a writing website geared towards instructors.

Adventures in paragraph writing: The development and refinement of scalable and effective writing exercises for large-enrollment engineering courses

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Adventures in paragraph writing: the development and refinement of scalable and effective writing exercises for large enrollment engineering coursesThe ability to communicate effectively is a highly desirable attribute for today’s graduatingengineers. Additionally, the inclusion of communication components in technical courses hasbeen shown to enhance learning of technical content and can be leveraged to satisfy non-technical learning outcomes. However, the incorporation of such components in undergraduateengineering curricula remains challenging due to resource limitations, credit hour crunches, andother issues. This paper presents the design considerations and preliminary results from ourongoing work to create an effective, transferrable, low-overhead approach to paragraph writingexercises suitable for inclusion in any large engineering course. Key considerations in thedevelopment of these exercises include: identification of the motivations and learning outcomesfor each exercise; development and tailoring of writing prompts (questions) appropriate for theseoutcomes; and the development and implementation of an assessment and feedback strategy,including resource-efficient grading rubrics and techniques.Results are reported from the application of the paragraph writing exercise in a large civilengineering undergraduate fluid mechanics course (120 students; approximately 15assignments). A primary focus of this first application centered on two key components thatmust be refined in order for the exercise to be effective and transferrable: (1) the selection ofwriting prompts, and (2) assessment and feedback. Analysis of student paragraphs highlights theimportance of the writing prompts in the success of the exercise, indicating that specific wordchoice, question focus, and supplemental instruction greatly affected the level of writing studentssubmitted. Some writing prompts were selected to address and enhance technical content in thecourse, while other writing prompts were developed to broaden student awareness of engineeringin societal, environmental, and global contexts. In addition to developing productive writingprompts, the assessment and feedback strategies were evaluated using student surveys andfeedback. While minimal marking and holistic rubric assessment methods proved effective froma grading resource standpoint, students were frustrated by the lack of feedback associated withthese techniques and uncomfortable with the holistic grading rubric. Data from student surveyspoint to the importance of giving meaningful feedback to students, and providing them withopportunities to revise their written submissions. Student surveys also highlighted an unforeseenobstacle to the exercise: student resistance to writing in technical courses. We provide severalsuggestions for overcoming student resistance, as well as improved assessment and feedbackstrategies that better meet student needs while still not over-burdening instructors and teachingassistants.

Spatial structure of internal Poincaré waves in Lake Michigan

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In this paper we examine the characteristics of near-inertial internal Poincaré waves in Lake Michigan (USA) as discerned from field experiments and hydrodynamic simulations. The focus is on the determination of the lateral and vertical structure of the waves. Observations of near-inertial internal wave properties are presented from two field experiments in southern Lake Michigan conducted during the years 2009 and 2010 at Michigan City (IN, USA) and Muskegon (MI, USA), respectively. Spectra of thermocline displacements and baroclinic velocities show that kinetic and potential baroclinic energy is dominated by near-inertial internal Poincaré waves. Vertical structure discerned from empirical orthogonal function analysis shows that this energy is predominantly vertical mode 1. Idealized hydrodynamic simulations using stratifications from early summer (June), mid-summer (July) and fall (September) identify the basin-scale internal Poincaré wave structure as a combination of single- and two-basin cells, similar to those identified in Lake Erie by Schwab, with near-surface velocities largest in the center of the northern and southern basins. Near-inertial bottom kinetic energy is seen to have roughly constant magnitude over large swathes across the basin, with higher magnitude in the shallower areas like the Mid-lake Plateau, as compared with the deep northern and southern basins. The near-bottom near-inertial kinetic energy when mapped appears similar to the bottom topography map. The wave-induced vertical shear across thermocline is concentrated along the longitudinal axis of the lake basin, and both near-bottom velocities and thermocline shear are reasonably explained by a simple conceptual model of the expected transverse variability.

