Contact velocities of small ellipsoids settling in turbulence

Collisions of small and heavy non-spherical particles settling in turbulence are very important for systems such as ice clouds and proto-planetary disks where the particle spectra evolution is strongly dependent on the collision induced growth rate. Still, the influence of the particle shape on the collision probability is virtually unknown....

Wall-shear stress measurements of turbulent flow over ribbed surfaces using the micro-pillar shear stress sensor MPS3

The drag reduction effect of a semi-circular riblet-structured surface in a turbulent boundary layer is experimentally investigated using the micro-pillar shear stress sensor MPS3. The MPS3 sensor is a novel tool for the quantitative measurement of the wall-shear stress distribution and possesses a high spatial and temporal resolution. The...

Tomographic particle-image velocimetry measurements in a turbulent wavy channel flow

To investigate small scale turbulent structures and their statistical properties in non-isotropic turbulent flow subjected to favorable and adverse pressure gradients, a novel method to divide the instantaneous flow field into strictly monotonic elements is applied to tomographic particle-image velocimetry data.Especially the scaling regimes of...

Assessment of propeller induced properties and active flow control using multiple image-based measurement systems

Multiple optical measurement techniques have been applied for the investigation of a propeller-wing wind tunnel model. The (half) wind tunnel model is equipped with a nine bladed propeller and its wing has active Coanda blowing over the whole span of the wing. The aim of the investigation is to gain understanding of the flow phenomena,...

Time-Resolved stereoscopic PIV measurements of cyclic variations in an internal combustion engine

The flow field during the intake and the compression stroke of an optical four-stroke, four-valve, single-cylinder gasoline type demonstrator engine is measured using time-resolved stereoscopic particle-image velocimetry (PIV) to analyze these flow structures. The flow is measured in the tumble plane at an engine speed of 1500 rpm in 50...

Dual-Volume and Four-Pulse Tomo PIV using polarized laser light

A demonstration experiment and first assessment of a dual-volume and four-pulse tomo PIV system operating with two pairs of perpendicularly polarized laser light pulses and respective polarizing filters for separation of the scattered particle light is presented. The polarizing filters are placed in front of eight sCMOS double-frame cameras...

Tomographic particle-image velocimetry in an IC engine

The flow structures during the intake and compression phase within the cylinder of an internal combustion(IC)engine strongly influence the mixing and combustion process. To gain a better understanding of the flow field, fully three-dimensional quantitative measurement techniques have to be applied to the flow field. Analog off-axis holographic...

‘Shake The Box’: A highly efficient and accurate Tomographic Particle Tracking Velocimetry (TOMO-PTV) method using prediction of particle positions

A novel approach to the evaluation of time resolved particle-based tomographic data is introduced. By seizing the time information contained in such datasets, a very fast and accurate tracking of nearly all particles within the measurement domain is achieved at seeding densities comparable to (and probably above) the thresholds for tomographic...

Self-healing phenomena in polymers based on the theory of porous media

Self healing materials are becoming more and more important for the construction of mechanical components due to their ability to detect and heal failures as well as cracks autonomously. Especially in polymers and polymer-composites, where the component can loose a high rate of strength and durability due to micro cracks, those damages are...

Noise Sources in Single and Coaxial Jets

The acoustic simulations of a cold single stream jet at Mach number 0.9 and Reynolds number 3,600 and two heated coaxial jets at Mach number 0.9 and Reynolds numbers 3,600 and 400,000 are performed. The computation of the acoustic field is performed by a two-step approach using a large-eddy simulation (LES) for the flow field and approximate...

Source Term Evaluation of the APE-RF System using DNS Data

Acoustic perturbation equations for reacting flows (APE-RF) in conjunction with direct numerical simulations (DNS) are used to investigate in detail the thermo-acoustic effects resulting from turbulent premixed flames. The basic procedure is a two-step DNS/APE-RF method, where the flow is simulated by direct numerical simulations and the...

Turbulence Simulation via the Lattice-Boltzmann Method on Hierarchically Refined Meshes

In the present work the application of hierarchical grid refinement for the Lattice-Boltzmann Method (LBM) to simulate turbulent flows has been investigated. A transformation and interpolation scheme has been developed based on a volumetric approach, independent of a specific collision model and therefore, generally applicable to all variants of...

Experimental investigation of turbulent boundary layer flow undergoing spanwise traveling transversal surface waves

The influence of spanwise traveling transversal surface waves on the near-wall flow field of turbulent boundary layers with and without adverse pressure gradient is investigated by particle-image velocimetry (PIV) and micro-particle tracking velocimetry (μ-PTV). A detailed analysis of the velocity profile immediately downstream of the actuated...