Nonlinear Coupling of Transient Analysis of Thermal Flow and Thermal Stress for T pipe 2007-01-0885

Researches of multiple physics phenomena become more and more important in industry and academy. Fluid Structure Interface (FSI) is one of these multiple phenomena that happen more often than not. During recent years, numerical analyses of FSI were fast in development with the constantly advancing progress of computer technology. MpCCI (Mesh based parallel Code Coupling Interface) is a typical product of FSI. MpCCI has been developed at the Fraunhofer-Institute SCAI in order to provide an application-independent interface for the coupling of different simulation codes. Although FSI includes both flow induced displacement and thermal flow induced thermal stress, latter has received less attention.

One of the authors has studied the methods of data transformation between the thermal fluid analysis and thermal stress analysis, and described the advantages and disadvantages of these methods in weak conjugate analysis ^[1]. In linear region, steady state and transient analysis have been checked for T-pipe models and two kind of practical exhaust port models to show the practicality and availability of weak conjugate analysis ^[2]. Although the maximum thermal stress is not very difficult to find in a linear region for a test problem, it is still not accurate enough for many practical designing in which the nonlinear material properties must be considered ^[3].

In last paper ^[3], temperature results of a transient thermal fluid analysis in a T pipe are used as transient loads for a nonlinear thermal stress analysis of the T-pipe. In the nonlinear analysis, linear proximity is used for both plastic region and elastic region. That is to say, 2-line kinematical hardening law is used to express the stress strain characteristic of the pipe. At the same time, different numbers of loads are used and the results are compared. When calculated stress of every node in the domain is less than the yielding stress, the behavior of the T-pipe shows linear characteristic. In another word, if the maximum total strain is less than the strain B1 related with specified yield stress C1 in Figure 1a and 1b, the load steps will not affect to each other and the necessary load steps become fewer than that in a real nonlinear analysis. With this method, the thermal stress calculation seems possible to run on a PC. We only need to select the load steps where we want to observe the thermal stress behavior ^[3].

In this paper, with the same T-pipe in Figure 2, a bigger coefficient of linear expansion and a higher inlet temperature of the pipe are used and nonlinear analyses are executed where the von Mises total strain exceeds the B1 in the Figure 1b.