The flow model of a peripheral turbulent jet curtain is proposed, assuming that the rate of growth of the curved jet is similar to that of the plane jet. Detailed pressure and velocity measurements have been carried out to determine the flow fieldof a curved and impinging jet. The measurements almost coincide with the predictions of this analysis based on the proposed flow model.
As known already by experimental study carried out previously the power required for a recirculating Air Cushion Vehicle depends on both the design and operating conditions, and the minimal values of the power can be achieved by the suitable combinations of parameters such as recirculating flow, hover height and the geometry of the recirculating air intake. In this study the simple flow model of recirculating jet based on the results of flow visuarization using air-bubble technique is proposed, and above mentioned characteristics of recirculating jet are explained by the analysis based on the flow model.
Some experimental investigations were carried out for axially symmetric open plenum chamber air cushion models. As to the influence of geometric configurations of a plenum chamber (i.e., chamber height, nozzle diameter and hovering height), the hovering lift performance can be conveniently expressed by using Figure of Merit. The experiments were also carried out for the effect of the peripheral edge shapes of plenum chamber on the lift performance. The effect of forward speed on the cushion lift was also tested in a wind tunnel with a moving belt rig.
This paper presents a theoretical method to calculate the static and dynamic spring constants of a peripheral-jet air cushion vehicle in heaving motion and to obtain the response characteristics of the vehicle to sinusoidal input. The analysis leads to the following results: (1) The static spring constant is affected by the characteristics of the fan.(2)The dynamic spring constant is affected by the air-supplying system (fan, duct, air-chamber).
The heaving motion of air cushion vehicles of plenum-chamber type which is induced by the sinusoidal irregularity of the ground is analysed and its non-linear effects are particularly demonstrated by the numerical experiment in a digital computer.
The heaving motion of a circular model GEM which is induced by the simple harmonic motion of the ground board is experimentally investigated. The model hovers by the air supplied from external blowers and is guided vertically by means of its cylindrical part which is inserted into the fixed air duct and is free for vertical translation. The peripheral jet type nozzle attached to the model is exchangeable, and the experiments were conducted on two type nozzles, i.e. wide and narrow. The static hover, free vibration and forced vibration characteristics were studied. The natural frequencies of each model calculated from the static characteristics are compared to the frequencies of the ground movement to which the models resonate, and the basic data for the heaving motion are presented in this report.
Several problems on the take-off and landing performances of a GETOL (Ground Effect TakeOff and Landing) airplane are pointed out and studied in this report. This GETOL airplane has a configuration equipped with an air cushion landing gear in place of a conventional one, and the wind tunnel experiments are carried out for a model of this configuration. After some calculations, principal results are obtained as follows: 1) Take-off and landing distances of a hypothetical GETOL airplane are estimated and compared with those of a conventional airplane, and it is shown that in some cases the GETOL airplane has STOL characteristics. 2) The energy absorption capability of the air cushion landing gear at the touch-down condition in landing flight is evaluated from a simple analysis, and it is indicated that the hypothetical GETOL airplane has the sufficient capacity as well as the conventional landing gears.