Hydrodynamic Impact of a System with a Single Elastic Mode II : Comparison of Experimental Force and Response with Theory

Hydrodynamic impact tests were made on an elastic model approximating a two-mass spring system to determine experimentally the effects of structural flexibility on the hydrodynamic loads encountered during seaplane landing impacts and to correlate the results with theory. A flexible seaplane was represented by a two-mass spring system consisting of a rigid prismatic float connected to a rigid upper mass by an elastic structure. The model had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. The tests were conducted in smooth water at fixed trims and included both high and low flight-path angles and a range of velocity. Theoretical and experimental comparisons indicated that the theoretical results agreed well with the experimental results

Effects of wing flexibility and variable air lift upon wing bending moment during landing impacts of a small seaplane

A smooth-water-landing investigation was conducted with a small seaplane to obtain experimental wing-bending-moment time histories together with time histories of the various parameters necessary for the prediction of wing bending moments during hydrodynamic forcing functions. The experimental results were compared with calculated results which include inertia-load effects and the effects of air-load variation during impact. The responses of the fundamental mode were calculated with the use of the measured hydrodynamic forcing functions. From these responses, the wing bending moments due to the hydrodynamic load were calculated according to the procedure given in R.M. No. 2221. The comparison of the time histories of the experimental and calculated wing bending moments showed good agreement both in phase relationship of the oscillations and in numerical values

NACA Technical Reports

From Summary: "Hydrodynamic impact tests were made on an elastic model approximating a two-mass spring system to determine experimentally the effects of structural flexibility on the hydrodynamic loads encountered during seaplane landing impacts and to correlate the results with theory. A flexible seaplane was represented by a two-mass spring system consisting of a rigid prismatic float connected to a rigid upper mass by an elastic structure. The model had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. The tests were conducted in smooth water at fixed trims and included both high and low flight-path angles and a range of velocity. Theoretical and experimental comparisons indicated that the theoretical results agreed well with the experimental results.

NACA Technical Notes

Report presenting an exploratory investigation of the dynamic effects of fuel sloshing in tip tanks on suddenly excited bending oscillations using two simplified model beam-tank systems. Several fluids of different densities and viscosities were used in combination with various conditions of tank fullness. Results regarding the large and small beam-tank system are provided

NACA Technical Reports

From Summary: "A smooth-water-landing investigation was conducted with a small seaplane to obtain experimental wing-bending-moment time histories together with time histories of the various parameters necessary for the prediction of wing bending moments during hydrodynamic forcing functions. The experimental results were compared with calculated results which include inertia-load effects and the effects of air-load variation during impact. The responses of the fundamental mode were calculated with the use of the measured hydrodynamic forcing functions. From these responses, the wing bending moments due to the hydrodynamic load were calculated according to the procedure given in R.M. No. 2221. The comparison of the time histories of the experimental and calculated wing bending moments showed good agreement both in phase relationship of the oscillations and in numerical values.

NACA Technical Notes

Report presenting a smooth-water-landing investigation with a small seaplane to obtain experimental wing-bending-moment time histories together with time histories of the various parameters necessary for the prediction of wing bending moments during hydrodynamic impact. Experimental results were compared with calculated results, including inertia-load effects and the effects of air-load variation during impact

Comparison of theoretical and experimental response of a single-mode elastic system in hydrodynamic impact /

Hydrodynamic impact tests wre made on an elastic model approximating a two-mass - spring system which had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. Tests were made at two combinations of trim and flight-path angles for a range of flight-path velocity. Comparison of the experimenatal results with results obtained from the theory of NACA TN 1398 showed good agreement.NACA TN No. 2343."April 1951."Includes bibliographical references.Hydrodynamic impact tests wre made on an elastic model approximating a two-mass - spring system which had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. Tests were made at two combinations of trim and flight-path angles for a range of flight-path velocity. Comparison of the experimenatal results with results obtained from the theory of NACA TN 1398 showed good agreement.Mode of access: Internet