Amplified crossflow disturbances in the laminar boundary layer on swept wings with suction

Solution charts of the Orr-Sommerfeld equation for stationary crossflow disturbances are presented for 10 typical velocity profiles on a swept laminar flow control wing. The critical crossflow Reynolds number is shown to be a function of a boundary layer shape factor. Amplification rates for crossflow disturbances are shown to be proportional to the maximum crossflow velocity. A computer stability program called MARIA, employing the amplification rate data for the 10 crossflow velocity profiles, is constructed. This code is shown to adequately approximate more involved computer stability codes using less than two percent as much computer time while retaining the essential physical disturbance growth model

Design of a laminar-flow-control supercritical airfoil for a swept wing

An airfoil was analytically designed and analyzed for a combination of supercritical flow and laminar flow control (LFC) by boundary layer suction. A shockless inverse method was used to design an airfoil and an analysis method was used in lower surface redesign work. The laminar flow pressure distributions were computed without a boundary layer under the assumption that the laminar boundary layer would be kept thin by suction. Inviscid calculations showed that this 13.5 percent thick airfoil has shockless flows for conditions at and below the design normal Mach number of 0.73 and the design section lift coefficient of 0.60, and that the maximum local normal Mach number is 1.12 at the design point. The laminar boundary layer instabilities can be controlled with suction but the undercut leading edge of the airfoil provides a low velocity, constant pressure coefficients region which is conducive to laminar flow without suction. The airfoil was designed to be capable of lift recovery with no suction by the deflection of a small trailing edge flap

Experimental studies on Goertler vortices

Goertler vortices arise in laminar boundary layers along concave walls due to an imbalance between pressure and centrifugal forces. In advanced laminar-flow control (LFC) supercritical airfoil designs, boundary-layer suction is primarily used to control Tollmien-Schlichting instability and cross-flow vortices in the concave region near the leading edge of the airfoil lower surface. The concave region itself is comprised of a number of linear segments positioned to limit the total growth of Goertler vortices. Such an approach is based on physical reasonings but rigorous theoretical justification or experimental evidence to support such an approach does not exist. An experimental project was initiated at NASA Langley to verify this concept. In the first phase of the project an experiment was conducted on an airfoil whose concave region has a continuous curvature distribution. Some results of this experiment were previously reported and significant features are summarized

Theoretical performance of cross-wind axis turbines with results for a catenary vertical axis configuration

A general analysis capable of predicting performance characteristics of cross-wind axis turbines was developed, including the effects of airfoil geometry, support struts, blade aspect ratio, windmill solidity, blade interference and curved flow. The results were compared with available wind tunnel results for a catenary blade shape. A theoretical performance curve for an aerodynamically efficient straight blade configuration was also presented. In addition, a linearized analytical solution applicable for straight configurations was developed. A listing of the computer program developed for numerical solutions of the general performance equations is included in the appendix

Predicted and hot-film measured Tollmien-Schlichting wave characteristics

The Tollmien-Schlichting (TS) instability is a time-dependence instability which can lead to transition of laminar boundary layers on airfoils. A comparison of theoretical predictions and experimental observations of the TS instability on the NLF(1)-0414F airfoil designed by Viken and Pfenninger. The theoretical predictions were obtained using the SALLY stability code. Test results, from the same hot films that were used to detect transition, revealed that TS waves could be detected by the hot films if the hot-film signal was adequately modified

Relationship of College Students\u27 Response Styles on the Strong Interest Inventory to Scores on the Beck Depression Inventory and the Career Thoughts Inventory

