Vortices behind a bluff body with an upswept aft section in ground effect

Description/Abstract

The vortices behind a bluff body equipped with an upswept aft section are studied in a model test. The bluff body operates in close proximity to ground. The principle measurement technique is laser Doppler anemometry (LDA), which is supported by surface flow, pressure and force measurements. The upswept surface has an angle of 17° to horizontal. With the presence of end-plates on the aft section, discontinuities in slope of the force curve exist at several heights in proximity to the ground. The characteristics of these changes are linked with edge vortices. The position and strength of the vortex are identified. Three main types of trailing vortices exist: (a) concentrated, symmetric with a high axial speed core, (b) diffused, symmetric with a low axial speed core, and (c) diffused and asymmetric. The study provides further clarification of major physics and a database for validating predictive methods.