THE CAUGHEY ABSORBING LAYER METHOD €“ IMPLEMENTATION AND VALIDATION IN ANSYS SOFTWARE

Abstract

THIS PAPER ADDRESSES THE CAUGHEY ABSORBING LAYER METHOD (CALM) PERFORMANCE IN THE ONE-DIMENSIONAL PROBLEM AND ITS IMPLEMENTATION IN COMMERCIAL SOFTWARE, WITH POSSIBILITY OF DIRECT EXTENSION TO TWO-DIMENSIONS. THE ADEQUACY AND NUMERICAL EFFI-CIENCY IS EVALUATED USING THREE DIFFERENT ERROR MEASURES AND FIVE DIFFERENT VARIATIONS OF THE DAMPING PROFILE. OTHER PARAMETERS THAT ARE SUBJECTED TO EVALUATION ARE THE LENGTH OF THE ABSORBING LAYER IN RELATION TO THE WAVELENGTH TO ABSORB, THE VALUE OF THE LOSS FACTOR AT THE END OF THE ABSORBING LAYER, AND THE RATIO OF THE LOAD TO LAYER FREQUENCY. THE PROBLEM IS FIRSTLY ANALYSED THEORETICALLY, RESULTING IN ESTIMATES FOR THE WAVE REFLECTION DUE TO TRANSITION AND TRUNCATION OF THE MODEL. IN ORDER TO CONFIRM THAT NO SPURIOUS WAVES WILL BE PRESENT IN THE FINITE ELEMENT SOLUTION, THE NUMERICAL IMPLEMENTATION IS VALIDATED BY COMPARISON WITH THE ANALYTICAL SOLUTION. THE ANALYSIS OF THE ERROR MEASURES ON THE NUMERICAL RESULTS OB-TAINED FOR VARIOUS COMBINATIONS OF THE MODELÂS PARAMETERS LEAD TO THE CONCLUSION THAT CALM IS EFFECTIVE AT MITIGATING WAVES REFLECT-ED FROM THE BOUNDARIES. THE OPTIMUM LOSS FACTOR AS A FUNCTION OF THE RATIO OF THE LENGTH OF THE ABSORBING LAYER TO THE WAVELENGTH TO ABSORB IS DETERMINED THROUGH PARAMETRIC ANALYSES. ALTHOUGH THE OPTIMAL DAMPING IS FREQUENCY DEPENDENT, IT WAS SHOWN THAT THE CALMÂS EFFECTIVENESS CAN BE EXTENDED TO A WIDER RANGE OF FRE-QUENCIES BY INCREASING THE SMOOTHNESS OF THE DAMPING PROFILE.