THEORETICAL ROAD DAMAGE DUE TO DYNAMIC TYRE FORCES OF HEAVY VEHICLES. PART 1: DYNAMIC ANALYSIS OF VEHICLES AND ROAD SURFACES.

Theory is presented for simulating the dynamic wheel forces generated by heavy road vehicles and the resulting dynamic response of road surfaces to these loads. Sample calculations are provided and the vehicle simulation is validated with data from full-scale tests. The methods are used in the accompanying paper to simulate the road damage done by a tandem-axle vehicle.

THEORETICAL ROAD DAMAGE DUE TO DYNAMIC TYRE FORCES OF HEAVY VEHICLES. PART 2: SIMULATED DAMAGE CAUSED BY A TANDEM-AXLE VEHICLE.

The literature relating to road surface failure and design is briefly reviewed and the conventional methods for assessing the road damaging effects of dynamic tire forces are examined. A new time domain technique for analyzing dynamic tire forces and four associated road damage criteria are presented. The force criteria are used to examine the road damaging characteristics of a simple tandem-axle vehicle model for a range of speed and road roughness conditions. It is concluded that for the proposed criteria, the theoretical service life of road surfaces that are prone to fatigue failure may be reduced significantly by the dynamic component of wheel forces. The damage done to approximately five per cent of the road surface area during the passage of a theoretical model vehicle at typical highway speeds may be increased by as much as four times.

Unsteady transition in an axial-flow turbine. Part 2. Cascade measurements and modeling

Part 1 of this paper reanalyzed previously published measurements from the rotor of a low-speed, single-stage, axial-flow turbine, which highlighted the unsteady nature of the suction surface transition process. Part 2 investigates the significance of the wake jet and the unsteady frequency parameter. Supporting experiments carried out in a linear cascade with varying inlet turbulence are described, together with a simple unsteady transition model explaining the features of seen in the turbine.

Unsteady transition in an axial-flow turbine. Part 1. Measurements on the turbine rotor

Previously published measurements in a low-speed, single-stage, axial-flow turbine have been reanalyzed in the light of more recent understanding. The measurements include time-resolved hot-wire traverses and surface hot film gage measurements at the midspan of the rotor suction surface with three different rotor-stator spacings. This paper investigates the suction surface boundary layer transition process, using surface-distance time plots and boundary layer cross sections to demonstrate the unsteady and two-dimensional nature of the process.

Wake, shock and potential field interactions in a 1.5 stage turbine: Part I: Vane-rotor and rotor-vane interaction

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows was studied, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries were considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were carried out at engine-representative Mach and Reynolds numbers. By comparing the results to time-resolved computational predictions of the flowfield, the accuracy with which the computation predicts blade interaction was determined. It was found that in addition to upstream vane-rotor and rotor-downstream vane interactions, a new interaction mechanism was found resulting from the interaction between the downstream vane's potential field and the upstream vane's trailing edge potential field and shock.

Wake, shock and potential field interactions in a 1.5 stage turbine: Part II: Vane-vane interaction and discussion of results

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows was studied, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries were considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were carried out at engine-representative Mach and Reynolds numbers. By comparing the results to time-resolved computational predictions of the flowfield, the accuracy with which the computation predicts blade interaction was determined. Evidence was obtained that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.