Analysis of deflection and dynamic plant characteristics of Cyperus malaccensis Lam

ABSTRACT In this study, flexural rigidity, natural frequency, and damping coefficient of Cyperus malaccensis Lam. with long stems were measured for application for fluid–structure interaction simulation in a field. Numerical solutions of deflection and natural frequency were calculated by ANSYS with finite element method (FEM). The triangular cross-section shape of C. malaccensis stem has a big neighbourhood of the root and the cross-section has taper structure to become small towards tip direction. Two numerical simulation models for FEM have Model A with a triangular prism shape and Model B with a truncated trigonal pyramidal shape to evaluate the effects of stem tapering. Because of large C. malaccensis stem deflection, an equation for nonlinear deflection was introduced to solve a problem regarding flexural rigidity. Natural frequencies of the stem were estimated using amplitude ratio during stem swinging by forced vibration, captured using a high-speed camera. The Model B corresponded with the measurement, and the results suggested that the stem characteristics were affected by cross-section shape. Damping coefficient was calculated using free vibration response, which was consistent with the analytical solution and numerical data calculated using measured characteristics. Abbreviations: C. malaccensis: Cyperus malaccensis; FEM: finite element method; GIAHS: Globally Important Agricultural Heritage Syste