Uncertainty Assessment for Towing Tank Tests With Example for Surface Combatant DTMB Model 5415

2005 ◽  
Vol 49 (01) ◽  
pp. 55-68 ◽  
Author(s):  
Joe Longo ◽  
Fred Stern
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Uncertainty Assessment ◽  
Wave Profile ◽  
Assessment Methodology ◽  
Towing Tank ◽  
Measurement Systems ◽  
Sinkage And Trim ◽  
Surface Combatant ◽  
Wave Elevations

Uncertainty assessment methodology, procedures, and results are presented for most typical towing tank tests using a 3.048 m geosym of naval combatant DTMB model 5415, which is an established benchmark for computational fluid dynamics validation. The tests include resistance, sinkage and trim, wave profile, wave elevations, and nominal wake. The procedures are summarized and follow International Towing Tank Conference Quality Manual Procedures. The facility and measurement systems are briefly described, and detailed uncertainty assessment examples for each test are provided with descriptions of bias and precision limits and total uncertainties.

CFD Calculation of Sinkage and Trim

2000 ◽  
Vol 44 (01) ◽  
pp. 59-82
Author(s):  
Anil K. Subramani ◽  
Eric G. Paterson ◽  
Fred Stern
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Boundary Layers ◽  
Quantitative Agreement ◽  
Wave Profile ◽  
Wave Fields ◽  
Surface Ship ◽  
Sinkage And Trim ◽  
Computational Fluid Dynamics Cfd

A computational fluid dynamics (CFD) code for surface-ship boundary layers, wakes, and wave fields is extended by incorporating into it the capability of predicting sinkage and trim. The method is described and results are presented for the naval combatant FF1052 and the Series 60, Cg = 0.6 parent hull. Resistance, sinkage and trim, and wave profile on the hull are compared between the calculations and the experimental data. The trends in the data are predicted correctly and there is also good quantitative agreement overall between the calculations and the data.

Computational Fluid Dynamics Applied to River Boat Hull Optimization

2021 ◽  
Vol 55 (5) ◽  
pp. 94-108
Author(s):  
Harlysson W. S. Maia ◽  
Said Mounsif ◽  
Jassiel V. Hernández-Fontes ◽  
Rodolfo Silva
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computer Aided Design ◽  
Resistance Coefficient ◽  
Wave Profile ◽  
Total Resistance ◽  
Nsga Ii ◽  
Pressure Distributions ◽  
Aided Design ◽  
Geometric Variation

Abstract This paper extends the work of Maia and Said (“Analysis for Resistance Reduction of an Amazon School Boat through Hull Shape Modification Utilizing a CFD Tool,” 2019), proposing the optimization of a school boat hull using genetic algorithms and computational fluid dynamics (CDF) simulations. The study examines a school boat used for the transportation of children to schools in riverine communities of the Brazilian Amazon. The optimization was focused on reducing the hydrodynamic hull resistance by modifying the hull lines, using the NSGA-II (non-dominated sorting genetic algorithm II) algorithm in the CAD (computer aided design) CAESES environment. The objective of the study was to reduce the resistance coefficients: C wp (wave profile) and C wp trans (transverse wave profile), thus reducing the total resistance coefficient (C t) and the generated wave amplitude. Pressure distributions and flow lines were then evaluated to obtain an optimal modified hull with reduced wave emission (lower wave resistance) and, consequently, lower forward resistance. The proposed methodology resulted in a maximum reduction of 5% in the total resistance coefficient C t and in the identification of a trend of geometric variation of the hull for investigation in further studies.

scholarly journals Trim Influence on Kriso Container Ship (KCS): An Experimental and Numerical Study

2017 ◽  
Author(s):  
Emil Shivachev ◽  
Mahdi Khorasanchi ◽  
Alexander H. Day
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Study ◽  
Computational Cost ◽  
Breaking Waves ◽  
Computational Techniques ◽  
Container Ship ◽  
Towing Tank ◽  
Operational Life ◽  
Computational Fluid Dynamics Cfd

