Book Reviews

Although this volume has only just come to hand it bears the date 1938 and it is, therefore, not surprising that most of the contents are considerably out of date. The book, which is written in French, begins by giving a general description of the wind tunnel at the Ecole Polytechnique at Bucarest. The general layout of the wind tunnel is very similar to that of the compressed air tunnel at the N.P.L. but the tunnel works with air at normal atmospheric pressure and the main structure is built of wood. The exterior casing of the tunnel is in effect an independent building exposed to the weather and takes the form of a horizontal octagonal prism with truncated pyramidal ends. The working section is 1·5 metres in diameter and a driving motor of 40 kw. gives a top speed of 46 metres per second or very roughly 150 ft. per second. Results of tests on a considerable variety of Joukowski aerofoils carried out at a Reynolds number of a little below half‐a‐million are given in the report. On account of this low Reynolds number and of the fact that the sections are not of types now used in practice, the data will be of little interest to the aircraft industry. One minor point of terminology which appears to be worthy of comment is that profit a didre means a profile having a finite trailing edge angle, the idea being that there is a dihedral angle between the tangent planes at the trailing edge.