FY2023 Annual Report

Complex Fluids and Flows
Assistant Professor Marco Edoardo Rosti


In the past year, Ianto Cannon become the first PhD student of the unit to graduate. We also welcomed Lorenzo Piana, Angel Ricardo Jara Jimenez, Riccardo Bertoncello and Marildo Kola as reserch intern, and Igors Dubanevics, Tatsuo Izawa and Chenming Zhen as rotations students. Also, Megumi Ikeda left her role as unit RUA, and she has been replaced by Tomoe Owan.

The unit research has continued to being focused on multiphase. The unit worked on the turbulence modulation by the presence of drops, particles, fibers and polymers. A great amount of work has focused on studying elastic turbulence in several configurations, from triperiodic homogenous flows to jets and channels.

In this period, 11 manuscripts were published in international journals, including 1 Nature Physics, 1 Proceedings of the National Academy of Sciences of the United States of America, 1 Physical Review Letter and 2 Journal of Fluid Mechanics, and 2 Physical Review Fluids Letters. Furthermore, the unit members were invited to give 1 invited talk and 6 seminars in international conferences and universities. Finally, 9 international guests were invited to present their works in seminars.

1. Staff

  • Giovanni Soligo, Postdoctoral Researcher
  • Rahul Kumar Singh, Postdoctoral Researcher
  • Aswathy M.S., Postdoctoral Researcher
  • Alessandro Chiarini, Postdoctoral Researcher
  • Ianto Cannon, Graduate Student (-2023 November), Junior Research Fellow (2023 December-)
  • Mohamed Abdelgawad, Graduate Student
  • Simone Tandurella, Graduate Student
  • Christian Amor Rodriguez, Graduate Student
  • Morie Koseki, Graduate Student
  • Jean-Paul van Woensel, Graduate Student
  • Giulio Foggi Rota, Graduate Student
  • Megumi Ikeda, Administrative Assistant (-2023 December)
  • Tomoe Owan, Administrative Assistant (2024 January-)

2. Collaborations

For all the cases: Type of collaboration: Joint research

Suspensions in porous media

  • Prof. Parisa Mirbod (University of Illinois at Chicago)
  • Prof. Marco E. Rosti (OIST)

Flexible fibres in turbulence

  • Ianto Cannon (OIST)
  • Dr. Stefano Olivieri (OIST)
  • Prof. Andrea Mazzino (University of Genova)
  • Prof. Marco E. Rosti (OIST)

Canopy flows

  • Giulio Foggi Rota (OIST)
  • Dr. Alessandro Monti (OIST)
  • Prof. Alfredo Pinelli (City University of London)
  • Prof. Marco E. Rosti (OIST)

Haemorheology of red blood cells

  • Prof. Naoki Takeishi (Osaka University)
  • Prof. Marco E. Rosti (OIST)

Immiscible Rayleigh-Taylor turbulence

  • Stefano Brizzolara (ETH Zurich)
  • Prof. Markus Holzner (ETH Zurich)
  • Prof. Andrea Mazzino (University of Genova)
  • Prof. Marco E. Rosti (OIST)

Marangoni effect

  • Alessandro Bevilacqua (OIST)
  • Dr. Giovanni Soligo (OIST)
  • Dr. Mirco Dindo (University of Perugia)
  • Prof. Paola Laurino (OIST)
  • Prof. Marco E. Rosti (OIST)

Hydrodynamics of clownfish

  • Dr. Manon Mercader (OIST)
  • Dr. Stefano Olivieri (OIST)
  • Prof. Vincent Laudet (OIST)
  • Prof. Marco E. Rosti (OIST)

Flow-structure interaction of perforated plates

  • Dr. Stefano Olivieri (OIST)
  • Dr. Jeffrey Cheng (University of Illinois at Urbana-Champaign)
  • Prof. Leonardo Chamorro (University of Illinois at Urbana-Champaign)
  • Prof. Marco E. Rosti (OIST)

