Browsing by Author "Titarev, Vladimir"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access Assessment of high-resolution methods in hypersonic real-gas flows(Cranfield University, 2010-07) Tissera, Shiroshana; Drikakis, Dimitris; Titarev, VladimirThe interest in hypersonic flow phenomena has peaked in recent years where number of experimental and computational work has been carried out. The Computational Fluid Dynamics (CFD) is fast becoming an invaluable tool to investigate compressible hypersonic flow phenomena that are extremely complex in nature. Mathematical models employed to describe complex physical phenomena that take place at hypersonic speeds inherit varying degrees of accuracy and reliability. Therefore, further studies, numerical and experimental, are needed to clarify and improve these models. Numerical computation is one of the tasks that are vital in the overall hypersonic flow research effort. This work investigated the applicability and performance of higher resolution methods to simulate high enthalpy real gas flows. Furthermore, gas-surface interaction and ablation effects are also investigated. In order to achieve the set task, it is imperative that the numerical code (CNS3D) used is equipped with necessary numerical and physical models to tackle flow behaviour typically unique to hypersonic flow. Therefore, the implementation of mathematical models that describe the real gas phenomena, such as vibrational effects, chemical dissociation, diffusion, and high enthalpy effects, has been carried out. The test cases, the HB-2 flare and the double-cone have been considered for the purposes of verification and validation. The experimental data for heat transfer and pressure are compared with numerical predictions to assess the behaviour of modified CNS3D overall and each numerical scheme with regards to reconstruction methods. The overall agreement between the predicted results for both cases and the experimental data is satisfactory. The stagnation point values of pressure and heat flux for HB-2 flare testcase at varying Mach numbers from 5 to 17.8 has been established; these values are expected aid future validation efforts. It was also found that very high-order schemes, such as WENO 5th and 9th -order methods, may provide slightly better results for free stream Mach numbers less than 10; however, there are no obvious benefits over second-order methods for Mach numbers greater than 10. Furthermore, it has been substantiated that increasing order of accuracy compared to increments in the grid resolution is much more effective way of gaining accuracy in the case of real gas flows.Item Open Access Suppression of stall on high-camber flap using upper-surface blowing(Cranfield University, 2011-01) Fang, Li; Titarev, Vladimir; Guo, Shijun J.For many years, high-lift devices of an aeroplane have been employed to enhancing the aerodynamic performance of the wing during take-off and landing. But their complex geometries not only increase the design and manufacture cost, but also result in lower maintainability and reliability. Further more, they have been thought to be a major noise source of civil airliners. As one of the possible solutions, single-slot variable-camber flap design can greatly decrease the system complexity and the design cost of the high-lift system. However, the deteriorated stall behaviour of the flap prevents this concept to obtain its full benefits at high flap deflection angle. Cont/d.Item Open Access UCNS3D: An open-source high-order finite-volume unstructured CFD solver(Elsevier, 2022-06-21) Antoniadis, Antonis F.; Drikakis, Dimitris; Farmakis, Pericles S.; Fu, Lin; Kokkinakis, Ioannis; Nogueira, Xesús; Silva, Paulo A. S. F.; Skote, Martin; Titarev, Vladimir; Tsoutsanis, PanagiotisUCNS3D is an open-source computational solver for compressible flows on unstructured meshes. State-of-the-art high-order methods and their associated benefits can now be implemented for industrial-scale CFD problems due to the flexibility and highly-automated generation offered by unstructured meshes. We present the governing equations of the physical models employed in UCNS3D, and the numerical framework developed for their solution. The code has been designed so that extended to other systems of equations and numerical models is straightforward. The employed methods are validated towards a series of stringent well-established test problems against experimental or analytical solutions, where the full capabilities of UCNS3D in terms of applications spectrum, robustness, efficiency, and accuracy are demonstrated.Item Open Access Very high-order methods for 3D arbitrary unstructured grids(Cranfield University, 2009-08) Tsoutsanis, Panagiotis; Drikakis, Dimitris; Titarev, VladimirUnderstanding the motion of fluids is crucial for the development and analysis of new designs and processes in science and engineering. Unstructured meshes are used in this context since they allow the analysis of the behaviour of complicated geometries and configurations that characterise the designs of engineering structures today. The existing numerical methods developed for unstructured meshes suffer from poor computational efficiency, and their applicability is not universal for any type of unstructured meshes. High-resolution high-order accurate numerical methods are required for obtaining a reasonable guarantee of physically meaningful results and to be able to accurately resolve complicated flow phenomena that occur in a number of processes, such as resolving turbulent flows, for direct numerical simulation of Navier-Stokes equations, acoustics etc. The aim of this research project is to establish and implement universal, high-resolution, very high-order, non-oscillatory finite-volume methods for 3D unstructured meshes. A new class of linear and WENO schemes of very high-order of accuracy (5 th ) has been developed. The key element of this approach is a high-order reconstruction process that can be applied to any type of meshes. The linear schemes which are suited for problems with smooth solutions, employ a single reconstruction polynomial obtained from a close spatial proximity. In the WENO schemes the reconstruction polynomials, arising from different topological regions, are non-linearly combined to provide high-order of accuracy and shock capturing features. The performance of the developed schemes in terms of accuracy, non-oscillatory behaviour and flexibility to handle any type of 3D unstructured meshes has been assessed in a series of test problems. The linear and WENO schemes presented achieve very high-order of accuracy (5 th ). This is the first class of WENO schemes in the finite volume context that possess highorder of accuracy and robust non-oscillatory behaviour for any type of unstructured meshes. The schemes have been employed in a newly developed 3D unstructured solver (UCNS3D). UCNS3D utilises unstructured grids consisted of tetrahedrals, pyramids, prisms and hexahedral elements and has been parallelised using the MPI framework. The high parallel efficiency achieved enables the large scale computations required for the analysis of new designs and processes in science and engineering.