Air Resistance of High-Speed Trains and Interurban Cars

Abstract

Abstract In this paper a study is made of the economics possible by reducing air resistance of high-speed passenger trains and interurban cars. A critical survey is given of the train-resistance formulas used hitherto and of the various methods of determining the coefficients of these formulas. It is shown that the general ideas on which the train-resistance formulas are based have to be corrected according to the more modern aerodynamic conceptions on air resistance. Data on the air resistance of train models of various shapes recently obtained in the Westinghouse wind tunnel are given in a number of curves. The methods employed and the experiment set-up are fully described. It is shown that a considerable reduction of air resistance of the present types of trains and interurban cars can be obtained by streamlining. The fundamental laws of air resistance are stated, and it is shown on what air resistance mainly depends. The importance of the critical Reynolds number is explained, particularly in connection with the reliability of model tests. A striking example is given showing how, by means of streamlining, the air resistance of a body can be reduced to 1/20 of its original value. A more rational method of determining the total resistance of trains and interurban cars is given, and it is shown that the streamlining of present-type cars for high-speed service is more justifiable from an economical standpoint than the streamlining of the fuselage of an airplane.