Seakeeping – Wet Deck Slamming on Offshore Ships

How can we accurately predict wave impact loads on ships for seakeeping? Some of the important parameters related to ship hull design include ship motions, vertical accelerations, wave impact/slamming loads, and deck wetness. The ABS Guide for Building and Classing High Speed Naval Craft (HSNC 2007) clearly states that slamming impact load is one of the most critical factors for the scantling design of hull structures. Accurate prediction of wave impact loads requires solving three problems. First is the prediction of wave kinematics, second is the prediction of the pressure and viscous forces and the third is the prediction of ship motion during the wave impact. It is possible to simulate all of these problems with ANSYS computational fluid dynamics (CFD) software. Continue reading

High-Fidelity Modeling for Installation of Subsea Structures in the Splash Zone

subsea manifold

3D Computational Domain including Detailed Geometry of a Subsea Manifold

Lowering subsea structures and equipment into the splash zone is a critical part of offshore installation campaigns. In preparation, engineering teams perform many installation analyses to ensure sufficient crane capacity, clearance and accessibility, structural integrity, and equipment/structure stability. Traditional low-fidelity approaches rely on simplified formulations or empirical equations; some consist of model tests to determine wave loads on structures. But these traditional approaches cannot simulate wave-structure interaction nor the dynamic stress and deformation of structure/equipment due to wave slamming. And hence the accuracy is always a key concern. Continue reading

Ocean Waves – A Nightmare for Offshore Structures

You may have heard about the grounding of an Alaskan oil rig in January, 2013. The 28,000-tonne rig was pushed toward the shore by waves up to 35 feet and winds up to 62 mph, dragging its main towing vessel and a tug behind it. There have been several such oil rig incidents over the past few decades. The below image shows the failure of an another oil rig platform due to extreme wave forces. A huge wave hitting the offshore platform leads to high wave impact loads that can eventually result in significant platform damage and collapse. These incidents can cause fatalities and damages that can cost hundreds of millions of dollars. Continue reading

Durability and Reliability for Sea-Floor Oil and Gas Processing Equipment

Developing more efficient water processing units for oil and gas production is becoming an industry focus. Water occurs naturally within oil and gas reserves and can also be introduced as part of enhanced oil and gas recovery process. The water involved in oil and gas production is called produced water and is an undesired by-product in that industry. Both onshore and offshore produced water requires large amounts of pumping energy and the costs for water management and disposal are rising.  The problem is greatest for old wells and for offshore production. Exciting new technologies are being developed to address these issues and engineering simulation can help.

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Simulation and Engineering: State of the Art?

In conversations with work colleagues, we often discuss and debate the question, “What constitutes a state-of-the-art simulation tool?” Having worked in the simulation world for 25 years, I say that the time for a “state-of-the-art simulation tool” has passed. I now answer anyone who asks me, “It is not a tool that represents the state of the art but, rather, a methodology.”

There are many tools that simulate various things, and many of them are quite good. For example, I am firmly convinced that ANSYS HFSS represents the gold standard of 3-D computational electromagnetic simulation tools. However, this is simply one tool in a bag of tools used by engineers; individual tools by themselves do not represent the state of  the art in simulation.

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The State of Industrial Flares

This week, I attended the American Flame Research Committee’s Combustion Symposium in Houston where I presented a paper on radiation modeling.

Most of the papers presented were about industrial flares. If you live near a process plant, you must have seen these large stacks reaching into the clear blue sky. At the end of these stacks are large flames that can be seen from a distance. For most urban area residents, these flares create a concern about public health and safety especially if there is some black smoke as well in the fireball.

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