*heading LONGITUDINAL VIBRATION OF "CLAMPED-FREE" (CANTILEVER) BEAM WITH AND WITHOUT ADDED MASS ******************************************************************* *** RESULTS/ANALYTICAL SOLUTION *** *** Analytical solution: *** f_n = (n + 0.5) * (1 / 2L) * sqrt (E/(rho + rho_w)) *** where *** f is the frequency in cycles/time *** n is the number of the mode *** r is the radius of circular cross-section *** L is the length of the structure *** E is the Young's modulus of the material (of the structure) *** rho is the density of material *** rho_w is the density of fluid (or water) *** *** F R E Q U E N C Y T A B L E *** Mode Analytical ABAQUS Analytical ABAQUS *** No Added Mass Added Mass *** 1 4.2554 4.2554 3.9959 3.9958 *** 2 12.766 12.765 11.988 11.986 *** 3 21.277 21.272 19.979 19.974 *** 4 29.788 29.773 27.971 27.957 *** 5 38.299 38.267 35.963 35.933 ******************************************************************* **************MODEL******** *node 1, 0.0, 0.0 1001, 1000.0, 0.0 *ngen, nset=all_nodes 1,1001,10 *ngen, nset=nodes_bend 11,991,10 *nset,nset=loaded_nodes 1,991 *element, type=b21 1, 1,11 *elgen, elset=b21_elements 1, 100, 10, 10 *************AQUA********** *aqua -100.0, 100.0, 32.2, 2.0 0., 0., 0., 0. *************MATERIAL/SECTION******* *beam section, elset=b21_elements, section=circ, material=mat1 3.0, *material, name=mat1 *elastic 4.32e9, *density 14.91, **************BOUNDARY*********** *boundary all_nodes,2,2,0.0 1 ,1,1,0.0 1 ,6,6,0.0 **************HISTORY/LOADING******* *restart,write,f=100 ***** *step,perturbation Without added mass *frequency, eigensolver=lanczos, SIM=NO 5, , *endstep ***** *step,perturbation With added mass (FI1 and FI2 simulating lumped mass) *frequency, eigensolver=lanczos, SIM=NO 5, , *d added mass b21_elements, fi1, 1.0, 141.37 b21_elements, fi2, 1.0, 141.37 *endstep ***** *step,perturbation With added mass (TSI simulating lumped mass) *frequency, eigensolver=lanczos, SIM=NO 5, , *c added mass loaded_nodes, tsi, 1.0, 141.37 1.0, 0.0, 0.0 nodes_bend, tsi, 1.0, 282.74 1.0, 0.0, 0.0 *endstep