Drew Landman

The incorporation of experimental test data into the optimization process is accomplished through the use of Bayesian-validated surrogates. In the surrogate approach, a surrogate for the experiment (e.g., a response surface) serves in the optimization process. The validation step of the framework provides a qualitative assessment of the surrogate quality, and bounds the surrogate-for-experiment error on designs "near" surrogate-predicted optimal designs. The utility of the framework is demonstrated through its application to the experimental selection of the trailing edge flap position to achieve a design lift coefficient for a three-element airfoil.

A wind tunnel test program was conducted at the Langley Full Scale Tunnel (LFST) to evaluate the performance of five passive drag reduction configurations on a modern straight truck at full scale. Configurations were tested in a build-up fashion with results representing a cumulative effect. Tested configurations include a front valance, a front box fairing, a boat-tail, an ideal side-skirt, and a practical side-skirt. Configurations were evaluated over a nominal 9 degree yaw sweep to establish wind averaged drag coefficients using SAE J1252. Genuine replicate yaw sweeps were used in an uncertainty analysis. Results show up to 28% improvement in wind-averaged drag coefficient and that significant gains can be made in straight truck fuel economy, even at non-highway speeds. INTRODUCTION Aerodynamic performance in commercial trucks is becoming increasingly more important due to fuel costs as well as pressures due to environmental concerns. Currently the literature primarily contains i...

Ships produce vortices and air-wakes while either underway or stationary in a wind. These flow fields can be detrimental to the conduction of air operations in that they can adversely impact the air vehicles and flight crews. There are potential solutions to these problems for both frigates/destroyers and carriers through the use of novel vortex flow or flow control devices. This appendix highlights several devices which may have application and points out that traditional wind-tunnel testing using smoke, laser-vapor screen, and Particle Image Velocimetry can be useful in sorting out the effectiveness of different devices.

The problem of efficient wind tunnel testing for multi-element airfoils was first addressed by the author during a previous ASEE fellowship. A modern three element model with internal actuators to position a flap in two degrees of freedom was designed and later built. Some preliminary testing proved that the approach was viable. The purpose of this summer's work was to fully develop experimental methods including efficient data acquisition. The final goal is to develop dense data sets for both lift and drag measurements as a function of flap position for both take-off and landing configurations. The model has a span of 36 in. and chord of 18 in. and is currently being fitted for a 3 ft. x 4 ft. low speed wind tunnel. The flap was reworked to allow all pressure taps to function after initial tests showed two blocked ports. The serial method of obtaining pressures from the surface taps was found to be exceedingly slow so a new method using 12 pressure transducers and a 12 port par...

Four Wright brothers’ propellers have been carefully reproduced by The Wright Experience for the purpose of measuring their performance using modern instrumentation. Reproductions of a 1903 Flyer propeller, a 1904 ‘Le Mans’ propeller, and two circa 1910 ‘bent end’ propellers have been manufactured, duplicating materials, construction and dimensional geometry. As evidenced by the correlation between static thrust measurements reported originally by the Wright brothers and our recent measurements in Old Dominion University’s Langley Full Scale Tunnel, the propeller reproductions match the static thrust performance of the original propellers to within experimental accuracy. Using modern instrumentation, it has been possible to measure the overall performance of these propeller reproductions covering their full speed ranges. Our tests have shown that the 1903 Wright propeller had a peak efficiency greater than 80 percent (Wilbur appears to have estimated its efficiency to be 66 percent)...

