Abstract
We discuss methods of multiscale forcing to enhance the mixing efficiency of an incompressible flow. To introduce a variety of length- and time-scales into a flow, we focus on two methods. First, we concentrate on effects due to guiding a fluid over a complex-shaped object placed in the flow domain. Specifically, we apply direct numerical simulation to predict flow through a cylindrical pipe in which a periodic array of orifice plates with a fractal perimeter is mounted. To represent the complex orifice, a volume penalisation immersed boundary method is used. Adding a periodic array of fractal orifice plates, derived from the Koch snowflake, to a cylindrical pipe is shown to increase the average laminar stretching rate by a factor of up to five, compared to pipe flow without orifice plates. Second, we consider the inclusion of multiple length- and time scales at inflow boundaries to enhance mixing efficiency for combustion in Bunsen-type flames. By using a combination of large- and small-scale flow perturbations at an inflow, a two-fold increase of flame wrinkling and flame intensity could be realised. The scale-dependency of the intensification of the combustion is investigated, showing a narrow range of length-scales with strongest response, reminiscent of 'resonant turbulence' conditions.
| Original language | English |
|---|---|
| Pages (from-to) | 353-365 |
| Journal | Computers & Fluids |
| Volume | 176 |
| DOIs | |
| Publication status | Published - 1 Nov 2018 |
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Keywords
- Bunsen flame
- Enhanced mixing
- Multiscale forcing
- Pipe flow
- Turbulence modulation
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Recent developments in multiscale forcing for enhanced mixing. / Geurts, Bernard J.; Cardoso de Souza, Thiago.
In: Computers & Fluids, Vol. 176, 01.11.2018, p. 353-365.Research output: Contribution to journal › Article › Academic › peer-review
TY - JOUR
T1 - Recent developments in multiscale forcing for enhanced mixing
AU - Geurts, Bernard J.
AU - Cardoso de Souza, Thiago
PY - 2018/11/1
Y1 - 2018/11/1
N2 - We discuss methods of multiscale forcing to enhance the mixing efficiency of an incompressible flow. To introduce a variety of length- and time-scales into a flow, we focus on two methods. First, we concentrate on effects due to guiding a fluid over a complex-shaped object placed in the flow domain. Specifically, we apply direct numerical simulation to predict flow through a cylindrical pipe in which a periodic array of orifice plates with a fractal perimeter is mounted. To represent the complex orifice, a volume penalisation immersed boundary method is used. Adding a periodic array of fractal orifice plates, derived from the Koch snowflake, to a cylindrical pipe is shown to increase the average laminar stretching rate by a factor of up to five, compared to pipe flow without orifice plates. Second, we consider the inclusion of multiple length- and time scales at inflow boundaries to enhance mixing efficiency for combustion in Bunsen-type flames. By using a combination of large- and small-scale flow perturbations at an inflow, a two-fold increase of flame wrinkling and flame intensity could be realised. The scale-dependency of the intensification of the combustion is investigated, showing a narrow range of length-scales with strongest response, reminiscent of 'resonant turbulence' conditions.
AB - We discuss methods of multiscale forcing to enhance the mixing efficiency of an incompressible flow. To introduce a variety of length- and time-scales into a flow, we focus on two methods. First, we concentrate on effects due to guiding a fluid over a complex-shaped object placed in the flow domain. Specifically, we apply direct numerical simulation to predict flow through a cylindrical pipe in which a periodic array of orifice plates with a fractal perimeter is mounted. To represent the complex orifice, a volume penalisation immersed boundary method is used. Adding a periodic array of fractal orifice plates, derived from the Koch snowflake, to a cylindrical pipe is shown to increase the average laminar stretching rate by a factor of up to five, compared to pipe flow without orifice plates. Second, we consider the inclusion of multiple length- and time scales at inflow boundaries to enhance mixing efficiency for combustion in Bunsen-type flames. By using a combination of large- and small-scale flow perturbations at an inflow, a two-fold increase of flame wrinkling and flame intensity could be realised. The scale-dependency of the intensification of the combustion is investigated, showing a narrow range of length-scales with strongest response, reminiscent of 'resonant turbulence' conditions.
KW - Bunsen flame
KW - Enhanced mixing
KW - Multiscale forcing
KW - Pipe flow
KW - Turbulence modulation
UR - http://www.scopus.com/inward/record.url?scp=85028438085&partnerID=8YFLogxK
U2 - 10.1016/j.compfluid.2017.06.014
DO - 10.1016/j.compfluid.2017.06.014
M3 - Article
AN - SCOPUS:85028438085
VL - 176
SP - 353
EP - 365
JO - Computers & Fluids
JF - Computers & Fluids
SN - 0045-7930
ER -