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NASA NTRS1999

TCA High Lift Preliminary Assessment

This paper presents a TCA (Technology Concept Airplane) High lift Preliminary Assessment. The topics discussed are: 1) Model Description; 2) Data Repeatability; 3) Effect of Inboard L.E. (Leading Edge) Flap Span; 4) Comparison of 14'x22' TCA-1 With NTF (National Transonic Facility) Modified Ref. H; 5) Comparison of 14'x22' and NTF Ref. H Results; 6) Effect of Outboard Sealed Slat on TCA; 7) TCA Full Scale Build-ups; 8) Full Scale L/D Comparisons; 9) TCA Full Scale; and 10) Touchdown Lift Curves. This paper is in viewgraph form.

Wyatt, G. H.↗

NASA NTRS2003

CFD Variability for a Civil Transport Aircraft Near Buffet-Onset Conditions

A CFD sensitivity analysis is conducted for an aircraft at several conditions, including flow with substantial separation (buffet onset). The sensitivity is studied using two different Navier-Stokes computer codes, three different turbulence models, and two different grid treatments of the wing trailing edge. This effort is a follow-on to an earlier study of CFD variation over a different aircraft in buffet onset conditions. Similar to the earlier study, the turbulence model is found to have the largest effect, with a variation of 3.8% in lift at the buffet onset angle of attack. Drag and moment variation are 2.9% and 23.6%, respectively. The variations due to code and trailing edge cap grid are smaller than that due to turbulence model. Overall, the combined approximate error band in CFD due to code, turbulence model, and trailing edge treatment at the buffet onset angle of attack are: 4% in lift, 3% in drag, and 31% in moment. The CFD results show similar trends to flight test data, but also exhibit a lift curve break not seen in the data.

Rumsey, Christopher L.↗

NASA NTRS2015

Description, Usage, and Validation of the MVL-15 Modified Vortex Lattice Analysis Capability

MVL-15 is the most recent version of the Modified Vortex-Lattice (MVL) code developed within the Aerodynamics Systems Analysis Branch (ASAB) at NASA LaRC. The term "modified" refers to the primary modification of the core vortex-lattice methodology: inclusion of viscous aerodynamics tables that are linked to the linear solution via iterative processes. The inclusion of the viscous aerodynamics inherently converts the MVL-15 from a purely analytic linearized method to a semi-empirical blend which retains the rapid execution speed of the linearized method while empirically characterizing the section aerodynamics at all spanwise lattice points. The modification provides a means to assess non-linear effects on lift that occur at angles of attack near stall, and provides a means to determine the drag associated with the application of design strategies for lift augmentation such as the use of flaps or blowing. The MVL-15 code is applicable to the analyses of aircraft aerodynamics during cruise, but it is most advantageously applied to the analysis of aircraft operating in various high-lift configurations. The MVL methodology has been previously conceived and implemented; the initial concept version was delivered to the ASAB in 2001 (van Dam, C.), subsequently revised (Gelhausen, P. and Ozoroski, T. 2002 / AVID Inc., Gelhausen, P., and Roberts, M. 2004), and then overhauled (Ozoroski, T., Hahn, A. 2008). The latest version, MVL-15 has been refined to provide analysis transparency and enhanced to meet the analysis requirements of the Environmentally Responsible Aviation (ERA) Project. Each revision has been implemented with reasonable success. Separate applications of the methodology are in use, including a similar in-house capability, developed by Olson, E. that is tailored for structural and acoustics analyses. A central premise of the methodology is that viscous aerodynamic data can be associated with analytic inviscid aerodynamic results at each spanwise wing section, thereby providing a pathway to map viscous data to the inviscid results. However, a number of factors can sidetrack the analysis consistency during various stages of this process. For example, it should be expected that the final airplane lift curve and drag polar results depend strongly on the geometry and aerodynamics of the airfoil section; however, flap deflections and flap chord extensions change the local reference geometry of the input airfoil, the airplane wing, the tabulated non-dimensional viscous aerodynamics, and the spanwise links between the linear and the viscous aerodynamics. These changes also affect the bound circulation and therefore, calculation and integration of the induced angle of attack and induced drag. MVL-15 is configured to ensure these types of challenges are properly addressed. This report is a comprehensive manual describing the theory, use, and validation of the MVL-15 analysis tool. Section 3 summarizes theoretical, procedural, and characteristic features of MVL-15, and includes a list of the files required to setup, execute, and summarize an analysis. Section 4, Section 5, Section 6, and Section 7 combine to comprise the User's Guide portions of this report. The MVL-15 input and output files are described in Section 4 and Section 5, respectively; the descriptions are supplemented with example files and information about the file formats, parameter definitions, and typical parameter values. Section 6 describes the Wing Geometry Setup Utility and the 2d-Variants Utility files that simplify and assist setting up a consistent set of MVL-15 geometry and aerodynamics input parameters and input files. Section 7 describes the use of the 3d-Results Presentation Utility file that can be used to automatically create summary tables and charts from the MVL-15 output files. Section 8 documents the Validation Results of an extensive and varied validation test matrix, including results of an airplane analysis representative of the ERA Program. A start-to-finish example of the airplane analysis procedure is described in Section 7.

