Space-time modulation of turbulence in co-flow jets
| Autor: | Bernardus J. Geurts, Rob Bastiaans, L.P.H. de Goey, T. Cardoso de Souza |
|---|---|
| Přispěvatelé: | Power & Flow, Group Bastiaans, Group De Goey, Center for Computational Energy Research, EIRES Eng. for Sustainable Energy Systems, EAISI Foundational, Multiscale Modeling and Simulation |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Fluid Flow and Transfer Processes
Physics Jet (fluid) Plane (geometry) Turbulence Oscillation Mechanical Engineering UT-Hybrid-D 22/2 OA procedure 02 engineering and technology Inflow Mechanics Dissipation Condensed Matter Physics 01 natural sciences 010305 fluids & plasmas Turbulent mixing Modulated turbulence 020303 mechanical engineering & transports 0203 mechanical engineering Modulation 0103 physical sciences Turbulent jets Frequency modulation |
| Zdroj: | International Journal of Heat and Fluid Flow, 83:108567. Elsevier International journal of heat and fluid flow, 83:108567. Elsevier |
| ISSN: | 0142-727X |
| DOI: | 10.1016/j.ijheatfluidflow.2020.108567 |
| Popis: | This paper focuses on the effects of a space-time dependent periodic stirring of a moderately turbulent planar co-flow jet configuration. The baseline flow is agitated in time and in space by small-scale turbulent perturbations in combination with large-scale modulation imposed at the inflow plane of a rectangular domain of size L × L × 2L in the x, y and z directions respectively. The prescribed large-scale modulation is characterized by a single modulation frequency ω and modulation wave-number, K. A parametric study at different modulation frequencies and wave-numbers is performed. We evaluate the system response to the external agitation in terms of key dynamic properties of the flow, e.g., the total kinetic energy ET, the global averaged dissipation rate and additional flow mixing properties. For low modulation frequencies, e.g., ω=0.5ω0, where ω0 is the large scale-turn over frequency, ω0=U1/D, with U1 and D being relevant velocity and length scales, and at given wave-number K, we observe that ET follows the imposed oscillation with a periodic amplitude response that is sustained at locations further from the inflow plane, whereas for higher frequencies, the response amplitude rapidly decays. Results of the global dissipation rate show the development of a definite maximum value of the response amplitude at frequencies on the order of ω0 for any modulation wave-number K. To investigate in more detail the effects of modulated turbulence on the jet mixing properties, a passive scalar was injected at the inflow plane. The spreading of the scalar surface in the agitated jet was monitored for a wide range of modulation frequencies. In general, results show enhanced mixing efficiency when the main jet is modulated at frequencies near ω0 and low K values. |
| Databáze: | OpenAIRE |
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