Study On Inverse Design Method And Wave Bandgap Characteristics Of Wave-dissipating Structure

The wave dissipating effect of wave-dissipating structure is closely related to the wave frequency,the enhancement of wave-eliminating effect of wave-dissipating structure is influenced by the coupling of structure boundary and wave frequency.In this way,two research topics are introduced.One is,the acting wave frequency bandwidth is known,the boundary design problem of wave-dissipating structure under a certain wave-eliminating level.The second problem is,the boundary of wave-dissipating structure is known,to calculate the wave frequency bandwidth of wave-dissipating structure under the condition that the wave-eliminating level of the wave-dissipating structure is given.The boundary design problem of wave-dissipating structure and the calculation problem of optimal wave frequency bandwidth of wave-dissipating structure under a certain wave reflection level can be summarized as the inverse design problem of the optimal boundary of the wave-dissipating structure and the optimal wave frequency bandwidth of the wave-dissipating structure based on wave reflection characteristics of the wave-dissipating structure.By optimizing the boundary of wave-dissipating structure,the width of wave-dissipating frequency band under low reflection level of wave-dissipating structure can be expanded appropriately,and the adaptability of wave-dissipating structure can be enhanced.Aiming at the above problems,after lots of related researches,analyses and verification have been carried out,and the concept of wave bandgap structure that can appropriately be widen the frequency width of "Wave-trapping"has been proposed in this paper.And then,the characteristic equipped by the wave bandgap structure-wave bandgap characteristics is given.The idea of inverse design is introduced into the optimization design of wave-dissipating structure,which takes the wave reflection performance as the target control,the boundary of wave-dissipating structure as the design variable,to inverse design the wave-dissipating structure boundary,so as to widen the optimal wave-dissipating bandwidth of wave-dissipating structure.The specific research contents and the main achievements are as follows:Firstly,an inverse design model of wave-dissipating structure size based on adaptive neural fuzzy reasoning system(ANFIS),which can include the influence of uncertainty in nature,is developed.And the nonlinear relationship between wave reflection coefficient and wave-dissipating structure size is established by ANFIS.Then,based on the advantages of plate structure to reduce wave reflection to a lower level and perforated structure to broaden the frequency bandwidth to eliminate waves in a wider frequency band,a new wave-dissipating structure-COMBLOCK wave-dissipating structure is proposed.For the numerical scale waves with a period of 0.8s-1.6s(the wave period in the real sea area is 4.0s-8.0s when the model scale is 1/25),the optimal sizes of COMBLOCK wave-dissipating structure with the reflection level below 0.4 are designed through the inverse design model of wave-dissipating structure size based on ANFIS.Secondly,the inverse design method of the boundary shapes of wave-dissipating structure is proposed based on the discrete adjoint method.And the discrete adjoint method is introduced into the inverse design optimization of wave-dissipating structure combined with the hydrodynamic model of fluid,then the numerically driven intelligent optimal design method of wave-dissipating structure is developed.Using the inverse design method based on the adjoint method,the boundary shapes of three different initial types of wave-dissipating structure is optimized,and the optimum boundary shape of wave-dissipating structure with low wave reflection level is obtained under the action of design frequency wave.Then,a method for calculating the bandgap of wave bandgap structures is developed.The bandgap widths of different types of wave bandgap structures with the reflection level below 0.4 are calculated,and the specific positions of band gap width including the starting frequency and the termination frequency are determined.The influence factors of wave bandgap width are studied,and it is concluded that the boundary size and shape of wave bandgap structure are the main factors affecting wave bandgap width under the condition that the wave bandgap structure type has been determined.Finally,the numerical wave flume is used to validate the wave bandgap characteristics of wave bandgap structure for the calculation results of wave bandgap width,and the numerical simulations of testing waves including waves in the bandwidth and waves near bandgap boundaries interacted with different types of wave-dissipating structures and wave bandgap structures are carried out to compare the wave reflection characteristics and the flow field characteristics.