Aeroelastic Modeling of a Nozzle Startup Transient
Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,
Effect of Coolant Flow Distribution on Transient Side Load of Film Cooled Nozzles
The objective of this study was to investigate the effect of film coolant distribution on nozzle side loads generated during an engine start transient. The rocket engine studied encompasses a regeneratively cooled chamber and nozzle, along with a film cooled nozzle extension. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and transient inlet boundary conditions calculated from an engine system simulation. Computations were performed for engine startup with two turbine exhaust manifold geometries that produce two different distributions of film coolant mass flow: one with a higher mass flow deviation, while the other has a near uniform distribution. The results show that the configuration with the higher mass flow deviation produced a higher peak side load, manifested by the biased turbine exhaust gas pumping of the supersonic jet of the Mach disk flow; while the configuration with the more uniform coolant flow distribution maintained a more symmetric Mach disk flow throughout the filling process, resulting in a lower peak side load.
Modelling environmental impacts of marine finfish aquaculture
Summary Our understanding of the interactions between fish farms and the environment has reached the stage where it is reasonable to expect that quantitative estimates of the possible environmental consequences of aquaculture development can be provided for regulatory and mitigation purposes. This paper summarizes recent developments in this area and provides several case histories of areas where theoretical analyses appear to have direct practical relevance. Fish wastes