Flight-measured laminar boundary-layer transition phenomena including stability theory analysis

Flight experiments were conducted on a single-engine turboprop aircraft fitted with a 92-in-chord, 3-ft-span natural laminar flow glove at glove section lift coefficients from 0.15 to 1.10. The boundary-layer transition measurement methods used included sublimating chemicals and surface hot-film sensors. Transition occurred downstream of the minimum pressure point. Hot-film sensors provided a well-defined indication of laminar, laminar-separation, transitional, and turbulent boundary layers. Theoretical calculations of the boundary-layer parameters provided close agreement between the predicted laminar-separation point and the measured transition location. Tollmien-Schlichting (T-S) wave growth n-factors between 15 and 17 were calculated at the predicted point of laminar separation. These results suggest that for many practical airplane cruise conditions, laminar separation (as opposed to T-S instability) is the major cause of transition in predominantly two-dimensional flows

Open-loop frequency acquisition for suppressed-carrier biphase signals using one-pole arm filters

Open loop frequency acquisition performance is discussed for suppressed carrier binary phase shift keyed signals in terms of the probability of detecting the carrier frequency offset when the arms of the Costas loop detector have one pole filters. The approach, which does not require symbol timing, uses fast Fourier transforms (FFTs) to detect the carrier frequency offset. The detection probability, which depends on both the 3 dB arm filter bandwidth and the received symbol signal to noise ratio, is derived and is shown to be independent of symbol timing. It is shown that the performance of this technique is slightly better that other open loop acquisition techniques which use integrators in the arms and whose detection performance varies with symbol timing

A comparison of the in vitro and in planta responses of Phytophthora cinnamomi isolates to phosphite

Research in plant pathology often relies on testing interactions between a fungicide and a pathogen in vitro and extrapolating from these results what may happen in planta. Likewise, results from glasshouse experiments are used to estimate what will happen if the fungicide is applied in the field. However, it is difficult to obtain conditions in vitro and in the glasshouse which reflect the conditions where the fungicide may eventually be used, in the field. The aim of this paper is to compare results of the effect of phosphite on P. cinnamomi isolates in vitro and in planta

Natural laminar flow experiments on modern airplane surfaces

Flight and wind-tunnel natural laminar flow experiments have been conducted on various lifting and nonlifting surfaces of several airplanes at unit Reynolds numbers between 0.63 x 10 to the 6th power/ft and 3.08 x 10 to the 6th power/ft, at Mach numbers from 0.1 to 0.7, and at lifting surface leading-edge sweep angles from 0 deg to 63 deg. The airplanes tested were selected to provide relatively stiff skin conditions, free from significant roughness and waviness, on smooth modern production-type airframes. The observed transition locations typically occurred downstream of the measured or calculated pressure peak locations for the test conditions involved. No discernible effects on transition due to surface waviness were observed on any of the surfaces tested. None of the measured heights of surface waviness exceeded the empirically predicted allowable surface waviness. Experimental results consistent with spanwise contamination criteria were observed. Large changes in flight-measured performance and stability and control resulted from loss of laminar flow by forced transition. Rain effects on the laminar boundary layer caused stick-fixed nose-down pitch-trim changes in two of the airplanes tested. No effect on transition was observed for flight through low-altitude liquid-phase clouds. These observations indicate the importance of fixed-transition tests as a standard flight testing procedure for modern smooth airframes

A flight evaluation of a trailing anemometer for low-speed calibrations of airspeed systems on research aircraft

Research airspeed systems on three low-speed general aviation airplanes were calibrated by the trailing anemometer method. Each airplane was fitted with an NASA pitot-static pressure tube mounted on either a nose or wing boom. The uncalibrated airspeed systems contained residual static-pressure position errors which were too large for high-accuracy flight research applications. The trailing anemometer calibration was in agreement with the tower flyby calibration for the one aircraft for which the comparison was made. The continuous deceleration technique for the trailing anemometer method offers reduced test time with no appreciable loss of accuracy for airspeed systems with pitot-static system lag characteristics similar to those described

Jamming transitions in a schematic model of suspension rheology

We study the steady-state response to applied stress in a simple scalar model of sheared colloids. Our model is based on a schematic (F2) model of the glass transition, with a memory term that depends on both stress and shear rate. For suitable parameters, we find transitions from a fluid to a nonergodic, jammed state, showing zero flow rate in an interval of applied stress. Although the jammed state is a glass, we predict that jamming transitions have an analytical structure distinct from that of the conventional mode coupling glass transition. The static jamming transition we discuss is also distinct from hydrodynamic shear thickening.Comment: 7 pages; 3 figures; improved version with added references. Accepted for publication in Europhysics Letter