A detailed flow survey of the test section of the Langley Full-Scale Tunnel is described. Flow angularity, dynamic pressure, and turbulence intensity were measured in the test section volume over a matrix with three foot spacing. Instrumentation consisted of a rake of four five hole probes and two hot-wire anemometers. Details of probe calibration, installation, and use are presented in addition to survey results. Facility Description Old Dominion University (ODU), working under a Memorandum of Agreement with NASA Langley Research Center, has operated the Langley Full-Scale Tunnel (LFST) since 1997. This facility is the second largest in the United States in terms of test section size and is the largest university run wind tunnel in the world. During its seventy years of service, a wide variety of aerospace test programs have been undertaken. Sub-scale model testing has included high angle of attack testing of current U.S. front-line fighters, high-lift systems on supersonic and subsonic transports, parachutes, and even an airship, submarine, and building complex. Recently testing has included fullscale automobiles, trucks, and UAVs. The open jet test section of the LFST (formerly the NASA 30 by 60) is semi-elliptical in cross section with a width of 60 ft and a height of 30 ft as shown in figure I. The elevated ground board is 42.5 ft wide by 52.3 ft long and features a turntable with a diameter of 28.5 ft. * Graduate Research Assistant Student Member AIAA t Associate Professor of Aerospace Engineering, Senior Member AIAA Copyright © 2002 by the American Institute of Aeronautics and Astronautics, Inc. Power is supplied by two 4000 HP electric motors driving two 35.5 ft diameter fourbladed fans. The dual return tunnel circuit design has a nozzle contraction ratio of approximately 5:1, and no flow conditioning devices such as honeycombs or screens anywhere in the circuit. The test section ground board and balance shield represent the only major modifications to the circuit since the commissioning of the facility. Introduction The large test section and open jet design are ideal for testing large models and UAVs with negligible boundary effects. Special vents provide fresh air exchange, useful when testing with power on. There are two model aircraft support systems available depending on size and weight. Both systems allow a 100° angle of attack sweep and a ±90° yaw sweep. A large scale x-y-z traverse (survey carriage) can be used to position a second model or survey probes in the test section. Interest in a modern flow survey originally stemmed from a planned NASA Blended Wing Body (BWB) test using a large scale model. There have been several flow surveys in the history of the tunnel and much folklore surrounding the flow quality on the tunnel centerline.'' The merging streams of the dual return design were thought to have created a measureable shear layer on the centerline with an elevated turbulence intensity. This report describes the flow quality in the Langley Full-Scale Tunnel (LFST) in terms of flow angularity, dynamic pressure and turbulence intensity. Aerodynamic flow field surveys were made over the entire test section volume. The instrumentation consisted of four five hole hemispherical-head probes for dynamic pressure and flow angularity measurements, two constant-temperature hot-wire anemometers for 1 American Institute of Aeronautics and Astronautics (c)2002 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.

Flight testing using a designed experiment was used to model pitch damping in the longitudinal shortperiod mode of an aircraft. Multi-step elevator maneuvers were flown at different angles of attack and power levels on an electrically powered, propeller-driven UltraStick 120 remotely controlled model. A Central Composite Response Surface Design was used to select angle of attack and power levels for each maneuver. During post flight analysis it was discovered that power was not measured correctly for this purpose so advance ratio was selected as a replacement factor. Parameter estimation results for each maneuver were modeled globally using a single response surface. This experiment allowed global modeling of the pitch damping to be performed from just a few flight test maneuvers. Identified global models of pitch damping are plotted against angle of attack and advance ratio in a surface response plot, for non-linear piloted simulations and for flight test data.

Wind tunnel tests of a Wright Model B airfoil have been conducted using two-dimensional models in full and third-scale at flight Reynolds numbers. In an effort to ascertain the effect of rib and covering construction on airfoil aerodynamics, the full-scale model was fabric covered and maintained the original dimensions of the Wright Model B Flyer wing. Since the full-scale model could only be tested over a small angle-of-attack range, a solid surface, third-scale pressure model was constructed. Lift and pitching moment polars from the tests are presented over a range of angles-of-attack spanning zero-lift to post stall. A drag polar is presented for an angle-of-attack range from -4 to 6 degrees. Surface static pressure distributions are presented from the third-scale model. Flow visualization study results are presented from surface mounted tufts on both models and are used to corroborate force and pressure data findings.

