Flow characteristics in median plane of a backward-inclined elevated transverse jet

•Backward inclination angle strongly affect flow behavior of a jet in crossflow.•Critical jet-to-crossflow momentum flux ratio increases with increasing backward inclination angle.•Transverse jet dispersion decreases with increasing backward inclination angle.•Strouhal number of jet instabilities increases with increasing backward inclination angle.•At backward inclination angle greater than 25°, downwash-induced tube-tip recirculation disappears.

The time-averaged flow patterns and instantaneous upwind-side shear-layer vortex flow modes of a backward-inclined elevated transverse jet were studied in an open-loop wind tunnel by laser-assisted smoke flow visualization method and hot-wire anemometry. The characteristic flow modes at various backward inclination angles θ and jet-to-crossflow momentum flux ratios R were identified from long- and short-exposure pictures of flow visualization. The jet width, which may denote the transverse dispersion characteristics of the jet, in the near and far fields were determined from the long-exposure picture by using a binary edge-detection method. The frequency and Strouhal number of the upwind-side shear-layer vortices were measured by the hot-wire anemometer. At θ < 25°, large downwash recirculation bubble always appeared at small R’s. Increasing θ would quickly decrease the size of the downwash recirculation bubble. At θ > 25°, no downwash recirculation bubble was observed in the near wake of the tube tip region. The jet width decreased with increasing θ. The Strouhal number of the upwind-side vortices increased with increasing θ. At a fixed θ, the Strouhal number of the upwind-side vortices decreased with increasing R at R < 1. At R > 1, the decrease rate became small. The ultimate Strouhal numbers at large R at different backward inclination angles θ did not converge to a single value—the larger the θ, the larger the Strouhal number.