| The development of the national economy has brought about tremendous development space to the transportation industry, the large investment in air transport, rail transport, and the numerous acceleration of highway transport network which expanded continuously, which have brought about unprecedented challenges to the transport industry of ship, and the high speed craft research has become the focus of public attention in maritime transportation, which has developed to be a comprehensive subject for the speed improvement of the ship, While how to reduce the resistance of ships will be the crucial significanceoAir Cavity Craft is the most excellent performance of ship models for reducing resistance, the working principle is to guide air to the bottom of ships to become the gas-water mixture, which reduces fluid density near the bottom of ships, changes the structure of boundary layer flow, so it can reduce friction of surface ships, and also can reach the energy-saving purpose。This paper has preceded numerical simulation by using hull of the approximate two-dimensional and three-dimensional model. The author selected a five meter long Bengdechuan body which similar to the hull of the two-dimensional model, the first quarter is an arc of the ellipse (oval Semiaxle radius of 0.5 meter long, 0.25 meter width Semiaxle radius, the junctions in arc and Bengdechuan body is a 0.1 meter long jet mouth. paper select the approximate three-dimensional model of the hull is added a 1 meter wide the model on the basis of the horizontal two-dimensional model and on both sides added the baffle, and a closure board was used at the rear hull.In this article, the author, constructed model by the software Gambit and computed by the commercial software Fluent, simulated the simplified model of Air Cavity Craft. In numerical compute, the discrete equations of limited volume, the mixture model and the standard k-e torrent equations are adopted, and the velocity-pressure coupling is using the method of Simplec with the Body Force Weight of pressure discrete。 The author has draw the fallowing conclusion through the numerical simulation:Two-dimension model: The density of the bubbles and the air-jet velocity make the major effects on reducing the resistance, but the opposite effects are being in the bubble diameter (10um～100um) and air-jet angle; In addition, the bubble diameter variation is not formed the significant effects on reducing the resistance。The reducing resistance effect became more obvious along with the enlargement of the bubble density when the bubbledensity is 10%～30% in the rangeo There has been no correlation relationship between the air-jet and the reducing resistance. The author found , however, the resistance effect is not better when have larger deviation angles。Three-dimension model: Under the circumstance of upright floating, the bubble mainly escapes from the stern, and form a longer trail in the stern which can be eliminated by take some corresponding measures in military; The bubble escaping trend was existed and showed in both sides of the bottom of the ship, however, because of some reason, the bubbles didn't escape to the surface of the water from the both sides。Under the circumstance of trim, the bubble escaped from both sides and the stem, The trail in stem is not much longer than that in both sides。There was a critical situation when the bubbles were being under the ship, at the back of the critical value, namely the bubbles didn't adhere to the bottom of the ship。Under the circumstance of trim, because of the larger pressure in the stem, the bubbles escaped from the both sides basically, and the effects on reducing resistance has sharply down; when in the state of the trim, we can increase the instrument of preventing to escape in the sides of the ship in order to reduce the bubble escape from the sides, so this can make a ideal reducing resistance results; Aiming at the critical value in heel, we can make the consideration to modify the stem shape of the ship in order to reduce the isolation design to improve effects。... |
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