A Year of Internal Poincaré Waves in Southern Lake Michigan

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A unique set of full year, deep water observations from the middle of Lake Michigan’s southern basin are analyzed to quantify the seasonal variability of the dominant near-inertial internal Poincaré wave. At this mid-lake location, the Poincaré wave is seen to describe more than 80% of the observed surface current variability for much of the year, with characteristic near-inertial frequency and clockwise-rotating velocities. The dominance of the near-inertial seiche on the flow decreases with depth. The wave persists during the “stratified period,” roughly May through late December, and is supported by as few as 1–2 degrees of thermal stratification over 150 m; only after complete water column mixing does the wave go dormant for January through April. The strongest Poincaré wave activity is seen to correspond to the period of strongest summer thermal stratification (August), in spite of the relatively weak winds at this time. A simple inertial slab model optimized with linear friction is shown to capture the seasonal variability of the near-inertial energy at this location reasonably well. The vertical structure of the wave shows good agreement with that calculated with a standard normal modes formulation, which is in turn used to characterize the potential shear and mixing caused by the wave. Late-spring and summer events of elevated Poincaré wave activity are shown to generate sufficiently strong shear with persistent periods of sub-1 Richardson numbers within the thermocline, suggesting that the near-inertial seiche is likely generating thermocline instabilities in the lake’s interior.

Cross-shelf thermal structure in Lake Michigan during the stratified periods

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Results from a field experiment in southern Lake Michigan are used to quantify the cross-shelf nearshore variability in Great Lakes temperatures during the stratified season. The experiment was conducted along the Indiana coast of southern Lake Michigan, with temperature and velocity moorings arranged in a cross-shelf transect that extended to approximately 20 km from shore (40 m depth). The field site is noteworthy because of its location at the end of a major axis of an elliptical Great Lake, the relatively mild bathymetric slope, and local shoreline orientation that is perpendicular relative to the dominant summer winds. Measurements demonstrate that the location of the thermocline-bottom intersection is highly variable, causing a wide zone of extreme thermal variability in the nearshore region with time scales of variability ranging from hours to months. Near-inertial internal Poincaré waves are shown to cause large thermocline excursions but primarily only during periods of elevated activity. Several full upwelling events were observed, but in general, they were brief, lasting only 1–2 days, and had very limited spatial extent (2.5 km or less). Nonetheless, the offshore extent of the upwelling front was shown to be reasonably estimated with a simple estimate of the cross-shelf transport caused by alongshore wind events. A persistent feature that determined the zone of elevated thermal variability (the thermocline-shelf intersection point) was the strongly tilted thermocline, which resulted in the thermocline being located very close to shore. No evidence was found to support the hypothesis that internal Kelvin waves affect thermal variability at the study location.

The mixing efficiency of interfacial waves breaking at a ridge. Part I: Overall mixing efficiency

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The overall mixing efficiency of periodic, interfacial waves breaking at a Gaussian ridge is investigated through laboratory experiments. Cumulative measurements are used to investigate the fraction of the wave energy lost in the breaking event that contributes to irreversible mixing of the background density gradient. Using the tank as a control volume, the distribution of energy into reflected waves, transmitted waves, and dissipation and irreversible mixing from the breaking event is determined. The overall fraction of wave energy lost in the breaking event that is converted irreversibly to mixing is found to be 3–8%, which is low compared with typical values of around 20% for steady, parallel, stratified shear instabilities. Spatial variability in the mixing event may contribute to the relatively low overall efficiency of the event.

