Rarefied hypersonic flow simulations using the Navier-Stokes equations with non-equilibrium boundary conditions

This paper investigates the use of Navier-Stokes-Fourier equations with non-equilibrium boundary conditions (BCs) for simulation of rarefied hypersonic flows. It revisits a largely forgotten derivation of velocity slip and temperature jump by Patterson, based on Grad’s moment method. Mach 10 flow around a cylinder and Mach 12.7 flow over a flat plate are simulated using both computational fluid dynamics using the temperature jump BCs of Patterson and Smoluchowski and the direct simulation Monte-Carlo (DMSC) method. These flow exhibit such strongly non-equilibrium behaviour that, following Patterson’s analysis, they are strictly beyond the range of applicability of the BCs. Nevertheless, the results using Patterson’s temperature jump BC compare quite well with the DSMC and are consistently better than those using the standard Smoluchowski temperature jump BC. One explanation for this better performance is that an assumption made by Patterson, based on the flow being only slightly non-equilibrium, introduces an additional constraint to the resulting BC model in the case of highly non-equilibrium flows

Some consequences of non-local-equilibrium in hypersonic aerodynamic flows

In simulating high-speed, high-altitude aerodynamics it is important to be able to capture physical phenomena that are due to the non-local-equilibrium nature of the rarefied gas flow (this is in addition to any effects due to dissociation, ionisation and energy partition in diatomic molecules). The physical effects of the gas rarefaction can be particularly important close to any solid surface, where they have implications for the heat transfer and mechanical stresses experienced by the surface, and hence on the design of the leading edges and control surfaces of aerodynamic vehicles

Freshwater biology and water supply in Britain

This paper is designed to give a general account of freshwater biology as it bears on waterworks practice. Most water that is used for consumption will commonly go through a storage reservoir. Here special reference is given to the biological relations in standing waters, the biological control of water supplies, methods of plankton estimation, the biology of slow sand filtration and the use of algicides

The structure of hypersonic shock waves using Navier-Stokes equations modified to include mass diffusion

Howard Brenner has recently proposed modifications to the Navier-Stokes equations that relate to a diffusion of fluid volume that would be significant for flows with high density gradients. In a previous paper (Greenshields & Reese, 2007), we found these modifications gave good predictions of the viscous structure of shock waves in argon in the range Mach 1.0-12.0 (while conventional Navier-Stokes equations are known to fail above about Mach 2). However, some areas of concern with this model were a somewhat arbitrary choice of modelling coefficient, and potentially unphysical and unstable solutions. In this paper, we therefore present slightly different modifications to include molecule mass diffusion fully in the Navier-Stokes equations. These modifications are shown to be stable and produce physical solutions to the shock problem of a quality broadly similar to those from the family of extended hydrodynamic models that includes the Burnett equations. The modifications primarily add a diffusion term to the mass conservation equation, so are at least as simple to solve as the Navier-Stokes equations; there are none of the numerical implementation problems of conventional extended hydrodynamics models, particularly in respect of boundary conditions. We recommend further investigation and testing on a number of different benchmark non-equilibrium flow cases.Comment: written for the 2nd European Conference on AeroSpace Sciences (EUCASS), Belgium, 200

The structure of shock waves as a test of Brenner's modifications to the Navier-Stokes equations

Brenner has recently proposed modifications to the Navier-Stokes equations that are based on theoretical arguments but supported only by experiments having a fairly limited range. These modifications relate to a diffusion of fluid volume that would be significant for flows with high density gradients. So the viscous structure of shock waves in gases should provide an excellent test case for this new model. In this paper we detail the shock structure problem and propose exponents for the gas viscosity-temperature relation based on empirical viscosity data that is independent of shock experiments. We then simulate shocks in the range Mach 1.0-12.0 using the Navier-Stokes equations, both with and without Brenner's modifications. Initial simulations showed Brenner's modifications display unphysical behaviour when the coefficient of volume diffusion exceeds the kinematic viscosity. Our subsequent analyses attribute this behaviour to both an instability to temporal disturbances and a spurious phase velocity-frequency relationship. On equating the volume diffusivity to the kinematic viscosity, however, we find the results with Brenner's modifications are significantly better than those of the standard Navier-Stokes equations, and broadly similar to those from the family of extended hydrodynamic models that includes the Burnett equations. Brenner's modifications add only two terms to the Navier-Stokes equations, and the numerical implementation is much simpler than conventional extended hydrodynamic models, particularly in respect of boundary conditions. We recommend further investigation and testing on a number of different benchmark non-equilibrium flow cases

