Join us at ASCE V-Tech 2020, September 14-18, 2020, to learn about the US Offshore Wind Market. Bil Stewart is co-moderator and organizer of the COPRI Offshore Wind session. vtech.asce.org

Bil has been Chairman of the COPRI Marine Renewable Energy Committee for the last 10 years. Bil was Chairman of the Board of COPRI in 2017.

STA provides advanced dynamic analysis of floating offshore wind turbines, using OrcaFlex and other tools.

The huge size of the US Offshore Wind market in the next two decades is only just being recognized by Offshore Engineers in the USA. The chart below shows what is in the pipeline according to the 2019 US DOE report Wind Energy Data & Technology Trends.

The above data shows the total wind farm energy that each of 13 states is planning to develop. The US total is a little over 25 GW. Remember that the first and only (as of August 2020) US offshore wind farm, Block Island (Rhode Island) has a Nameplate Capacity of just 30 MW, or 0.03 GW.

The current guideline investment cost for offshore wind farms is estimated to be around $3 billion/GW. This puts the US recognized offshore wind project pipeline at a value of $75 billion in the next decade.

A Wood McKenzie 2020 report estimates that the total investment in US offshore wind will reach $166 billion by 2035. By that time the industry will have become about one third the size of the US Offshore Oil & Gas industry and will be supporting around 80,000 US jobs.

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The October 4 2018 COPRI Houston Conference lecture Breakwater Caisson Design was presented a few days before the first Nador Caisson was loaded out in Morocco.

This video illustrates a success story.  The loading out the 3,000 tonne caisson (that had been slipformed on land) is shown onto a semi-submersible barge.  The barge is towed to relatively deep water and ballasted down, until the caisson can be floated off.  The caisson is then towed to a moderate water depth where it is ballasted down and stored until all caissons are ready for final installation.

All phases of the operation required naval architecture calculations for the hydrostatic stability of the caisson and barge. About 100 Caissons make up the breakwater for the new harbor at Port Nador.

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The full lecture can be viewed at CAISSON DESIGN VERIFICATION.  This lecture was presented at the ASCE COPRI 2018 Houston Chapter Conference.

A cross section through the main breakwater is shown below:

Wave forces and safety factors against sliding and overturning are computed with Excel and shown in the Excel chart below:

The installation requires afloat stability checks as the caisson is removed from the semi-submersible barge.

The Excel package goes on to calculate motions of the floating structure in waves, based on closed form analytical solutions.

For each degree of freedom, the diffraction and Froude-Krilov forces are discretely calculated for wave attack in the primary plane of motion, at a range of wave periods.  Mechanical admittance is calculated and dynamic response is computed.  Response at intermediate attack angles is interpolated.

This paper describes coastal civil engineering and naval architecture good practices applied to design optimization of concrete caissons, typically constructed by slipforming.

Always check results with experienced engineers and naval architects.  It is easy to make mistakes in input data.

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Finite element analysis of the non-linear foam buoyancy in floats for articulated navaid (articulated navigation aids). Click picture below to go to article on Simscale website.

STA has used many FEA tools.  The cloud-based FEA service from Simscale is new, efficient and high quality.

The engineering strength and stiffness properties of polyurethane foam were investigated.  The relationship between foam density and elastic modulus is shown below for a range of foam types.

The articulated navaids are on the north west coast of Australia on the Chevron Wheatstone LNG project.  The design, dynamic analysis and fatigue analysis of the navaid structure was performed with OrcaFlex.

The figure above shows the extreme motions of the navaid in 100-year storm conditions.  The screenshot below shows part of the time domain analysis of one load case in OrcaFlex.

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Hydrodynamic analysis with OrcaFlex is used to confirm and improve upon closed form analytical solutions developed by STA.

Designs have been developed for cruise ships up to 333m length with gross tonnage 150,000 and a starting collision velocity  of 6 knots.

Efforts on the project were interrupted in September 2017, by Hurricanes Harvey, which effected our Houston office, and Irma, which effected our Caribbean interests.

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Specializing in marine and offshore structures, fluid dynamics and related disciplines, here are just a few of the services that our marine consultants at Stewart Technology Associates can provide:

1) Hydrodynamic Analysis

Hydrodynamic analysis is used to accurately simulate the forces at work on a structure in a marine environment. This includes the movement of the waves, the action of the tides, the effects of undersea pressures, turbulence from structures or seafloor features, and the effect of high winds and inclement weather. By learning how these forces affect a structure, its design can be improved to eliminate possible failure points and to reduce costs and maintenance requirements. Hydrodynamic analysis can be used to examine both new and existing designs, and it can also be used after a maritime accident to help determine the cause of the problem.

