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It is generally agreed that adequate resolution is required to reproduce the structure of spray and gas jets in numerical computations. It has not been clarified what this resolution should be although it would appear reasonable to assume that it should be such that the physical scales of the problem are resolved. In the case of a jet, this implies that near the orifice, the jet diameter has to be resolved since this is the appropriate length scale. It is shown in this work that if such a resolution is not used in computing transient jets, the structure of the jet is not reproduced with adequate accuracy. In fact, unexpected, erroneous and misleading dependence on ambient turbulence length and time scales will be predicted when the initial ambient turbulence diffusivity is small relative to the jet diffusivity. When the ambient turbulence diffusivity is of the same order as the jet diffusivity or greater, entrainment rates are significantly underpredicted.

Financial planners are always anxious to assist engineers and scientists in making retirement decisions. Many engineers, especially Industrial Engineers (IE), have had courses that provide the knowledge to make these retirement financial plans themselves. This paper will provide a method of estimating retirement needs utilizing Excel software and IE college coursework.

In recent years, Nearfield Acoustical Holography (NAH) has been used to identify stationary vehicle exterior noise sources. However that application has usually been limited to individual components. Since powertrain noise sources are hidden within the engine compartment, it is difficult to use NAH to identify those sources and the associated partial field that combine to create the complete exterior noise field of a motor vehicle. Integrated Nearfield Acoustical Holography (INAH) has been developed to address these concerns: it is described here. The procedure entails sensing the sources inside the engine compartment by using an array of reference microphones, and then calculating the associated partial radiation fields by using NAH. In the second part of this paper, the use of farfield arrays is considered. Several array techniques have previously been applied to identify noise sources on moving vehicles.

Most airline maintenance human factors training programs miss the mark when it comes to producing optimal behavioral and procedural changes among participating maintenance professionals. While there are many causes for training outcomes which are less than desired and anticipated, principal among these are the failure of most programs to address the pragmatic learning needs of those technicians as adult learners. Attention to andragogical principles such as clear learning goals, readily apparent relevance and direct applicability of material, immediate feedback, learner directed inquiry and self assessment can contribute greatly to achieving optimal results. A program currently under development at Purdue University utilizes a combination of classroom instruction, group discussion, and learner participation in aviation maintenance scenarios as a method for improving human factors education.

The authors relate their experience in teaching a senior level Computer-Aided Design (CAD) course in Mechanical Engineering using advanced Computer-Aided Engineering software. The course balances the theory and the need for hands-on experience with commercial CAD software in solving practical design problems. Students are given assignments ranging from simple 3D modeling exercises and 2D finite element analyses to an optimization project requiring more advanced 3D modeling and analysis. Where possible, analytical solutions are found and compared to the finite element results. The software allows the students to explore much more complex problems than would have otherwise been possible.

It has been noted that there are consistent differences between sideline sound levels measured on the two track types used for standardized motor vehicle passby testing: i.e., ISO and SAE surfaces. When the two-microphone transfer function method was first used in conjunction with a two parameter ground model to characterize the acoustical properties of these asphalt surfaces it was found that there were significant acoustical differences between the ISO and SAE surfaces. However, it was also noted that environmental conditions, e.g., wind and temperature gradients, affected the estimates of surface properties obtained by using that method. In the present work, a ray tracing algorithm has been used to model the effects of environmental refraction on short range propagation over asphalt, and a physically-based single parameter ground model has been used to characterize the asphalt surfaces.

In this paper it is shown that time-frequency analysis of a transient structural response may be used to identify the wave-types carrying significant energy through a multi-element structure. The identification of various wave-types is possible since each is characterized by its own dispersion relation, with the result that each wave-type may be associated with characteristic features in the time-frequency domain representation of a structural response. For multi-element structures, propagating energy can be converted from one wave-type to another at the junction of the elements. Consequently, for those structures, the characteristic features in the time-frequency domain consist of the superposition of features associated with propagation in each element. In the work described here, the Wigner Distribution has been used to obtain time-frequency domain representations of structural transient responses.