Rayleigh-Taylor instability

  • Prof. Gustavo Gioia (OIST)
  • Prof. Pinaki Chackraborty (OIST)
  • Prof. Marco E. Rosti (OIST)

Turbulent pulsating flow

  • Giulio Foggi Rota (OIST)
  • Prof. Maurizio Quadrio (Politecnico di Milano)
  • Prof. Marco Edoardo Rosti (OIST)

Polymeric flows at low Reynolds numbers

  • Dr. Rahul K. Singh (OIST)
  • Prof. Prasad Perlekar (TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research)
  • Prof. Dhrubaditya Mitra (Nordita, KTH Royal Institute of Technology and Stockholm University)
  • Prof. Marco E. Rosti (OIST)

Inertial particle Rayleigh-Taylor turbulence

  • Simone Tandurella (OIST)
  • Prof. Stefano Musacchio (University of Turin)
  • Prof. Guido Boffetta (University of Turin)
  • Prof. Marco E. Rosti (OIST)

2D turbulence in non-Newtonian, planar jets

  • Christian Amor Rodríguez (OIST)
  • Dr. Giovanni Soligo (OIST)
  • Prof. Andrea Mazzino (University of Genova)
  • Prof. Marco E. Rosti (OIST)

Elastic turbulence in non-Newtonian jets

  • Christian Amor Rodríguez (OIST)
  • Dr. Giovanni Soligo (OIST)
  • Adrián Corrochano (Universidad Politécnica de Madrid)
  • Prof. Soledad Le Clainche (Universidad Politécnica de Madrid)
  • Prof. Marco E. Rosti (OIST)

Device to prevent virus transmisison

  • Prof. Riccardo Vinuesa (KTH Royal Institute of Science and Technology)
  • Prof. Soledad Le Clainche (Universidad Politécnica de Madrid)
  • Prof. Marco E. Rosti (OIST)

Transition to turbulence in rough-walled channel flow

  • Prof. Pinaki Chakraborty (OIST)
  • Prof. Marco E. Rosti (OIST)

Tuning the extensional behavior of elastoviscoplastic fluids

  • Mohamed Abdelgawad (OIST)
  • Dr. Simon Haward (OIST)
  • Prof. Amy Shen (OIST)
  • Prof. Marco E. Rosti (OIST)


3. Activities and Findings

Turbulence in elastoviscoplastic fluids

Non-Newtonian fluids have a viscosity that varies with applied stress. Elastoviscoplastic fluids, the elastic, viscous and plastic properties of which are interconnected in a non-trivial way, belong to this category. We have performed numerical simulations to investigate turbulence in elastoviscoplastic fluids at very high Reynolds-number values, as found in landslides and lava flows, focusing on the effect of plasticity. We find that the range of active scales in the energy spectrum reduces when increasing the fluid plasticity; when plastic effects dominate, a new scaling range emerges between the inertial range and the dissipative scales. An extended self-similarity analysis of the structure functions reveals that intermittency is present and grows with the fluid plasticity. The enhanced intermittency is caused by the non-Newtonian dissipation rate, which also exhibits an intermittent behaviour. These findings have relevance to catastrophic events in natural flows, such as landslides and lava flows, where the enhanced intermittency results in stronger extreme events, which are thus more destructive and difficult to predict.

Non-Newtonian turbulent jets

We perform direct numerical simulations of planar jets of non-Newtonian fluids at low Reynolds number, in typical laminar conditions for a Newtonian fluid. We select three different non-Newtonian fluid models mainly characterized by shear-thinning (Carreau), viscoelasticity (Oldroyd-B) and shear-thinning and viscoelasticity together (Giesekus), and perform a thorough analysis of the resulting flow statistics. We observe that, the jet transitions from a laminar flow at low elasticity, to a turbulent flow at high elasticity. We show that the different non-Newtonian features and their combination give rise to rather different flowing regimes, originating from the competition of viscous, elastic and inertial effects. We observe that both viscoelasticity and shear-thinning can develop the instability and the consequent transition to a turbulent flowing regime; however, the purely viscoelastic Oldroyd-B fluid exhibits the onset of disordered fluid motions at a lower value of than what observed for the purely shear-thinning Carreau fluid. When the two effects are both present, an intermediate condition is found, suggesting that, in this case, the shear-thinning feature is acting against the fluid elasticity. Despite the qualitative differences observed in the flowing regime, the bulk statistics, namely the centerline velocity and jet thickness, follow almost the same power-law scalings obtained for laminar and turbulent Newtonian planar jets.

