Pramote Dechaumphai

Flow-thermal-structural study of aerodynamically heated leading edges

A finite element approach for integrated fluid-thermal-structural analysis of aerodynamically heated leading edges is presented. The Navier-Stokes equations for high speed compressible flow, the energy equation, and the quasi-static equilibrium equations for the leading edge are solved using a single finite element approach in one integrated, vectorized computer program called LIFTS. The fluid-thermal-structural coupling is studied for Mach 6.47 flow over a 3-inch diameter cylinder for which the flow behavior and the aerothermal loads are calibrated by experimental data. Issues of the thermal-structural response are studied for hydrogen cooled, super thermal conducting leading edges subjected to intense aerodynamic heating.

Coupled flow, thermal, and structural analysis of aerodynamically heated panels

A finite-element approach for coupling flow, thermal, and structural analyses of aerodynamicaly heated panels is presented. The Navier-Stokes equations for laminar compressible flow are solved, together with the energy equation and quasistatic structural equations of the panel. Interactions between the flow, panel heat transfer, and deformations are studied for thin stainless steel panels aerodynamically heated by Mach 6.6 flow.

Application of integrated fluid-thermal structural analysis methods

Hypersonic vehicles operate in a hostile aerothermal environment which has a significant impact on their aerothermostructural performance. Significant coupling occurs between the aerodynamic flow field, structural heat transfer, and structural response creating a multidisciplinary interaction. Interfacing state-of-the-art disciplinary analysis methods is not efficient, hence interdisciplinary analysis methods integrated into a single aerothermostructural analyzer are needed. The NASA Langley Research Center is developing such methods in an analyzer called LIFTS (Langley Integrated Fluid-Thermal-Structural) analyzer. The evolution and status of LIFTS is reviewed and illustrated through applications.

A Taylor-Galerkin finite element algorithm for transient nonlinear thermal-structural analysis

A Taylor-Galerkin finite element method for solving large, nonlinear thermal-structural problems is presented. The algorithm is formulated for coupled transient and uncoupled quasistatic thermal-structural problems. Vectorizing strategies ensure computational efficiency. Two applications demonstrate the validity of the approach for analyzing transient and quasistatic thermal-structural problems.

Thermal-Structural Finite Element Analysis Using Linear Flux Formulation

A linear flux approach is developed for a finite element thermal-structural analysis of steady-state thermal and structural problems. The element fluxes are assumed to vary linearly in the same form as the element unknown variables, and the finite element matrices are evaluated in closed form. Because numerical integration is avoided, significant computational time-saving is achieved. Solution accuracy and computational speed improvements are demonstrated by solving several two- and three-dimensional thermal-structural examples.

Fluid-thermal-structural interaction of aerodynamically heated leading edges

A two-dimensional finite element approach is presented for the integrated fluid-thermal-structural analysis of aerodynamically heated leading edges. The approach is combined with an adaptive unstructured remeshing technique to solve the Navier-Stokes equations for high speed compressible flow, the energy equation for the structure thermal response, and the quasi-static equilibrium equations for the structural response. Coupling and interaction between the three disciplines are demonstrated using two applications for high speed flow over a cylinder and a simulated engine leading edge verification test.

Finite element prediction of aerothermal-structural interaction of aerodynamically heated panels

A finite element approach is used to study the aerothermal-structural interaction of aerodynamically heated panels. The Navier-Stokes equations for laminar compressible flow are solved together with the energy equation and quasi-static structural equations of the panel. Interactions between the flow, panel heat transfer and deformations are studied for a thin stainless steel panel aerodynamically heated by a Mach 6.6 flow and for a convectively cooled panel heated by a shock-boundary layer interaction.

Finite Element Methodology for Integrated Flow-Thermal-Structural Analysis

Thermal deformations and stresses induced by aerodynamic heating are important considerations in the design of hypersonic flight vehicles. Aerodynamic heating has a significant effect on the performance of the structure, and effective techniques for predicting the heating rates and thermal-structural response are required. In the past, the heating and thermal-structural analyses have typically been uncoupled. Structural heating rates have been computed for viscous flows over undeformable aerodynamics surfaces with prescribed thermal boundary conditions. In realistic high speed flows, aerodynamic surfaces deform as a result of the thermal loads, and thermal conditions are not constant at the fluid-structure interface. During the aerodynamic heating of a structure the fluid-structure interface deforms, and the structure continuously absorbs thermal energy from the flow. These interaction effects may in fact alter the heating rates to the structure. In [1–2], experiments and analyses conducted at the NASA Langley Research Center show that actual heating rates experienced by metallic thermal protection systems can be significantly higher than rates based on undeformed flat plate computations. For example, for deformed heights less than the boundary layer thickness, heating rates can be increased by as much as 40 percent; moreover, heating rates increase rapidly when deformed heights exceed the boundary layer thickness.