Modelling Thruster-Hull Interaction With CFD

Abstract

The application of CFD for the analysis of thruster interactions effects (or degradation effects) is still a largely unexplored area. Quantifying these effects is essential to the design of dynamic positioning (DP) vessels. Presently, thruster interactions can be quantified using data available from literature, which unfortunately is often scarce, too general or not applicable to specific designs. Dedicated model tests, on the other hand, do provide detailed results but are relatively expensive and tend to become available relatively late in the design process. Alternatively, with CFD different vessel designs and thruster layouts can be investigated for thruster interaction effects in a cost-efficient manner early in the design process. This paper presents a practical method for modelling thrusters, describing the propeller blades as an actuator disk. Numerical choices for the calculations are discussed and steady state calculations are performed. This approach is evaluated on thruster-hull interaction cases in both bollard pull and under current conditions, for a series of configurations with increasing complexity: a thruster in open water, a thruster positioned under a flat plate and a thruster under a barge. A comparison to experimental results is presented for the flow field (against PIV experimental data) and forces on the thrusters and hull of the vessel. A modern Verification and Validation procedure is used to quantify uncertainties. The results are encouraging, both in a qualitative and quantitative sense. In this context, the modelling approach employed proves to be a robust and accurate solution, with low computational effort, and therefore appropriate to be used for much more complex real applications.

Formalization of design for physical model of the azimuth thruster with two degrees of freedom by computational fluid dynamics methods

“…Authors of article [19] used as software for computational fluid dynamics the package Marin ReFRESCO (Reliable&Fast Rans Equations (solver for) Ships, Cavitation (and) Offshore, Netherlands) which is widely employed for the visualization of flows around different objects. Re-FRESCO solves the RANS equations (averaged Reynolds Navier-Stokes equations) for multiphase non-stationary incompressible flows.…”

Mineração de dados eleitorais: descoberta de padrões de candidatos a vereador na região da campanha do Rio Grande do Sul

“…Compreende-se que um problema a ser tratado em KDD é a transformação de um conjunto de dados em um modelo utilizável, com determinado propósito, e que possibilite o entendimento humano [20]. A análise de dados tem sido realizada desde seus primórdios da computação por meios estatísticos, mas somente esse método matemático não proporciona a descoberta de informações desconhecidas em uma base de dados [10].…”

Thrust Allocation With Dynamic Power Consumption Modulation for Diesel-Electric Ships

“…This mapping is nontrivial. For example, [15] proposes a feedback-based strategy that ensures the propeller torque can be set as needed, and in [16] the thruster-hull interactions are modeled, which could make it possible to create local thruster controllers that could compensate for those effects automatically.…”

“…Again, the rotation matrix R(ψ) can reasonably be assumed to be constant in (16) as long as the high-pass filter time constant T dp is small enough to mostly filter out the parts of the signal that are old enough for the ship to turn enough to affect the kinematics. Observing that both ν T ∆ = ν(T ) and η T ∆ = η(T ) are known and determined at the current time T , and that f (t) and thus also the inner part of the integral (15) are constant from current time T until the time T e = T + δt when the solution from the next iteration of the thrust allocation algorithm becomes available, the integrals can be separated into past and future terms.…”