Aerodynamic Forces on Freight Trains. Volume II. Full-Scale Aerodynamic Validation Tests of Trailer-on-a-Flat Car (Series II).

摘要

Aerodynamic forces were measured on full-scale Trailer-on-a-Flat Car (TOFC) configurations and a reliable data base was established for validation of wind tunnel test programs. The drag,side and lift forces were determined on two trailers mounted on an instrumented flat car,each by means of a specially designed force-balance system. Two TOFC configurations (Configuration 1with a loaded buffer car leading the instrumented flat car and Configuration 2with an empty buffer car) were tested under different wind conditions. In addition to the aerodynamic resistance of the trailers,total tractive resistance of the TOFC was measured via instrumented couplers. The results indicate good agreement between the full-scale aerodynamic drag data and the wind tunnel data from the tests at the Calspan Corporation. The wind tunnel tests conducted at the California Institute of Technology exhibited significantly higher drag values than the full-scale measurements,especially at high wind angles. The foregoing conclusions apply to both Configurations 1and 2. It was found that Configuration 2experienced consistently larger drag than Configuration 1. Measurement of the total tractive resistance enabled a rough estimation of the rolling resistance of the instrumented flat car. The present tests show that at 50mph the aerodynamic drag accounts for 50to 60percent of total train resistance and the rolling resistance takes the remaining share. At 90mph,the drag force amounts to approximately 55to 70percent of the total resistance.