Migration of a deformable capsule in pulsatile channel flows

We study the lateral movement of a deformable spherical capsule in a pulsatile channel flow, with a Newtonian fluid in an almost inertialess condition and at a small confinement ratio. We find that the speed of the axial migration of the capsule can be accelerated by the flow pulsation at a specific frequency. The migration speed increases with the oscillatory amplitude, while the most effective frequency remains basically unchanged and independent of the amplitude. Our numerical results form a fundamental basis for further studies on cellular flow mechanics, since pulsatile flows are physiologically relevant in human circulation, potentially affecting the dynamics of deformable particles and red blood cells, and can also be potentially exploited in cell focusing techniques.

Drag reduction in a turbulent channel flow

We show that the energy required by a turbulent flow to displace a given amount of fluid through a straight duct in a given time interval can be reduced by modulating in time the pumping power. The control strategy is hybrid: it is passive, as it requires neither a control system nor control energy, but it manipulates how pumping energy is delivered to the system (as in active techniques) to increase the pumping efficiency. Our control employs a temporally periodic pumping pattern, where a short and intense acceleration (in which the pumping system is on) followed by a longer deceleration (in which the pumping system is off) makes the flow alternately visit a quasi-laminar and a turbulent state. The computational study is for a plane channel flow, and employs direct numerical simulations, which present specific computational challenges, for example the highly varying instantaneous value of the Reynolds number, and the importance of discretisation effects. Particular care is devoted to a meaningful definition of drag reduction in the present context. The ability of the forcing to yield significant savings is demonstrated. Since only a small portion of the parameter space is investigated, the best performance of the control technique remains to be assessed.

Dense bidisperse suspensions

We study the rheological behaviour of bidisperse suspensions in three dimensions under a non-uniform shear flow, made by the superimposition of a linear shear and a sinusoidal disturbance. Our results show that (i) only a streamwise disturbance in the shear-plane alters the suspension dynamics by substantially reducing the relative viscosity, (ii) with the amplitude of the disturbance determining a threshold value for the effect to kick-in and its wavenumber controlling the amount of reduction and which of the two phases is affected. We show that, (iii) the rheological changes are caused by the effective separation of the two phases, with the large or small particles layering in separate regions. We provide a physical explanation of the phase separation process and of the conditions necessary to trigger it. We test the results in the whole flow curve, and we show that the mechanism remains substantially unaltered, with the only difference being the nature of the interactions between particles modified by the phase separation.

Forced and natural dynamics of a clamped flexible fiber in wall turbulence

We characterize the dynamical behavior of a clamped flexible fiber immersed in wall turbulence over a wide range of natural frequencies by means of direct numerical simulations. Only two flapping states are possible: one where the fiber oscillates at the characteristic frequency of the largest turbulent eddies and another where the natural structural response dominates. The former is obtained in the more flexible cases, while the latter in the more rigid ones. We observe that in the turbulence-dominated regime, the fiber always sways at a frequency proportional to the largest scale of the flow, regardless of its structural parameters. The hindrance of the clamp to the wall prevents the synchronization of the fiber with turbulent eddies of comparable size.

Finite-size spherical particles in turbulent flows

We investigate the influence of dispersed solid spherical particles on the largest scales of the turbulent Arnold-Beltrami-Childress (ABC) flow. The ABC flow is an ideal instance of a complex flow: it does not have solid boundaries, but possesses an inhomogeneous and three-dimensional mean shear. By tuning the parameters of the suspension, we show that particles modulate the largest scales of the flow toward an anisotropic, quasi-two-dimensional and more energetic state. In this regime, particles move along quasistraight trajectories and exhibit anomalous transport.

