MBDA (United Kingdom)

This paper provides an introduction and background to a program of activities undertaken during the 2025 AIAA Aviation Forum in which groups of turbulence modelling and turbulence measuring specialists were brought together in ways that were intended to help further the state-of-the-art in Computational Fluid Dynamics (CFD) validation. The main text is accompanied by an extensive appendix which provides further insight into the thinking that guided the preparation for these activities.

There is an evolving need to increase reliance on physics-based simulation to develop, design, and optimize a wide range of engineering systems. This increased reliance on modeling and simulation has highlighted a growing need to better assess the confidence that modeling and simulation analysts have in their computational results. More specifically, analysts and designers are being asked to reduce physical testing, but still ensure the performance, reliability and safety in their designs. For isolated components of a complex system, where a single discipline may drive product design, this is less of a concern because a single physics process is often straightforward and easy to explain. However, when these isolated components are integrated, and are expected to operate in a multidisciplinary context, new concepts and model assurance standards are required. In this paper, we address this challenge by showing how a model validation hierarchy can be exploited to identify those model validation experiments that will contribute most to increasing confidence and credibility of modeling and simulation predictions. The approach that is adopted contains four main steps. The first step is the construction of a model validation hierarchy that links subsystems, assemblies, and components to a hierarchy of physical experiments that can be used to support model validation. This hierarchy connects in a clear and logical way the perspective of systems engineers focusing on system design, to the perspective of the modeling and simulation analyst who is concerned in simulation accuracy. The structure and content of this hierarchy is then used in a second step to establish which physical phenomena have the greatest impact on overall system performance metrics. A gap analysis technique is then used to prioritize the important computational activities that may damage the accuracy of the simulation results. Unfortunately, a common outcome of such gap analyses is the identification of many important gaps. In the final step of our process, we advocate for the use of a global sensitivity analysis to improve the prioritization of the weaknesses in computational activities.

A research program has been underway for four years to study vortex interaction aerodynamics that are relevant to military air vehicle performance. The program has been conducted under the auspices of the NATO Science and Technology Organization (STO), Applied Vehicle Technology (AVT) panel by a Task Group with the identification of AVT-316. The Task Group was split into two facets: an aircraft facet and a missile facet, each focusing on the vortex interactions associated with airframes of direct interest to NATO. This paper is one of a series being presented at this conference to provide a technical overview of the activities and accomplishments of the AVT-316 missile facet. A substantial body of work has been established pertaining to two generic missile airframes: OTC1 and LK6E2. The test cases studied incorporate multiple vortices and associated interactions and pose a variety of challenges for CFD. Significant progress has been made in consolidating understanding of these challenges and in assessing the current capabilities of CFD to simulate such flows. In so doing, the importance of solution verification has been reinforced, with fine resolution of the flow being required to avoid excessive dissipation. The use of multi-fidelity analysis has also afforded various insights into the physical models being used: for instance, this has allowed compelling demonstrations of the limitations of linear eddy viscosity turbulence models to be provided without recourse to physical test data. As a result of the progress made in these fundamental areas with OTC1, it has been possible to identify features of the overall aerodynamic characteristics of LK6E2 that had been obscured in previous CFD analyses and to subject them to better informed – and therefore more incisive – analysis. The work of the missile facet is ongoing: a final output, constituting a more detailed and consolidated technical record, will be published by NATO STO towards the end of 2022.

Abstract Background: Hepatocellular carcinoma (HCC) is the sixth most common cancer and the third most frequent cause of cancer-related mortality worldwide. The genetic and physiological complexity of HCC is a major barrier to the study of tumorigenesis and identification of therapeutic targets. The three-dimensional (3D) culture of cancer cells within an extracellular matrix (ECM) provides an in vitro tumor model that best recapitulates in vivo tumor pathophysiology.Methods: In the current study, we cultured cells and made spheroids by aggregating cells or diffusing cells in Matrigel attached on the tip of the 96-pillar plate. According to the initial cell position in Matrigel, two 3D-HCC cancer in-vitro models (diffused spheroid model and aggregated spheroid model) were established. These two models were applied to drug sensitivity assays to identify drug sensitivity changes. The protein expression and cytokine activation related to the drug resistance and maintenance of the physiological properties of HCC cells were analyzed in both models. This 3D culture method not only maintained the phenotype of the tumor but allowed easy high-throughput screening (HTS) due to its 96-array plate configuration.Results: The Aggregated Spheroid Model (ASM) showed higher expression of cancer markers associated with proliferation, tight junctions formation and epithelial cell identity in HCC cells, as well as cytokine factors associated with immune cell recruitment/activation, ECM regulation, cancer interaction, and angiogenesis regulation.Conclusions: Overall, the proposed ASM better recapitulates the tumor microenvironment, demonstrating the involvement of the ECM/tight junctions in the cell-to-cell signaling processes. This provides more instructive data for in vitro screening of tumor cells.