2) Finite Element Analysis

Finite element analysis can be used to model how real-world conditions will affect the operation of a product or of a component of a larger system when subjected to forces such as vibration, heat, high pressures, fluid flow or other physical challenges. The results of the modeling can be used to improve the product’s design, reducing component failures and wear that can shorten its lifespan or lead to increased maintenance costs. Finite element analysis can also make a product safer, and help to determine the cause of failure in an existing design.

3) Structural Design and Analysis

STA can help design and analyze marine structures, such as drilling rigs, jack-ups and liftboats, to make sure that they will perform efficiently and safely in a specified environment. They can work directly with a client to create a structure that will withstand the forces in a particular marine or sub-sea environment safely, while increasing productivity and reducing long-term costs. They can also analyze existing designs to improve their structural performance, productivity and safety.

4) Riser Design and Analysis

Risers are one of the most critical components in an offshore oil drilling or production platform. They carry mud and drilling fluids to the well during drilling operations and carry oil and gas to the surface during production operations. To operate safely while maximizing production, they must be able to withstand the movement and pressure below the surface, while moving fluids efficiently. Engineer consultants can be used to design an efficient riser system for production or drilling operations, determining what type of riser will be needed, rigid, flexible or hybrid, effective mooring solutions, what equipment will be required and other factors. They can also improve the efficiency of fluid moment withing the riser, increasing production, and analyze existing designs to suggest structural, efficiency and safety improvements.

5) Anchor Performance Analysis

Anchors are critical to securing marine vessels and other structures in place temporarily, permanently or semi-permanently, and if they fail to perform adequately, they can allow vessels to drift off course or to collide with other structures, leading to injuries, property damage, productivity losses or environmental concerns. To perform effectively, the design of an anchor must take into account the weight and movement of the vessel, the surface conditions and the composition of the sea floor. With an anchor analysis, engineer consultants can model the forces at work on the anchor and suggest improvements that will make it stronger, safer and more effective.

6) Mooring Design and Analysis

Mooring systems in the offshore oil industry are critical to keep the platform in place during operation, to secure tankers while transferring oil and gas and to secure other vessels as needed. They must be able to withstand the weight of the vessel or platform, while compensating for motion at the surface of the sea and keeping transfer pipes and equipment safe. Engineering consultants can analyze the design of a mooring system, including the anchors, mooring lines and surface structure, ensuring that it can perform both safely and effectively. They can also create new designs for specific applications and analyze the performance of transfer systems.

7) Oil Spill Clean-Up and Containment

Oil spills can have far-reaching consequences, from polluting the water supply and harming animal and plant life, to making beaches less inviting and hurting economies that depend on fishing or tourism. When the worst does happen, the key to minimizing the damage is to contain the oil as close as possible to the source and to clean it up as quickly as possible. Engineering consultants can help to design effective measures for both containing the oil and cleaning it up, including effective boom systems to contain the oil and techniques that can adequately model the currents and conditions at the site to make clean-up more successful and efficient.

8) Forensic Analysis

After a maritime accident or an oil spill, the original cause of the accident can be difficult to determine and, often, there are many contributing factors that make the origin even less clear. Engineer consultants can use hydrodynamic analysis, finite element analysis and other techniques, along with advanced software and extensive knowledge of marine systems, to analyze the events leading up to the accident, as well as the accident itself and its effects, to help determine the original cause. This information can be used to determine liabilities in the aftermath of the accident, to improve designs to prevent future accidents and to establish new safety protocols and programs that can help avoid or mitigate such incidents in the future.

Sources:

https://stewart-usa.com

https://stewart-usa.com/overview.php

http://usa.oceana.org/sites/default/files/tourism_impacts_fact_sheet_9-8-15.pdf

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Sewol Salvage: Stewart Technology Associates worked as Technical Advisors to Shanghai Salvage Company using STA software and were responsible for all dynamic analysis of the complex lifts in the open ocean environment.  All lifts are dynamically sensitive and involved cutting edge marine salvage dynamics. Analyses were performed with waves in the time domain using FEA (OrcaFlex).

Marine Salvage Dynamics of Sewol Salvage raised with ZPMC 12,000 ton floating crane and 1,200 ton lifting frame.

32 HMPE upper slings, 8 balance slings, 34 pairs of steel lower slings.

Fully coupled 6 DOF time-domain dynamic analyses in OrcaFlex with diffraction forces on the Sewol and ZPMC crane barge.  All individual sling tensions computed during all stages of the Sewol Salvage.

