Turbulent Fluid Flow Over Aerodynamically Rough Surfaces Using Direct Numerical Simulations

Incompressible turbulent fluid flow in aerodynamically rough channels is investigated using direct numerical simulations. A comprehensive database of simulation data for rough surfaces with different topographical properties has been developed for 17 industrially relevant rough surface samples. It includes numerous commonlyseen industrial rough surfaces such as concrete, graphite, carbon-carbon composite and ground, shotblasted and spark-eroded steel. Other surfaces such as cast, filed and gritblasted steel are also studied, along with replicas of ship propeller surfaces eroded by periods of service. The Reynolds number considered is Reτ = 180, for which the flow is in the transitionally rough regime. A study with variable δ/Sq ratio while keeping S + q constant, where Sq is the root mean squared roughness height, is conducted for one of the samples with the mean profiles showing convergence for δ/Sq >≈ 25. A Reynolds number dependence study is conducted for two of the samples with Reτ up to 720 showing a more complete range up to the fully rough flow regime, allowing the equivalent sandgrain roughness height, ks to be computed. A correlation based on the frontal and wetted roughness area is found to be superior to the surface skewness in predicting ∆U + based on the topographic surface parameters

Analysis of data on the relation between eddies and streaky structures in turbulent flows using the placebo method

An artificially synthesized velocity field with known properties is used as a test data set in analyzing and interpreting the turbulent flow velocity fields. The objective nature of this approach is utilized for studying the relation between streaky and eddy structures. An analysis shows that this relation may be less significant than is customarily supposed

Artificial neural network algorithm for online glucose prediction from continuous glucose monitoring.

Background and Aims: Continuous glucose monitoring (CGM) devices could be useful for real-time management of diabetes therapy. In particular, CGM information could be used in real time to predict future glucose levels in order to prevent hypo-/hyperglycemic events. This article proposes a new online method for predicting future glucose concentration levels from CGM data. Methods: The predictor is implemented with an artificial neural network model (NNM). The inputs of the NNM are the values provided by the CGM sensor during the preceding 20 min, while the output is the prediction of glucose concentration at the chosen prediction horizon (PH) time. The method performance is assessed using datasets from two different CGM systems (nine subjects using the Medtronic [Northridge, CA] Guardian® and six subjects using the Abbott [Abbott Park, IL] Navigator®). Three different PHs are used: 15, 30, and 45 min. The NNM accuracy has been estimated by using the root mean square error (RMSE) and prediction delay. Results: The RMSE is around 10, 18, and 27 mg/dL for 15, 30, and 45 min of PH, respectively. The prediction delay is around 4, 9, and 14 min for upward trends and 5, 15, and 26 min for downward trends, respectively. A comparison with a previously published technique, based on an autoregressive model (ARM), has been performed. The comparison shows that the proposed NNM is more accurate than the ARM, with no significant deterioration in the prediction delay

Change in drag, apparent slip and optimum air layer thickness for laminar flow over an idealised superhydrophobic surface

Analytic results are derived for the apparent slip length, the change in drag and the optimum air layer thickness of laminar channel and pipe flow over an idealised superhydrophobic surface, i.e. a gas layer of constant thickness retained on a wall. For a simple Couette flow the gas layer always has a drag reducing effect, and the apparent slip length is positive, assuming that there is a favourable viscosity contrast between liquid and gas. In pressure-driven pipe and channel flow blockage limits the drag reduction caused by the lubricating effects of the gas layer; thus an optimum gas layer thickness can be derived. The values for the change in drag and the apparent slip length are strongly affected by the assumptions made for the flow in the gas phase. The standard assumptions of a constant shear rate in the gas layer or an equal pressure gradient in the gas layer and liquid layer give considerably higher values for the drag reduction and the apparent slip length than an alternative assumption of a vanishing mass flow rate in the gas layer. Similarly, a minimum viscosity contrast of four must be exceeded to achieve drag reduction under the zero mass flow rate assumption whereas the drag can be reduced for a viscosity contrast greater than unity under the conventional assumptions. Thus, traditional formulae from lubrication theory lead to an overestimation of the optimum slip length and drag reduction when applied to superhydrophobic surfaces, where the gas is trapped