4. Publications

4.1 Journals

  1. Immiscible Rayleigh–Taylor turbulence: Implications for bacterial degradation in oil spills
    S. Brizzolara, R. Naudascher, M. E. Rosti, R. Stocker, G. Boffetta, A. Mazzino, M. Holzner
    Proceedings of the National Academy of Sciences, National Academy of Sciences, 121, 11, e2311798121, 2024
    DOI: 10.1073/pnas.2311798121
  2. Direct numerical simulations of a novel device to fight airborne virus transmission
    J. A. Martin, M. E. Rosti, S. Le Clainche, R. Navarro, R. Vinuesa
    Physics of Fluids, AIP Publishing, 36, 023352, 2024
    DOI: 10.1063/5.0187736
  3. Anisotropic mean flow enhancement and anomalous transport of finite-size spherical particles in turbulent flows
    A. Chiarini, I. Cannon, M. E. Rosti
    Physical Review Letters, APS, 132, 054005, 2024
    DOI: 10.1103/PhysRevLett.132.054005
  4. Forced and natural dynamics of a clamped flexible fiber in wall turbulence
    G. Foggi Rota, M. Koseki, R. Agrawal, S. Olivieri, M. E. Rosti
    Physical Review Fluids, APS, 9, L012601, 2024
    DOI: 10.1103/PhysRevFluids.9.L012601
  5. Gap-modulated dynamics of flexible plates
    S. Cheng, S. Olivieri, M. E. Rosti, L. Chamorro
    Journal of Fluid Mechanics, Cambridge University Press, 974, A12, 2023
    DOI: 10.1017/jfm.2023.806
  6. Dense bidisperse suspensions under non-homogeneous shear
    A. Monti, M. E. Rosti
    Scientific Reports, Nature Publishing Group, 13, 14310, 2023
    DOI: 10.1038/s41598-023-41587-3
  7. On–off pumping for drag reduction in a turbulent channel flow
    G. Foggi Rota, A. Monti, M. E. Rosti, M. Quadrio
    Journal of Fluid Mechanics, Cambridge University Press, 966, A12, 2023
    DOI: 10.1017/jfm.2023.451
  8. Enhanced axial migration of a deformable capsule in pulsatile channel flows
    N. Takeishi, M. E. Rosti
    Physical Review Fluids, APS, 8, L061101, 2023
    DOI: 10.1103/PhysRevFluids.8.L061101
  9. Non-Newtonian turbulent jets at low-Reynolds number
    G. Soligo, M. E. Rosti
    International Journal of Multiphase Flows, Elsevier, 167, 104546, 2023
    DOI: 10.1016/j.ijmultiphaseflow.2023.104546
  10. Numerical modelling of the extensional dynamics in elastoviscoplastic fluids
    M. Abdulrazaq, A. Shahmardi, M. E. Rosti, L. Brandt
    Journal of Non-Newtonian Fluid Mechanics, Elsevier, 318, 105060, 2023
    DOI: 10.1016/j.jnnfm.2023.105060
  11. Scaling and intermittency in turbulent flows of elastoviscoplastic fluids
    M. Abdelgawad, I. Cannon, M. E. Rosti
    Nature Physics, Nature Publishing Group, 19, 1059-1063, 2023
    DOI: 10.1038/s41567-023-02018-2

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

Invited Talks

  1. M. Rosti “Turbulent flows with polymers” International Conference on Viscoelastic Flow Dynamics: from Theory to Mechanisms, China (2024.01.08)

