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Huntsville, AL, United States

Wang T.-S.,NASA | Zhao X.,Alabama A&M University | Zhang S.,ESI CFD Inc. | Chen Y.-S.,Applied Research Laboratory
Journal of Propulsion and Power | Year: 2014

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during testing. Although 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 coupled aeroelastic modeling capability 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, whereas the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed to demonstrate the successful simulation of nozzle wall deformation with the proposed tightly coupled algorithm, and the computed results pertinent to fluid-structure interaction presented. Source

Zhao X.,Alabama A&M University | Montgomery T.,Alabama A&M University | Zhang S.,ESI CFD Inc.
Annals of Nuclear Energy | Year: 2015

This paper presents a numerical study of the stationary and moving pebbles in a pebble bed reactor (PBR) by means of discrete element method (DEM). The packing structure of stationary pebbles is simulated by a filling process that terminates with the settling of the pebbles into a PBR. The packing structural properties are obtained and analyzed. Subsequently, when the outlet of the PBR is opened during the operation of the PBR, the stationary pebbles start to flow downward and are removed at the bottom of the PBR. The dynamic behavior of pebbles is predicted and discussed. Our results indicate the DEM can offer both macroscopic and microscopic information for PBR design calculations and safety assessment. © 2015 Elsevier Ltd. All rights reserved. Source

Zhao X.,Alabama A&M University | Montgomery T.,Alabama A&M University | Zhang S.,ESI CFD Inc.
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2013

The nuclear thermal rocket is one of the candidate propulsion systems for future space exploration including traveling to Mars and other planets of the solar system. Nuclear thermal propulsion can provide a much higher specific impulse than the best chemical propulsion available today. A basic nuclear propulsion system consists of one or several nuclear reactors that heat hydrogen propellant to high temperatures and then allow the heated hydrogen and its reacting product to flow through a nozzle to produce thrust. This paper presents computational study on a single flow element in a nuclear thermal rocket. The computational results provide both detailed and global thermo-fluid environments of a single flow element for thermal stress estimation and insight for possible occurrence of mid-section corrosion. Copyright © 2013 by ASME. Source

Zhao X.,Alabama A&M University | Zhu Y.,Beihang University | Zhu Y.,Aviation Industry Corporation of China AVIC | Zhang S.,ESI CFD Inc.
Computers and Fluids | Year: 2012

This paper presents transonic wing flutter predictions by coupling Euler/Navier-Stokes equations and structural modal equations. This coupling between Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) is achieved through a Multi-Disciplinary Computing Environment (MDICE), which allows several computer codes or 'modules' to communicate in a highly efficient fashion. The present approach offers the advantage of utilizing well-established single-disciplinary codes in a multi-disciplinary framework. The flow solver is density-based for modeling compressible, turbulent flow problems using structured and/or unstructured grids. A modal approach is employed for the structural response. Flutter predictions performed on an AGARD 445.6 wing at different Mach numbers are presented and compared with experimental data. © 2012 Elsevier Ltd. Source

Zhang S.J.,ESI CFD Inc. | Zhu Y.,Aviation Industry Corporation of China AVIC
10th AIAA/ASME Joint Thermophysics and Heat Transfer Conference | Year: 2010

Thermal protection systems (TPS) have to withstand very large heat loads. Whereas the TPS "absorbs" a large portion of the aerodynamic heating during re-entry conditions for example, heat is still conducted to the inside of the aircraft. This study is dedicated to investigating the heat loads and cooling possibilities for the payload in the capsule. The primary task in this work was to develop a fully coupled simulation tool that would allow the external hypersonic flow field to be predicted as well as to take the heat conduction into the capsule volume. This paper will focus on the coupling and the results obtained within the scope of a feasibility study. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source

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