There has been a lot of interest in trim optimisation to reduce fuel consumption and emissions of ships. Many existing ships are designed for a single operational condition with the aim of producing low resistance at their design speed and draft with an even keel. Given that a ship will often sail outside this condition over its operational life and moreover some vessels such as LNG carriers return in ballast condition in one leg, the effect of trim on ships resistance will be significant. Ship trim optimization analysis has traditionally been done through towing tank testing. Computational techniques have become increasingly popular for design and optimization applications in all engineering disciplines. Computational Fluid Dynamics (CFD), is the fastest developing area in marine fluid dynamics as an alternative to model tests. High fidelity CFD methods are capable of modelling breaking waves which is especially crucial for trim optimisation studies where the bulbous bow partially emerges or the transom stern partially immerses. This paper presents a trim optimization study on the Kriso Container Ship (KCS) using computational fluid dynamics (CFD) in conjunction with towing tank tests. A series of resistance tests for various trim angles and speeds were conducted at 1:75 scale at design draft. CFD computations were carried out for the same conditions with the hull both fixed and free to sink and trim. Dynamic sinkage and trim add to the computational cost and thus slow the optimisation process. The results obtained from CFD simulations were in good agreement with the experiments. After validating the applicability of the computational model, the same mesh, boundary conditions and solution techniques were used to obtain resistance values for different trim conditions at different Froude numbers. Both the fixed and free trim/sinkage models could predict the trend of resistance with variation of trim angles; however the fixed model failed to measure the absolute values as accurately as the free model. It was concluded that a fixed CFD model, although computationally faster and cheaper, can find the optimum trim angle but cannot predict the amount of savings with very high accuracy. Results concerning the performance of the vessel at different speeds and trim angles were analysed and optimum trim is suggested.

Detailed Bow-Flow Data and CFD for a Series 60 CB = 0.6 Ship Model for Froude Number 0.316

1996 ◽  
Vol 40 (03) ◽  
pp. 193-199
Author(s):  
F. Stern ◽  
J. Longo ◽  
Z. J. Zhang ◽  
A. K. Subramani
Keyword(s):  
Thin Film ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Froude Number ◽  
Wave Profile ◽  
Flow Data ◽  
The Real ◽  
Ship Model ◽  
Wave Elevation ◽  
Computational Fluid Dynamics Cfd

The bow flow of the Series 60 CB = 0.6 ship model is reinvestigated using both experiments and computational fluid dynamics (CFD). More detailed bow-flow data are obtained by taking measurements of the wave elevation with a point gauge very near the bow. In the CFD, the bow flow is resolved in more detail by using the real bow geometry instead of the simplified vertical zero-thickness bow used in previous studies, which requires a much finer grid in the bow region. The experiments and CFD are briefly described; results are presented; and discussions are made concerning comparisons of the new and old CFD solutions with the extended data regarding the wave profile and elevation at the bow, the thin film and beads (i.e. attached spray sheet and bow vortices), and the stagnation effects.

Pitch and Heave Tests and Uncertainty Assessment for a Surface Combatant in Regular Head Waves

2008 ◽  
Vol 52 (02) ◽  
pp. 146-163
Author(s):  
Martin Irvine
Keyword(s):  
Transfer Functions ◽  
Uncertainty Assessment ◽  
Maximum Response ◽  
Third Order ◽  
Validation Data ◽  
Data Set ◽  
Towing Tank ◽  
Head Waves ◽  
Surface Combatant ◽  
Regular Head Waves

Towing-tank experiments of coupled pitch and heave motions are presented for a surface combatant advancing in regular head waves. The data include ballasting parameters, time histories, fast Fourier transform (FFT), Fourier series amplitudes, and pitch and heave transfer functions and phases for a range of speeds, wave steepnesses, and wave frequencies. The geometry is David Taylor Model Basin (DTMB) model 5512, which is a 1/46.6 scale geosim of DTMB model 5415 (DDG-51) with Lpp = 3.048 m. The experiments are performed in a 3.048 × 3.048 × 100 m towing tank equipped with a plunger-type wave maker. The test program is undertaken to provide a validation data set for unsteady Reynolds-averaged Navier-Stokes and other computational fluid dynamics (CFD) codes, including rigorous uncertainty assessment of the experimental results following standard procedures. Results indicate that the regular head waves are linear with second- and third-order magnitudes consistent with third-order Stokes waves. Pitch and heave responses and phases show expected trends for long and short wavelengths and are linear or Ak independent for all test conditions. Maximum response occurs for frequency of encounter equal to pitch and heave natural frequencies and Lpp / λ = 0.75. Under these conditions, an equation is derived that predicts the Froude number for maximum response as a function of ship geometrical coefficients.

