Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Analysis of Bow and Aft Modification Effect on DTMB 5115 Ship Resistance

Karim Akbari Vakilabadi*, Hojat Motahari

Department of Marine Faculty, Imam Khomeini Maritime University, Noshahr, Iran

Abstract: Resistance reduction is the most important goal in ship design that causes higher speed and lower fuel consumption. Hydrodynamic optimization is an effective and robust design method that plays an indispensable role in ship hull form optimization. Designers and shipyards are required to produce vessels according to draft and speed specifications which have superior hydrodynamic performance under calm water conditions (the contract condition), and the optimization of ship hull designs is a vital part of achieving this goal. Resistance value of DTMB 5415 model has been measured by Maxsurf software and compared with CD Adabco Stare-CCM+ CFD based software results. These methods are used to compare the calm-water drags of several bow and aft forms and to define optimized hull for which the total (friction + wave) calm-water drag is minimized. The total drag is estimated using Holtrop method in Maxsurf. Comparisons of CFD calculations and experimental measurements for DTMB 5415 hull form show that CFD calculations are reliable. Bow type has been replaced with bulb and few changes have been done on aft that has better behavior than other types of aft on resistance and total resistance on hull has been decreased with replaced bulb and modified aft.

Keywords: resistance, bulbous-bow, hull form, DTMB 5415

Citation: Karim Akbari Vakilabadi, Hojat Motahari, Analysis of Bow and Aft Modification Effect on DTMB 5115 Ship Resistance. American Journal of Mechanical Engineering, 5 (1). 14-17. January 2017. doi:10.12691/ajme-5-1-3

1. Introduction

Although CFD-based hull form optimization is not routinely used for ship design, a significant number of applications of CFD tools for hydrodynamic optimization attest to growing interest in hydrodynamic optimization. This growing interest in hydrodynamic optimization is a useful development because ship design implies optimization, e.g. minimization of a functional that appropriately weighs payload, ship speed, motions, and calm water drag. Achieving to a hull form with the least resistance, good stability and good maneuverability due to specific sea area, is very important on military ships. Basic resistance components is shown on Figure 1.

Figure 1. Basic resistance components

The main component of total resistance divided to two components of the frictional resistance and pressure resistance and second one divided to viscous pressure resistance and wave resistance. An important factor in the resistance change due to modification of the bow and aft form is viscous pressure and wave resistance that could be decreased by optimized bow and aft modification. These modifications almost has no effect on friction resistance.

2. Model Introduction

The DTMB model 5415 has been designed in David Taylor Model Basin in 1980 and was first studied extensively using CFD techniques when it was chosen to be one of three test cases in the Gothenburg 2000 workshop for computational fluid dynamics applied to ship flows. Participants were asked to focus particularly on the total resistance, the wave profile along the hull and the selected locations close to the ship, the overall wave pattern in the near field, and the mean flow velocities near the stern, particularly at the propeller plane. Experimental data for this model has been obtained by three laboratories; DTMB, IIHR, and INSEAN (Instituto Nazionale per Studi ed Esperienze di Architettura Navale). Geometry and dimensions are illustrated in Table 1.

Table 1. Dimensions and coefficients of DTMB 5415

Figure 2. DTMB 5415 geometry

A series of four hull forms are considered in this study. These hull forms are original DTMB, bow modified vessel, aft modified vessel and DTMB with bow and aft modification. These four hull forms are compared with each other to show which one has lower drag in the particular speed range. These comparisons has been done by Star CCM+ and Maxsurf software to find how accurate the Maxsurf is. In Star-CCM+ software, drag value has been computed at 10, 24 and 30 knots and no more speeds was necessary.

3. Numerical Setup and Mesh Generation

The commercial software CD Adapco Star-CCM+ V.10.04.011 has been used for the resistance calculations. It is well known that the accuracy of CFD results and the calculation time strongly depends on the type of the mesh and number of cells used. So calculations has been done several times to find optimum mesh number. Two million meshes is suitable for three meter geometry to get correct results as shows in Figure 3. The free surface is modeled with the two phase VOF technique. A segregated flow solver approach is used for all simulations. The Reynolds stress problem is solved by means of k-ε turbulence model. Mesh scene on bow and free surface view has been shown on Figure 4 and Figure 5.

