The Properties Of Heat Conduction In The One Dimensional Thermal Wave Crystal

In ultra-fast heat conduction systems,the orders of magnitude of time or space are extremely short,and thus the traditional Fourier conduction law with its implicit assumption of instantaneous thermal propagation is no longer applicable.As a result,special treatments are required to model the thermal transport phenomena that Cat-taneo and Vernotte proposed a thermal wave model with a single phase time lag.This results in that the classical diffusive heat conduction process turns into a wave-like phenomenon.The published literature contains many investigations into ther-mal wave behavior under different boundary conditions in simi-infinite medium,finite medium and thin films.However,the CV model assumes an instantaneous thermal transport across the same material volume.The temperature gradient is al-ways the cause for thermal transfer,which the heat flux is always the effect pre-sumed in the CV model.In order to remove the precedence assumption made in the CV model,Tzou proposed a model with two phase time lags.It is well known that wave manipulation is an eternal,important and challeng-ing issue.In past decades,the control of electromagnetic waves by photonic crystals and the control of acoustic or elastic waves by phononic crystals have been received considerable attention.This thesis focuses on manipulating thermal behaviors by the artificial periodical structures,thermal wave crystal,from the perspective of wave manipulating.In this thesis,the transfer matrix method is applied to simulate the thermal waves predicted by CV model and DPL model propagating through sin-gle-layer and multi-layer one dimensional structures.And the temperature responses are obtained by using the FDTD method,which is also used to verify the correct-ness of the band structure.Numerical analyses are presented for the temperature distributions induced within periodical structure by these non-Fourier propagation modes.Band gaps induced by Bragg scattering do exist according to both the theo-retical and numerical result.And parameters determining the first band gap have been discussed.The effect of thermal resistance has also been discussed.The result show:1.The band gap is affected by the structure parameters(filling rate,nondimen-sional length)and material parameters(the ratio of thermal conductivity,the ra-tio of volumetric heat capacity,and the ratio of relaxation time).The key param-eter of the generation of band gap is the ratio of thermal conductivity and the ra-tio of relaxation time.The damping rate within the band gaps is effect by all of the parameters except the nondimensional length.2.The frequency of band gaps is controlled by the nondimensional length,and the band gap is submerged when the nondimensional length is far too large.The physical interpretation of nondimensional length is the ratio between the peri-odic length and effective man free path for phonon.3.Interface thermal resistances will accelerates the damping of thermal waves,and making the dispersion curves based on CV model and DPL mode becoming the same.But the thermal resistance based on Fourier thermal transfer model will bring a brand new band gap in low frequencies.