Abstract The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.

Abstract The thermophysical properties of carbon fiber‐based ultra‐high temperature ceramic matrix composites have been determined to aid designers who need these properties when considering using the composites in ultra‐high temperature aerospace applications. The coefficient of thermal expansion (CTE) and thermal diffusivity of the composites were measured parallel and perpendicular to the ply direction; the thermal conductivity was measured using the laser‐flash method and the heat capacity calculated from the relationship between the thermal diffusivity, density, and thermal conductivity. Both the CTE and thermal conductivity showed higher values across the ply and increased with increasing temperature as expected, whilst the thermal diffusivity showed higher values parallel to the ply and increased smoothly with temperature. In addition, two different but related oxyfuel torch tests, based on oxyacetylene and oxypropane, were used to evaluate the thermo‐ablation behavior of the composites. The tests showed how good the composites were at withstanding the ultra‐high temperatures, high heat fluxes, and gas velocities involved.

The technologies of: Anthropometric Modelling, Game Engine animation and Virtual Reality were integrated to facilitate early design decisions in the design of future Naval weapon systems and their integration into current and future Naval platforms. CAD Models of existing or future ships were imported into a 3D Games engine (Unity) along with CAD Models from the ship architect/designer of specific compartments where weapon system installations were proposed. Extremes of the user population (e.g. 3rd percentile Navy female and 97th percentile Navy male) were modelled performing the installation / maintenance tasks on the equipment and this was then exported/imported into the 3D Unity environment and viewed from predefined eye height perspectives. Within the Unity 3D environment, realistic dynamic aspects of the real world were added – e.g. ship movement in light or heavy seas as well as consequent human head / body movement (compensating for ship movement) and the effects that this may have on the task. In addition weather and visibility effects can be added which may affect the user’s ability to perform the tasks. Design engineers viewing the model in VR were able to get a sense of the distances / gaps / access from within the 3D model itself and make/feedback design recommendations from the unique perspective of being immersed within the design itself.

The HMS Dryad scenarios were a highly complex interaction of crew and communication channels. This chapter describes a study conducted to analyse aspects of command and control in the Naval domain. The operation sequence diagrams give a graphical representation of each of the scenarios with the circles representing transmissions in communication. The anti-air warfare officer was the main agent observed in the air threat scenario and the principal warfare officer was the main agent observed for the subsurface and surface threat scenarios. The knowledge objects identified represent the ideal collection of knowledge objects for the scenarios that were used in the Critical Decision Method analyses. To simplify the analyses, a single network has been presented, comprising both types of knowledge object, but only the knowledge objects relevant to each scenario are highlighted. The knowledge objects pertinent to each phase have been highlighted in each of the propositional networks.

The performance of a triggered spark-gap has been investigated in which the gas and electrodes are illuminated with UV. A test circuit was produced in which the intensity and relative timing of the UV could be adjusted. The effect that this had on the voltage required to trigger the spark-gap was measured. It was demonstrated that the presence of UV reduces the required trigger voltage to initiate the closure of the spark-gap. The pulse to pulse variation of this trigger voltage is also decreased in the presence of UV. It was also shown that the relative timing between the application of the trigger pulse and the UV illumination has a marked effect on the triggering of the spark-gap. Lastly a drive circuit has been developed which selftimes the UV illumination of the spark-gap when the trigger pulse is applied and sustains the generation of UV for the duration of the trigger pulse. Results are presented demonstrating the improvement seen as a result of these design modifications.

A comprehensive review of aerofoil shape parameterization methods that can be used for aerodynamic shape optimization is presented. Seven parameterization methods are considered for a range of design variables: class–shape transformations; B-splines; Hicks–Henne bump functions; a radial basis function domain element approach; Bèzier surfaces; a singular-value decomposition modal extraction method; and the parameterized sections method. Because of the large range of variables involved, the most effective way to implement each method is first investigated. Their performances are then analyzed by considering the geometric shape recovery of over 2000 aerofoils using a range of design variables, testing the efficiency of design space coverage with respect to a given tolerance. It is shown that, for all the methods, between 20 and 25 design variables are needed to cover the full design space to within a geometric tolerance, with the singular-value decomposition method doing this most efficiently. A set of transonic aerofoil case studies are also presented, with geometric error and convergence of the resulting aerodynamic properties explored. These results show a strong relationship between geometric error and aerodynamic convergence and demonstrate that between 38 and 66 design variables may be needed to ensure aerodynamic convergence to within one drag and one lift count.