Micro Ramps in Supersonic Turbulent Boundary Layers: An experimental and numerical study

The micro vortex generator (MVG) is used extensively in low speed aerodynamic problems and is now extended into the supersonic flow regime to solve undesired flow features that are associated with shock wave boundary layer interactions (SWBLI) such as flow separation and associated unsteadiness of the interaction system. Numerous experimental...

Material Derivative Measurements in High-Speed Flows by Four-Pulse Tomographic PIV

A tomographic PIV system is introduced for the instantaneous measurement of the material derivative of velocity (VMD). The system is able to operate with very short temporal separation and is therefore suitable for applications in high-speed flows. The method of operation consists of the imaging of a measurement volume using an array of 12 CCD...

High-speed PIV analysis of trailing edge aeroacoustics

Tonal noise generated by airfoils observed at low to moderate Reynolds numbers is related to laminar boundary layer instabilities, which has lead to the term laminar boundary layer instability noise. The particular features of the acoustic spectrum have been discussed and a number of theories have been proposed in literature over the past 50...

Three-dimensional wake reconstruction of a flapping-wing MAV using a Kriging regression technique

The work explores the three-dimensional unsteady wake of a flapping-wing Micro Air Vehicle (MAV) ‘DelFly II’, applying a Kriging regression technique for the spatial regression of time-resolved Stereoscopic Particle Image Velocimetry (Stereo-PIV) data. In the view of limited number of measurement planes, the particular objective of the...

Time-resolved image analysis for turbulent flows

Classical Particle Image Velocimetry (PIV) uses two representations of the particle image distribution to determine the displacement of the particle image pattern by spatial cross-correlation. The accuracy and the robustness are however limited by the fact that only two representations at t and t +?t are present. Thus, only a first order...

An experimental study of reconstruction accuracy using a 12-Camera Tomo-PIV system

A tomographic PIV system composed of a large number of cameras is used to experimentally investigate the relation between image particle density, number of cameras and the reconstruction quality. The large number of cameras allows to determine an asymptotic behavior for the object reconstruction over a wide range of values for the tracer...

On the universality of PIV uncertainty quantification by image matching

The topic of uncertainty quantification in particle image velocimetry (PIV) is recognized as very relevant in the experimental fluid mechanics community, especially when dealing with turbulent flows, where PIV plays a prime role as diagnostic tool. The issue is particularly important when PIV is used to assess the validity of results obtained...

3D organization of high-speed compressible jets by tomographic PIV

This work investigates the three dimensional organization of compressible jets at high-speed regime by tomographic particle image velocimetry (TOMO PIV). Experiments are conducted at Mach numbers 0.3, 0.9 and 1.1 (underexpanded regime) across the end of the potential core within a large cylindrical domain (1.6Dx8D, with D=22mm the jet diameter)....

Higher order implicit time integration schemes to solve incompressible Navier-Stokes on co-located grids using consistent unsteady Rhie-Chow

Noting that time-accurate computations of the unsteady incompressible Navier-Stokes (INS) equations can be computationally expensive, a family of higher order implicit multi-stage time integration schemes (namely ESDIRK) is used for advancing the solution to the unsteady INS in time. The higher order time integration schemes have the potential...

Multi-frame pyramid correlation for time-resolved PIV

A novel technique is introduced to increase the precision and robustness of time-resolved particle image velocimetry (TR-PIV) measurements. The innovative element of the technique is the linear combination of the correlation signal computed at different separation time intervals. The domain of the correlation signal resulting from different...

Navier-Stokes simulations in gappy PIV data

Velocity measurements conducted with particle image velocimetry (PIV) often exhibit regions where the flow motion cannot be evaluated. The principal reasons for this are the absence of seeding particles or limited optical access for illumination or imaging. Additional causes can be laser light reflections and unwanted out-of-focus effects. As a...

A super-resolution approach for uncertainty estimation of PIV measurements

A super-resolution approach is proposed for the a posteriori uncertainty estimation of PIV measurements. The measured velocity field is employed to determine the displacement of individual particle images. A disparity set is built from the residual distance between paired particle images of successive recordings. Within each interrogation window...

Accelerated partitioned fluid-structure interaction using space-mapping

The focus of this paper is on acceleration of strong partitioned coupling algorithms for fluid-structure interaction. Strong partitioned coupling requires the solution of a coupled problem at each time step during the simulation. Hereto, an interface residual is defined such that the kinematic and dynamic interface conditions on the fluid...

Applications of a discrete viscous adjoint method for aerodynamic shape optimisation of 3D configurations

Within the next few years, numerical shape optimisation based on high-fidelity methods is likely to play a strategic role in future aircraft design. In this context, suitable tools have to be developed for solving aerodynamic shape optimisation problems, and the adjoint approach—which allows fast and accurate evaluations of the gradients with...

Decomposition of time-resolved tomographic PIV

An experimental study has been conducted on a transitional water jet at a Reynolds number of Re = 5,000. Flow fields have been obtained by means of time-resolved tomographic particle image velocimetry capturing all relevant spatial and temporal scales. The measured threedimensional flow fields have then been postprocessed by the dynamic mode...

Measurement of the body force field of plasma actuators

A novel technique is proposed and investigated for the estimation of the body force field resulting from the operation of a dielectric barrier discharge plasma actuator. The technique relies on the measurement of the spatio-temporal evolution of the induced velocity field using high-speed particle image velocimetry (PIV). The technique has the...

High-resolution PIV analysis of compressibility effects in turbulent jets

An investigation on the compressibility effects arising into the near field of turbulent jets operated at high Reynolds number at Mach numbers M=0.3, 0.9 and 1.1 (under-expanded regime) is carried out with two-components planar PIV experiments with high resolution cameras. The arrangement of the PIV system allows for mapping out the flow field...