Journal Of Hydraulics

[Amalia Antill]

TheIAHR Journal of Hydraulic Research (JHR) contains scientific and technical material of broader interest in the areas of theoretical, experimental and computational hydraulics and fluid mechanics in various fields of application (rivers, coasts, environment, structures and industrial flows). This may also include results of field studies and interdisciplinary studies. Further included is publication of state-of-the-art papers, information which is suitable for the end-user (design and consultancy) and forum articles. Discussions to papers and technical notes are welcomed. The scope of the Journal covers the fields in which IAHR is active.

The Journal has been published (currently six issues per year) since 1964 and is distributed to all IAHR Members as part of their Membership Subscription. JHR is published in print and electronic format. From 2010 JHR is published by Taylor & Francis on behalf of IAHR. Please visit the journal's webpage to find out more about JHR, the latest news and offers, and for submission information.

"It is indeed a privilege to take on the role of the next Editor of the Journal of Hydraulic Research. Together with a high quality and experienced Editorial Board, will make every effort to contribute to the reputation of this journal and serve the scientific community in the broad landscape of hydro-environmental engineering".

The online edition of IAHR Journal of Hydraulic Research is freely offered to all members.The printed version fee remains EUR 60.

IAHR Institute Members receive printed and online version as a membership benefit.

Non-members should go directly to the Taylor & Francis website to subscribe, or become members at IAHR website.

The H.J. Schoemaker Award is granted to the author(s) of the paper judged the most outstanding paper published in the IAHR Journal of Hydraulic Research in the two years preceding the IAHR World Congress. The award was established in 1980 to recognise the efforts made by Professor Schoemaker, IAHR Secretary (1960-1979), in guiding the Journal of Hydraulic Research in its formative years.

The Journal of Ecohydraulics is an online journal from the International Association for Hydro-Environment Engineering and Research (IAHR) published twice a year with the support of China Institute of Water Resources and Hydropower Research (IWHR).

The Journal of Ecohydraulics embodies the varied research undertaken in ecohydraulics covering water resources and aquatic life, ecology, biology, hydraulics, engineering, geoscience, environmental science, climate change and other related fields, with an emphasis on the integration of these disciplines.

The Journal of Ecohydraulics Best Paper Award and Best Reviewer Award recognise outstanding papers and reviewers who contributed to the Journal of Ecohydraulics and aims at encouraging scientists to contribute to the varied research in the field of ecohydraulics.

The set of journals have been ranked according to their SJR and divided into four equal groups, four quartiles. Q1 (green) comprises the quarter of the journals with the highest values, Q2 (yellow) the second highest values, Q3 (orange) the third highest values and Q4 (red) the lowest values.

The SJR is a size-independent prestige indicator that ranks journals by their 'average prestige per article'. It is based on the idea that 'all citations are not created equal'. SJR is a measure of scientific influence of journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where such citations come from It measures the scientific influence of the average article in a journal, it expresses how central to the global scientific discussion an average article of the journal is.

Evolution of the total number of citations and journal's self-citations received by a journal's published documents during the three previous years.

Journal Self-citation is defined as the number of citation from a journal citing article to articles published by the same journal.

International Collaboration accounts for the articles that have been produced by researchers from several countries. The chart shows the ratio of a journal's documents signed by researchers from more than one country; that is including more than one country address.

Not every article in a journal is considered primary research and therefore "citable", this chart shows the ratio of a journal's articles including substantial research (research articles, conference papers and reviews) in three year windows vs. those documents other than research articles, reviews and conference papers.

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Viscous flows are laminar and deterministic. Robust linear laws accurately predict their streamlines in geometries as complex as blood vessels, porous media and pipe networks. However, biological and synthetic active fluids defy these fundamental laws. Irrespective of their microscopic origin, confined active flows are intrinsically bistable, making it challenging to predict flows in active fluid networks. Although early theories attempted to tackle this problem, quantitative experiments to validate their relevance to active hydraulics are lacking. Here we present a series of laws that accurately predict the geometry of active flows in trivalent networks. Experiments with colloidal rollers reveal that active hydraulic flows realize dynamical spin ices: they are frustrated, non-deterministic and yield degenerate streamline patterns. These patterns split into two geometric classes of self-similar loops, which reflect the fractionalization of topological defects at subchannel scales. Informed by our measurements, we formulate the laws of active hydraulics in trivalent networks as a double-spin model. We then use these laws to predict the random geometry of degenerate streamlines. We expect our fundamental understanding to provide robust design rules for active microfluidic devices and to offer avenues to investigate the motion of living cells and organisms in complex habitats.

In this Article, we perform large-scale active hydraulics experiments. We show that spontaneous laminar flows are frustrated in networks including nodes with an odd coordination number. Focusing on fully frustrated trivalent networks, we show that the resulting active flows realize dynamical spin ices signalled by extensively degenerate random flow patterns even when the channels are spatially ordered. Unlike passive fluids, and at odds with the current AFN theory, we find that the random geometry of streamlines depends on the aspect ratio of the elementary channels. We explain this polymorphism by combining experiments and numerical simulations, and show that it originates from topological-defect fractionalization at the subchannel level. We then elucidate the self-similar geometry of the flow patterns by mapping them on the frustrated structures of magnetic spin ices and on so-called loop O(n) models19,20,21,22. Altogether, our findings allow us to identify the full set of laws ruling the steady flows of active matter circulating through interconnected channels forming trivalent networks.

The geometry of the streamlines must, therefore, accommodate the conflicting imperatives set by activity and mass conservation. The resulting local frustration defines a set of seven possible flow rules at the vertices, which are classified in Fig. 2c. From a condensed-matter perspective, they are akin to the spin-ice rules responsible for the ground-state degeneracy of magnetic textures in frustrated magnets19,20,21,22. More specifically, the six-most probable vertices (Fig. 2c) define a three-colouring model on the honeycomb lattice24,25, as evident in Fig. 2b. This first analogy with spin-ice physics explains the vast degeneracy of the flow patterns found in our experiments. Active hydraulic flows are not deterministic. Repeating the same experiment in the same periodic geometry, we observe a plethora of disordered flow patterns. We illustrate them in Fig. 2d and their overlap distribution shows that they hardly feature any correlation (Fig. 2e).

We are now equipped to state the laws of active hydraulics in trivalent networks and map them on a double-spin model. This mapping will allow us to predict the self-similar geometry of the streamlines, their gyration radius, degree of nesting and pair correlation. The four laws are as follows.

The topological defects of the flow field in channels hosting no net current impose effective ferromagnetic, or antiferromagnetic, interactions between adjacent streamlines. The sign of the interactions is set by the channel aspect ratio.

The first three laws above define the spin-ice rules shown in Fig. 2c and are akin to the AFN model discussed elsewhere14,15,17. They must be complemented by the law in (iv) above to explain the polymorphism of streamlines observed in all our experiments and quantified in Fig. 3.

We compare our numerical and experimental findings in Fig. 3b. The excellent agreement between the computed and measured structural properties confirms the predictive power of our active hydraulic laws.

As a final remark, we stress that the four local laws of active hydraulics apply broadly, beyond the specifics of periodic lattices and polar active matter. They should describe the flows of any form of active fluid animated by spontaneous laminar flows in complex trivalent networks, from cell tissues to bacteria suspensions to active gels and liquid crystals.

We, therefore, expect our findings to provide a robust set of design rules for active microfluidic devices and offer new insights into the dynamics of groups of living cells and animals in heterogeneous environments and complex habitats36,37,38.

3a8082e126