Contributed Talks

  1. M. Rosti “Morphology of droplets in homogeneous isotropic turbulence”IUTAM Symposium, Japan (2023.12.03)
  2. M. Rosti “Elastic range scaling in polymeric turbulence at high and low Reynolds number” APS – DFD meeting, USA (2023.11.16)
  3. I. Cannon “Morphology of surfactant-free and surfactant-laden droplets in homogeneous isotropic turbulence” APS – DFD meeting, USA (2023.11.16)
  4. S. Tandurella “Flexible fibers” Annual Meeting of the Japanese Society of Fluid Mechanics, Japan (2023.09.20)
  5. M. Koseki “The effect of wall elasticity on turbulent channel flow” Annual Meeting of the Japanese Society of Fluid Mechanics, Japan (2023.09.20)
  6. I. Cannon “Spheres and fibres in turbulent flows at a range of Reynolds numbers” Annual Meeting of the Japanese Society of Fluid Mechanics, Japan (2023.09.20)
  7. G. Foggi Rota “Turbulent canopy flows: dynamics & fluid-structure interaction” Annual Meeting of the Japanese Society of Fluid Mechanics, Japan (2023.09.20)
  8. C. Amor “Waves and their implication in elastic turbulence in planar jets” Annual Meeting of the Japanese Society of Fluid Mechanics, Japan (2023.09.20)
  9. M. S. Aswathy “Dynamics of fibers dispersed in viscoelastic fluids” Annual Meeting of the Japanese Society of Fluid Mechanics, Japan (2023.09.20)
  10. M. Rosti “Elastic range scaling in polymeric turbulence at large Reynolds and Deborah numbers” European Turbulence Conference, Spain (2023.09.04)
  11. S. Tandurella “Inertial particles Rayleigh-Taylor turbulence” European Turbulence Conference, Spain (2023.09.04)
  12. J. P. van Woensel “Turbulent viscoelastic mixing layers” European Turbulence Conference, Spain (2023.09.04)
  13. G. Foggi Rota “Flapping states of clamped fibres in wall turbulence” European Turbulence Conference, Spain (2023.09.04)
  14. C. Amor “On the structure of turbulence in shear-thinning planar jets” European Turbulence Conference, Spain (2023.09.04)
  15. A. Chiarini “Mean-flow enhancement and turbulence modulation by finite-size spherical particles” European Turbulence Conference, Spain (2023.09.04)
  16. M. S. Aswathy “Dynamics of fibres dispersed in viscoelastic fluids” European Turbulence Conference, Spain (2023.09.04)
  17. R. K. Singh “Intermittent elastic turbulence” European Turbulence Conference, Spain (2023.09.04)
  18. M. E. Rosti “Elastic turbulence in free and wall-shear flows” Universidad Politécnica de Madrid, Spain (2023.06.30)
  19. C. Amor “Unveiling elastic turbulence in free and wall-shear flows with data-analysis tools” Universidad Politécnica de Madrid, Spain (2023.06.16)
  20. S. Tandurella “Numerical simulations of flexible fibers” European Young Rheologists Symposium, online (2023.05.08)
  21. G. Foggi Rota “Dynamic behaviour of flexible filaments canopies in turbulent flows” International Conference of Multiphase Flows, Kobe, Japan (2023.04.06)
  22. M. E. Rosti “Simulations of viscoelastic turbulent jets at high Reynolds and Weissenberg numbers” International Conference of Multiphase Flows, Kobe, Japan (2023.04.06)
  23. G. Soligo “Numerical simulation of surfactant-laden flows” International Conference of Multiphase Flows, Kobe, Japan (2023.04.04)
  24. R. K. Singh “Energy spectrum scaling depends on the Re number in polymeric turbulence” International Conference of Multiphase Flows, Kobe, Japan (2023.04.04)
  25. M. Abdelgawad “Turbulence modulation in elastoviscoplastic fluid flows” International Conference of Multiphase Flows, Kobe, Japan (2023.04.04)
  26. I. Cannon “Coalescence and breakup of droplets in a viscoelastic turbulent fluid” International Conference of Multiphase Flows, Kobe, Japan (2023.04.04)