In experimental work, it is well known that measured values are not exact. Statistical treatment of uncertainty in measured values is common. The propagation of uncertainty in measured values into calculated values is examined. This technique of uncertainty analysis presented provides a rigorous mathematical technique for the analysis of uncertainty propagation from experimentally measured values into calculated results. The method of uncertainty analysis is introduced in general and an application to the momentum equation is examined to demonstrate the technique. The example presented demonstrates the effectiveness of the technique by demonstrating the growth of uncertainty in the calculated results around a singularity in the equations.

Purdue University Aviation Technology at West Lafayette and Indianapolis, in concert with a number of industry participants, initiated research at West Lafayette and industry locations on ways and means to address safety concerns affecting a number of air transport carriers as well as general aviation operations. The outcome of the research resulted in a program with airlines and general aviation operators that lead to the development of an interactive instructional technique primarily based on empirical studies at the various facilities. Subsequent to the observation periods were sessions addressing recommendations for resolution of these jointly recognized issues. Part of this effort involved developing innovative methods to report these incidents in a manner that would ensure open, effective communications amongst all the concerned parties. This ongoing research involves the use of students to assess the utilization of current safety resources, or lack thereof, in industry.

The turbocharger, consisting of a radial or axial flow turbine and an radial flow compressor presents perhaps one of the most challenging tasks to the turbomachinery designer. Due to the necessity of speed changes in the diesel engine, the turbocharger transits a wide variety of operating points in its normal operation. During an engine speed acceleration or deceleration there will be a lag in the required air delivery to the engine, resulting in increased smoke emission and limiting the power delivered by the engine. In order to investigate the dynamic performance of a turbocharged engine, an essential first step must be the development of an adequate model for transient characteristics of the turbocharger. One of the significant problems that must be overcome for the modeling effort to be successful is a detailed experimental description of the transient performance of the device.

Governing equations have been derived to model the space- and frequency-averaged behavior of structural acoustic systems. These equations were derived using assumptions similar to the approximations made in SEA. The equations can be used to develop continuous models of 1-D, 2-D, and 3-D subsystems. The equations have been formulated into a finite element approximation referred to as the Energy Finite Element Method (EFEM). In this paper the theory for coupling plate-like structural systems to acoustical systems is derived and implemented into the EFEM. The results of a verification study using a plate mounted on a rectangular acoustical enclosure are shown for two cases, a mechanically driven plate and an acoustically driven enclosure.

Acoustic array techniques are presented as alternatives to intensity measurements for source identification in automotive and industrial environments. With an understanding of the advantages and limitations described here for each of the available methods, a technique which is best suited to the application at hand may be selected. The basic theory of array procedures for Nearfield Acoustical Holography, temporal array techniques, and an Inverse Frequency Response Function technique is given. Implementation for various applications is discussed. Experimental evaluation is provided for tire noise identification.

Structural sound transmission through primary bulb (PB) sealing systems was investigated. A two-degrees-of-freedom analytical model was developed to predict the sound transmission characteristics of a PB seal assembly. Detailed sound transmission measurements were made for two different random excitations: acoustic and aerodynamic. A reverberation room method was first used, whereby a seal sample installed within a test fixture was excited by a diffuse sound field. A quiet flow facility was then used to create aerodynamic pressure fluctuations which acted as the excitation. The space-averaged input pressure within the pseudo door gap cavity and the sound pressure transmitted on the quiescent side of the seal were obtained in each case for different cavity dimensions, seal compression, and seal designs. The sound transmission predictions obtained from the lumped element model were found to be in reasonable agreement with measured values.

