Vortex-induced vibration (VIV) of a two degree-of-freedom (DOF) circular cylinder, placed in the test section of a recirculating water tunnel and free to oscillate in its first two vibrational modes in the crossflow direction, is studied experimentally. The dynamic response of the cylinder is studied for a reduced velocity range of $U^*=4\unicode{x2013}30$ for eigenfrequency ratios in the range of 1.3–3.0. For the two DOF system, while the onset of the VIV response followed a similar lock-in region as those observed for a classical VIV response of a single DOF system, by increasing the reduced velocity a secondary lock-in region was observed over which the oscillations of the cylinder were locked into the system's second mode. In addition, there existed an intermediate range of reduced velocity over which the VIV response consisted of oscillations at a combination of the first two natural modes of the system. As the eigenfrequency ratio between the first two modes increased, the secondary lock-in range was extended to higher reduced velocities and the reduced velocity range over which multi-modal oscillations were observed was decreased. A full map of vortex dynamics in the wake of the cylinder was developed qualitatively and quantitatively using hydrogen bubble flow visualization and time-resolved volumetric particle tracking velocimetry techniques, respectively. A Q-criterion analysis revealed the existence of highly three-dimensional vortex structures in the wake of the cylinder. The spatiotemporal mode analysis using the proper orthogonal decomposition technique revealed strong coupling between the vortex shedding modes in the wake of the cylinder and the structural vibration modes.

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This study presents a teaching methodology developed through a 3-year-long iterative-study in order to incorporate hands-on experiences in engineering courses and expose sophomore students to engineering design. Sophomore engineering technology students enrolled in a 200level Computer Aided Design course participated in this study. An innovative Project-Based-Learning (PBL) approach with an embedded Agile Project Management (APM) is implemented to promote skills such as critical thinking, problem solving, communication, and selfmanagement. These are skills that students need to have to succeed in senior capstone projects or in professional practice. APM is used to respond to students' struggles with PBL's project management. APM is an iterative approach with ability to respond to issues as they arise throughout the course of the project. In this approach, students performed a series of agile rituals such as showcases, retrospectives, stand-up meetings and iteration reviews.However, in PBL approach, student learning is significantly correlated with quality of implemented PBL. Students, who are provided with low quality PBL, even show a negative learning growth [10]. High quality PBL has six criteria, each of which must be at least minimally met in a project in order for it to be considered high quality. These six criteria are [11]: