Periodic Reporting for period 2 - CTFF (Control of turbulent friction force)
Reporting period: 2019-12-01 to 2022-09-30
CTFF is a major interdisciplinary project that combines wisdoms in three academic disciplines: Heat Transfer, Fluid Physics and Plasma Physics, to address the research problem on both active and passive control of turbulent friction force. The main focus is on developing techniques for the control of near-wall turbulent structures and the reduction of turbulent friction force, specifically at conditions relevant to engineering practices, by coordinating the efforts of European, the US and Chinese experts specialized in these three different but overlapping domains. New materials will be examined, novel numerical algorithms will be developed, and the numerical results will be tested in physical experiments. In brief, the main objective of this project is to coordinate the action of a group of Universities and enterprises, with complementary expertise in three disciplines from European countries, China and the US, to build and test an optimal solution for the reduction of turbulent friction drag, thereby facilitating the successful implementation of friction force control in engineering practices.
1. optimal control
Algorithms of the control were derived and implemented in the code and were applied to test cases including both boundary layer flow and cylinder flow.
Particular attention was paid to the surface condition, such as drag reduction on oscillating bodies. A resonance frequency at which free-stream disturbance is greatly amplified was found at such oscillating conditions.
Reduced-order model of the evolution of free-stream disturbance was further developed, aiming at generating signal for control systems based on remote sensing. This has been tested in flow around a flat plate.
Other forms of drag reduction control were also tested including plasma-based actuation, flexible filaments, polymer materials, etc.
2. fluid & heat transfer
The interaction of fluid flow and heat transfer in a nanoscale pipe was thoroughly studied. An analytical solution was obtained and it is further validated by molecular dynamics simulations.
Drag reduction in lubricated pipe flow with a slip boundary condition and a sudden contraction was also studied and the results have been submitted for journal publication.
Coupled solver for fluid and heat transfer was developed for simulations in turbomachinery. It was observed that the heat transfer has limited influence to the fluid flow, which, however, imposes significant feedback to the heat transfer.
3. surface texture.
Experimental study was performed to design supericephobic surfaces in joint projects. This has been submitted for journal submission.
Various surfaces, such as superhydrophobic, deformable, permeable, etc, have been numerically modelled and simulated to find their drag reduction potentials.
13 journal papers were published / submitted.
Two conferences, two workshops and two summer schools are organized.
International conference on drag redution has been organised as a part of the Deliverable D5.3.
Project website to disseminatoin our activities and results was established as a part of the Deliverables D5.1.
Business modelling of the research conducted and the exploitation plan has been made as a part of the Deliverable D5.4.
Dissemination and communication report has been completed as a part of the Deliverable D5.5.
Algorithms of the control were derived and implemented in the code and were applied to test cases including both boundary layer flow and cylinder flow.
Particular attention was paid to the surface condition, such as drag reduction on oscillating bodies. A resonance frequency at which free-stream disturbance is greatly amplified was found at such oscillating conditions.
Reduced-order model of the evolution of free-stream disturbance was further developed, aiming at generating signal for control systems based on remote sensing. This has been tested in flow around a flat plate.
Other forms of drag reduction control were also tested including plasma-based actuation, flexible filaments, polymer materials, etc.
2. fluid & heat transfer
The interaction of fluid flow and heat transfer in a nanoscale pipe was thoroughly studied. An analytical solution was obtained and it is further validated by molecular dynamics simulations.
Drag reduction in lubricated pipe flow with a slip boundary condition and a sudden contraction was also studied and the results have been submitted for journal publication.
Coupled solver for fluid and heat transfer was developed for simulations in turbomachinery. It was observed that the heat transfer has limited influence to the fluid flow, which, however, imposes significant feedback to the heat transfer.
3. surface texture.
Experimental study was performed to design supericephobic surfaces in joint projects. This has been submitted for journal submission.
Various surfaces, such as superhydrophobic, deformable, permeable, etc, have been numerically modelled and simulated to find their drag reduction potentials.
13 journal papers were published / submitted.
Two conferences, two workshops and two summer schools are organized.
International conference on drag redution has been organised as a part of the Deliverable D5.3.
Project website to disseminatoin our activities and results was established as a part of the Deliverables D5.1.
Business modelling of the research conducted and the exploitation plan has been made as a part of the Deliverable D5.4.
Dissemination and communication report has been completed as a part of the Deliverable D5.5.
The progress listed above are all those beyond the state of the art and are either under consideration of publication or just published.
Expected results and impacts:
1. The nonlinear optimal control acting on a boundary layer that is computed over a sufficiently long time beyond the current limit due to the divergence of the adjoint method.
This will enable real optimal control in vehicles, a revolution of the control actuation and systems.
2. Drag reduction by plasma actuation, combining micro-scale plasma simulation, mesoscale fluid simulation and fluid experiments.
This research will integrate and validate a large number of previous studies and clarify the challenges for the future development of plasma actuations.
3. The mechanism or possibility of joint control of drag and heat transfer in turbomachinery.
The work has significant impacts to engine design since the previous rule is to design the aerodynamic geometry and test the heat transfer afterwards without considering the coupling at the original design stage.
Expected results and impacts:
1. The nonlinear optimal control acting on a boundary layer that is computed over a sufficiently long time beyond the current limit due to the divergence of the adjoint method.
This will enable real optimal control in vehicles, a revolution of the control actuation and systems.
2. Drag reduction by plasma actuation, combining micro-scale plasma simulation, mesoscale fluid simulation and fluid experiments.
This research will integrate and validate a large number of previous studies and clarify the challenges for the future development of plasma actuations.
3. The mechanism or possibility of joint control of drag and heat transfer in turbomachinery.
The work has significant impacts to engine design since the previous rule is to design the aerodynamic geometry and test the heat transfer afterwards without considering the coupling at the original design stage.