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This study investigates the particle dispersion characteristics in the turbulent wake of a simplified vehicle model (Ahmed body) for two values of the rear slant angle ϕ (25 ° and 40 °) to study the effect of flow separation. In the experiments (Reynolds number Rel=1.90 × 10 5 ), smoke particles were released from a source and visualized with a laser sheet. Concentration fields were analyzed to calculate the vertical (Sy) and lateral (Sz) smoke spread. The findings indicate that the flow topology and concentration fields in the wake are highly dependent on ϕ. In the ϕ = 40 ° case, separation on the rear slant disrupts the trailing vortices originating on the rear slant edges and significantly alters the wake topology. The growth of vertical smoke spread saturates after the recirculation region. The uniform mixing and absence of trailing vortices concentrate the smoke particles in the model midplane. In the ϕ = 25 ° case, the signatures of trailing vortices were observed in the concentration fields behind the model. The vertical smoke spread is less, and the lateral smoke spread is more compared to the ϕ = 40 ° case. The growth of the smoke spread ( S y , S z ) driven by the trailing vortices persists for a long distance, even after the recirculation region. The disruption of trailing vortices brought about by the flow separation appears to be an important effect driving the vertical smoke spread in the wake. The connection between the turbulent velocity structures and concentration structures will need to be explored with combined velocity and concentration measurements in the wake. [ABSTRACT FROM AUTHOR]

Moving vehicles pick up the particulates/dust on the road surface, and the wake structures behind the vehicle determine the dispersion of these particles. This study aims at understanding the characteristics of particle dispersion in the turbulent wake of a moving vehicle. The flow over a simplified vehicle model known as the Ahmed body is analysed. Experimental measurements and computational simulations of particle dispersion in the near wake of Ahmed body are presented. Unsteady simulations are performed for the prediction of the flow topology and particle dispersion around the Ahmed body, at R e l = 0.7 × 10 5 (Reynolds no. based on vehicle model length 'l'), the rear slant angle of Ahmed body considered is ϕ = 25 o . Governing equations solved are unsteady Reynolds Averaged Navier–Stokes (URANS) equations, and the turbulence model employed was SST k - ω . Experiments involved the release of fog particles (Ethylene-Glycol, d p ≈ 1 μ m ) from a source behind the model. Dispersion of the particles was measured in the wind tunnel using a laser sheet for fog particle visualisation at three downstream locations, X=1, 2, and 3, at R e l = 1.4 × 10 5 . It was observed that the flow structure in the near wake of the model consisted of two counter-rotating spanwise vortices and a pair of trailing vortices. URANS simulations capture both the turbulent flow features in the near wake. Experimental results were compared with the URANS simulation results, and it was found that the dominant turbulent structures (recirculation vortices and trailing vortices) in the near wake contribute to particle dispersion. The dispersion patterns obtained are dependent on the size and strength of turbulent structures. The URANS simulations perform reasonably well in capturing the vertical dispersion of particles. However, they do not accurately estimate the lateral dispersion of smoke particles. The lateral dispersion is underestimated by the URANS simulations. [ABSTRACT FROM AUTHOR]

Mycetoma or Maduramycosis is a localized chronic suppurative infection characterized by exuberant granulation tissue, discharging sinuses, and bone involvement later in the course of the disease. Early clinical diagnosis before the appearance of sinuses and grains (aggregates of organism surrounded by granulation tissue, which are discharged from the draining sinuses) is difficult. Delay in diagnosis may lead to amputation of the affected part. Definitive diagnosis is through biopsy and microbiological examination. However, at times diagnosis may still be difficult. The recently described "dot in circle" sign on magnetic resonance imaging (MRI) is easy to recognize and highly specific. We present a case of mycetoma foot with characteristic MRI features. [ABSTRACT FROM AUTHOR]