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Research Papers: Ocean Engineering

Hydrodynamics of the Interceptor Analysis Via Both Ultrareduced Model Test and Dynamic Computational Fluid Dynamics Simulation

[+] Author and Article Information
M. Mansoori

Program of Ocean Engineering, COPPE,
Federal University of Rio de Janeiro,
Rio de Janeiro 22050-002, Brazil

A. C. Fernandes

Professor
Program of Ocean Engineering, COPPE,
Federal University of Rio de Janeiro,
Rio de Janeiro 22241-160, Brazil

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received April 6, 2016; final manuscript received August 20, 2016; published online November 29, 2016. Assoc. Editor: Jonas W. Ringsberg.

J. Offshore Mech. Arct. Eng 139(2), 021101 (Nov 29, 2016) (15 pages) Paper No: OMAE-16-1036; doi: 10.1115/1.4034615 History: Received April 06, 2016; Revised August 20, 2016

This work investigates the hydrodynamic effects of introducing interceptors on fast vessels. Interceptors are vertical flat blades installed at the bottom of the stern vessel. They cause changes in pressure magnitudes around the vessel bottom and especially at the end of the hull where they are located. The pressure variations have an effect on resistance, draft height, and lifting forces which may result in a better control of trim. This work uses a combination of computational fluid dynamics (CFD) and ultrareduced experimental tests. The investigation applies the Reynolds-averaged Navier–Stokes (RANS) equations to model the flow around the ultrareduced model with interceptors with different heights. Our model is analyzed based on a finite-volume method using dynamic mesh. The boat motion is only with two degrees-of-freedom. The results show that the interceptor causes an intense pressure gradient, decreasing the wet surface of the vessel and, quite surprisingly, the resistance. At last, this paper shows that, within a range, a better trim control is possible. The height of the interceptor has an important effect on interceptor efficiency, and it should be especially selected according to the length of the vessel and boundary layer thickness at the transom. The ultrareduced model tests were performed in the Current Channel of the Laboratory of Waves and Current of COPPE/UFRJ (LOC in Portuguese acronym).

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Figures

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Fig. 1

The implementation of an interceptor at the aft of a planning craft

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Fig. 2

A sample of the generated grid around the vessel

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Fig. 3

The divisions of generated grid around the vessel

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Fig. 4

The grid generated on second region

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Fig. 5

Scheme of reconnection of cells in the ring

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Fig. 6

The simultaneous translational motion of the grid along the coordinate axes

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Fig. 8

Domain of flow, shape, and dimension

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Fig. 10

Computational time versus grid size

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Fig. 11

(a) The model of boat at the LOC and (b) 5 mm interceptor at the end of the model

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Fig. 12

Two cameras to capture trim motions

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Fig. 13

View of (a) model setup, (b) motion caused by lift force, and (c) motion caused by trim moment

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Fig. 14

Velocities measured by velocity meter (X (1)………X (9), X (10))

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Fig. 18

Effect of interceptor height changes on interceptor behavior

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Fig. 19

Effect of interceptor on pressure changes at transom (along the hull centerline)

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Fig. 20

Forces and moment created by interceptor

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Fig. 21

Pressure distribution along all wetted surface of the model boat (d/L = 0) and at the stern with interceptors (d/L = 0.003, d/L = 0.012, and d/L = 0.02)

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Fig. 22

Effect of interceptor on wetted surface reduction

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Fig. 23

Sinkage of model with and without interceptor

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Fig. 24

Boundary layer thickness at transom and the interceptor height

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Fig. 25

Boundary layer thickness at transom versus volume Froude number

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Fig. 26

(a) General behavior of a planning boat versus speed (m/s) and (b) changes in resistance and trim of the model boat versus volume Froude number. In both figures, the limits of hump regime are identified in terms of length Froude number.

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Fig. 27

Comparison of CFD and experiments of the interceptor effects with a weak interceptor (d/L = 0.0038) on (a) resistance and (b) trim, also the case without interceptor (d/L = 0.0000)

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Fig. 28

View of both the case without interceptor and the weak interceptor experiments (C is the draft height at the stern)

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Fig. 29

Some d/h ratios for the weak interceptor versus volume Froude numbers, also the case without interceptor

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Fig. 30

Comparison of CFD and experiments of the interceptor effects (d/L = 0.012) on (a) resistance and (b) trim, also the case without interceptor (d/L = 0.0000)

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Fig. 31

View of the optimal interceptor experiments (C is thedraft height at the stern), also the case without interceptor (d/L = 0.0000)

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Fig. 32

Some d/h ratios for optimal interceptor at several volume Froude numbers, also the case without interceptor

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Fig. 33

Comparison of CFD and experiments of the interceptor effects with the unfit interceptor (d/L = 0.020) on (a) resistance and (b) trim, also the case without interceptor (d/L = 0.0000)

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Fig. 34

View of the unfit interceptor experiments which leads to capsize of the model (M1 and M2 are, respectively, the sense of the intense trim moment and the sense of the interceptor moment)

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Fig. 35

Some d/h ratios in unfit interceptor versus volume Froude numbers, also the case without interceptor (d/L = 0.0000)

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Fig. 36

The general view of the d/h ratio effect on interceptor performance

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Fig. 37

View of offset frames

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