631Active control of skin friction and convective heat transfer in wall-bounded flows


22 May 2023 – 24 May 2023


Madrid, Spain




Dr. Stefano Discetti
Aerospace Engineering Research Group
Universidad Carlos III de Madrid
Avda. Universidad 30,
28911, Leganés


Email: sdiscett@ing.uc3m.es 


Marios Kotsonis
Delft University of Technology
The Netherlands


Andrea Ianiro
Universidad Carlos III de Madrid


Woutijn Baars
Delft University of Technology
The Netherlands

 Active control of wall-bounded flows is an everlasting topic of research in the fluid dynamics community. Skin friction drag reduction and convective heat transfer control are of paramount importance in an overwhelming amount of applications, involving transportation means, renewable energy exploitation, industrial processes, turbomachinery for power generation and propulsion, etc.
Fast-paced advancement of experimental hardware and computational power have fostered, on one hand, the establishment of efficient techniques for sensing and actuation, and on the other hand, the development of techniques to efficiently distil the information available from sensors and select the most effective control strategy.
This colloquium is expected to create fertile soil for discussion, exchange of ideas and networking between leading scientists in flow control, specifically in the areas of wall-bounded flows. The structure of the colloquium will target specifically the identification of open- and closed-loop control laws, sensing strategies and actuation solutions in applications of drag reduction and convective heat transfer control.
Numerical, theoretical and experimental contributions in laminar, transitional and turbulent flows will be welcome as well as surveys and comparative studies of competing control strategies.

Identification of open- and closed-loop control laws
A grand challenge in spectrally-rich wall-bounded flows is the identification of effective open- and closed-loop control laws for both transitional and turbulent flows. Opposition control has been standing for long as a very efficient, rugged and simple strategy for this purpose. Recent advances in data-driven techniques and machine-learning methods are paving the way toward more refined solutions, with higher potential for transition delay, skin friction drag and convective heat transfer control. In this section, we aim to foster discussion on:

- Classical control theory
- Model-based control
- Opposition control for instabilities and turbulent flows
- Control based on Reduced-Order Models
- System identification algorithms
- Machine learning techniques

Sensing strategies
The challenge of controlling wall-bounded flows has triggered interesting developments over the years in open-loop, with remarkable histories of success (see e.g. transition delay). Closed-loop control, on the other hand, promises a higher potential for transition control, turbulent skin friction reduction and heat transfer enhancement but requires proper state characterization to optimise the control action. Hardware and software advancements are leading to first pieces of evidence of the possibility of achieving efficient closed-loop control in realistic applications, and at the same time pushing towards a better understanding of flow physics. In this section, we target the following research lines:

- Data-driven techniques for flow estimation from wall measurements
- Model-based control
- Sensing hardware and applications
- Low-order modelling
- Theoretical developments (stability analysis, resolvent analysis, etc.)

Applications in skin friction and convective heat transfer control
This section will focus on applications in laboratory and full-scale conditions. We will stimulate discussion on the basis of applications targeted to friction and convective heat transfer control in wall-bounded flows. Exchange of ideas on pitfalls and practical aspects in real-life implementation will be promoted, especially targeting:

- Actuator concepts for flow control
- Experimental/numerical demonstrations
- Robustness of control strategies to uncertainty and noise
- Real-time control implementations
- Feasibility of scaling to full-scale applications

In addition to the above specific topics, adjacent contributions to the general topic of wall-bounded flow control will also be considered.