排序方式: 共有22条查询结果,搜索用时 15 毫秒
21.
Self-propulsion computations using a speed controller and a discretized propeller with dynamic overset grids 总被引:2,自引:0,他引:2
Pablo M. Carrica Alejandro M. Castro Frederick Stern 《Journal of Marine Science and Technology》2010,15(4):316-330
A method that can be used to perform self-propulsion computations of surface ships is presented. The propeller is gridded
as an overset object with a rotational velocity that is imposed by a speed controller, which finds the self-propulsion point
when the ship reaches the target Froude number in a single transient computation. Dynamic overset grids are used to allow
different dynamic groups to move independently, including the hull and appendages, the propeller, and the background (where
the far-field boundary conditions are imposed). Predicted integral quantities include propeller rotational speed, propeller
forces, and ship’s attitude, along with the complete flow field. The fluid flow is solved by employing a single-phase level
set approach to model the free surface, along with a blended k−ω/k−ɛ based DES model for turbulence. Three ship hulls are evaluated: the single-propeller KVLCC1 tanker appended with a rudder,
the twin propeller fully appended surface combatant model DTMB 5613, and the KCS container ship without a rudder, and the
results are compared with experimental data obtained at the model scale. In the case of KCS, a more complete comparison with
propulsion data is performed. It is shown that direct computation of self-propelled ships is feasible, and though very resource
intensive, it provides a tool for obtaining vast flow detail. 相似文献
22.
URANS simulations of catamaran interference in shallow water 总被引:1,自引:0,他引:1
Teresa Castiglione Wei He Frederick Stern Sergio Bova 《Journal of Marine Science and Technology》2014,19(1):33-51
This paper investigates the interference effects of wave systems on a multi-hull vessel in shallow water. A numerical analysis is made using the URANS code CFDSHIP-Iowa V.4 on the DELFT Catamaran model 372. The test matrix for numerical computations includes two separation distances (s = 0.17; 0.23) and the depth values of h/T = 8.2, 2.5 and 2, at several speeds ranging within Fr H = 0.775–1.739. Numerical results are compared with the experimental data of the Bulgarian Ship Hydrodynamic Center, and verification and validation for resistance, sinkage and trim are also performed. Results show that, at critical speed (Fr H ≈ 1), the presence of a finite depth significantly affects the catamaran total resistance, which, in shallower water, increases considerably with respect to deep water. At low h/T, small effects of the water depth on resistance occur at subcritical and supercritical speeds. The interference effects seem to be more relevant in shallow, rather than in deep water, with maximum IF values registered at critical speeds (Fr H ≈ 1). Similarly to deep water, the lower the separation distance the greater the interference value. Moreover, in shallow water some negative interference is observed at Fr > 0.5. Wave patterns and wave profiles are analyzed and a comparison is made between several configurations of catamaran and a mono-hull vessel, in order to analyze how water depth and separation distance determine resistance and interference. Finally, a vortex instability study is also included. 相似文献