A consolidated method for predicting laminar boundary layers on rotating axi-symmetric bodies

The boundary layer equations for axi-symmetric laminar flow are transformed in a manner which can be applied to rotating bodies in both still and axial flow. Terms pertaining specifically to quiescent or axial flow are clearly identified by the approach. The transformed equations are shown to deliver the same velocity profiles as a number of case-specific formulations presented in the literature, albeit with one or two exceptions, while being substantially simpler in formulation

Systems driven HLFC design

The paper presents an aerodynamic study carried out in parallel with the EU AFLoNext project to assess the issues involved in combining hybrid laminar flow control (HLFC) technology for drag reduction with wing ice protection systems (WIPS). The paper describes the selection of appropriate test cases in the literature which are representative of wings designed for HLFC system and the progression from an initial baseline HLFC chamber layout to layouts driven by practical constraints such as WIPS requirements and aircraft structure. The resulting HLFC system is a compromise between all concerned systems. Conclusions are drawn about design driven not purely by performance but by the ability to physically implement the system on a commercial aircraft

On the controllability of saturating crossflow vortices

This thesis examines the suitability of the crossflow generated by rotating boundary layers for investigating crossflow amplification control thresholds at scales suitable for university wind tunnels. Using rotating disk flow as a starting point, it was postulated that the addition of a concentric annulus, rotating at a different angular velocity to the inner disk, would allow controlled changes in crossflow growth just prior to non-linear saturation. A novel formulation for the boundary layer a rotating disk with radially variable angular velocity was derived for application on the disk-annulus system, though ultimately it was determined that the resultant equations were elliptical in character and therefore no longer representative of the physics of the swept-wing boundary layer. In order to ensure parabolicity, a configuration involving a rotating body in an axial flow was proposed. It was speculated that local variations in edge velocity, induced by the body geometry, would provide an appropriate analogue to the variable pressure gradients found in the vicinity of swept-wing leading edge. A novel formulation for the boundary layer equations for a generalised rotating body of revolution, both with and without an incompressible axial flow, was subsequently derived, implemented within the QinetiQ BL2D boundary layer method and validated against other shape-specific formulations. The formulation employs a velocity switch, u*, which allows for a seamless transition between quiescent and axial flow investigations and provides a valuable alternative to other shape and flow specific formulations. The perturbation and stability equations in a general orthogonal curvilinear coordinate system were derived to include Coriolis accelerations terms, as well as retaining viscous curvature. The existing QinetiQ e^N method, CoDS, was modified and extended to enable the analysis of rotating boundary layers and provided qualitatively good agreement with results published by Garrett (2002), with quantitative differences attributed mainly to scaling. The methods were combined in order to answer the original research question, whether the boundary layer due to a rotating body could be used as a viable analogue for swept-wing flow in the context of crossflow growth control. Velocity profiles for rotating axi-symmetric bodies were shown to provide a good match to those of swept-wing flow, with differences only in the second wall-normal derivatives. Results showed that geometries could be selected which demonstrated non-monotonic N-factor growth, of the type encountered during HYLTEC and AFLoNext. An axi-symmetric body derived from the upper surface of the RAE2822 demonstrated N-factor amplification followed by sudden stabilisation

Caries associated with orthodontic care part 2: management

It is recognized that wearing an orthodontic appliance increases the caries risk of the individual. The prevalence of demineralization has been reported to be as high as 73%. When demineralization occurs a number of treatments exist: fluoride application, acid microabrasion, casein phosphopeptide-amorphous calcium phosphate (CCP-ACP), resin infiltration and self-assembling peptides. Of these, topical fluoride has the most evidence to support its use. CPD/Clinical Relevance: Demineralization is the most common complication of orthodontic care. The clinician should understand how to manage this when it occurs