The relationship of slip resistance (or coefficient of friction) to safe climbing system maneuvers on high profile vehicles has become an issue because of its possible connection to falls of drivers. To partially address this issue, coefficients of friction were measured for seven of the more popular fabricated metal step materials. Evaluated on these steps were four types of shoe materials (crepe, leather, ribbed-rubber, and oil-resistant-rubber) and three types of contaminant conditions (dry, wet-water, and diesel fuel). The final factor evaluated was the direction of sole force application. Results showed that COF varied primarily as a function of sole material and the presence of contaminants. Unexpectedly, few effects were attributible to the metal step materials. Numerous statistical interactions suggested that adequate levels of COF are more likely to be attained by targeting control on shoe soles and contaminants rather than the choice of a particular step material.

This paper describes sensors and systems developed, or under development, by researchers at Purdue University including: an automated soil nutrient mapping system; a real-time acoustic soil texture sensor; an improved, real-time soil organic matter (SOM) sensor; a real-time soil compaction sensor; and an animal manure application monitoring and control system. Issues to consider for sensor use and development, criteria for evaluating the potential for successful sensor implementation, and likely future sensors for site-specific crop management (SSCM) are also discussed.

The identification of the propulsion noise of turbofan engines plays an important role in the design of low-noise aircraft. The noise generation mechanisms of a typical turbofan engine are very complicated and it is not practical, if not impossible, to identify these noise sources efficiently and accurately using numerical or experimental techniques alone. In addition, a major practical concern for the measurement of acoustic pressure inside the duct of a turbofan is the placement of microphones and their supporting frames which will change the flow conditions under normal operational conditions. The measurement of acoustic pressures on the surface of the duct using surface-mounted microphones eliminates this undesirable effect. In this paper, a generalized acoustical holography (GAH) method that is capable of estimating aeroacoustic sources using surface sound pressure is developed.

Presented in this paper is a nonlinear modeling and a controller design methodology for engine control. For illustrative purposes, the methodology is applied to the idle speed of a Ford 4.6L-2 valve V-8 fuel injected engine. The nonlinear model of the engine is based on a Hammerstein type model which is identified through input-output data without a priori knowledge of the engine dynamics. The nonlinear model is subsequently used in a frequency domain controller design methodology to achieve the performance goal of maintaining the engine idle speed within a prespecified asymmetric output tolerance despite external torque disturbances. An experimental verification of the proposed control law is included.

The lack of effective and efficient communication between pilots and maintenance technicians has been recognized as a problem in general aviation by both members of the industry and academia. The goal of this paper is to provide an accounting of the impact that communication between maintenance technicians and pilots, or the lack thereof, can have upon both the bottom line and the experience of those who operate within the general aviation arena. The researchers interviewed and observed maintenance technicians and pilots in general aviation operations to identify what members on both sides of the communication process identified as being problematic and troubling. Several of the major barriers to communication, as well as several strategies to overcome those barriers, are discussed.

The flow-induced pressure fluctuations in a door gap cavity model were investigated experimentally using a quiet wind tunnel facility. The cavity cross-section dimensions were typical of road vehicle door cavities, but the span was only 25 cm. One cavity wall included a primary bulb rubber seal. A microphone array was used to measure the cavity pressure field over a range of flow velocities and cavity configurations. It was found that the primary excitation mechanism was an “edge tone” phenomenon. Cavity resonance caused amplification around discrete frequencies, but did not cause the flow disturbances to lock-on. Possible fluid-elastic coupling related to the presence of a compliant wall was not significant. A linear spectral decomposition method was then used to characterize the cavity pressure in the frequency domain, as the product of a source spectral distribution function and an acoustic frequency response function.

Wavenumber domain methods have been developed to experimentally determine the flexural group speeds and loss factors in beam elements and the flexural power transmission and reflection coefficients of joints in a structure. These techniques are used in this paper to measure uncertain information for an Energy Finite Element Method (EFEM) model of a ladder frame structure. The loss factors and group speeds in each element in the structure were measured and found to compare well with the analytical predictions. However, the flexural power transmission and reflection coefficients of the joints in the structure were found to be significantly different from analytically predicted values. EFEM predictions and measured velocities for several components are compared.