Ozoroski, Thomas A.↗

NASA NTRS2018

Computational Investigation of Nominally-Orthogonal Pneumatic Active Flow Control for High-Lift Systems

We explore the feasibility of using nominally-orthogonal jets as active aerodynamic load control for multi-element high-lift systems, and whether the nominally-orthogonal jets can offer a variety of performance improvements. These nominally-orthogonal jets inject momentum normal to the airfoil surface near the flap trailing edge, where they create a vortex that entrains flow from the opposing side and change the airfoil circulation. Lift-enhancement opportunities of trailing edge nominally-orthogonal jets have previously been studied by Malavard et al. and Blaylock et al. on single-element airfoils; however, their effect on drag was not thoroughly investigated. In this study, we investigate two- dimensional nominally-orthogonal jet effects on both lift and drag on a two-element airfoil, NLR7301. We utilize Chimera Grid Tools to generate structured curvilinear overset grids, and the Reynolds-averaged Navier-Stokes solver OVERFLOW-2 to solve for the flow field around the airfoil. We perform various computational sensitivity studies on the baseline airfoil without a jet to validate computational results against benchmark experimental data. Using a Chimera overset grid topology, we demonstrate a similar lift-enhancement effect between a nominally-orthogonal jet and a nominally-orthogonal physical tab employed at the same location on the studied airfoil. After we introduce the nominally-orthogonal jet concept, we investigate nominally-orthogonal jets with various momentum coefficient settings, C(sub µ) = 0.00 − 0.04 and present a lift-enhancement relationship ∆C(sub l) ≃ 3.59 (C(sub µ)) for this airfoil. We discuss that utilizing a nominally-orthogonal jet with C(sub µ) = 0.01 can shift the linear region of the lift curve by a ∆C(sub l) = 0.36 for the pressure side jet and by a ∆C(sub l) = −0.27 for the suction side jet. Employing a nominally-orthogonal jet is also shown effective in altering the drag. To study the impact, we carry out a drag decomposition study in the form of drag polars. We show for a given C(sub l) = 2.50, a nominally-orthogonal jet with C(sub µ) = 0.01 on the pressure and suction side of the airfoil results in 113 drag count decrements and 41 drag count increments, respectively, compared to the baseline airfoil with no jet. These results show that large and controllable changes in aerodynamic performance can be achieved by relatively small active flow control inputs using the nominally-orthogonal jets presented in this study.

Nominally-Orthogonal↗

NASA NTRS2020

Computational Simulations of a Mach 0.745 Transonic Truss-Braced Wing Design

A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data. The fidelity of the computational representation of the wind tunnel experiment, such as utilizing a porous wall boundary condition to model the ventilated test section, was varied to examine how different tunnel effects influence CFD predictions. LAVA and USM3D results both show an approximate 0.5 angle of attack shift from experimental lift curve data. This drove an investigation that revealed that the trailing edge of the experimental model was rounded in comparison to the CAD model, due to manufacturing tolerances, which had not been accounted for in the initial simulations of the experiment. Simulating the TTBW with an approximation of this rounded trailing-edge reduces error by approximately 60%. An accurate representation of the tested TTBW geometry, ideally including any wing twists and deflections experienced during the test under various loading conditions, will be necessary for proper validation of the CFD.