Candidate passive flow control devices were chosen from a NASA flow visualization study to investigate their effectiveness at improving flow quality over a flat-top carrier model. Flow over the deck was analyzed using a particle image velocimeter and a 1/120th scaled carrier model in a low-speed wind tunnel. Baseline (no devices) flow quality was compared to flow quality from combinations of bow and deck-edge devices at both zero and 20 degrees yaw. Devices included plain flaps and spiral cross-section columnar vortex generators attached in various combinations to the front and sides of the deck. Centerline and cross plane measurements were made with velocity and average turbulence measurements reported. Results show that the bow/deck-edge flap and bow/deck-edge columnar vortex generator pairs reduce flight deck turbulence both at zero yaw and at 20 degrees yaw by a factor of approximately 20. Of the devices tested, the most effective bow-only device appears to be the plain flap.

A research program to investigate helicopter downwash/frigate airwake interaction has been initiated using a statistically robust experimental program featuring Design of Experiments. Engineering analysis of the helicopter/frigate interface is complicated by the fact that two flowfields become inherently coupled as separation distance decreases. The work presented was performed in the Old Dominion University Low Speed Wind Tunnel using a simplified 1/50 scale frigate waterline model and traverse mounted powered rotor with thrust measurement. Initially, PIV surveys of the frigate model landing deck in isolation and the rotor in isolation were performed to provide a baseline flow understanding. Next a designed experiment was devised yielding a response model for thrust coefficient as a function of vertical and longitudinal distance from the hangar door (base of the step), both with and without the rotor. This first experiment showed that thrust coefficient could be measured with enoug...

Engineers with experience in ground test can attest that, although the confines of wind tunnels permit low noise testing, what is lacking many times are efficient test plans and the full use of the massive amount of data collected. From the perspective of industrial statisticians and engineers specializing in efficient design of experiments via statistical methods, the wind tunnel environment offers unique challenges for determining a bestpractices approach to test design. Both variants of practitioners have realized the benefit of adapting classical statistically-based experimental design techniques to wind tunnel testing. With this general approach to test, the number of tests required is significantly reduced, the true underlying cause/effect relationship between aircraft configuration and aerodynamic performance is realized and uncertainty can be precisely determined in the presence of testing condition alterations. This paper makes use of case studies to discuss and illustrate the conditions common in low-speed wind tunnel testing which require adaptations to standard experimental design application. Remedies for each of these conditions based on methods successfully used elsewhere are provided.

The current approach used to apply uncertainty intervals to balance estimated loads is based on the root mean square error from calibration. Using the root mean square error, a constant interval is applied around the estimated load and it is expected that a predetermined percentage of the check-loads applied fall within this constant uncertainty interval. However, this approach ignores additional sources of uncertainty and assumes constant uncertainty regardless of the load combination and magnitude applied to the balance. Rigorous prediction interval theory permits varying interval widths but fails to account for the additional error sources that are unrelated to the mathematical modeling. An engineered solution is proposed that combines prediction interval theory and the need to account for the additional sources of uncertainty from calibration and check loading. Results from a case study using the in-situ load system show improved probabilistic behavior in terms of uncertainty interval capture percenta...

A research program to investigate helicopter downwash and frigate airwake interaction has been initiated using a statistically robust experimental program featuring design of experiments. Engineering analysis of the helicopter/frigate interface is complicated by the fact that two flow fields become inherently coupled as a separation distance decreases. The work presented was performed in the Old Dominion University 7 × 8 ft Low-Speed Wind Tunnel using a simplified 1/50-scale frigate waterline model and traverse-mounted powered rotor with thrust measurement capability. Particle image velocimetry velocity surveys were acquired with rotor thrust coefficient measurements at coincident locations to help understand the underlying flow physics.

Commercial heavy trucks are characterized as bluffbodies and have unsteady wake flows and high base drag. Base drag has been studied for many years as a primary target for aerodynamic drag reduction. Many aftend devices have been created for active or passive reduction of ...

A road simulation system has been developed at the Langley Full-Scale Tunnel (LFST) to support the aerodynamic testing of road vehicles, particularly NASCARclass race cars. The leading edge of the existing ground board was recontoured to alleviate a separation bubble and an active suction boundary layer control system, incorporating a bleed slot and axial flow blower, has been implemented. Performance evaluations include boundary layer surveys at various locations in the vicinity of the car balance with the empty tunnel as well as force measurements with a representative vehicle both with and without the boundary layer control system operating.