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National advisory committee for aeronautics.
640
BOOK R E V I E W S .
[J. F. I.
T h e pressure-distribution tests incidentally demonstrated the favorable interference produced by the horizontal tail surfaces on t h e part of the vertical surfaces below them and the unfavorable interference produced on the part above them. Report No. 566, Ground-Handling Forces on a I/4o-Scale Model of the U. S. Airship " A k r o n , " by Abe Silverstein and B. G. Gulick. 14 pages, diagrams, 23 X 29 cms. Washington, Superintendent of Documents, I936. Price ten cents. An investigation was conducted in the N. A. C. A. full-scale wind tunnel to determine the ground-handling forces on a I/4O-scale model of the U. S. airship " A k r o n . " Ground-handling conditions were simulated by establishing a velocity gradient above a special ground board in the tunnel comparable with t h a t encountered over a landing field. The tests were conducted at Reynolds Numbers ranging from 5,000,000 to I9,OOO,OOO at each of six angles of yaw between o ° and I8O ° and at four heights of the model above the ground board. T h e ground-handling forces vary greatly with the angle of yaw and reach large values at appreciable angles of yaw. Small changes in height, pitch, or roll did not critically affect the forces on the model. In the range of Reynolds Numbers tested, no significant variation of the forces with the scale was disclosed. Report No. 563, Calculated and Measured Pressure Distributions Over the Midspan Section of the N. A. C. A. 4412 Airfoil, by Robert M. Pinkerton, x6 pages, illustrations, tables, 23 X 29 cms. Washington, Superintendent of Documents, I936. Price ten cents. Pressures were simultaneously measured in the variable-density tunnel at 54 orifices distributed over the midspan section of a 5- by 3o-inch rectangular model of the N. A. C. A. 4412 airfoil at 17 angles of a t t a c k ranging from --20 ° to 3o ° at a Reynolds Number of approximately 3,000,000. Accurate data were thus obtained for studying the deviations of the results of potential-flow theory from measured results. The results of the analysis and a discussion of the experimental technique are presented. It is shown t h a t theoretical calculations made either at the effective angle of a t t a c k or at a given actual lift do not accurately describe the observed pressure distribution over an airfoil section. There is therefore developed a modified theoretical calculation t h a t agrees reasonably well with the measured results of the tests of the N. A. C. A. 4412 section and t h a t consists of making the calculations and evaluating the circulation by means of the experimentally obtained lift at the effective angle of attack; i.e., the angle t h a t the chord of the model makes with the direction of the flow in the region of the section under consideration. In the course of the computations the shape parameter , is modified, thus leading to a modified or an effective profile shape t h a t differs slightly from the specified shape. R.
BOOK R E V I E W S .
[J. F. I.
T h e pressure-distribution tests incidentally demonstrated the favorable interference produced by the horizontal tail surfaces on t h e part of the vertical surfaces below them and the unfavorable interference produced on the part above them. Report No. 566, Ground-Handling Forces on a I/4o-Scale Model of the U. S. Airship " A k r o n , " by Abe Silverstein and B. G. Gulick. 14 pages, diagrams, 23 X 29 cms. Washington, Superintendent of Documents, I936. Price ten cents. An investigation was conducted in the N. A. C. A. full-scale wind tunnel to determine the ground-handling forces on a I/4O-scale model of the U. S. airship " A k r o n . " Ground-handling conditions were simulated by establishing a velocity gradient above a special ground board in the tunnel comparable with t h a t encountered over a landing field. The tests were conducted at Reynolds Numbers ranging from 5,000,000 to I9,OOO,OOO at each of six angles of yaw between o ° and I8O ° and at four heights of the model above the ground board. T h e ground-handling forces vary greatly with the angle of yaw and reach large values at appreciable angles of yaw. Small changes in height, pitch, or roll did not critically affect the forces on the model. In the range of Reynolds Numbers tested, no significant variation of the forces with the scale was disclosed. Report No. 563, Calculated and Measured Pressure Distributions Over the Midspan Section of the N. A. C. A. 4412 Airfoil, by Robert M. Pinkerton, x6 pages, illustrations, tables, 23 X 29 cms. Washington, Superintendent of Documents, I936. Price ten cents. Pressures were simultaneously measured in the variable-density tunnel at 54 orifices distributed over the midspan section of a 5- by 3o-inch rectangular model of the N. A. C. A. 4412 airfoil at 17 angles of a t t a c k ranging from --20 ° to 3o ° at a Reynolds Number of approximately 3,000,000. Accurate data were thus obtained for studying the deviations of the results of potential-flow theory from measured results. The results of the analysis and a discussion of the experimental technique are presented. It is shown t h a t theoretical calculations made either at the effective angle of a t t a c k or at a given actual lift do not accurately describe the observed pressure distribution over an airfoil section. There is therefore developed a modified theoretical calculation t h a t agrees reasonably well with the measured results of the tests of the N. A. C. A. 4412 section and t h a t consists of making the calculations and evaluating the circulation by means of the experimentally obtained lift at the effective angle of attack; i.e., the angle t h a t the chord of the model makes with the direction of the flow in the region of the section under consideration. In the course of the computations the shape parameter , is modified, thus leading to a modified or an effective profile shape t h a t differs slightly from the specified shape. R.