can anybody explain dynamic model in simple word? especially the relationship between the test filter and sgs filter, the process of its application. or suggest some references.

Refer these:

1) A dynamic subgrid scale eddy viscosity model., Germano et al., Physics of fluids A, (3), 1760-1765

2) A proposed modification of the Germano subgrid scale closure method., Lilly, D.K., Physics of fluids A, (4), 633-635.

In simple words, the dynamic model utilizes the resolved velocities of the flow field to come up with a coefficient rather than specify it apriori as in the standard Smagorinsky model. In this way, the method is independent of the geometry and application.

Thank you very much first. In my mind, I think the most important point of Dynamic model is to set up a iterative relationship for the calculation of the model parameter Cd(x,y,z,t)

The procedure for calculating C is not iterative, but purely algebraic.

The original papers are simple and straight forward (easier than many texts) ... so go through them.

It is iterative in the paper of Poimelli and Liu and one equation model, at least something similar to it.