Wave pattern Prediction
General information
Both MARIN codes (PARNASSOS and ReFRESCO) can deal with free surface flows. The VoF method ReFRESO does this by means of a surface capturing method. The PARNASSOS code uses a surface fitting method with a structured grid. It has a unique way of treating the free water surface in computations. By the use of a particular formulation of the boundary conditions, an iterative solution of the steady problem has been achieved. This makes the method very efficient: in a recent comparison, 50 times faster than a more standard method for the same problem. Moreover, a large accuracy can be achieved, leading to a realistic and precise prediction of the wave pattern; essential for understanding and improving a ship’s wave making characteristics.

Example 1: transom flow
Below is an example of application to the flow off a transom stern. The colours indicate the longitudinal flow velocity relative to the ship. A dry transom is found for the ship (right figure), but for the model (left figure) there is an area of wetted-transom flow, visible as a recirculation area. Only accurate computations can indicate such differences, and the consequences for the full-scale power. Therefore PARNASSOS is used more often to predict the speed power relation with the RNS-BEM method.

Example 2: trim wedge optimization
A second example shows the application of PARNASSOS for trim wedge optimization. With the high accuracy to determine ship resistance within 1-2 % PARNASSOS is very suitable of performing this kind of study in an early design stage. Especially when only the relative changes between the different wedges are of importance PARNASSOS can rather quickly determine which wedge is optimal. The most recent development couples the PARNASSOS Free Surface technique to the PARNASSOS Explorer technique. This enables trim wedge optimization studies with a wide range of shapes in a short throughput time.

From left to right: Three trim wedges and a neutral wedge, results for power levels and a comparison of the transom wave pattern for two configurations

Recent Papers:
Multi-Objective Surrogate Based Hull-Form Optimization Using High-Fidelity RANS Computations
Scholcz, T.P. and Veldhuis, C.H.J., VII International Conference on Computational Methods in Marine Engineering (MARINE2017), Nantes, France, 2017

Optimization of a ship with a large diameter propeller
Ploeg, A. van der, Bles, G. van der, and Zelderen, J. van, 19th Numerical Towing Tank Symposium (NuTTS), St. Pierre d'Oléron, France, 2016

Viscous Free-Surface Power Predictions For Self-Propulsion Using A Hybrid RANS-BEM Coupling Procedure (PARNASSOS-PROCAL)
Starke, B. S., Tokyo 2015, A Workshop on CFD in Ship Hydrodynamics, Tokyo, Japan, 2015

Integrated design of asymmetric aftbody and propeller to maximize energy efficiency
Rueda, L. and Dang, J., RINA Energy Efficient Ships, Rotterdam, The Netherlands, 2015

Optimization of the STREAMLINE tanker using RANS/FS computations
Van der Ploeg, A., NUTTS 2014, Gothenburg, Sweden, 2014

Promising Hydrodynamic Improvements For Inland Vessels
Van der Meij, K.H. and Raven, H.C., European Inland Waterway Navigation Conference, Budapest, Hungary, 2014

A computational study of shallow-water effects on ship viscous resistance
Raven, H.C., 29th Symposium on Naval Hydrodynamics (ONR), Gothenburg, Sweden, 2012

Object Functions for Optimizing a Ship’s Aft Body
Ploeg, A. van der, 11th International Conference on Computer and IT Applications in the Maritime Industries (COMPIT), Liège, Belgium, 2012

Prediction Of The Transom Flow Regime With Viscous Free Surface Computations
Ploeg, A. van der and Starke, A.R., IV International Conference on Computational Methods in Marine Engineering (ECCOMAS MARINE), Lisbon, Portugal, 2011

Trim wedge optimization using RANS/FS
Starke, A.R., Ploeg, A. van der, and Veldhuis, C.H.J., RINA Developments in Marine CFD, 2011

Computation of Scale Effects in Free-Surface Flows near a Ship’s Transom
Ploeg, A. van der, Chao, K., Marzi, J. and Wackers, J., 13th Numerical Towing Tank Symposium (NuTTS'10), Duisburg, 2010

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