Sewol wreck transfered to semi-submerged floating dry dock in open ocean.  OrcaFlex time domain dynamic analysis of three main vessels, lifting frame and all slings.

The following video describes how STA has examined the issues of unusually low freeboard and trapped water on the pontoon deck.

The video provides a description of how OrcaFlex is used to cope with time domain calculations of the wave motions of the floating dry dock when the deck becomes submerged and the buoyancy of the wing tanks is of critical importance.

More details of the accident can be found at:

gCaptain

Wikipedia

The  portfolio item below provides a short OrcaFlex Tutorial with a Mooring Analysis example.

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Wireline view of SPM CALM Buoy modeled in OrcaFlex.

A Suezmax tanker is moored via a hawser.  View list of STA software.

Suezmax tanker seen in shaded perspective view in OrcaFlex, moored to SPM CALM buoy during squall analysis.

The portfolio item below provides a short OrcaFlex Tutorial with a Mooring Analysis example.

The post SPM Squall Analysis appeared first on Stewart Technology Associates.

Example of hydrodynamic analysis at CALM buoy SPM with VLCC tanker moored when a squall, or sudden wind shift, occurs.  The time domain analysis is performed with OrcaFlex and hydrodynamic characteristics (diffraction forces, added mas and radiation damping) are taken from analyses in the frequency domain with MDL Hydro.

Ship hydrodynamic and aerodynamic drag terms are calculated by STA using shallow water effects and OCIMF coefficients.

Published by Stewart Technology Associates on June 20, 2016

View list of STA software.

The portfolio item below provides a short OrcaFlex Tutorial example of Mooring Analysis.

Water can behave in many different ways, depending on the circumstances, and any structure or equipment that is in a marine environment or to be used near the water, must be thoroughly prepared for the forces that will operate on it. These forces are constantly changing and include tidal forces, wave action, undersea currents, high pressures, corrosion and chemical reactions. If a structure or piece of equipment is not designed properly for a marine setting, it could have a significantly reduced lifespan, require increased maintenance and pose a threat to nearby personnel.

Industry personnel can use hydrodynamic analysis to improve marine equipment and structure designs. By modeling the behavior of the water and the structure or equipment exposed to it, design problems and structural deficiencies can be discovered, and the design can be improved before the equipment or structure is put into production. This process can save large amounts of time and money, and can improve the safety of marine structures and equipment.

Here are a few examples of projects that can benefit from thorough hydrodynamic analysis:

#1 Oil Rig Design

Large, off-shore oil rigs are often limited-production designs, with only a few examples actually being built. This means it is difficult to test the designs thoroughly before production, and any mistakes in the design can be difficult and expensive to repair later. By using hydrodynamic analysis, the manufacturer can thoroughly test the design before it is put into production, and improve it to minimize any problems.

The hydrodynamic analysis will model the effects of the marine environment on every part of the oil rig, from the anchors that tie it to the seafloor, to the platform legs, risers and superstructure. It can pinpoint structural deficiencies, where forces like wave action slowly wear away at sensitive components, such as moving joints, and eventually cause dangerous structural failures or prolonged maintenance problems. This allows the designers and engineers to redesign these components to better withstand the forces at work in the marine environment, reducing maintenance costs, increasing the design life and protecting the safety of the personnel.

#2 Pump Design

Pumps are critical in a marine environment. Bilge pumps remove excess water from a ship’s hull to prevent an over-accumulation that could cause the ship to sink. Fresh water pumps circulate drinking water through the plumbing for ship personnel, and other pumps may be used for fire protection. Oil pumps are used to keep the moving parts of a ship lubricated, or to transfer oil from production wells to tankers. Fuel pumps provide ships and generators with the fuel they need to run.

Pumps used in a marine environment must be able to withstand corrosion and electrochemical reactions caused by saltwater exposure, and they must be able to transfer fluids quickly and efficiently without overheating and failing. Hydrodynamic analysis can be used to model both the behavior of water on the exterior of the pump and the behavior of liquids as they travel through the pump.

The models can be used to design pumps which are better suited to the forces at work in a marine environment, making them stronger and more resistant to the effects of pressure and corrosion that cause maintenance problems. They can also be used to increase the efficiency of the pump, by showing how the fluids travel through the body and the impellers. By using the results to eliminate unnecessary cavitation and friction, the pump design can be made much more efficient, saving energy, reducing maintenance requirements, and extending the pump’s lifespan.

