Computer simulation of the dynamic development of triad interactions created by dual vortex shedding*

Interactions between modes in a turbulent flow, so-called triad interactions, are essential to the process of turbulence development. We present results of a computer simulation of an experiment with vortex shedding from two rectangular rods mounted in the core of a laminar jet [1]. The purpose is to follow the cascade process initiated by two clean oscillatory modes created by vortex shedding from two slightly different rectangular rods mounted parallel to and near each other.

We briefly describe the computer program, which is able to describe the dynamic development of a velocity time record exposed to the full Navier Stokes equation [2]. In this case, we insert the real time record measured close to the rods as input to the program and compute the time record and power spectrum resulting from the Navier Stokes equation operating on the initial record during a time corresponding to the convection time in the experiment.

We compare the results of the simulation to the measured time records and power spectra described in [1] and find excellent agreement. The results illustrate the dynamic processes that are the core of turbulence development.

1. "Dynamic triade interactions by dual vortex shedding in air jet" APS DFD 2021 session 36

2. Buchhave P, Velte CM "A 1D 'Navier-Stokes Machine' and its application to turbulence studies", arXiv:2002.10184 [physics.flu-dyn]