  1. M. Rosti “Morphology of droplets in turbulence” Kyoto Institute of Technology, Japan (2024.03.11)
  2. I. Cannon “Morphology of droplets in turbulent flows” New Jersey Institute of Technology, USA (2023.11.27)
  3. M. Rosti “Polymeric turbulence at large Reynolds and Deborah numbers” University of British Columbia, Canada (2023.11.23)
  4. M. Rosti “Polymeric turbulence” Laboratoire de Mécanique des Fluides de Lille - Kampé de Fériet, France, online (2023.10.06)
  5. M. Rosti “Particles, fibers and drops in turbulent flows” The University of Tokyo, Japan (2023.09.14)
  6. M. Rosti “Turbulent flows over flexible canopies” Delft University of Technology, Netherlands (2023.01.16)
  7. M. Rosti “Turbulence in elastoviscoplastic fluids” Universidad Politécnica de Madrid, Spain (2023.06.12)


  1. I. Cannon “Intermittency in turbulent flows of elastoviscoplastic fluids” Pre-APS-DFD Satellite Meeting on Environmental and Biological Fluid Dynamics, USA (2023.11.16)
  2. I. Cannon “Turbulence modulation in multiphase flows at high Reynolds number” HPCI Project Report Meeting (2023.10.26)
  3. G. Soligo “Direct numerical simulations of turbulence of non-Newtonian fluids” HPCI Project Report Meeting (2023.10.26)
  4. G. Soligo “Drops and surfactant in turbulent flows” HPCI Project Report Meeting (2023.10.26)
  5. M. Abdelgawad “Tuning extensional behavior of elastoviscoplastic fluids with polymer additives” International Conference on Rheology, Greece (2023.08.02)

    5. Intellectual Property Rights and Other Specific Achievements

    Nothing to report

    6. Meetings and Events

    A Lagrangian journey in compressible turbulence

    • Date: February 27 2024
    • Venue: OIST
    • Speaker: Prof. Dhrubaditya Mitra / NORDITA, Sweden

    Computational science of turbulence - Universality, intermittency, and connection to real turbulence phenomena

    • Date: February 22 2024
    • Venue: OIST
    • Speaker: Prof. Takashi Ishihara / Okayama University, Japan

    Turbulent heat transfer over non-smooth walls

    • Date: January 31 2024
    • Venue: OIST
    • Speaker: Associate Prof. Yusuke Kuwata / Osaka Metropolitan University, Japan

    Peculiar decay of turbulence: 3D Navier-Stokes and shell model

    • Date: October 16 2023
    • Venue: OIST
    • Speaker: Prof. Takeshi Matsumoto / Kyoto University, Japan

    Entropy and active elasticity

    • Date: July 25 2023
    • Venue: OIST
    • Speaker: Prof. Dhurubaditya Mitra / NORDITA, Sweden

    Bubble clustering and the related phenomena

    • Date: July 18 2023
    • Venue: OIST
    • Speaker: Prof. Shu Takagi / The University of Tokyo, Japan

    Energy transfer in two-dimensional turbulent flow affected by polymers and surfactants

    • Date: July 5 2023
    • Venue: OIST
    • Speaker: Associate Prof. Ruri Hidema / Kobe University, Japan

    Diffuse-interface framework for boiling flows with contact-line model

    • Date: Apr 10 2023
    • Venue: OIST
    • Speaker: Prof. Luca Brandt / KTH, Sweden

    7. Others

    External Grants

    • Marco E. Rosti, Giulio Foggi Rota, Alessandro Chiarini, HPCI, " HPCI Fugaku Small-Scale Projects”, hp220402
    • Marco E. Rosti, Giovanni Soligo, HPCI, " Direct numerical simulations of elastoviscoplastic jets”, hp230018


    • Christian Amor - Career talk to middle school students from the Okinawa International School
    • Christian Amor - Assistance and feedback to poster session of students from Yokohama Science Frontier High School
    • Aswathy MS – OIST Science Festival
    • Aswathy MS – talk to high school students from Utsunomiya Junior Colege, Japan
    • Aswathy MS - facilitating Nobel Prize public lecture in Urasoe

    CFF unit - Visit of the Plasma and Fusion Young Researchers Forum from the Graduate University for Advanced Studies (GUAS, SOKENDAI)

    OIST news - Towards a deeper understanding of turbulence in elastoviscoplastic fluids