Towards A Unified Solution Method For Fluid-Structure Interaction Problems: Progress And Challenges

The paper presents the progress in the development of a novel unified method for solving coupled fluid-structure interaction problems as well as the associated major challenges. The new approach is based on the fact that there are four fundamental equations in continuum mechanics: the continuity equation and the three momentum equations that describe Newton’s second law in three directions. These equations are valid for fluids and solids, the difference being in the constitutive relations that provide the internal stresses in the momentum equations: in solids the stress tensor is a function of the strain tensor while in fluids the viscous stress tensor depends on the rate of strain tensor. The equations are written in such a way that both media have the same unknown variables, namely the three velocity components and pressure. The same discretisation method (finite volume) is used to discretise the four partial differential equations and the same methodology to handle the pressure-velocity coupling. A common set of variables as well as a unified discretisation and solution method leads to a strong coupling between the two media and is very beneficial for the robustness of the algorithm. Significant challenges include the derivation of consistent boundary conditions for the pressure equation in boundaries with prescribed traction as well as the handling of discontinuity of pressure at the fluid-structure interface

Linear stability analysis and application of a new solution method of the elastodynamic equations suitable for a unified fluid-structure-interaction approach

In the conventional approach for fluid-structure-interaction problems, the fluid and solid components are treated separately and information is exchanged across their interface. According to the conventional terminology, the current numerical methods can be grouped in two major categories: partitioned methods and monolithic methods. Both methods use separate sets of equations for fluid and solid that have different unknown variables. A unified solution method has been presented in the previous work of Giannopapa and Papadakis (2004, "A New Formulation for Solids Suitable for a Unified Solution Method for Fluid-Structure Interaction Problems," ASME PVP 2004, San Diego, CA, July, PVP Vol. 491-1, pp. 111-117), which is different from these methods. The new approach treats both fluid and solid as a single continuum; thus, the whole computational domain is treated as one entity discretized on a single grid. Its behavior is described by a single set of equations, which are solved fully implicitly. In this paper, the elastodynamic equations are reformulated so that they contain the same unknowns as the Navier-Stokes equations, namely, velocities and pressure. Two time marching and one spatial discretization scheme, widely used for fluid equations, are applied for the solution of the reformulated equations for solids. Using linear stability analysis, the accuracy and dissipation characteristics of the resulting difference equations are examined. The aforementioned schemes are applied to a transient structural problem (beam bending) and the results compare favorably with available analytic solutions and are consistent with the conclusions of the stability analysis. A parametric investigation using different meshes, time steps, and beam dimensions is also presented. For all cases examined, the numerical solution was stable and robust and therefore is suitable for the next stage of application to full fluid-structure-interaction problem

Modeling the Blow-Blow Forming Process in Glass Container Manufacturing: A Comparison Between Computations and Experiments

The blow-blow forming process is a widely used technique in glass container manufacturing (e.g., production of glass bottles and jar

Innovation performance in the space sector

The space sector is a high tech industry. It is generally considered as a major driver of growth and provides solutions to a number of socioeconomic challenges. This paper focuses on the role of national innovation systems on a country's capacity to innovate in the space sector. The paper analyzes the national innovation system through two dimensions: a) the innovation infrastructure; and b) the cluster environment. Longitudinal data is gathered to cover eleven countries in the space sector for nine time periods. To our knowledge, this paper is among the very first which provides evidence to showcase the dynamic relationship of national innovation systems and innovation capacity in the space sector, as it involves a panel data structure based on two dimensions simultaneously: a cross-sectional dimension and a timeseries dimension. Based on studying the number of space-related publications in Web of Science, our research results show that the number of individual researchers has a significant positive effect on a country's innovative performance. In contrast, no significant relationship between highly skilled workforce and innovative performance is found. These results indicate that research funds and policies of national governments directly targeting upstream scientific activities are more beneficial to improve innovative performances than a focus on downstream activities

The effects of institutional logics on entrepreneurship in the space sector: The case of the Czech Republic

This paper is part of a continuing effort to investigate constraining and enabling effects of institutional logics on entrepreneurship in the European space sector. The goal is mapping rules, regulations, ideas and cultural standards hindering or stimulating entrepreneurship in ESA Member States in general, and in particular on the subject of this paper, the Czech Republic. Interviews with various Czech space actors were conducted, analyzed and related to archival data on the Czech space sector. On an agency level, two logics are identified, perceived as being either supporting or constraining by entrepreneurs and small companies: the country cooperation logic and the European institution logic. On a national level, the new sector logic, the prime contractor and a product logic are identified as driving and constraining forces for Czech entrepreneurs. The new sector logic entails challenges of entrepreneurs and SMEs arising from new or inadequate regulation, conservative government funding decisions and a misalignment of national priorities for space activities with the expectations of Czech space actors. The prime contractor logic encompasses entrepreneurial activities concerning building, growing and changing relations to traditional, large ESA contractors that govern entrepreneurial decisions on a national level. The product logic describes the constraints and drivers imposed on entrepreneurs by the quality requirements of space products, as well as the competition of new products with ESA quality standards

Wave Propagation in Thin-Walled Aortic Analogues

Research on wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flows. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one-dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models, well defined in vitro experiments are of great importance. The objective of this paper is to present a frequency domain analytical model based on the one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogs. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, volumetric flow rate, and wall distention obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical results and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account