A prediction of 3-D viscous flow and performance of the NASA low-speed centrifugal compressor

A prediction of the 3-D turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation for high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modelling. Recommendations are made for future flow studies in the NASA impeller

Explicit finite-volume time-marching calculations of total temperature distributions in turbulent flow

A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. This paper investigates the introduction of a new formulation of the energy equation which gives improved transient behavior as the calculation converges. The effect of variable Prandtl number on the temperature distribution through the boundary layer is also investigated. A turbulent boundary layer in an adverse pressure gradient (M = 0.55) is used to demonstrate the improved transient temperature distribution obtained when the new formulation of the energy equation is used. A flat plate turbulent boundary layer with a supersonic free-stream Mach number of 2.8 is used to investigate the effect of Prandtl number on the distribution of properties through the boundary layer. The computed total temperature distribution and recovery factor agree well with the measurements when a variable Prandtl number is used through the boundary layer

An explicit finite-volume time-marching procedure for turbulent flow calculations

A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite-volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. Control volumes are chosen so that smoothing of flow properties, typically required for stability, is not required. Different time steps are used in the different governing equations. A new pressure interpolation scheme is introduced which improves the shock capturing ability of the method. A multi-volume method for pressure changes in the boundary layer allows calculations which use very long and thin control volumes (length/height - 1000). The method is compared with two test cases. Essentially incompressible turbulent boundary layer flow in an adverse pressure gradient is calculated and the computed distributions of mean velocity and shear are in good agreement with the measurements. Transonic viscous flow in a converging diverging nozzle is calculated; the Mach number upstream of the shock is approximately 1.25. The agreement between the calculated and measured shock strength and total pressure losses is good

Thermodynamic evaluation of transonic compressor rotors using the finite volume approach

The development of a computational capability to handle viscous flow with an explicit time-marching method based on the finite volume approach is summarized. Emphasis is placed on the extensions to the computational procedure which allow the handling of shock induced separation and large regions of strong backflow. Appendices contain abstracts of papers and whole reports generated during the contract period

A study of the relationship of death anxiety to openness toward change and sense of well-being

Several writers have suggested a similarity between the loss process experienced by the dying person and the loss process experienced by individuals making changes in their lives. This concept has been incorporated into several areas of therapy yet little research has been done to substantiate the idea. A sense of well-being has also been suggested as important within the Existential concept that death resolution enhances mental health and functioning. This study explores the possible relationship between death attitudes and both openness to change and sense of well-being. Three hypotheses were investigated: (1) there is an inverse relationship between death anxiety and measures of openness to change, (2) there is an inverse relationship between death anxiety and measures of a sense of well-being and (3) there is a positive inter-relationship between measures of openness to change and measures of a sense of well-being.;To test these hypotheses, a variety of scales considered representative of openness to change and a sense of well-being were extracted from three instruments; the California Psychological Inventory, the Adjective Check List and the Edwards Personal Preference Schedule. The Templer Death Anxiety Scale was used to measure death attitudes.;The scales were randomly combined into a single instrument and administered to 191 adult individuals from five diverse occupational and age groups. These groups were chosen for the purpose of gaining heterogeneity within the total sample measured. Participation was voluntary and subjects were naive as to the specific variables being measured. Statistical analysis consisted of subjecting the hypotheses to a Pearson Product-Moment correlation.;Results for the total sample (N = 191) indicated that: (1) There was no relationship between death anxiety and measure of openness to change except for the n Change Scale from the Edwards Personal Preference Schedule. Significance was obtained between this scale and death anxiety in an inverse direction. (2) There was a significant inverse relationship between death anxiety and measures of a sense of well-being. (3) There was a significant positive interrelationship between 14 of the 15 scales used to measure openness to change and sense of well-being.;Results for each of the five groups were also evaluated and included in the discussion. Directions for future research were suggested

What Academic Grades Mean to Seventh Grade Students

This study explores how seventh grade students in an urban school district make meaning for their teacher-assigned report card grades. A great deal of research has been done on report card grades from the perspective of teachers and administrators, but few studies have examined what teacher-assigned grades mean to middle school students. This qualitative study attempts to develop an understanding of the meanings attributed to teacher-assigned grades by 56 seventh grade English Language Arts (ELA) students in an urban middle school in Massachusetts. Three major research questions were addressed: 1) How do 56 seventh-grade English Language Arts students in an urban middle school make meaning of their teacher-assigned grades? 2) What do 56 seventh grade ELA students in an urban middle school believe about their control over teacher assigned grades? 3) What evidence, if any, can be found supporting a relationship between attribution for success or failure and the academic performance of these students? A set of students was observed receiving third quarter report cards. Then 56 students responded to a prompt asking them what they thought their report card grade would be and why they thought that. Two focus groups of students were recruited from the 56 students and were asked to respond to vignettes describing various scenarios relating to hypothetical students and grades. Analysis of data revealed patterns of attributions. The most frequent attributions were to work completed or not completed, behavior, and compliance. Students did not attribute grades to mastery of skills and content. Recommendations for future research include more investigation of this topic through the lens of critical social theory to determine the effects of systemic acculturation, power dynamics, effects of hidden curriculum, and individual teacher bias on how students understand or fail to understand the relationship between their mastery of skills and content and their teacher-assigned grades