The main purpose is to investigate one-dimensional calculation method of cavities. The general one-dimensional modeling rule was put forward for complex cavities with nonstandard structure and multi-connections. The method of characteristics was adopted

and the one-dimensional unsteady flow and heat transfer of cavity structure was simulated. One-dimensional compressible partial differential equations of cavities generally integrating variations of variable cross section

friction and heat transfer were transformed to ordinary differential equations

so characteristic numerical solutions of pressure

flow

temperature and other parameters along the flow direction in cavity were derived. Results were verified by commercial computational fluid dynamics software CFX. Result shows that

the method adopted for one-dimensional unsteady flow and heat transfer simulation of cavity is visual and accurate

so it's capable of simulating complex cavity with multi-connections. The results of the method are about 9.4% away from that of the CFX model. Thus

it can be a useful way of one-dimensional unsteady research on cavity in secondary air system.