Maldonado, Daniel↗

NASA NTRS2020

Computational Simulations of a Mach 0.745 Transonic Truss-Braced Wing Design

A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data. The fidelity of the computational representation of the wind tunnel experiment, such as utilizing a porous wall boundary condition to model the ventilated test section, was varied to examine how different tunnel effects influence CFD predictions. LAVA and USM3D results both show an approximate 0.5o angle of attack shift from experimental lift curve data. This drove an investigation that revealed that the trailing edge of the experimental model was rounded in comparison to the CAD model, due to manufacturing tolerances, which had not been accounted for in the initial simulations of the experiment. Simulating the TTBW with an approximation of this rounded trailing-edge reduces error by approximately 60%. An accurate representation of the tested TTBW geometry, ideally including any wing twists and deflections experienced during the test under various loading conditions, will be necessary for more thorough validation of the CFD.

Maldonado, Daniel↗

NASA NTRSDate not supplied

The Effects of Freestream Turbulence on Wing-Gust Interactions

There is a growing interest in the experimental study of discrete vertical gusts motivated by the proliferation of small Uncrewed Air Systems. However, gusts are not the only unsteady flow disturbances that these vehicles are expected to encounter. Freestream turbulence is also a serious consideration. Previous work has indicated that freestream turbulence has significant effects on the flow around airfoils, so this work investigates the interaction of these two unsteady flow disturbances. Airfoils are pitched to mimic the flow angle change caused by a gust at different levels of incoming freestream turbulence. The lift generated during the gust encounters with elevated incoming freestream turbulence show that the effects on the performance of the airfoil are dependent on the turbulence intensity. Low turbulence intensity has beneficial effects, delaying stall and increasing the maximum lift, whereas higher freestream turbulence intensity delays stall without a corresponding increase in the maximum lift. A preliminary investigation of 15-trial ensemble-averaged flow fields suggests that freestream turbulence dominates the flow, but the flow features associated with the dynamic lift seen in the "clean" case are still somewhat present. However, lift curves and flow fields from individual trials indicates that the turbulence increases the unsteadiness in the interaction, but the general trends are dominated by the gust interaction. Further work is still needed to better determine the flow physics of these interactions and the interplay between repeatable and stochastic flow phenomena.

Unsteady Aerodynamics↗

NASA NTRSDate not supplied

Sensitivity Analysis for Takeoff and Landing Distance Parameters for Regional Air Mobility (RAM) Aircraft

Takeoff and landing performance models require low-speed aerodynamic and thrust characteristics that are difficult to predict in the conceptual design stage. Although an empirical approach can be utilized to predict takeoff and landing performance, this approach is inadequate for aircraft incorporating novel technologies and design such as those proposed for regional air mobility aircraft. The focus of this paper is to understand the sensitivity of takeoff and landing distance to aerodynamic, propulsive, and other parameters of interest for regional air mobility class vehicles. The aerodynamic and propulsive characteristics are generated and modified using simplified approximations based on fundamental physics and integrated into the equations of motion to calculate takeoff and landing distances. The most impactful parameters for takeoff and landing were those related to propulsion and the lift curve. Additional impactful parameters for landing included braking coefficient, approach angle, and wing incidence. Lesser impact was observed for the parameters describing the low-speed drag polar.

Gabino Martinez Rodriguez↗

NASA NTRS1981

Flight-test evaluation of STOL control and flight director concepts in a powered-lift aircraft flying curved decelerating approaches

Flight tests were carried out to assess the feasibility of piloted steep curved, and decelerating approach profiles in powered lift STOL aircraft. Several STOL control concepts representative of a variety of aircraft were evaluated in conjunction with suitably designed flight directions. The tests were carried out in a real navigation environment, employed special electronic cockpit displays, and included the development of the performance achieved and the control utilization involved in flying 180 deg turning, descending, and decelerating approach profiles to landing. The results suggest that such moderately complex piloted instrument approaches may indeed be feasible from a pilot acceptance point of view, given an acceptable navigation environment. Systems with the capability of those used in this experiment can provide the potential of achieving instrument operations on curved, descending, and decelerating landing approaches to weather minima corresponding to CTOL Category 2 criteria, while also providing a means of realizing more efficient operations during visual flight conditions.

