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Report No. 478, Experimental verification of the theory of wind tunnel boundary interference
274
BOOK REVIEWS.
[J. F. I.
Last but not least is a consideration of the Human Factor. An observer exercises both judgment and physical action when manipulating an instrument. Human judgment is influenced by irrelevant as well as relevant sensations, and it is the task of the instrument maker to keep all irrelevant factors at a minimum if reasonable accuracy is to be expected. A llst of possible psychologically disturbing factors is given. The matter of physical action also receives respi~ctful attention. The most accurate adjustments are made by the smoothest working controls. Smooth action also prevents muscular fatigue and its attendant psychological repercussions. T. K. CLEVELAND. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
Report No. 478, Experimental Verification of the Theory of Wind Tunnel Boundary Interference, by Theodore Theodorsen and Abe Silverstein. I7 pages, illustrations, 23 X 29 cms. Washington, Superintendent of Documents, I934. Price ten cents. The results of an experimental investigation on the boundary-correction factor, conducted at the N. A. C. A. laboratories at Langley Field, Va., are presented in this report. The values of the boundary-correction factor from the theory, which at the present time is virtually completed, are given in the paper ;for all conventional types of tunnels. With the isolation of certain disturbing effects, the experimental boundarycorrection factor was found to be in satisfactory agreement with the theoretically predicted values, thus verifying the soundness and sufficiency of the theoretical analysis. The establishment of a considerable velocity distortion, in the nature of a unique blocking effect, constitutes a principal result of the investigation. The major portion of the investigation was carried on in the N. A. C. A. fullscale wind tunnel, which afforded the unusual opportunity of a direct comparison with flight results as a final verification. Report No. 480, The Aerodynamic Effects of Wing Cut-Outs, by Albert Sherman, 8 pages, illustrations, 33 X 29 cms. Washington, Superintendent of Documents, I934. Price five cents. In connection with the interference program being conducted in the N. A. C. A. varlable-denslty wind tunnel, an analysis was made of available material with the object of presenting a qualitative discussion of wing characteristics as affected by cut-outs and of determining means for their quantitative calculation. The analysis indicated that extending a cut-out in the chord direction has much greater effect than extending it in the span direction. Unfairness in profile over the leading edge of the cut-out sections adversely affects the lift and induced drag as well as the profile drag. Lifting-line airfoil theory can be successfully used to calculate the characteristics of a wing as affected by a cut-out when the section characteristics of the profiles along the span are known. It is useful, in such a problem, to employ the method of successive approximation for obtaining the span load distribution. The information derived from the analysis was applied for illustration to the prediction of the characteristics of a wing with a center-section cut-out. The
BOOK REVIEWS.
[J. F. I.
Last but not least is a consideration of the Human Factor. An observer exercises both judgment and physical action when manipulating an instrument. Human judgment is influenced by irrelevant as well as relevant sensations, and it is the task of the instrument maker to keep all irrelevant factors at a minimum if reasonable accuracy is to be expected. A llst of possible psychologically disturbing factors is given. The matter of physical action also receives respi~ctful attention. The most accurate adjustments are made by the smoothest working controls. Smooth action also prevents muscular fatigue and its attendant psychological repercussions. T. K. CLEVELAND. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
Report No. 478, Experimental Verification of the Theory of Wind Tunnel Boundary Interference, by Theodore Theodorsen and Abe Silverstein. I7 pages, illustrations, 23 X 29 cms. Washington, Superintendent of Documents, I934. Price ten cents. The results of an experimental investigation on the boundary-correction factor, conducted at the N. A. C. A. laboratories at Langley Field, Va., are presented in this report. The values of the boundary-correction factor from the theory, which at the present time is virtually completed, are given in the paper ;for all conventional types of tunnels. With the isolation of certain disturbing effects, the experimental boundarycorrection factor was found to be in satisfactory agreement with the theoretically predicted values, thus verifying the soundness and sufficiency of the theoretical analysis. The establishment of a considerable velocity distortion, in the nature of a unique blocking effect, constitutes a principal result of the investigation. The major portion of the investigation was carried on in the N. A. C. A. fullscale wind tunnel, which afforded the unusual opportunity of a direct comparison with flight results as a final verification. Report No. 480, The Aerodynamic Effects of Wing Cut-Outs, by Albert Sherman, 8 pages, illustrations, 33 X 29 cms. Washington, Superintendent of Documents, I934. Price five cents. In connection with the interference program being conducted in the N. A. C. A. varlable-denslty wind tunnel, an analysis was made of available material with the object of presenting a qualitative discussion of wing characteristics as affected by cut-outs and of determining means for their quantitative calculation. The analysis indicated that extending a cut-out in the chord direction has much greater effect than extending it in the span direction. Unfairness in profile over the leading edge of the cut-out sections adversely affects the lift and induced drag as well as the profile drag. Lifting-line airfoil theory can be successfully used to calculate the characteristics of a wing as affected by a cut-out when the section characteristics of the profiles along the span are known. It is useful, in such a problem, to employ the method of successive approximation for obtaining the span load distribution. The information derived from the analysis was applied for illustration to the prediction of the characteristics of a wing with a center-section cut-out. The