Report No. 581. Measurements of intensity and scale of wind-tunnel turbulence and their relation to the critical Reynolds Number of spheres

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Book REVIEWS.

[J. F. I.

Report No. 58I. Measurements of Intensity and Scale of Wind-Tunnel Turbulence and Their Relation to the Critical Reynolds Number of Spheres, by Hugh L. Dryden, G. B. Schubauer, W. C. Mock, Jr., and H. K. Skramstad. 32 pages, illustrations, tables, 23 M 29 eros. Washington, Superintendent of Documents, I937. Price fifteen cents. The investigation of wind-tunnel turbulence, conducted at the National Bureau of Standards with the co6peration and financial assistance of the National Advisory Committee for Aeronautics, has been extended to include a new variable, namely, the scale of the turbulence. This new variable has been studied together with the intensity of the turbulence, and the effect of both on the critical Reynolds Number of spheres has been investigated. By the use of a modification of the usual hot-wire apparatus incorporating two hot wires suitably connected and mounted so that the cross-stream distance between them may be varied, it has been found possible to determine the correlation between the speed fluctuations existing at the two wires. Report No. 582. A Theory for Primary Failure of Straight Centrally Loaded Columns, by Eugene E. Lundquist and Claude M. Fligg. 27 pages, illusi~rations, 23 N 29 cms. Washington, Superintendent of Documents, I937 . Price fifteen cents. The primary failure of straight centrally loaded columns is defined as any type of failure in which the cross sections are translated, rotated, or translated and rotated but not distorted in their own planes. In the derivation of the general equation for the critical stress, the cross sections are assumed to rotate about any axis parallel to the column. When the location of the axis of rotation varies from zero to infinity in every direction, all combinations of translation and rotation of the column cross section are obtained. For illustration, the theory is applied to a column of I section. The conclusions, however, are generalized to include any column with a cross section symmetrical about its principal axes. It is shown that, for such columns, the theories for bending failure and twisting failure are special cases of this general theory and that primary failure will occur by bending about the axis of minimum moment of inertia or by twisting about the centroid, depending upon which gives the lower critical stress. It is shown how the effective width of skin that may be considered to act with the column and carry the same stress as the column alters the section properties of the column and how the bending stiffness of the skin resists twisting of the column and raises the critical stress. Finally, the effective moduli that apply when the column is stressed above the proportional limit are discussed. Report No. 584. Strength of Welded Aircraft Joints, by W. C. Brueggeman. 32 pages, illustrations, 23 X 29 cms. Washington, Superintendent of Documents, I937. Price fifteen cents. The work described in N.A.C.A. Technical Report No. 348 showed that the insertion of gusset plates was the most satisfactory way of strengthening a joint. The additional tests of the present series show that joints of this type could be improved by cutting out the portion of the plate between the intersecting tubes. T and lattice joints in thin-walled tubing I½ by o.o2o inch have somewhat lower strengths than joints in tubing of greater wall thickness because of failure