Hindson, W. S.↗

NASA NTRS1987

Numerical analysis of a NACA0012 airfoil with leading edge ice accretions

Analysis of a NACA0012 airfoil with leading edge ice has been performed using a Navier-Stokes code coupled with a grid generation code. The computed results were compared to experimental information obtained for an airfoil with a well defined artificial ice shape. The computations were performed at angles of attack ranging from zero to ten degrees. This range is sufficient to show the development of the separation bubble aft of the ice shape on both the upper and lower surfaces. Velocity profile plots in the separation bubble are examined in order to determine if recirculation patterns are predicted properly and if separation and reattachment points are found within the resolution of the experimental information. Also, the massive separation near the point of stall is examined in order to more accurately evaluate the lift coefficient curve in that region. Lift, drag, and moment coefficients are computed and compared to experiment.

Potapczuk, Mark G.↗

NASA NTRS1975

Theoretical aerodynamics of upper-surface-blowing jet-wing interaction

A linear, inviscid subsonic compressible flow theory is formulated to treat the aerodynamic interaction between the wing and an inviscid upper-surface-blowing (USB) thick jet with Mach number nonuniformity. The predicted results show reasonably good agreement with some available lift and induced-drag data. It was also shown that the thin-jet-flap theory is inadequate for the USB configurations with thick jet. Additional theoretical results show that the lift and induced drag were reduced by increasing jet temperature and increased by increasing jet Mach number. Reducing jet aspect ratio, while holding jet area constant, caused reductions in lift, induced drag, and pitching moment at a given angle of attack but with a minimal change in the curve of lift coefficient against induced-drag coefficient. The jet-deflection effect was shown to be beneficial to cruise performance. The aerodynamic center was shifted forward by adding power or jet-deflection angle. Moving the jet away from the wing surface resulted in rapid changes in lift and induced drag. Reducing the wing span of a rectangular wing by half decreased the jet-circulation lift by only 24 percent at a thrust coefficient of 2.

Lan, C. E.↗

NASA NTRS1981

Comparisons of AEROX computer program predictions of lift and induced drag with flight test data

The AEROX aerodynamic computer program which provides accurate predictions of induced drag and trim drag for the full angle of attack range and for Mach numbers from 0.4 to 3.0 is described. This capability is demonstrated comparing flight test data and AEROX predictions for 17 different tactical aircraft. Values of minimum (skin friction, pressure, and zero lift wave) drag coefficients and lift coefficient offset due to camber (when required) were input from the flight test data to produce total lift and drag curves. The comparisons of trimmed lift drag polars show excellent agreement between the AEROX predictions and the in flight measurements.

Axelson, J.↗

NASA NTRS1960

An Analysis of the Corridor and Guidance Requirements for Supercircular Entry into Planetary Atmospheres

An analysis is presented of supercircular entry into a planet's atmosphere giving particular attention to the corridor through which spacecraft must be guided in order to accomplish various maneuvers. A dimensionless parameter based on conditions at the conic perigee altitude is introduced for characterizing supercircular entries and conveniently pre-scribing corridor widths associated with elliptic, parabolic, or hyperbolic approach trajectories. The analysis applies to vehicles of arbitrary weight, shape, and size. Illustrative calculations are made for Venus, Earth, Mars, Jupiter, and Titan. For nonlifting vehicles having fixed aerodynamic coefficients, curves are presented of dimensionless parameters from which can be calculated the maximum deceleration, maximum rate of laminar convective heating, and total laminar heat absorbed during single-pass entry at velocities up to twice circular velocity. For lifting vehicles, curves are presented of the maximum deceleration and overshoot boundary of an entry corridor; equations are presented for estimating laminar aerodynamic heating from the maximum deceleration. It is shown that the corridor width is independent of vehicle weight, dimensions, and drag coefficient, provided these are the same at the overshoot boundary as at undershoot. The corridors of certain planets can be broadened markedly by the application of aerodynamic lift; for example, the 10-earth-g corridor width for single- pass, nonlifting, parabolic entry is increased from 0 miles for Jupiter, 7 for Earth, and 8 for Venus, to 52, 51, and 52 miles, respectively, by employing a lift-drag ratio of 1. The use of aerodynamic lift does not increase appreciably the corridors of Mars and Titan. All corridor widths decrease rapidly as the entry velocity is increased. Terminal guidance requirements on accuracy of velocity and flight path angle for successfully entering various corridors are compared with analogous requirements for putting a satellite into orbit, for hitting the moon from the earth, and for achieving ICBM accuracy. Consideration is given to the terminal guidance problem involved in using a planet's atmosphere-rather than rocket fuel-to effect orbital transfers from heliocentric to planetocentric motion, thereby converting a hyperbolic approach trajectory to an elliptic orbit about the target planet. This fuel saving maneuver appears technologically feasible for certain planetary voyages, and implies the possibility of achieving a large reduction in required Earth lift-off weight of chemical propulsion systems.