The knowledge and confidence of school nurses following training to promote nutritional health

This study is part of a larger project that aims to develop evidence-based training and resources for school nurses to support young people with their nutritional health (Burdett, 2015). The purpose of this action research study was to explore the impact upon the knowledge and confidence of school nurses following the completion of the nutritional health training. A pre-training questionnaire was provided to all school nurses prior to attending the ‘champion training’ in order to gather baseline information on the knowledge and confidence of the school nurse. A further questionnaire was provided to the school nurses one month following the training, along with the provision of resources. One focus group of five school nurses who attended the training was then completed, to explore the themes from the questionnaires. When analysing the post-course questionnaires, there was a significant impact upon the school nurses self-assessed confidence levels as well as the ability to articulate the health impact of obesity on young people. The questionnaires suggest that the training had a positive impact on school nurses' confidence in particular. The themes highlighted from the focus group were ‘increased knowledge but particularly confidence’, ‘barriers going forward’ and ‘areas for improvement’. Both the returned questionnaires and the focus group were able to highlight barriers going forward, which may inhibit the sustained impact on the knowledge and confidence discussed above. The area for improvement that the focus group appeared to be most vocal and passionate about was how to disseminate the training as ‘champion’. It is unknown as to whether the training has had an impact on practice in the long term and how it translates when the ‘champions’ disseminate the training within their own teams. It would be beneficial to complete further longitudinal qualitative research to explore these themes

Anaphylaxis in children and young people

Anaphylaxis can be defined as a severe, life-threatening and generalised allergic reaction (Grabenhenrich et al., 2016). There are a vast number of triggers which can cause anaphylaxis although those most commonly identified include food, drugs and venom. The Resuscitation Council (2012) reported that the UK incidence of anaphylaxis is rising particularly in children and young people. Experiencing anaphylaxis is frightening and anxiety provoking for both the client and their family. It is vital that nurses are able to not only recognise and respond to the condition but also provide significant emotional support

Neurological assessment in children and young people

Neurological assessment and observation are important nursing skills. They are founded upon an accurate collection and documentation of information on the function and status of the client’s nervous system. Assessing and then monitoring the impact on the client will ensure timely response to any change or deterioration. This article will discuss the main tools used in neurological observation and assessment, as well as consideration given to the vital role of parents and carers within the assessment

An introduction to nursing children and young people with epilepsy

Epilepsy is a condition which affects the brain and is defined as a tendency to have unprovoked seizures. It is one of the most common neurological conditions. A seizure is a sudden burst of unnecessary electrical activity in the brain. This electrical activity disrupts the way the brain usually functions. There are numerous different types and presentation of seizure. This article will explore these and briefly consider the nursing care required

Why Formal Stop Work Schemes Do Not Work

Stopping unsafe work is not only a legal but moral necessity for those that perform work in safety critical industries. Stop Work Authority Cards, Interventions, Refusals of Unsafe Work and the Andon Cord have become symbolic and physical abstractions of decentralization – a shifting of authority down to those which perform the dirty and dangerous work. Paradoxically, the manner in which these formal stop work schemes work is divergent to what these industries and organizations often advocate. I undertook six semi-structured interviews with employees experienced in varying safety critical industries in Western Canada to investigate how decentralization is operationalized in practice. The study found that individual work stoppages through formal stop work schemes have good intentions but in reality, become counterproductive due to ensuing bureaucracy and the possibility of reprimand. Furthermore, this study finds that stopping unsafe work is actually achieved through informal means; that is, casually informing a co-worker that they are in a line of fire or that they are in a situation potentially hazardous which could cause harm to themselves or others. This informal ‘brother’s keepers’ approach appears more effective; however, it runs the risk of potential unsafe acts and conditions being misconstrued as incidences (near misses) within their organizations incident reporting structure. In reality, this ‘social interplay’ is not only encouraged amongst crew members but necessary for creating a safer work environment for the organization as a whole