Stochastic analysis of the time evolution of Laminar-Turbulent bands of plane Couette flow

This article is concerned with the time evolution of the oblique laminar-turbulent bands of transitional plane Couette flow under the influence of turbulent noise. Our study is focused on the amplitude of modulation of turbulence. In order to guide the numerical study of the flow, we first perform an analytical and numerical analysis of a Stochastic Ginzburg-Landau equation for a complex order parameter. The modulus of this order parameter models the amplitude of modulation of turbulence. Firstly, we compute the autocorrelation function of said modulus once the band is established. Secondly, we perform a calculation of average and fluctuations around the exponential growth of the order parameter. This type of analysis is similar to the Stochastic Structural Stability Theory. We then perform numerical simulations of the Navier-Stokes equations in order to confront these predictions with the actual behaviour of the bands. Computation of the autocorrelation function of the modulation of turbulence shows quantitative agreement with the model: in the established band regime, the amplitude of modulation follows an Ornstein-Uhlenbeck process. In order to test the S3T predictions, we perform quench experiments, sudden decreases of the Reynolds number from uniform turbulence, in which modulation appears. We compute the average evolution of the amplitude of modulation and the fluctuations around it. We find good agreement between numerics and modeling. The average trajectory grows exponentially, at a rate clearly smaller than that of the formation of laminar holes. The actual time evolution remains in a flaring envelope, centred on the average, and expanding at the same rate. These results provide further validation of the stochastic modeling for the time evolution of the bands for further studies. They stress on the difference between the oblique band formation and the formation of laminar holes.Comment: 17 pages, 6 figures. Followed by a Graphical abstract summarising the article. Accepted for publication in Eur. Phys. J E (last submitted version

Turbulent spot growth in plane Couette flow: statistical study and formation of spanwise vorticity

This article presents direct numerical simulations of the growth of turbulent spots in the transitional regime of plane Couette flow. A quantitative description of the growth process and of the detail of the quadrupolar flow around the spot is given. Focus is put on formation of spanwise vorticity in the velocity streaks that resembles a secondary shear instability. The main features of the instability (coherence lengths, advection velocity) are studied in the context of the turbulent spot, below and above the threshold Reynolds number of appearance of the oblique turbulent bands of plane Couette flow.Comment: 10 pages, 9 figure

Introducing Fortenbaugh Intern Abby

Hi I’m Abby – the last of three Fortenbaugh Interns to post! I am a senior with a History major and Political Science and Anthropology minors and I hail from Kokomo, Indiana. I am so excited to be working in Special Collections – I love working with history first-hand! Here’s a brief write-up of what I have completed so far in my time on the 4th Floor. [excerpt

Muslim Women Political Leaders and Electoral Participation in Muslim-Majority Countries

This paper focuses on Muslim women political leaders and their agency in the modern world. While some Muslim women have a difficult time participating politically, others actively act in policy and government. Culture, identity, location, and political parties are some of the factors leading to different levels of participation from Muslim women in various countries

MS-175: Kate Burr Whiting Travel Journal

This collection consists one of one 177 page travel journal, with 136 images included. A letter from 1928 is also included with the journal. The photographs document all the places Kate Burr Whiting traveled around the world. Special Collections and College Archives Finding Aids are discovery tools used to describe and provide access to our holdings. Finding aids include historical and biographical information about each collection in addition to inventories of their content. More information about our collections can be found on our website http://www.gettysburg.edu/special_collections/collections/.https://cupola.gettysburg.edu/findingaidsall/1144/thumbnail.jp

Last Post

I cannot believe this is my last week working in Special Collections and there are less than three weeks until graduation. My time up here has gone by so fast and I’m sad it’s coming to an end! I’ve made a lot of progress and learned a lot as well. [excerpt

Introduction to Library Trends 18 (3) Winter 1970: Problems of Acquisition for Research Libraries

published or submitted for publicatio