The purpose of this study was to examine the relationships among college students’ response styles on the Occupations section of the Strong Interest Inventory (SII), as indicated by the “Like,” “Dislike,” and “Indifferent” percent indexes, and their scores on the Career Thoughts Inventory (CTI) and the Beck Depression Inventory – Second Edition (BDI-II). The SII is a career interest inventory that measures a person’s level of interest across a wide range of areas including occupations and leisure activities. When presented with an item on the SII, an individual indicates whether he or she likes, dislikes, or is indifferent to that particular occupation or activity. The CTI measures dysfunctional thinking in career problem solving and decision making. The higher a person’s scores on the CTI, the more dysfunctional are his or her career thoughts. The BDI-II is a self-report instrument for measuring the severity of depression in adolescents and adults. The higher a person’s scores on the BDI-II, the more severe is his or her level of depression. This study also explored gender differences among the aforementioned variables. The participants were 170 college students who had enrolled in a First Year Studies course during Fall 2003. This study was primarily correlational in design, and the statistical methods used were the Pearson product moment correlation and regression analysis. Results indicated that there was a significant positive relationship between the BDI-II and the CTI (r = .405, p \u3c .01). There was a significant positive relationship between the CTI total scores and the Occupations “Like” percent index of the SII (r = .184, p = .016), and significant negative relationship between the CTI total and the Occupations “Dislike” percent index (r = -.194, p = .011). There was a significant negative relationship between the Decision Making Confusion subscale of the CTI and the Occupations “Dislike” percent index of the SII (r = -.155, p = .044). In addition, there was a significant positive relationship between the Commitment Anxiety subscale and the Occupations “Dislike” percent index (r = -.206, p = .007). Analyses revealed that there were no significant gender differences between the BDI-II and the CTI total score. However, females scored significantly higher than males o the Commitment Anxiety subscale of the CTI (Mm=51.96, Mf=55.50, p = .022). Results also indicated that males endorsed more items as “Indifferent” on the SII higher than females (Mm=25.93, Mf=21.43, p = .036). Analyses revealed that the BDI-II, the CTI total and subscales, and gender do not significantly interact to predict the response style of students on the Occupations Scale of the SII. It was concluded that career counselors and counseling psychologists should consider the influence of a student’s career thoughts and depression when interpreting the SII and throughout the career decision-making process. Implications for practitioners and university training programs, and directions for future research were discussed

Crossflow Stability and Transition Experiments in a Swept-Wing Flow

An experimental examination of crossflow instability and transition on a 45 degree swept wing is conducted in the Arizona State University Unsteady Wind Tunnel. The stationary-vortex pattern and transition location are visualized using both sublimating-chemical and liquid-crystal coatings. Extensive hot-wire measurements are conducted at several measurement stations across a single vortex track. The mean and travelling-wave disturbances are measured simultaneously. Stationary-crossflow disturbance profiles are determined by subtracting either a reference or a span-averaged velocity profile from the mean-velocity data. Mean, stationary-crossflow, and travelling-wave velocity data are presented as local boundary-layer profiles and as contour plots across a single stationary-crossflow vortex track. Disturbance-mode profiles and growth rates are determined. The experimental data are compared to predictions from linear stability theory

Rethinking Studio Pedagogy: Teaching Introductory Architectural Design at the Graduate Level

Over the last two years, our Architecture Program committed considerable intellectual capital to the rethinking of graduate level introductory design studio pedagogy for students entering our Masters of Architecture 1/3? year program. This reevaluation concentrates on several unique challenges intrinsic to the graduate level introductory design curriculum, which include: The inherent differences between the age and personality profiles of undergraduate and graduate students. Many programs treat the curricula as equal, with graduate students executing the same exercises as undergraduates, only at a faster pace. The developmental gap that exists in the second year of most M. Arch 1 programs between students with architecture and non-architecture backgrounds. Our goal is to retool the core design studio pedagogy in order to bring those students with undergraduate degrees in non-architecture disciplines up to the same level of design skill development as I st year graduate students with 4 year Bachelors of Science in Architecture degrees. In short, these incoming students are disciplined, mature and educated and need a highly structured environment that works to: develop skills in design and the conventions of representation; teach theory as a part of everyday studio work instead of a separate activity; and introduce an understanding of design strategy to enable mature projects to emerge more quickly. This paper focuses specifically on innovations in and the implementation of the pedagogy in the pivotal Core II Studio, which is taught in the Fall