The mixing efficiency of interfacial waves breaking at a ridge. Part II: Local Energetics

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The efficiency with which internal wave energy is converted irreversibly to diapycnal mixing in bathymetry-induced mixing events is of great importance to larger-scale ocean modeling efforts. High-resolution laboratory measurements are used to investigate the spatial and temporal variability of interfacial wave breaking events at a submerged bathymetric ridge. From high spatial resolution measurements, it appears the local efficiency can vary significantly. Parameterizations based on the turbulent Reynolds number and Froude number suggest that the local mixing efficiency within the overturning patch at the interface is 10–17% but the local efficiency is near zero within the relatively homogenous layers. When the local mixing efficiency is integrated over the entire event, the resulting overall efficiency is consistent with the result from Part 1 that the overall event efficiency is 3–8%. This spatial variation in the mixing efficiency reinforces the importance of dynamic mixing efficiency parameterizations based on local stratified turbulence parameters.

The breaking of interfacial waves at a submerged bathymetric ridge

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The breaking of periodic progressive two-layer interfacial waves at a Gaussian ridge is investigated through laboratory experiments. Length scales of the incident wave and topography are used to parameterize when and how breaking occurs. Qualitative observations suggest both shear and convection play a role in the instability of waves breaking at the ridge. Simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) measurements are used to calculate high resolution, two-dimensional velocity and density fields from which the local gradient Richardson number Rig is calculated. The transition to breaking occurred when 0.2 ≤ Rig ≤ 0.4. In these wave-ridge breaking events, the destabilizing effects of waves steepening in shallow layers may be responsible for breaking at higher Rig than for similar waves breaking through shear instability in deep water (Troy & Koseff, J. Fluid Mech., vol. 543, 2005b, p. 107). Due to the effects of unsteadiness, nonlinear shoaling and flow separation, the canonical Rig > 0.25 is not sufficient to predict the stability of interfacial waves. A simple model is developed to estimate Rig in waves between finite depth layers using scales of the incident wave scale and topography. The observed breaking transition corresponds with a constant estimated value of Rig from the model, suggesting that interfacial shear plays an important role in initial wave instability. For wave amplitudes above the initial breaking transition, convective breaking events are also observed.

The viscous decay of progressive interfacial waves

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The viscous damping of progressive, two-layer interfacial waves is examined theoretically and experimentally. Traditional water wave theory is modified to derive the damping rates associated with interfacial wave propagation in a rectangular channel. The individual wave damping contributions are considered from the bottom, side, and interfacial boundary layers, as well as the damping associated with the wave-induced velocities within the homogenous fluid layers. These results show that for most laboratory-scale experiments, sidewall friction plays the dominant role in wave damping. Laboratory experiments are conducted to verify the damping rates for progressive two-layer internal waves in a rectangular channel. Experiments are conducted on both monochromatic and polychromatic wave trains. The results of these experiments are in good agreement with the derived damping rates, but show poorer agreement for large-amplitude waves when the sidewall boundary layers become turbulent. More work is necessary to quantify the damping associated with nonlinear internal waves in order to allow for accurate interpretation of the results from laboratory experiments.

The instability and breaking of long internal waves

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Laboratory experiments are carried out to determine the nature of internal wave breaking and the limiting wave steepness for progressive, periodic, lowest-mode internal waves in a two-layer, miscible density stratification. Shoaling effects are not considered. The waves investigated here are long relative to the thickness of the density interface separating the two fluid layers. Planar laser-induced fluoresence (PLIF) flow visualization shows that wave breaking most closely resembles a Kelvin–Helmholtz shear instability originating in the high-shear wave crest and trough regions. However, this instability is strongly temporally and spatially modified by the oscillations of the driving wave shear. Unlike a steady stratified shear layer, the wave instability discussed here is not governed by the canonical $it Ri{=}1/4$ stability limit. Instead, the wave time scale (the time scale of the destabilizing shear) imposes an additional constraint on instability, lowering the critical Richardson number below 1/4. Experiments were carried out to quantify this instability threshold, and show that, for the range of wavenumbers considered in this study, the critical wave steepness at which the wave breaking occurs is wavenumber-dependent (unlike surface waves). The corresponding critical wave Richardson numbers at incipient wave breaking are well below 1/4, in consonance with a modified instability analysis based on results from stratified shear flow instability theory.