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,
Radial basis function for mesh-to-mesh interpolation in parallel solving fluid-structure interaction problem
In strongly coupled fluid-structure interaction simulations, the fluid dynamics and solid dynamics problems are solved independently on their own meshes. Therefore, it becomes necessary to interpolate physical properties (pressure, displacement) across two meshes. In this paper, we propose the acceleration of the interpolation process by using the matrix-free approach of the interpolation problem on GPU based on radial basis function method. Also, we reduce the number of equations of the system by using the adaptive algorithm of the choice of the interpolation points.
Parametric Study on the Influence of a Discontinuous Step in a Nozzle Contour on Side-load
From our previous research on the side-load of the LE-7A engine, it was found that a discontinuous step in the nozzle caused large side-load. Fast movement of separation, termed "separation jump," was observed with such large side-load. To clarify the influence of step height and step location on the phenomenon of separation jump and on side-load peak due to the separation jump, a parametric study with cold-flow tests was conducted. Based on the test results, it was clarified that the key phenomenon ruling the separation jump is the base flow behind the step. The influence of design parameters of the step on the separation jump can be explained by the base flow characteristics. The strength of side-load was found to be related only to the location of the step. As the location of the step shifted downstream, the strength of side-load increased. Nomenclature : boundary layer thickness at 70% of nozzle length δ h : step height s x: distance from the throat x : step location s x : position of the separation sep x : distance over which the separation jumps jump L: nozzle length ca NPR: nozzle pressure ratio, P /P NPR : NPR at which nozzle flow separates at each sep position P : ambient pressure around the nozzle a P : stagnation pressure in the chamber c