#3 Accident Reconstruction

Working in a marine environment can be especially dangerous for personnel and equipment. Bad weather, rogue waves, fire, equipment failures and other common problems can quickly lead to dangerous situations in the contained environment of a ship, drilling rig or other marine platforms. Accidents can and do happen, including collisions, fires, oil spills, sunken vessels and other catastrophes. Determining the cause of an accident and the results are often the key to improving marine designs and preventing similar accidents in the future.

Hydrodynamic analysis is one of the most powerful tools for determining the cause of a marine accident. The process can be used to model the behavior of the water and any structures, vessels, or equipment that are in the water. It can help determine why two ships collided using accurate modeling, which part of a structure failed, why fire protections systems malfunctioned during an emergency, or how an oil leak was caused and where the oil will be traveling.

With accurate modeling, hydrodynamic analysis in conjunction with other tools can reconstruct every variable at play during an accident, and determine the cause and effect of each action taken. The results can be used to improve the designs of marine equipment and structures to prevent similar accidents in the future, to institute new safety procedures that minimize casualties, and to take further action to protect the safety of ship personnel and minimize liability issues.

Other Applications

These are just a few of the ways that hydrodynamic analysis can be employed in real-world applications. It can also be used to improve the designs of sea-faring vessels, mooring systems, sub-sea pipelines, floating pipelines, drilling risers, anchors, mooring lines, liquid-storage systems, buoys, marine weapon systems, off-shore wind turbines and wave power generators. Furthermore, it can be used to help during oil spill cleanup or containment operations, for forensic analysis, marine training simulations, risk assessments, financial assessments, emergency preparedness and accident prevention. Hydrodynamic analysis is a versatile tool, and it has many critical applications across multiple industries, including oil and gas production, energy production, shipping services, defense, maritime entertainment and oceanography.

With so many applications, hydrodynamic analysis is very important to any marine based-operation, and through its accurate modeling, it can help improve the design and operation of many marine-based structures, tools and equipment. It can help cut design costs and minimize production delays, and improve the safety of marine-based personnel.

Sources:

The post 3 Projects That Can Benefit From Hydrodynamic Analysis appeared first on Stewart Technology Associates.

Cable dynamics may not be something you think of when you talk about going out on an oil rig. Any time you are on the water with an anchor, drilling equipment, or anything else, you have to look at the dynamics of a cable because there are various factors that need to be considered.

Decoupling Deep Ocean Cable Dynamics

Above figure shows lazy-wave geometry for a Tyco SL14 SPA cable in 6000 meters water depth for US Navy application.  Cable floats have been designed by STA for a section (shown blue) and analyzed in OrcaFlex in a sea state 6.  The tension range at the top end is low and easily tolerable.  The tension range at the touchdown has been reduced to less than 1 kN.

Cable laying and support vessel in OrcaFlex, shown above.

There are going to be cables connected to your rig. They go up and down as the water goes up and down. When you are drilling, you have to consider the depth of the sea. It is very much like an anchor. An anchor is only going to be effective if it is able to reach the bottom. Otherwise, it is simply going to dangle from the boat and cause you to drift. The anchor is therefore not as effective as it could be and all because you were unprepared for the depth of water that you would be in. the same goes for the cables. Understanding depth is vital to the success of your project.

Waves

The physics of waves should be explored in depth when you’re going to be out on the water. You need to know when they are going to occur, where, the height of the waves, and more. All of these are going to play a role in the equipment you choose and the training you give your employees. Failure to recognize the importance of waves can result in problems on the water – and you could end up injuring someone or destroying a part of the rig.

Movement on the Rig

There’s going to be movement on the rig due to all sorts of factors – wind, weight of what’s on the surface, and even movement of employees. These are going to be factors when calculating the cable dynamics.

Overall Stability

Stability is critical and when you’re on a rig or even fishing, there are going to be cables or other lines in the water and then connected to your boat or rig. When working with steel catenary risers, they are responsible for the fluid transfer from one area to another. If the cable dynamics haven’t been explored to the fullest, the transfer could be broken simply because of one variable that was missed during the setup, such as bigger waves or deeper water.

Accident Prevention

It’s important to prevent accidents and when you are dealing with being on a rig that could be on the water for months at a time, you have to think about everything. The more you know about potential accidents on the water, the more you can prepare your employees for what could happen. Having analysis at your fingertips as to what you could experience can be invaluable when you are looking to train employees, purchase equipment, and stock the rig before leaving the shore.

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