A Quality Control Case Study of Kitchen Appliance Production: An Engineering Case for Graduate Education

This case study presents CoolKast, a leading household appliance company, which focuses on problems in the assembly line of new refrigerators. The refrigerator plant keeps a record of all the quality problems reported within the organization and its customers. Part A of the case study concentrates on current issues that involve a lack of attention to quality, inadequate production planning, and a failure to communicate and engage with employees. Quality procedures for past products and new products on the line are discussed in detail. There are concerns regarding the cost and improving the quality of the production processes. The quality control, process, and maintenance teams should address the underlying problems in the assembly and manufacturing of the refrigerators, especially with respect to the process of inserting foam into the refrigerators. Part B of the case study presents data on the foaming process for the refrigerators in order to identify areas and evaluate root causes in the foaming process for these refrigerators

DNS of Laminar to Turbulent Transition on NACA 0012 Airfoil with Sand Grain Roughness

The Lattice-Boltzmann-based solver PowerFLOW is used to perform direct numerical simulations of the transitional flow over an airfoil at Reynolds number equal to 0.657 million. The leading edge of the airfoil is covered with sand particles, represented by polyhedra, to mimic the grit used in experiments. The sensitivity of the laminar to turbulent transition to the size of these particles, grid resolution, spanwise length is evaluated and rectangular trips are also tested

Direct Numerical Simulation of Acoustic Disturbances in the Rectangular Test Section of a Hypersonic Wind Tunnel

Direct numerical simulations (DNS) of the full-scale rectangular nozzle of a hypersonic wind tunnel are conducted to study the acoustic freestream fluctuations radiating from turbulent boundary layers (TBLs) along the nozzle walls. The nozzle geometry and the flow conditions of the DNS match those of the NASA 20-Inch Mach 6 Tunnel, and the DNS has been completed for a domain without spanwise sidewall boundary conditions. The turbulent boundary layer parameters based on the DNS compare well with those derived from Reynolds Averaged Navier-Stokes (RANS) calculations as well as with the predictions based on Pates correlation. A similarly good comparison is observed for both the Mach number distribution and the Reynolds stresses obtained from the DNS and RANS calculations, respectively. Various characteristics of the acoustic pressure fluctuations within the inviscid core of the nozzle flow are compared with those associated with a single flat plate at a similar freestream Mach number. The frequency spectrum and bulk propagation speeds match well between the nozzle and the flat plate, but the rms pressure fluctuation is higher for the nozzle configuration, likely due to the combined effect of acoustic radiation from the top and bottom walls. Spatial contours of the two-point correlation coefficient display elliptical tails with approximately equal but opposite angles corresponding to the preferred directionality of acoustic structures radiated from both walls. Future work will focus on DNS of the full nozzle configuration, including the effects of the nozzle side walls

The Variation of Slat Noise with Mach and Reynolds Numbers

The slat noise from the 30P30N high-lift system has been computed using a computational fluid dynamics code in conjunction with a Ffowcs Williams-Hawkings solver. By varying the Mach number from 0.13 to 0.25, the noise was found to vary roughly with the 5th power of the speed. Slight changes in the behavior with directivity angle could easily account for the different speed dependencies reported in the literature. Varying the Reynolds number from 1.4 to 2.4 million resulted in almost no differences, and primarily served to demonstrate the repeatability of the results. However, changing the underlying hybrid Reynolds-averaged-Navier-Stokes/Large-Eddy-Simulation turbulence model significantly altered the mean flow because of changes in the flap separation. However, the general trends observed in both the acoustics and near-field fluctuations were similar for both models

Noise Radiation From a Leading-Edge Slat

This paper extends our previous computations of unsteady flow within the slat cove region of a multi-element high-lift airfoil configuration, which showed that both statistical and structural aspects of the experimentally observed unsteady flow behavior can be captured via 3D simulations over a computational domain of narrow spanwise extent. Although such narrow domain simulation can account for the spanwise decorrelation of the slat cove fluctuations, the resulting database cannot be applied towards acoustic predictions of the slat without invoking additional approximations to synthesize the fluctuation field over the rest of the span. This deficiency is partially alleviated in the present work by increasing the spanwise extent of the computational domain from 37.3% of the slat chord to nearly 226% (i.e., 15% of the model span). The simulation database is used to verify consistency with previous computational results and, then, to develop predictions of the far-field noise radiation in conjunction with a frequency-domain Ffowcs-Williams Hawkings solver

