Computational fluid dynamics benchmark dataset of airflow in tracheas

Computational Fluid Dynamics (CFD) is fast becoming a useful tool to aid clinicians in pre - surgical planning through the ability to provide inform ation that could otherwise be extremely difficult if not impossible to obtain. However, in order to provide clinically relevant metrics, the accuracy of the computational method must be sufficiently high. There are many alternative methods employed in the process of performing CFD simulations within the airways, including different segme ntation and meshing strategies, as well as alternative approaches to solving the Navier - Stokes equations. However, as in vivo validation of the simulated flow patter ns within the airways is not possible, little exists in the way of validation of the various simulation techniques. The data presented here consists of very highly resolved flow data. The degree of resolution is compared to the highest necessary resolution s of the Kolmogorov length and time scales. Therefore this data is ideally suited to act as a benchmark case to which cheaper comput ational methods may be compared. A dataset and solution setup for one such more efficient method, large eddy simulation (LES ), is also presented

Assessing changes in airflow and energy loss in a progressive tracheal compression before and after surgical correction

The energy needed to drive airflow through the trachea normally constitutes a minor component of the work of breathing. However, with progressive tracheal compression, patient subjective symptoms can include severe breathing difficulties. Many patients suffer multiple respiratory co-morbidities and so it is important to assess compression effects when evaluating the need for surgery. This work describes the use of computational prediction to determine airflow resistance in compressed tracheal geometries reconstructed from a series of CT scans. Using energy flux analysis, the regions that contribute the most to airway resistance during inhalation are identified. The principal such region is where flow emerging from the zone of maximum constriction undergoes breakup and turbulent mixing. Secondary regions are also found below the tongue base and around the glottis, with overall airway resistance scaling nearly quadratically with flow rate. Since the anatomical extent of the imaged airway varied between scans - as commonly occurs with clinical data and when assessing reported differences between research studies - the effect of sub-glottic inflow truncation is considered. Analysis shows truncation alters the location of jet breakup and weakly influences the pattern of pressure recovery. Tests also show that placing a simple artificial glottis in the inflow to a truncated model can replicate patterns of energy loss in more extensive models, suggesting a means to assess sensitivity to domain truncation in tracheal airflow simulations

Does facial soft tissue protect against zygomatic fractures?: results of a finite element analysis

Introduction: Zygomatic fractures form a major entity in craniomaxillofacial traumatology. Few studies have dealt with biomechanical basics and none with the role of the facial soft tissues. Therefore this study should investigate, whether facial soft tissue plays a protecting role in lateral midfacial trauma

Diverse definitions of the early course of schizophrenia - a targeted literature review

Schizophrenia is a debilitating psychiatric disorder and patients experience significant comorbidity, especially cognitive and psychosocial deficits, already at the onset of disease. Previous research suggests that treatment during the earlier stages of disease reduces disease burden, and that a longer time of untreated psychosis has a negative impact on treatment outcomes. A targeted literature review was conducted to gain insight into the definitions currently used to describe patients with a recent diagnosis of schizophrenia in the early course of disease ('early' schizophrenia). A total of 483 relevant English-language publications of clinical guidelines and studies were identified for inclusion after searches of MEDLINE, MEDLINE In-Process, relevant clinical trial databases and Google for records published between January 2005 and October 2015. The extracted data revealed a wide variety of terminology and definitions used to describe patients with 'early' or 'recent-onset' schizophrenia, with no apparent consensus. The most commonly used criteria to define patients with early schizophrenia included experience of their first episode of schizophrenia or disease duration of less than 1, 2 or 5 years. These varied definitions likely result in substantial disparities of patient populations between studies and variable population heterogeneity. Better agreement on the definition of early schizophrenia could aid interpretation and comparison of studies in this patient population and consensus on definitions should allow for better identification and management of schizophrenia patients in the early course of their disease

Power loss mechanisms in pathological tracheas

The effort required to inhale a breath of air is a critically important measure in assessing airway function. Although the contribution of the trachea to the total flow resistance of the airways is generally modest, pathological alterations in tracheal geometry can have a significant negative effect. This study investigates the mechanisms of flow energy loss in a healthy trachea and in four geometries affected by retrosternal goitre which can cause significant distortions of tracheal geometry including constriction and deviation with abnormal curvature. By separating out the component of energy loss related to the wall shear (frictional loss), striking differences are found between the patterns of energy dissipation in the normal and pathological tracheas. Furthermore the ratio of frictional to total loss is dramatically reduced in the pathological geometries

Mixing Through Stirring of Steady Flow in Small Amplitude Helical Tubes

Accepted versio

Influence of boundary layer transition on the trajectory optimisation of a reusable launch vehicle

Based on flight experience from the Space Shuttle programme, it is well known that mis-prediction of the effects of boundary layer transition represents one of the highest technical risks when designing a Reusable Launch Vehicle. Indeed, mis-prediction of the boundary layer behaviour at hypersonic speeds could impinge on the overall survivability of a given design, whereas excessive conservatism in the analyses could result in an overweight vehicle not capable of attaining orbit with a useful payload mass on-board. From the standpoint of conceptual design, it is therefore of paramount importance to develop engineering means of predicting the effects of uncertainty in the behaviour of the boundary layer on the vehicle as far as transition is concerned. Indeed, a robust preliminary analysis should ensure thermal survival of the spaceplane structure and give a measure of confidence in the ability of the conceptual vehicle to maintain sufficiently good controllability during re-entry in the presence of possibly asymmetric boundary layer transition. A reduced-order model has been used to evaluate the sensitivity of a particular design of hypersonic reusable launch vehicle to the uncertainty in predicting its aero-thermodynamic behavior that results from variability in the onset of boundary layer transition on its surface, especially when optimising the re-entry trajectory of the vehicle. The results of the simulations presented here seem to suggest that the effects of boundary layer transition on the vehicle's performance during re-entry might largely be ameliorated through careful aerodynamic design and appropriate scheduling of the control surface deflections along the vehicle's trajectory