This paper presents experimental validations of the Helmholtz Equation Least Squares (HELS) method [Wang and Wu, J. Acoust. Soc. Am. 102, 2020-2032 (1997); Wu and Wang, U.S. Patent Number 5712805 (1998); Wu, J. Acoust. Soc. Am. 107, 2511-2522 (2000)] on reconstruction of the radiated acoustic pressures from a complex vibrating structure. The structure under consideration has geometry and dimensions similar to those of a real passenger vehicle front end. To simulate noise radiation from a vehicle, a high fidelity loudspeaker installed inside the structure at the location of the engine is employed to generate both random and harmonic acoustic excitations. The radiated acoustic pressures are measured over a finite planar surface above the structure by a microphone. The measured data are taken as input to the HELS formulation to reconstruct the acoustic pressures on the top surface of the structure as well as in the field. The reconstructed acoustic pressures are then compared with measured ones at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the surface. Results show that satisfactory reconstruction can be obtained on the top surface of the structure subject to both random and harmonic excitations. Moreover, the more measurements and the closer their distances to the source surface, the more accurate the reconstruction. The efficiency of the HELS method may decrease with increasing of the excitation frequency. This high frequency difficulty is inherent in all expansion theories.
This paper presents visualization of acoustic radiation from a vibrating bowling ball using the Helmholtz equation least squares (HELS) method. In conducting the experiments, the ball is excited by a vibration shaker using stationary random signals. The radiated acoustic pressures are measured using two microphones and taken as input to the HELS formulations. The reconstructed acoustic pressures on the bowling ball surface are compared with those measured at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the bowling ball surface. Results demonstrate that the accuracy of reconstruction based on measurements over a conformal surface is much higher than that over a finite planar surface. This is because the latter often extends beyond the near-field region, making the accuracy of measurements inconsistent. Nevertheless, satisfactory reconstruction of acoustic pressure fields over the entire bowling ball surface can still be obtained based on the measurements taken over a finite planar surface on one side of the source. In a similar manner, the normal component of the surface velocity is reconstructed. Once these acoustic quantities are determined, the time-averaged acoustic intensity is calculated. Also presented are the formulations for estimating a priori the numbers of expansion functions and measurements required by the HELS method and the guidelines for determining the reconstruction error and optimum measurement locations, given the overall dimensions of the source and the highest frequency of interest in reconstruction.
The course "Fundamentals of Engineering Design" was developed at University of Detroit Mercy in response to the need for introducing the entrepreneurial mindset to engineering students at a very early stage. The course is required of all undergraduate students in Mechanical Engineering, Electrical Engineering and Robotics/Mechatronic Systems Engineering. The course is centered on a recently developed commercial technology where the students are tasked with analyzing that technology and associated intellectual property. They are then tasked with proposing ventures in other markets using that technology and to do so in business terms. Assessment results indicate an increased level of self-confidence and self-efficacy in relation to developing and presenting product ideas. The balance between technical and business content was brought into question with a small but vocal minority indicating a desire for less business content.
1-IntroductionThe pedagogical goals, academic motivation and models of freshman engineering design experiences are many. A survey paper 1 lists eight models: reverse engineering; creating something useful from a preset number of objects; full scale project; small scale projects; case studies; competitions; non-profit project; and, redesign of a local project. The reader is invited to read Reference 1 for details.
The paper presents how a U.S. university was able to implement curricular content in a specially designed engineering course to teach students critical non-technical skills of the engineers of 2020, as described by educational, industrial and governmental organizations. The course targeted issues that directly affect the engineering profession, i.e., nature of the knowledge-based economy, the nature and need for innovation, the various kinds and advantages of entrepreneurship and business models associated with it, public speaking and communication skills, working in teams, and the need for life-long learning. The course also included content targeting the ability for an engineer to manage his/herself with a corporate setting in today's knowledge-based economy. This paper describes the course design, content and rubric that were used to assess some of the course outcomes, as well as the results of the assessment. In general, the results show that the vast majority of students agreed that the course had been effective in teaching and making them aware of.
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