Use of Superposition in Digital Computers to Obtain Wind-tunnel Interference Factors for Arbitrary Configurations, with Particular Reference to V/STOL Models


Book Description

A superposition method utilizing a digital computer is developed to obtain wall interference for arbitrary configurations. A variety of specific configurations are treated. Sample numerical results indicate that a large number of variables, such as wind-tunnel configuration, model configuration, wake deflection, model location, span of wing and tail, load distribution, sweep, angle of attack, pivot location, tail length, and tail height, may individually or collectively produce substantial effects on wall interference. Interference is particularly severe at the rear rotor of tandem systems; the maximum size of such systems for reasonable wall effects is discussed.







NASA Technical Report


Book Description




Approximate Treatment of V/STOL Wall Interference for Closed Circular Tunnels


Book Description

An approximate treatment of V/STOL wall interference in a circular tunnel indicates that the interference factors at the model for this tunnel should be of the same order of magnitude as those presently available for a square tunnel of equal cross-sectional area. There is a greater degree of uncertainty with respect to the lateral and longitudinal distributions of interference; however, the available results for the square tunnel should be reasonably close to those of the circular tunnel provided that the model is relatively small in comparison with the test section.




Low-Speed Wind Tunnel Testing


Book Description

A brand-new edition of the classic guide on low-speed wind tunnel testing While great advances in theoretical and computational methods have been made in recent years, low-speed wind tunnel testing remains essential for obtaining the full range of data needed to guide detailed design decisions for many practical engineering problems. This long-awaited Third Edition of William H. Rae, Jr.'s landmark reference brings together essential information on all aspects of low-speed wind tunnel design, analysis, testing, and instrumentation in one easy-to-use resource. Written by authors who are among the most respected wind tunnel engineers in the world, this edition has been updated to address current topics and applications, and includes coverage of digital electronics, new instrumentation, video and photographic methods, pressure-sensitive paint, and liquid crystal-based measurement methods. The book is organized for quick access to topics of interest, and examines basic test techniques and objectives of modeling and testing aircraft designs in low-speed wind tunnels, as well as applications to fluid motion analysis, automobiles, marine vessels, buildings, bridges, and other structures subject to wind loading. Supplemented with real-world examples throughout, Low-Speed Wind Tunnel Testing, Third Edition is an indispensable resource for aerospace engineering students and professionals, engineers and researchers in the automotive industries, wind tunnel designers, architects, and others who need to get the most from low-speed wind tunnel technology and experiments in their work.










NASA Technical Note


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General Theory of Wall Interference for Static Stability Tests in Closed Rectangular Test Sections and in Ground Effect


Book Description

A theory is developed which predicts the interference velocities and interference velocity gradients caused by the walls of the tunnel. Large wake deflections are allowed in both the lateral and vertical directions. The theory includes V/STOL and conventional wall-interference theories and ground effect as special cases. Symmetry and interchange relationships between the interference factors are developed and extensive numerical results are presented. Use of the interference factors to correct data depends upon the availability of detailed aerodynamic treatments in nonuniform flow of the model under test. In most tests the available aerodynamic treatments will be found either inadequate or too time consuming for rigorous routine correction of data relating to lateral-directional stability.




Theoretical Study of Conditions Limiting V/STOL Testing in Wind Tunnels with Solid Floor


Book Description

Under sufficiently large wake deflections, the forward portion of the wake is found to flow forward along the floor leading to a vortex pattern which results in Rae's limits (Journal of Aircraft, May-June 1967). Although wind-tunnel data cannot normally be corrected successfully beyond these limits, it may be possible to obtain ground-effect data for conditions more severe than those implied by Rae.