Applying a transdisciplinary mixed methods research design to explore sustainable diets in rural South Africa

This article describes a conceptual framework for exploring sustainable diets, using a case study example of ongoing research in the Vaalharts region, a rural setting in South Africa. A qualitative research approach is followed with an integrated transdisciplinary mixed methods research design with multiple concurrent components employed during two sequential phases. A successful application of the framework is achieved through a collaborative team effort of researchers with qualitative and quantitative research expertise transcending different disciplines, as well as participation of community members throughout the research process. We demonstrate that transdisciplinary mixed methods research designs are essential to gain a better understanding of the complex concept of sustainable diets

The far green country.

This work was inspired by a beautiful image from J.R.R. Tolkien’s The Lord of the Rings: “And then it seemed to him that as in his dream in the house of Bombadil, the grey rain-curtain turned all to silver glass and was rolled back, and he beheld white shores and beyond them a far green country under a swift sunrise.” ~The Return of The King, Book VI chapter 9. This imagery inspired the three movements of this work. The first, The Gray Raincurtain, depicts a violent end, the world crashing down around you. The musical material of this movement gradually unravels – the piece is built in several waves, each becoming more and more tumultuous and disturbed, until the final crest shatters and leaves a deafening silence in its wake. The second movement, Silver Glass, is an in-between place – a transformation from one state of being to another. The sound of silver glass is created with bowed percussion instruments, the rest of the orchestra gradually adding their voices to create a glistening halo of sound. The final movement, The Far Green Country, emerges from this halo and embodies the excitement and joy of arriving home after a long absence. This movement rotates through key centers, slowly adding accidentals to the orchestral texture, creating the feeling of running ever upward and upward, each step of the way more euphoric than the last

Simulation of rough wall turbulent channel flow using a parametric forcing approach

The effects of rough walls on turbulent channel flow are simulated by adding a simple forcing term to the Navier-Stokes equations. An extensive parameter study is used to explore the effects of this term on turbulent channel flow. By varying the roughness height parameter and the roughness factor contained in the forcing term it is possible to simulate roughnesses of various strengths ranging from transitionally rough to very rough cases. A good qualitative agreement is found with the results of recent experimental and numerical studies of rough-wall turbulent channel flow for the mean flow statistics. The streamwise velocity shows a very good preservation of the outer layer similarity for both its mean and its fluctuations. The flow structure shows a weakening of the streamwise streaks above the roughness sublayer. Within the roughness sublayer the turbulent structure changes to a more isotropic state, while close to the wall a mixing layer-like turbulent state emerges in extremely rough cases. The roughness force term is a possible candidate for a wall model in large eddy and direct numerical simulations where the small-scale structure of the flow over a rough surface can be neglected

A Bitter Adjustment for German Family Capitalism: Succession and a Changing Ownership Transfer Regime