Chapman, Dean R.↗

NASA NTRS1977

Determination of longitudinal aerodynamic derivatives from steady-state measurement of an aircraft

A method for the estimation of aerodynamic derivatives from steady-state symmetric flight data is developed. The derivatives considered are the longitudinal static stability and control derivatives, damping derivatives due to tail, and the derivatives expressing the speed effect on the lift and pitching moment coefficients. The method is an extension of the well known theory of longitudinal static stability and control, and corresponding flight data interpretation. Measured data is assumed in the form of trim curves and lift vs angle of attack. The expressions for the derivative estimates are in the form of algebraic relationships containing known constants, and directly or indirectly measured quantities.

Klein, V.↗

NASA NTRS1994

Computation of wind tunnel wall effects for complex models using a low-order panel method

A technique for determining wind tunnel wall effects for complex models using the low-order, three dimensional panel method PMARC (Panel Method Ames Research Center) has been developed. Initial validation of the technique was performed using lift-coefficient data in the linear lift range from tests of a large-scale STOVL fighter model in the National Full-Scale Aerodynamics Complex (NFAC) facility. The data from these tests served as an ideal database for validating the technique because the same model was tested in two wind tunnel test sections with widely different dimensions. The lift-coefficient data obtained for the same model configuration in the two test sections were different, indicating a significant influence of the presence of the tunnel walls and mounting hardware on the lift coefficient in at least one of the two test sections. The wind tunnel wall effects were computed using PMARC and then subtracted from the measured data to yield corrected lift-coefficient versus angle-of-attack curves. The corrected lift-coefficient curves from the two wind tunnel test sections matched very well. Detailed pressure distributions computed by PMARC on the wing lower surface helped identify the source of large strut interference effects in one of the wind tunnel test sections. Extension of the technique to analysis of wind tunnel wall effects on the lift coefficient in the nonlinear lift range and on drag coefficient will require the addition of boundary-layer and separated-flow models to PMARC.

Ashby, Dale L.↗

DOE OSTI2024

Leaf gas exchange, leaf water potential and spectral reflectance, BIONTE, Brazil, 2023

Leaf traits measured at the top of the canopy on 30 tree species in the BIONTE experimental forest, near Manaus, Brazil, at three time points during August to November, 2023. The aim of this study was to test the relationship between leaf water use efficiency and wood density. Leaf gas exchange was measured on top-of-canopy leaves accessed by an articulated boom lift. Response curves (A-Ci and A-Q), and dark adapted respiration were measured on cut branches. Survey gas exchange measurements were performed on attached leaves at various times during the day. Following gas exchange, leaves were harvested, and measured for leaf water potential and spectral reflectance. Data in this data package is presented in csv files, with metadata in csv and descriptive experimental protocols as pdf. Gas exchange data and metadata meets the requirements of the ESS-DIVE reporting format for leaf-level gas exchange data and metadata.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1990

Patterns of vortex shedding from an oscillating circular cylinder

Vortex shedding from an oscillating circular cylinder was numerically investigated at Re = 100 with the Navier-Stokes equations and the new boundary conditions. The detailed shedding patterns are characterized by means of streakline plotting and lift-coefficient curves. A parameter map is presented which distinguishes the synchronized shedding from the asynchronous and the double vortices shedding from the single vortex shedding. The computational result is in good agreement with earlier experimental results.

Chang, Keun-Shik↗

NASA NTRS1992

Vortex trapping on a 60 degree delta wing

An experiment was conducted to examine the vortex trapping concept on a 60 deg sweep delta wing at low angles of attack. Using tapered leading edge fences, stable vortices have been successfully trapped. The resulting increase in lift coefficient can be as high as 0.4, which amounts to a 6.5 deg shift in the lift coefficient curve of the delta wing. The corresponding increase in drag coefficient, however, is also significant.

Buchholz, Mark D.↗