The Influence of Realistic Reynolds Numbers on Slat Noise Simulations

The slat noise from the 30P/30N high-lift system has been computed using a computational fluid dynamics code in conjunction with a Ffowcs Williams-Hawkings solver. Varying the Reynolds number from 1.71 to 12.0 million based on the stowed chord resulted in slight changes in the radiated noise. Tonal features in the spectra were robust and evident for all Reynolds numbers and even when a spanwise flow was imposed. The general trends observed in near-field fluctuations were also similar for all the different Reynolds numbers. Experiments on simplified, subscale high-lift systems have exhibited noticeable dependencies on the Reynolds number and tripping, although primarily for tonal features rather than the broadband portion of the spectra. Either the 30P/30N model behaves differently, or the computational model is unable to capture these effects. Hence, the results underscore the need for more detailed measurements of the slat cove flow

The Effect of Cross Flow on Slat Noise

This paper continues the computational examination (AIAA Journal, Vol. 45, No. 9, 2007, pp. 2174-2186) of the unsteady flow within the slat cove region of a multi-element high-lift airfoil configuration. Two simulations have been performed to examine the effect of cross flow on the near-field fluctuations and far-field acoustics. The cross flow was imposed by changing the free-stream velocity vector and modifying the Reynolds number. The cross flow does appear to alter the dynamics in the cove region, but the impact on the noise seems to be more dependent on the flow conditions. However, separating out the true effects of the cross flow from those of the Mach and Reynolds number would require additional calculations to isolate those effects

Assessment of Aeroacoustic Simulations of the High-Lift Common Research Model

This paper presents further validation of PowerFLOWR aeroacoustic simulations of the High-Lift Common Research Model through comparisons with experimental data from a recently completed wind tunnel test. Preliminary time- averaged surface pressure and microphone array data from the experiment are in reasonably good agreement with the simulations, and the slat is shown to be a dominant noise source on this model. The simulations did not predict slat tones that were very prominent in the experiment, but they did capture the broadband component of slat noise in the low-frequency range up to 1 kHz at full scale. Future tests are planned to demonstrate slat noise reduction technology, and simulations are being used to guide this development

Assessment of Slat Noise Predictions for 30P30N High-Lift Configuration From BANC-III Workshop

This paper presents a summary of the computational predictions and measurement data contributed to Category 7 of the 3rd AIAA Workshop on Benchmark Problems for Airframe Noise Computations (BANC-III), which was held in Atlanta, GA, on June 14-15, 2014. Category 7 represents the first slat-noise configuration to be investigated under the BANC series of workshops, namely, the 30P30N two-dimensional high-lift model (with a slat contour that was slightly modified to enable unsteady pressure measurements) at an angle of attack that is relevant to approach conditions. Originally developed for a CFD challenge workshop to assess computational fluid dynamics techniques for steady high-lift predictions, the 30P30N configurations has provided a valuable opportunity for the airframe noise community to collectively assess and advance the computational and experimental techniques for slat noise. The contributed solutions are compared with each other as well as with the initial measurements that became available just prior to the BANC-III Workshop. Specific features of a number of computational solutions on the finer grids compare reasonably well with the initial measurements from FSU and JAXA facilities and/or with each other. However, no single solution (or a subset of solutions) could be identified as clearly superior to the remaining solutions. Grid sensitivity studies presented by multiple BANC-III participants demonstrated a relatively consistent trend of reduced surface pressure fluctuations, higher levels of turbulent kinetic energy in the flow, and lower levels of both narrow band peaks and the broadband component of unsteady pressure spectra in the nearfield and farfield. The lessons learned from the BANC-III contributions have been used to identify improvements to the problem statement for future Category-7 investigations

Assessment of prescription pattern using WHO drug prescribing indicators in medicine wards of a tertiary care teaching hospital: a retrospective observational study

Background: Rational prescribing is an essential skill for every prescriber. However many times it seems a difficult task for various reasons. Such practices ultimately increase the mortality, morbidity and financial burden on the patient. Hence, we aimed our study to evaluate appropriateness of prescription pattern according to WHO drug prescribing indicators, few complementary indicators and classify prescription errors.Methods: A retrospective observational study, conducted in medical record section of tertiary care teaching hospital of Maharashtra during the period of 6 months. Total 400 randomly selected prescriptions from Medicine inpatient wards were scrutinized.Results: Average number of drugs per prescription was 5.20 trending towards polypharmacy. Drugs prescribed by generic name were 13.88%, injectable drugs were part of 93.50% prescriptions, 78.25% prescriptions contained an antimicrobial agent and Percentage of drugs prescribed from NELM 2011 was 72.36%. Illegible handwriting in 68% cases was the important cause of prescription errors. These errors found in 73% of prescriptions.Conclusions: The present study showed that the practices were trending towards irrational prescribing. Polypharmacy and illegible prescriptions were dominated. Regular prescription audit will help to rectify such practices. Also, there is an urgent need of sensitization of prescriber through new treatment guidelines, seminar, presentations and discussions on regular basis