Infrared thermography investigation of transitional flow over isolated roughness at high speed

The transitional flow features over and downstream of isolated roughness elements in hypersonic flow are investigated by means of infrared thermography. The local heat flux distribution in the wake of the roughness element reveals the footprint of multiple streamwise counter-rotating vortex pairs. The formation of a turbulent wedge with the...

On Reynolds Number Dependence of Micro-ramp-Induced Transition

The transitional flow features past a micro-ramp are investigated in the incompressible flow regime at critical and supercritical roughness-height based Reynolds number (Reh). Tomographic PIV is adopted as the diagnostic technique to identify the instantaneous three-dimensional flow behaviour in the domain of 73 ramp height streamwise. The...

Low-frequency wake instability of an axisymmetric bluff body in pitch

The backflow instability in the wake past a cylindrical blunt-based body in pitch is investigated at a Reynolds number ReD = 6.7 · 104 based on the cylinder diameter. Time-resolved stereoscopic particle image velocimetry measurements have been performed in a cross-flow plane located 0.3 D downstream of the model base. An increasing displacement...

Very-low frequency wake dynamics of an axisymmetric body

The so-called very-low-frequency (VLF) azimuthal meandering of the reversed-flow region has been shown to contribute significantly to the unsteadiness of the turbulent wake flow past a bluff body of revolution (Rigas et al. 2014; Grandemange et al. 2014). Such an erratic behavior causes a continuous change in the wake topology and, particularly...

PIV-based study of a cylindrical roughness element in a hypersonic laminar-boundary layer

In this study, the mean flow organization in the symmetry plane of the recirculation region ahead of a cylindrical roughness element immersed in an incoming laminar boundary layer at Mach number equal to 6.5 is investigated. The flow topology is inspected with planar particle image velocimetry (PIV), InfraRed (IR) Thermography and Schlieren flow...

Time-dependent behaviour of the recirculation region behind an axisymmetric bluff-body

Roughness Induced Boundary Layer Transition in Incompressible Flow

The fluid dynamics process leading to laminar-turbulent transition behind an isolated roughness element is investigated in the incompressible regime using particle image velocimetry. The study covers the effect of roughness size and geometry on the promotion of transition. The measurement domain covers a large streamwise range from the near wake...

Roughness Induced Boundary Layer Transition in Incompressible Flow

The fluid dynamics process leading to laminar-turbulent transition behind an isolated roughness element is investigated in the incompressible regime using particle image velocimetry. The study covers the effect of roughness size and geometry on the promotion of transition. The measurement domain covers a large streamwise range from the near wake...

Organization of an axisymmetric turbulent wake in presence of a central protrusion

Stereoscopic Particle Image Velocimetry (PIV) was used to study the wake of an ogive-cylinder with after-body at a diameter-based Reynolds number ReD = 6.7 · 104. The vertical fluctuations reduced from a maximum of 0.18 U? in absence of rear-protrusion, up to 0.12 U? and 0.1 U? when the main-body to after- body diameter ratio d/D was increased...

Geometry effect of isolated roughness on boundary layer transition investigated by tomographic PIV

Transitional flow over isolated roughness elements is investigated in the incompressible flow regime using Tomographic PIV. Three different geometries are considered (micro-ramp, cylinder and square) with same height and span. Their effect on accelerating boundary layer transition is compared and discussed. The measurement domain encompasses the...

Decay of the turbulent wake from the supersonic micro-ramp

The wake resulting from two micro ramps operating in a supersonic boundary layer at Ma = 2:0 is investigated by means of PIV. Two micro ramps are investigated with height of 60% and 80% of the undisturbed boundary layer with thickness of 5.2 mm. The measurement domain encompasses the range from 10 to 32 ramp heights downstream of the device. The...

Experimental capsule afterbody flow investigation