Abstract Germany is known for its family-owned businesses that transfer ownership across generations. However, business owners in Germany increasingly envision selling their business beyond the family, which fundamentally changes the institutionalized way private ownership of businesses is transferred. In this paper, we analyze and explain this fundamental change in German family capitalism since the 1990s. Drawing on a sociology of ownership, we view family succession as a transfer regime and show how this regime has been problematized and gradually reframed. Based on analysis of a rich corpus of documents, archival materials, and twenty-seven expert interviews, we show how a new transfer regime – the exit regime – emerges, which coordinates ownership transfer among founders through matchmaking. Our study contributes to research on family capitalism and succession by demonstrating how family capital moves toward the financial sector without becoming financial capital as it loses the family and gains the founder as personalized points of reference.ZusammenfassungDeutschland ist für seine Familienunternehmen bekannt, die das Eigentum am Unternehmen innerhalb der Familie halten und es familienintern an die nächste Generation übergeben. Allerdings ziehen immer mehr Unternehmenseigentümer in Betracht, ihr Unternehmen an Externe zu verkaufen, wodurch sich die institutionalisierte Form des Eigentumstransfers von Unternehmen stark wandelt. In diesem Discussion Paper analysieren und erläutern wir diesen sich seit den 1990er-Jahren vollziehenden Wandel, der den Familienkapitalismus in Deutschland grundlegend verändert. Wir setzen uns aus der Perspektive einer Soziologie des Eigentums mit familieninterner Nachfolge als spezifischem Transferregime auseinander und zeigen, wie dieses Regime problematisiert und allmählich umgestaltet wurde. Anhand der Analyse einer umfangreichen Sammlung von Dokumenten und Archivmaterialien sowie von 27 Experteninterviews veranschaulichen wir, wie sich ein neues Transferregime – das Exit-Regime – herausbildet, das den Eigentumstransfer zwischen „Gründern“ über moderierte Vermittlung koordiniert. Unsere Studie leistet einen Betrag zur Forschung über Familienkapitalismus und Nachfolge, indem sie verdeutlicht, wie Familienkapital finanzialisiert wird, ohne dabei selbst zu Finanzkapital zu werden, solange die Familie mit dem Gründer als persönlichem Bezugspunkt ersetzt wird.Contents 1 Introduction 2 The bifurcation of family and financialized ownership in German family capitalism 3 Succession as a transfer regime 4 A pragmatist approach to studying regime change 5 From succession to exit Problematization: The rising uncertainty of the succession regime Collective inquiry: Campaigning and systematic intervention Experimenting with new forms of ownership transfer: The rise of intermediaries and matchmaking Norm substitution: Passing the business from family entrepreneur to founder 6 The exit regime: Reconfigured bifurcation of “family” and financialized ownership Reference

Cross cultural verbal cues to deception: truth and lies in first and second language forensic interview contexts

Introduction: The verbal deception literature is largely based upon North American and Western European monolingual English speaker interactions. This paper extends this literature by comparing the verbal behaviors of 88 south Asian bilinguals, conversing in either first (Hindi) or second (English) languages, and 48 British monolinguals conversing in English. Methods: All participated in a live event following which they were interviewed having been incentivized to be either deceptive or truthful. Event details, complications, verifiable sources, and plausibility ratings were analyzed as a function of veracity, language and culture. Results: Main effects revealed cross cultural similarities in both first and second language interviews whereby all liar’s verbal responses were impoverished and rated as less plausible than truthtellers. However, a series of cross-cultural interactions emerged whereby bi-lingual South Asian truthtellers and liars interviewed in first and second languages exhibited varying patterns of verbal behaviors, differences that have the potential to trigger erroneous assessments in practice. Discussion: Despite limitations, including concerns centered on the reductionary nature of deception research, our results highlight that while cultural context is important, impoverished, simple verbal accounts should trigger a ‘red flag’ for further attention irrespective of culture or interview language, since the cognitive load typically associated with formulating a deceptive account apparently emerges in a broadly similar manner

Improving professional observers’ veracity judgments by tactical interviewing

Understanding whether a person of interest is being truthful during an investigative interview is a constant challenge and is of concern to numerous criminal justice professionals, most of whom are not involved in conducting the interview itself. Here, we investigated police observers’ veracity detection performance having viewed interviews with truthtellers and deceivers using either the tactical use of evidence (TUE), strategic use of evidence (SUE) or a control technique. Thirty serving police officers participated as post-interview observers and each viewed 12 interviews in a counterbalanced order. After each interview, the officer made a veracity judgement. Overall, untrained police observers were significantly more accurate (68%) when making veracity judgements post-TUE interviews, whereas for both SUE and control performance was around chance (51% and 48%, respectively). Veracity performance for liars and truthtellers revealed a similar pattern of results (67% liars; 70% truthtellers) in the TUE condition. These results lend further support to the psychological literature highlighting the importance of how and when to reveal evidence or any other relevant event information during an investigative interview for ‘outing’ deceivers as well as allowing truthtellers early opportunities to demonstrate their innocence