Interaction, Identity & Social Class

Social class is a longstanding locus of sociological inquiry. Prior research has investigated the phenomenon in an array of domains through a myriad of methodologies and theoretical perspectives. The heterogeneity that is posed by previous studies empirically and theoretically, however, is predicated upon a homogenous set of epistemological and ontological assumptions. This has resulted in a number of programmatic, enduring omissions. Most notably, research has neglected how social class is conceptualised and made relevant by members in forms of talk-in-interaction. Aligning with the commitments of Ethnomethodology (EM), and using Conversation Analysis (CA) and Membership Categorisation Analysis (MCA) specifically, this thesis addresses this lacuna. Data are composed of ordinary, naturalistic forms of talk-in-interaction conducted synchronously in the English language over the last half-century (n=959). The empirical contributions of this research concern the ontological affordances, formulative possibilities and praxiological functions of two families of interactional practices that occasion the relevance of classed identities recurrently – namely, “membership categorisations” and “place references”. Chapter 4 addresses the former, canvassing the agentic, ontological and intersubjective dimensions of linguistically classed membership categories. Chapter 5 introduces the latter as a resource used to actuate classed identities in a designedly referential and metonymic faculty. Chapter 6 then recovers the activity of “accounting” for which both practices are employed across action-types; specifically, “assessments”, “complaints” and “teases”. The central objective of this thesis thus concerns the “respecification” of social class as a “members’ phenomenon”; one that is made relevant within ordinary instances of talk-in-interaction through a stable set of interactional practices in order to accomplish a diverse range of practical tasks. The thesis concludes with a review of several candidate lines of analysis for future EM/(M)CA inquiry that are anticipated by the findings of this research uniquely

Interaction, Identity & Social Class

Social class is a longstanding locus of sociological inquiry. Prior research has investigated the phenomenon in an array of domains through a myriad of methodologies and theoretical perspectives. The heterogeneity that is posed by previous studies empirically and theoretically, however, is predicated upon a homogenous set of epistemological and ontological assumptions. This has resulted in a number of programmatic, enduring omissions. Most notably, research has neglected how social class is conceptualised and made relevant by members in forms of talk-in-interaction. Aligning with the commitments of Ethnomethodology (EM), and using Conversation Analysis (CA) and Membership Categorisation Analysis (MCA) specifically, this thesis addresses this lacuna. Data are composed of ordinary, naturalistic forms of talk-in-interaction conducted synchronously in the English language over the last half-century (n=959). The empirical contributions of this research concern the ontological affordances, formulative possibilities and praxiological functions of two families of interactional practices that occasion the relevance of classed identities recurrently – namely, “membership categorisations” and “place references”. Chapter 4 addresses the former, canvassing the agentic, ontological and intersubjective dimensions of linguistically classed membership categories. Chapter 5 introduces the latter as a resource used to actuate classed identities in a designedly referential and metonymic faculty. Chapter 6 then recovers the activity of “accounting” for which both practices are employed across action-types; specifically, “assessments”, “complaints” and “teases”. The central objective of this thesis thus concerns the “respecification” of social class as a “members’ phenomenon”; one that is made relevant within ordinary instances of talk-in-interaction through a stable set of interactional practices in order to accomplish a diverse range of practical tasks. The thesis concludes with a review of several candidate lines of analysis for future EM/(M)CA inquiry that are anticipated by the findings of this research uniquely

An experimental and theoretical investigation of deposition patterns from an agricultural airplane

A flight test program has been conducted with a representative agricultural airplane to provide data for validating a computer program model which predicts aerially applied particle deposition. Test procedures and the data from this test are presented and discussed. The computer program features are summarized, and comparisons of predicted and measured particle deposition are presented. Applications of the computer program for spray pattern improvement are illustrated

Flight evaluation of an advanced technology light twin-engine airplane (ATLIT)

Project organization and execution, airplane description and performance predictions, and the results of the flight evaluation of an advanced technology light twin engine airplane (ATLIT) are presented. The ATLIT is a Piper PA-34-200 Seneca I modified by the installation of new wings incorporating the GA(W)-1 (Whitcomb) airfoil, reduced wing area, roll control spoilers, and full span Fowler flaps. The conclusions for the ATLIT evaluation are based on complete stall and roll flight test results and partial performance test results. The Stalling and rolling characteristics met design expectations. Climb performance was penalized by extensive flow separation in the region of the wing body juncture. Cruise performance was found to be penalized by a large value of zero lift drag. Calculations showed that, with proper attention to construction details, the improvements in span efficiency and zero lift drag would permit the realization of the predicted increases in cruising and maximum rate of climb performance