Computational fluid dynamics prediction of hydrodynamic forces on a manoeuvring ship including effects of dynamic sinkage and trim

2017 ◽  
Vol 233 (1) ◽  
pp. 251-266 ◽  
Author(s):  
Yi Liu ◽  
Lu Zou ◽  
Zao-Jian Zou
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Hydrodynamic Forces ◽  
Numerical Error ◽  
Navier Stokes ◽  
Container Ship ◽  
Navier Stokes Equations ◽  
Sinkage And Trim

Understanding the manoeuvring performance of a ship requires accurate predictions of the hydrodynamic forces and moments on the ship. In the present study, the hydrodynamic forces and moments on a manoeuvring container ship at various rudder and drift angles are numerically predicted by solving the unsteady Reynolds-averaged Navier–Stokes equations. The effects of dynamic sinkage and trim on the hydrodynamic forces are first investigated together with a grid dependency study to estimate the numerical error and uncertainty caused by grid discretization, and with a validation study combining the experimental data. The results show that the effect of dynamic sinkage and trim is non-negligible, since including it improves the hydrodynamic force predictions and reduces the numerical error and uncertainty, and the averaged error and uncertainty are smaller than the other computational fluid dynamics results where sinkage and trim were fixed with given values from model tests. Therefore, it is included in the subsequent systematic simulations regarding the influence of rudder and drift angles. The computed forces, moments and rudder coefficients at different rudder and drift angles on the container ship are compared with the benchmark model test data. From the computations, all the predicted quantities are in satisfactory agreement with the experimental data. The details of the flow filed and hydrodynamic forces, such as pressure distributions, transverse force distributions along the hull, velocity contours, streamlines and wave patterns are presented and discussed, and a deep insight into the physical mechanism in the hydrodynamic forces on a manoeuvring ship is obtained.

scholarly journals Assessment of appendage effect on forward resistance reduction

2013 ◽  
Vol 7 (13) ◽  
pp. 37 ◽  
Author(s):  
Marcos Salas ◽  
Gonzalo Tampier
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Energy Saving ◽  
Numerical Results ◽  
Combined Effect ◽  
Fuel Saving ◽  
Towing Tank ◽  
Resistance Reduction ◽  
Hydrodynamic Effects

This paper shows experimental and numerical results of three types of appendages on forward resistance reduction of displacement and semidisplacement hulls. Forward resistance results were obtained by using Computational Fluid Dynamics and towing tank tests. The appendages evaluated are stern flaps and interceptors for displacement hulls and spray railspray rails for a semiplaning hull. The experiments are independent from each other and no research was undertaken to include the combined effect of appendages on a single hull. The predicted reduction in forward resistance in all three tested devices is around 5-10%, showing potential for fuel saving through the evaluation of hydrodynamic effects of energy saving appendages.

Computational fluid dynamics analysis on the added resistance of submarine due to Deck wetness at surface condition

2016 ◽  
Vol 231 (1) ◽  
pp. 128-136
Author(s):  
Mohammad Moonesun ◽  
Mehran Javadi ◽  
Seyyed Hossein Mousavizadegan ◽  
Hosein Dalayeli ◽  
Yuri Mikhailovich Korol ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Surface Condition ◽  
Wave Profile ◽  
Added Resistance ◽  
Bow Wave ◽  
Computational Fluid Dynamics Analysis ◽  
Dynamics Method ◽  
Deck Wetness

This article describes the evaluation of the wave profile of submarine at surface condition and deck flooding which occurred by the wave making pattern at the bow. Movement of ships and submarines on the free surface of calm water creates the surface wave. Because of the difference in the bow shape and freeboard height, the wave making system in ships and submarines is different. Rounded or elliptical bow shape of submarines generates a high bow wave which causes deck and bow wetness. This is because of the fact that in submarines, this situation arises a small freeboard. In submarines, Deck wetness (because of deck flooding) is a very important subject that has some remarkable consequences, such as increase in resistance and added weigh. The focus of this article is on the added frictional resistance in the deck wetness condition. The bow wave profile, deck wetness and added resistance are studied in several Froude numbers by computational fluid dynamics method. This analysis is performed for a bare hull model at two different drafts by Flow Vision (V.2.3) software based on computational fluid dynamics method and solving the Reynolds-averaged Navier–Stokes equations.

The Effect of Counter Length on Hull Resistance

1989 ◽  
Author(s):  
Andrew R. Claughton
Keyword(s):  
Regression Analysis ◽  
Wave Profile ◽  
Full Scale ◽  
Hull Form ◽  
Towing Tank ◽  
Scale Resistance ◽  
Analysis Methods ◽  
Sinkage And Trim ◽  
Resistance Curves ◽  
Resistance Data

Towing Tank tests on a single 2.4 m LOA model hull form with 3 alternative counter lengths, and 2 alternative rudder configurations have been carried out in the Southampton Towing Tank. The results were used to derive predictions of full scale resistance curves for a 10m L WL racing yacht. In addition to the resistance data, sinkage and, trim were measured. Wave profile measurements were also made to determine the influence of counter length on the hull generated waves. The resistance curves are presented for the 5 configurations investigated and the results are compared with published regression analysis methods of estimating hull resistance based on geometric hull parameters.

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