Month: February 2021

National Shipbuilding Suppliers Association Elects Chris Deegan to the Board

Posted on by Cody Prince

Washington, DC, Feb. 18, 2021–Chris Cikanovich, Chairman of the Board of the American Shipbuilding Suppliers Association (ASSA), announced today that Chris Deegan, President and Chief Executive of Gibbs & Cox has been elected to the National Board of Directors.

Deegan joined Gibbs & Cox as the Engineering Group Vice President in 2013. After three years, he was promoted into the position of President and Chief Executive in June of 2016. Since this time, he has expanded the capabilities of Gibbs & Cox into cybersecurity and naval autonomy as well as the company’s presence both domestically and internationally with eight current corporate offices.

In his naval acquisition career, Deegan was a member of the Department of the Navy’s Senior Executive Service (SES) for nearly ten years, serving in executive positions in the Naval Sea Systems Command (NAVSEA), Program Executive Office, Integrated Warfare Systems (PEO IWS) and the Assistant Secretary of the Navy Financial Management Budget office. Before his SES tours, he spent much of his career in submarine program management. In 1997, he was selected as a Brookings Fellow and served on Congressman John Murtha’s (House Appropriations Committee – Defense ranking member) personal staff.

“Since our founding in 1929, 24 classes of combatants and nearly 7,000 vessels have been built to G&C designs,” said Deegan. Gibbs & Cox supports military and commercial clients in the U.S. and internationally with all phases of marine design, construction, and lifecycle management. “Our passion is solving our customers’ 21st century maritime challenges with quality and integrity,” he said.

ASSA is a member-driven, national association representing the American Shipbuilding Supplier Base to the US Congress, Navy, Coast Guard, and shipbuilders. This past year, ASSA received national publicity for its strong Buy American position. “In the absence of clear direction from the Navy on domestic sourcing of critical components, ASSA believes that Congress must provide direction requiring that key critical components be designed, engineered, manufactured, and assembled in the U. S.,” said Cikanovich.

“I am honored to serve on this prestigious board to join with other US companies to advocate for the American Shipbuilding Supplier Base,” said Deegan. “It’s time to make Buy American America’s priority.”

For more on ASSA, go to: https://www.shipbuildingsuppliers.com/

The Virginia Polytechnic Institute and State University

Posted on by Cody Prince

DLBA is continuing to support the Virginia Polytechnic Institute and State University in their effort to modernize the ocean engineering laboratory in Norris Hall. Over the last year, we have been working with the customer to develop a concept that meets their performance objectives. The project has recently moved into the detailed design and construction phase, and our team is working to have the new towing carriage up and running by the fall 2021 semester.

 

Virginia Tech’s existing tow carriage is over sixty years old, and this upgrade will improve the test capabilities of the laboratory significantly. The maximum carriage speed will double from 10 ft/sec to 20 ft/sec, and the maximum acceleration will increase from 2 ft/sec2 to 15 ft/sec2. The towing carriage will be unmanned when operating, which is also a change from the existing system. An artist’s impression of the new carriage is provided in the images below.

This updated carriage and drive system will achieve the speeds necessary to perform planing craft slamming experiments.  In this type of experiment, a ship model is driven at high speeds into waves.  At full scale, slamming events involve hydrodynamic forces of incredible magnitude.  These slamming experiments characterize the structural loads and seakeeping attributes of fast craft.

After successful installation of the carriage, a future upgrade will provide a vertical planar motion mechanism (VPMM) to the laboratory’s collection of testing apparatuses to enable Virginia Tech to perform these specialized planing craft experiments.  DLBA is currently developing a design for the VPMM, which will allow scale models to be controlled in the vertical plane over a stroke length of approximately 25 inches.

DLBA is partnering with Edinburgh Designs to execute this project.  Edinburgh Designs is an internationally recognized leader in the design and construction of hydrodynamic test equipment.

Pressure Recovery in Overflow Piping due to Siphonic Effects

Posted on by Cody Prince
ABSTRACT

By: Anthony DeFilippo, P.E.

The purpose of this study is to determine if siphonic effects are able to induce a pressure recovery in ship tank overflow piping in favorable flow conditions. The study will go over key features and flow parameters that will likely produce the siphonic effects and the potential that this knowledge imparts for the design of tank overflow arrangements.

Overflow piping is necessary when filling tanks on a large scale since allowing a closed tank to fill past its capacity will likely exceed its design strength resulting in failure. Investigating if a pressure recovery credit can be taken to minimize or negate the effects of frictional losses can have a positive effect to optimize tank and piping design. An optimized design can reduce cost and weight.

The methods implemented in this study include the use of a Pressure Drop Worksheet which uses the Darcy-Weisbach equation for friction loss through a pipe, a computational fluid dynamics simulation program (Star-CCM+), and a fluid flow analysis and design modeling software (Pipe-Flo Professional). Using these three tools, the effects of siphons on pressure drop can be compared across different flowrates. A baseline will be established in order to ensure that each tool will provide a similar result in a simplified scenario. Star-CCM+ and Pipe-Flo Professional will be tested to ensure that a siphon can actually be modeled within the program. A pressure drop vs. flowrate comparison between the three tools will be established. Future work can be performed to determine how upstream and downstream conditions will affect the magnitude of the siphon.

 

Figure 16: CFD Volume Fraction at 200 GPM

 

To learn more about Pressure Recovery in Overflow Piping Due to Siphonic Effects please reach out to Anthony DeFilippo at adefilippo@gibbscox.com.

Reproduced with permission from the American Society of Naval Engineers.

CFD simulations for Scout Boats

Posted on by Cody Prince

Since the founding of DLBA, we have always said that the design of high-speed boats requires the combination of rigorous science and a little bit of art. While a great designer relies on experience to understand the impact of the artistic decisions on a design, CFD allows the impacts of those artistic decisions to be quantified to ensure that the best possible vessel is delivered to our clients.

DLBA is doing just that with CFD simulations on a new double stepped planing hull for Scout Boats. From hump to maximum speed, stepped planing hulls exhibit complex hydrodynamic relationships that traditional tools for unstepped hulls fail to capture. When traditional tools fall short, we utilize CFD to provide performance predictions across the operating regime. However, it goes much further than that. With CFD, we can see in detail what is happening as the hull interacts with the water around it allowing a better understanding of why a hull is performing the way it does and informing the best possible design choices for the craft.


With the enhanced visualization provided by CFD, DLBA has been able to recommend tangible design modifications to improve performance. In the hands of an experienced Naval Architect, CFD allows invaluable insights into high-speed craft hydrodynamics, leading to reliable, concrete, and actionable design recommendations supported by data. This analysis allows the mitigation of previously unforeseen problems at the design stage rather than after construction and testing of the first vessel.