Figure 3. Mesh Independence

Figure 4. Mesh scene on bow

Figure 5. Mesh scene on free surface

4. Bow Modification

According to Bernoulli’s equation, bulb shaped bow can decrease drag by decreasing wave height. Bow shape of vessel has been changed to bulbous bow as shown in Figure 3 and bow sonar has been omitted. Although this type of bow is not the best, this modification has decreased total drag as shown in Figure 7.

A bulbous bow may yield five types of transformation: the longitudinal translation of the bulb length, the vertical translation of the bulb tip, the transverse translation of the bulb fullness, the sectional area translation of the bulb at the Forward Perpendicular (FP) position, and the corresponding fair transition translation of the ship main forepart and dimensions can optimize by genetic algorithm or other optimization methods. Just one type of bulbous-bow has been tested in this study to show behavior of flow around the hull.

Figure 6. Bow modification

Figure 7. Bow modification drag comparison (a) CFD (b) Maxsurf

5. Aft Modification

Aft shape of vessel has important effect on drag due to viscous pressure resistance. The aft was optimized for better pressure recovery and reduction of stern pressure losses. Figure 8 shows the modification of aft geometry, which was carried out using b-spline. The pressure contours indicate a better pressure recovery at the transom for the best transom design. In this case, total drag has been compared with original DTMB to find out the effect of aft modification on drag. The results are shown in Figure 9.

Figure 8. Aft modification

Figure 9. Aft modification drag comparison (a) CFD (b) Maxsurf

As the results are shown in Figure 9, Aft modification has a few positive effect on drag so transom is optimized.

6. Bow and Aft Modification

On the next step, modified bow and aft are used together to create a new optimized hull as shown in Figure 10. Total drag has been computed by CFD and Maxsurf and compared with original DTMB. All previous results also are shown in Figure 11 to observe and compare the charts better.

Figure 10. Bow and aft modification

Figure 11. Aft and bow modification total drag (a) CFD (b) Maxsurf

As shown in Figure 11, total drag of vessel with modified Bow and Aft is less than other hull forms which is because of desire coordination between bow and aft form that causes less wave making and viscous pressure resistance. Wave patterns around the hull are compared in DTMB with bulb and DTMB with aft and bow modification at the same speed in Figure 12.

Figure 12. Wave pattern around the hull

7. Conclusions

The comparison of charts resulted from CFD and Maxsurf indicated that both software show same difference in drag value of modifications, but usually values that resulted from Maxsurf are less than Star-CCM+ software values. Figure 7 shows that bulbous-bow decreases total drag of vessel due to the reduction of wave height. Then the aft type has been modified that results drag decreasing in comparison with original DTMB, but not so much. On the final step, as shows in Figure 11 and Figure 12, a vessel with bulbous-bow and modified aft have been tested by CFD and Maxsurf. This vessel has lower drag in comparison to the previous modified hull forms and original DTMB, in other words it is optimized. This optimization is due to good coordination between modified bow and aft that causes lower wave making resistance and lower viscous pressure resistance, as shows in Figure 12.

Acknowledgements

The authors wish to thank En. Nima Zaroudi and Dr. S. Saed Rezvani for many helpful guidance about simulating and analysis of vessel.

References

[1]   | Anthony, F., and Stephen Turnock, R., Ship Resistance and Propulsion, Cambridge university, 2011.
[2]   | Begovic. E, Mancini. S., Applicability of CFD Methods for Roll Damping Determination of Intact and Damaged Ship, Research Gate, 2016.
[3]   | Hendrix, D., Noblesse, F., Hydrodynamic optimization of ship hull forms, Applied Ocean Research, 2001.
[4]   | Jones, D.A., and Clarke, D.A., Fluent Code Simulation of Flow around a Naval Hull: the DTMB 5415, Defense Science and Technology Organization, Australia, 2010.
[5]   | Kandasamy, M., et al, CFD based Hydrodynamic Optimization and Structural Analysis of the Hybrid Ship Hul, 2016.
[6]   | Lu, Y., Chang, X., A hydrodynamic optimization design methodology for a ship bulbous bow under multiple operating conditions, Engineering Application of Computational Fluid Mechanics, 2016.
[7]   | Olivieri, A., et al, Towing Tank Experiments of Resistance, Sinkage and Trim, Boundary Layer, Wake, And Free Surface Flow around a Naval Combatant INSEAN 2340 Model, IIHR Technical Report, University of Iowa, 2001.
[8]   | Schneekluth, H., and Bertram, V., Ship Design for Efficiency and Economy, 1998.