Instrumentation and Measurement Techniques
New collaboration framework between VKI and DANTEC DYNAMICS
The von Karman Institute and Dantec Dynamics have signed in May 2019 an agreement to set up a long-term cooperation on several fields of experimental fluid mechanics. The collaboration aims at the joint development of improved methods and measurement solutions.
Dantec Dynamics (https://www.dantecdynamics.com/) delivers turnkey and customized solutions built on high-end laser optics, imaging, and electronical sensor technologies, and has over 70 years of experience in experimental fluid and solid mechanics.
The first research project aims at developing advanced pre-processing and post-processing tools for Particle Image Velocimetry (PIV), based on data-driven modal analysis. The first benchmark test case, recently measured at the VKI, consists of the flow past a cylinder in accelerating conditions, producing the famous Karman Street in non-stationary conditions. This flow has been analyzed using the recently proposed Multiscale Proper Orthogonal Decomposition (mPOD).
Time Resolved PIV (TR-PIV) of an accelerating Karman vortex street and mPOD based modal analysis; measurements performed by D. Hess (Dantec Dynamics) and
M. Mendez (VKI). Top Left figure: vorticity field revealing the Karman street.
Multiscale proper orthogonal decomposition (mPOD) of TR-PIV data - a case study on stationary and transient cylinder wake flows
Our article ' Multiscale Proper Orthogonal Decomposition (mPOD) of TR-PIV data-- a Case Study on Stationary and Transient Cylinder Wake Flows' is online: https://iopscience.iop.org/article/10.1088/1361-6501/ab82be/meta
This article results from the collaboration between the von Karman Institute and Dantec Dynamics on the development of data processing methods for PIV. In this work, we test the mPOD for Time-Resolved PIV measurements of a cylinder flow in transient conditions, with Reynolds number varying from 4000 to 2600 within a few seconds. PIV measurements were carried out at a sampling frequency of 3000 Hz and captured the vortex shedding's transient evolution.
The mPOD is designed to achieve a compromise between decomposition convergence and spectral purity of the resulting modes. In this work, the mPOD reveals the frequency jitter phenomenon in the stationary wake and identify the various phases of the wave evolution in the transient test case.
Multiscale proper orthogonal decomposition (mPOD) of TR-PIV data