2020 Fiscal Year Research-status Report
Modulation of turbulence by droplet coalescence
| Project/Area Number |
20K22402
|
|---|
| Research Institution | Okinawa Institute of Science and Technology Graduate University |
|---|
Principal Investigator |
ロスティ マルコエドアルド 沖縄科学技術大学院大学, 複雑流体・流動ユニット, 准教授 (80876227)
|
|---|
| Project Period (FY) |
2020-09-11 – 2022-03-31
|
| Keywords | Multiphase flows / Turbulence / Droplets / Bubbles |
|---|
| Outline of Annual Research Achievements |
I studied the effect of coalescence on dropelts suspensions in both laminar and turbulent flows. The effect of coalescence was first investigated in low-Reynolds laminar flows to have a better understanding of its effect. In particular, I have been investigating how the rheology of droplets is affected by colaescence when changing the viscosity ratio of the two phases and when the carrier fluid has a viscosity function of the local shear rate. Next, I have been studing the same effect in homogeneous isotropic turbulent flows and performing a scale-by-scale analysis of the resulting flow. And finally, I have been studying droplet laden turbulent channenl flows in two configurations, one in which coalescence is prevented and one where it is allowed.
All the above studies highlighted a very strong influence of coalscence on both the large and small scales of the flow. I found that coalescence has a general tendency of reducing the effective viscosity of the system as well as reducing the backreaction of the flow which results less disturbed by the presence of the dispersed phase. The scale-by-scale analysis showed that droplets provide a spectral shortcut, subtracting energy from the large scales and re-introducing it at smaller scales. Coalescence changes the scale of the dropelts and thus the scale at which the energy is re-introduced in the system. In the case of wall-bounded flows, the effect pf coalescence is even more pronounced, due to migration effects that are more pronounced when colascence is allowed.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The current pandemic situation slightly slowed down collaborations with other institutes due to the impossibility of travelling and attending conferences. Nonetheless, the project is progressing without any particular problem.
|
| Strategy for Future Research Activity |
In the second year of the project, I will finalize the work from the previous year completing the projects mentioned above. Manuscript writing and revisions will be done throughout the remaining part of the project. Furthermore, I am going to perform additional simulations in the framework of homogeneous isotropic turbulence preventing coalescence and varying the density ratio, in order to study in more details the backreaction of the flow.
|
| Causes of Carryover |
Because of the pandemic situation, all travels and conferences from last year have been postponed to the present fiscal year. Furthermore, manuscripts written last year will be published in the present year, so their costs will incur in the present fiscal year. Finally, the workstation was not purchased last year but it will be done this year.
|
Research Products
(1 results)
