Evaluation of Travelling Vortex Speed by Means of Dynamic Mode Decomposition and Residual Vorticity

Tomáš Hyhlík,Hana Netřebská,P Dančová,M Veselý

doi:10.1051/epjconf/201611402045

Tomáš Hyhlík, Hana Netřebská + Show 2 more

Open Access

https://doi.org/10.1051/epjconf/201611402045

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Abstract

The article deals with the analysis of synthetic jet flow field by means of dynamic mode decomposition (DMD) method. The speed of travelling vortex ring which is connected with synthetic jet creation is evaluated using the wavelength identified from DMD modes. Vortices are identified in the DMD modes by using residual vorticity which allows to identify regions in the flow field where fluid particles perform rotational motion. The analysis is based on the data from the numerical simulation of synthetic jet into quiescent air by using ANSYS Fluent code. The regime of synthetic jet with Re = 329 and Stk = 19.7 is chosen. An increase in the vortex speed close to the orifice and then the decrease is observed with maximum reaching almost one and half of averaged blowing orifice centerline velocity.

Highlights

Current work is dealing with the analysis of unsteady flow field with travelling vortex ring and from the point of view of modal decomposition is continuation of e.g. the works [1, 2]
The article deals with the analysis of synthetic jet flow field by means of dynamic mode decomposition (DMD) method
Vortices are identified in the DMD modes by using residual vorticity which allows to identify regions in the flow field where fluid particles perform rotational motion

Summary

Numerical Simulation

Current work is dealing with the analysis of unsteady flow field with travelling vortex ring and from the point of view of modal decomposition is continuation of e.g. the works [1, 2]. The visualization of vortex structures in the DMD modes is problematic. The aim is to refine identification of vortices in the DMD modes by using the concept of residual vorticity. The flow is assumed to be axisymmetric and is simulated on rectilinear grid with 81550 cells using non iterative time advancement method with second order implicit scheme. Convective terms are discretized using third order MUSCL scheme. Both the flow in the orifice and actuator cavity are included in the simulation to get more accurate results. The effect of oscillating diaphragm is replaced by velocity boundary condition which should guarantee achievement of required Reynolds number

Parameters of Synthetic Jet

Dynamic Mode Decomposition

Vortex Identification

Results

Conclusions