FY2022 Annual Report

Continuum Physics Unit
Professor Gustavo Gioia

Abstract

We studied frictional drag in turbulent rough-walled flows; classical, transitional and fully turbulent RT instabilities; and the etiology of poorly understood features of the turbulent mean velocity profile
 

1. Staff

  • Gustavo Gioia, Professor
  • Tomoe Owan, Research Unit Administrator

2. Collaborations

2.1 Frictional drag in rough-walled, turbulent flows between concentric rotating cylinders

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Professor Pinaki Chakraborty, OIST

2.2 Classical, transitional and fully turbulent RT instabilities

  • Type of collaboration: Scientific collaboration
  • Researchers:
    • Professor Marco Rosti, OIST
    • Professor Pinaki Chakraborty, OIST

3. Activities and Findings

3.1 Frictional drag in rough-walled, turbulent flows between concentric rotating cylinders

Frictional drag in rough-walled, turbulent pipe flows has long been a topic of intense research activity. Nikuradse's grounbreaking experiments, published in 1933, remain the empirical foundation of the Moody diagram used by engineers to design pipeline systems. Other types rough-walled flows are little understood. In this collaborative project with the Fluid Mechanics unit, we are carrying out theoretical, experimental and  computational research on frictional drag  in rough-walled turbulent flows between concentric rotating cylinders.

3.2 Classical, transitional and fully turbulent RT instabilities

The RT instability occurs at the interface between two layers of fluid, where the layer of fluid above the interface is more dense than the layer below the interface and gravity acts normal the interface and points towards the less dense fluid. In the classical RT instability, which has been extensively researched and may be said to be well understood, the instability is governed by the molecular viscosity (i.e., the usual viscosity). The classical RT instability is relevant to many applications, some of them notorious, but there are some applications in volcanology, notably in the highly energetic umbrellas that develop above co-ignimbrite columns, where the classical RT instability's wavelengths and timescales are erroneous by several  orders of magnitude. To grapple with such applications, a turbulent version of the RT instability must be developed. In previous work regarding a specific scalloped umbrella that developed on the slopes of Mexico's Volcan Reventador, we postulated a simple model capable of yielding predictions for the fully turbulent instabillity relevant to Reventador's umbrella. These predictions were shown to be in accord with wavelengths and timescales estimated via remote sensing. In the present project, we have developed an asymptotic formula based on dimensional analysis and similarity arguments, which formula allows us to make predictions bridging the entire transition between the pure classical instability and the fully turbulent instability. These new predictions will be tested by computational simulations currently under way in Prof. M. Rosti's unit. In addition, we have started theoretical work on a model aimed at elucidating the physical underpinning of that formula. This is an ongoing research project being carried out in collaboration with Prof. P. Chakraborty's unit and Prof. M. Rosti's unit.

3.3 Features of the turbulent mean velocity profile of pipe flow

This is is a multi-year research project aimed at elucidating the etiology of certain hitherto ignored features of the turbulent mean velocity profile (MVP) of turbulent pipe flow, which features we have been able to relate to certain well-known but poorly understoond features of the fabric of turbulence as embodied in the Kolmogorovian spectrum of turbulent energy. A recent development within this project has been an ongoing effort to build on the nonlocal character that is intrinsic to our theoretical approach, as we have reasons to believe they will unable us to gain insight into certain turbulent pipe-flow profiles (other than the MVP) which cannot be explained by means of the classical theoretical approach.

4. Publications

4.1 Journals

Nothing to report

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

  1. Gioia, G., El factor de fricción de flujos turbulentos: lo que le falta a Nikuradse y al diagrama de Moody., University of Buenos Aires, Buenos Aires, Argentina, March (2023).

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Towards Sustainability in Construction with Concrete

  • Date: September 12, 2022
  • Venue: OIST Campus Lab1
  • Speaker: Prof. Ravindra Gettu (Indian Institute of Technology Madras)

6.2 Formation of satellite systems around Jupiter and Saturn

  • Date: October 4, 2022
  • Venue: OIST Campus Lab1
  • Speaker: Prof. Yuri Fujii (Kyoto University)

7. Other

Nothing to report.