Fluorescence devices for the detection of dental caries

BACKGROUND: Caries is one of the most prevalent and preventable conditions worldwide. If identified early enough then non‐invasive techniques can be applied, and therefore this review focusses on early caries involving the enamel surface of the tooth. The cornerstone of caries detection is a visual and tactile dental examination, however alternative methods of detection are available, and these include fluorescence‐based devices. There are three categories of fluorescence‐based device each primarily defined by the different wavelengths they exploit; we have labelled these groups as red, blue, and green fluorescence. These devices could support the visual examination for the detection and diagnosis of caries at an early stage of decay. OBJECTIVES: Our primary objectives were to estimate the diagnostic test accuracy of fluorescence‐based devices for the detection and diagnosis of enamel caries in children or adults. We planned to investigate the following potential sources of heterogeneity: tooth surface (occlusal, proximal, smooth surface or adjacent to a restoration); single point measurement devices versus imaging or surface assessment devices; and the prevalence of more severe disease in each study sample, at the level of caries into dentine. SEARCH METHODS: Cochrane Oral Health's Information Specialist undertook a search of the following databases: MEDLINE Ovid (1946 to 30 May 2019); Embase Ovid (1980 to 30 May 2019); US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov, to 30 May 2019); and the World Health Organization International Clinical Trials Registry Platform (to 30 May 2019). We studied reference lists as well as published systematic review articles. SELECTION CRITERIA: We included diagnostic accuracy study designs that compared a fluorescence‐based device with a reference standard. This included prospective studies that evaluated the diagnostic accuracy of single index tests and studies that directly compared two or more index tests. Studies that explicitly recruited participants with caries into dentine or frank cavitation were excluded. DATA COLLECTION AND ANALYSIS: Two review authors extracted data independently using a piloted study data extraction form based on the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS‐2). Sensitivity and specificity with 95% confidence intervals (CIs) were reported for each study. This information has been displayed as coupled forest plots and summary receiver operating characteristic (SROC) plots, displaying the sensitivity‐specificity points for each study. We estimated diagnostic accuracy using hierarchical summary receiver operating characteristic (HSROC) methods. We reported sensitivities at fixed values of specificity (median 0.78, upper quartile 0.90). MAIN RESULTS: We included a total of 133 studies, 55 did not report data in the 2 x 2 format and could not be included in the meta‐analysis. 79 studies which provided 114 datasets and evaluated 21,283 tooth surfaces were included in the meta‐analysis. There was a high risk of bias for the participant selection domain. The index test, reference standard, and flow and timing domains all showed a high proportion of studies to be at low risk of bias. Concerns regarding the applicability of the evidence were high or unclear for all domains, the highest proportion being seen in participant selection. Selective participant recruitment, poorly defined diagnostic thresholds, and in vitro studies being non‐generalisable to the clinical scenario of a routine dental examination were the main reasons for these findings. The dominance of in vitro studies also means that the information on how the results of these devices are used to support diagnosis, as opposed to pure detection, was extremely limited. There was substantial variability in the results which could not be explained by the different devices or dentition or other sources of heterogeneity that we investigated. The diagnostic odds ratio (DOR) was 14.12 (95% CI 11.17 to 17.84). The estimated sensitivity, at a fixed median specificity of 0.78, was 0.70 (95% CI 0.64 to 0.75). In a hypothetical cohort of 1000 tooth sites or surfaces, with a prevalence of enamel caries of 57%, obtained from the included studies, the estimated sensitivity of 0.70 and specificity of 0.78 would result in 171 missed tooth sites or surfaces with enamel caries (false negatives) and 95 incorrectly classed as having early caries (false positives). We used meta‐regression to compare the accuracy of the different devices for red fluorescence (84 datasets, 14,514 tooth sites), blue fluorescence (21 datasets, 3429 tooth sites), and green fluorescence (9 datasets, 3340 tooth sites) devices. Initially, we allowed threshold, shape, and accuracy to vary according to device type by including covariates in the model. Allowing consistency of shape, removal of the covariates for accuracy had only a negligible effect (Chi(2) = 3.91, degrees of freedom (df) = 2, P = 0.14). Despite the relatively large volume of evidence we rated the certainty of the evidence as low, downgraded two levels in total, for risk of bias due to limitations in the design and conduct of the included studies, indirectness arising from the high number of in vitro studies, and inconsistency due to the substantial variability of results. AUTHORS' CONCLUSIONS: There is considerable variation in the performance of these fluorescence‐based devices that could not be explained by the different wavelengths of the devices assessed, participant, or study characteristics. Blue and green fluorescence‐based devices appeared to outperform red fluorescence‐based devices but this difference was not supported by the results of a formal statistical comparison. The evidence base was considerable, but we were only able to include 79 studies out of 133 in the meta‐analysis as estimates of sensitivity or specificity values or both could not be extracted or derived. In terms of applicability, any future studies should be carried out in a clinical setting, where difficulties of caries assessment within the oral cavity include plaque, staining, and restorations. Other considerations include the potential of fluorescence devices to be used in combination with other technologies and comparative diagnostic accuracy studies