Numerical and Experimental Investigations on Flow Interaction Effect for Water-Jet Intake Duct
Tsuyoshi Eguchi* and Naohiro Kamide**
ABSTRACT
In order to clarify the effect of flow interaction between the intake ducts on the loss and flow pattern in each intake, wind tunnel tests were performed. A "flush-type" water jet intake duct was chosen, and two types of intake combinations, i.e. "flat and flat" and "flat and tapered" were modeled based on the prototype configurations. Intake duct losses and flow patterns for both the two-intake operation and the single-intake operation were compared. Measurements were made for the flow pattern along the ship bottom and the wall static pressure inside the duct. The differences in the loss and flow behavior were observed in each intake combination. Also, a finite-volume based CFD (computational fluid dynamics) code was used and these results showed good agreement with the experimental ones to understand the flow interaction between the neighboring intake ducts.
The loss reduction of a water-jet intake duct for high-speed ships is one of the prime interests in the research and development as well as the design process. In Mitsubishi Heavy Industries (MHI), Ltd., various types of intake duct geometry has been studied through the wind tunnel tests for last 20 years[1-3], and the optimum duct shape were found. On the other hand, since actual ships have a variety of intake configurations and number of ducts, flow interaction effects on the loss and flow pattern in each intake duct should be considered. In this paper, a flush-type intake duct was chosen to study the interaction effect between two intake ducts. As an experimental approach, wind tunnel tests were performed to measure the intake pressure loss, flow pattern along the ship bottom and local static pressure inside the duct. For this objective, small-scale plastic models were prepared. Two combinations were considered; the one is "flat and flat" and the other "flat and tapered" combination. One flat intake was commonly used for both combinations. The intake pitch, the distance between the center of each intake, was determined based on the actual ship. Due to the limitation of the measuring method, a numerical approach was also applied to compensate measured data; to predict the loss and understand the detailed flow pattern inside the duct, which are not easy to obtain by the experiment.
* Takasago Research and Development Center, Mitsubishi Heavy Industries, Ltd.
2-1-1 Shinhama, Arai-cho, Takasago, Hyogo 676-8686 JAPAN
