L. J. Souverein

Effect of Interaction Strength on Unsteadiness in Shock-Wave-Induced Separations

The effect of the interaction strength on the unsteady behavior of a planar shock wave impinging on a low Reynolds turbulent boundary layer is investigated. This is achieved by means of a variation in incident shock angle under otherwise constant flow conditions. In addition, the effect of an order-of-magnitude variation in the Reynolds number is considered. This has been done for equivalent interaction strength, based on a similar probability of occurrence of instantaneous flow separations. The measurement technique employed is two-component planar particle image velocimetry. Common mechanisms for the large-scale reflected-shock unsteadiness are deduced by means of conditional statistics based on the separation bubble height. The results indicate that both upstream and downstream mechanisms are at work, the dominant mechanism depending on the interaction strength. No significant dependence on the Reynolds number was observed for interactions with a similar probability of instantaneous flow separations.

Application of a dual-plane particle image velocimetry (dual-PIV) technique for the unsteadiness characterization of a shock wave turbulent boundary layer interaction

The unsteady organization and temporal dynamics of the interaction between a planar shock wave impinging on a turbulent boundary layer at a free-stream Mach number of Me = 1.69 is investigated experimentally by means of dual-plane particle image velocimetry (dual-PIV). Two independent PIV systems were combined in a two-component mode to obtain instantaneous velocity fields separated by a prescribed small time delay. This enables us to obtain, in addition to mean and statistical flow properties, also instantaneously time-resolved data to characterize the temporal dynamics of the flow phenomenon in terms of time scales, temporal correlations and convective velocities. The characteristic time scales for the incoming boundary layer, the separation region and the reflected shock are determined by means of the temporal auto-correlation coefficient in the complete flow field for a range of time delays from 5 ?s to 2000 ?s. These auto-correlation fields are used to quantify the time scales in selected regions of the flow, with special interest for the vortex shedding and the low frequency reflected shock dynamics. This permits resolving the dominant time scales within the boundary layer and the interaction region.

Effect of Interaction Strength on the Unsteady Behavior of Shock Wave Boundary Layer Interactions

The e ect of the interaction strength on the unsteady behavior of a planar shock wave impinging on a turbulent boundary layer is investigated. This is achieved by means of a variation in incident shock angle under otherwise constant ow conditions. In addition, the e ect of an order of magnitude variation in the Reynolds number is considered. This has been done for equivalent interaction strength, with as criterion the extent of the occurrence of instantaneous ow separation. The measurement technique employed is two component planar particle image velocimetry. Common mechanisms for the large scale re ected shock unsteadiness are deduced by means of conditional statistics based on the separation bubble height. The results indicate that several upstream and downstream mechanisms are at work, the dominant mechanism depending on the interaction strength. No signi cant dependence on the Reynolds number was observed for equivalent interactions.

Unsteadiness Characterisation in a Shock Wave Turbulent Boundary Layer Interaction Through Dual-PIV

The unsteady organization and temporal dynamics of the interaction between a planar shock wave impinging on a turbulent boundary layer at a free stream Mach number of M∞=1.69 is investigated experimentally by means of dual-plane Particle Image Velocimetry (dual-PIV). Two independent PIV systems were combined in two component mode to obtain instantaneous velocity fields separated by a prescribed small time delay. This enables to obtain, in addition to mean and statistical flow properties, also instantaneously time resolved data to characterize the temporal dynamics of the flow phenomenon in terms of time scales, temporal correlations and convective velocities. The characteristic time scales for the incoming boundary layer, the separation region and the reflected shock are evaluated by means of measuring the temporal auto-correlation coefficient in the complete flow field for a range of time delays from 5 μs to 2000 μs. These auto-correlation fields are used to quantify the time scales in selected regions of the flow. This permits resolving the dominant time scales within the boundary layer and the interaction region.