The very latest install guide for PuTTY and Xming is here!

cubelogo-2014

This how to describes how to install PuTTY and Xming and then hook the two together to provide you the end-user with an X Window System display server, a set of traditional sample X applications and tools, and a set of fonts. These two products will help to eliminate many of your frustrations! Xming features support of several languages that many of our ANSYS Analyst’s use here at PADT, Inc. We truly enjoy and use these two products. One reason for why would should be interested is that by combining Xming and PuTTY for use in numerical simulation Mesa 3D, OpenGL, and GLX 3D graphics extensions capabilities work amazingly well! Kudos to the programmers, we love you!

Program references:

Xming

PuTTY

Server: CUBE Linux 64-bit Server
Client: Windows 7 Professional 64-bit

Step 1 – Install PuTTY first (accept defaults)

Step 2 – Install Xming (accept defaults)
o Download and install the program and fonts for XMING files:
 Program:
 Fonts:

Double-check that the Normal PuTTy link with SSH client is checked

xming1

Step 3 – After the program has completed installation.

Step 4 – Install the Xming fonts that you had downloaded earlier.

Verify that Xming has been started. You will notice a new running task inside of your task bar. If you hover over the X icon in your taskbar. It should Say something like “Xming Server:0.0”

Now let us hook them together. It is X and PUTTY time!

Step 5 – Open your PUTTY application.

xming2

  • Enter the hostname or IP address.
  • Enter in a Session name:
  • On the left side bar within PUTTY. Locate –> Connection  and then expand out –> SSH –> X11
    o Check –> Enable X11 forwarding

xming3

Save the new session –> Locating on the left panel of your PUTTY program (you may need to scroll up a little bit).

Click on the text –> Session and then Save the new session.

xming2

 

Yay! now open your newly saved session and login to a CUBE linux server to test and verify.

I always forget to remember tell people this TIP but for multi display types:  Start Xming in -multiwindow mode.

How? from Command Prompt (the Windows cmd console) or create a desktop shortcut.

“C:\Program Files\Xming\Xming.exe” -multiwindow -clipboard

Have a Happy Valentines Day Weekend and do not forget to show the penguin some love too. This penguin looks lonely and maybe needs a date?

penguin_sh

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Webinar Content: Answers to your Questions on Metal 3D Printing

Download a recording and the slides from this this informative webinar.

3d-metal-printing-webinar-slide-1Metal Additive Manufacturing, or Metal 3D Printing, is a topic that generates a lot of interest, and even more questions.  So we held a webinar on February 9th, 2016 to try and answer the most common questions we encounter. It was a huge success with over 150 people logging in to watch live.  But many of you could not make it so we have put the slides and a recording of the webinar out there.  Just go to this link to access the information.

The presentation answered the fllowing common questions:

  • Introductory:
    • Who are PADT and Concept Laser?
    • How does laser-based metal 3D printing work?
    • Are there other ways to 3D print in metal and how do they compare?
  • Technical:
    • What are the different process steps involved?
    • How “good” are 3D printed metal parts?
  • Strategic:
    • What materials and machines do you offer?
    • Who uses this technology today?
    • What is the value proposition of metal 3D printing for me?
    • What can I do after this webinar?

As always, our technical team is available to answer any additional questions you may have. Just shoot an email to metal-am@padtinc.com or give us a call at 480.813.4884.

3d-metal-printing-webinar-slide-23d-metal-printing-webinar-slide-3

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Keyless SSH in two easy steps. Wait, What?!

cubelogo-2014Within the ANSYS community and even more specifically, in regards to the various numerical simulation techniques the ANSYS users use to solve their problems.

One of the most powerful approaches to overcome the limitations of new complex problems is take multiple CPU’s and link them together over a distributed network of computers. Further unpacking this for you the reader, one critical piece to using parallel processing using a quality high performance message passing interface (MPI). The latest IBM® Platform™ MPI version 9.1.3 Fix Pack 1 is provided for you in your release with ANSYS 17.0.

When solving a model using distributed parallel algorithms, lately the communication for authenticating your credentials to make this login process seamless is known as Secure Shell, or SSH. SSH is a cryptographic (encrypted) network protocol to allow remote login and other network services to operate securely over an unsecured network.

Today let us all take the mystery and hocus pocus out setting up your keyless or password ssh keys. As you will see this very easy process to complete.

I begin my voyage into keyless freedom by first logging into one of our CUBE Linux server’s.

ssh-1

STEP 1 – Create the key

  • Type ssh-keygen –t rsa
  • Press the enter key three times
    •  (in some instances as shown in the screen capture below, You may see a prompt asking you to overwrite. In that case type y)

ssh-2

STEP 2 – Apply the key

  • Type ssh-copy-id –i ~/.ssh/id_rsa.pub mastel@cs0.padtinc.com
  • Type ssh-copy-id –i ~/.ssh/id_rsa.pub mastel@cs1.padtinc.com
  • Enter your current password that you would use to login to cs1.padtinc.com

ssh-4

All Done!

Now give it a try and verify test.
Login to the first server you setup, In my case CS0.
At the terminal command prompt type ssh cs1

ssh-5

BEST PRACTICE TIP:

I find it is my best practice is to also repeat the ssh-copy-id command using the simple name at the same time on each of the server.

That command would look like:
1. After you have completed Step 2.a listed out below you will also perform the same command locally.
a. ssh-copy-id –i ~/.ssh/id_rsa.pub mastel@cs0
b. enter your old password press enter.

Done, Done!

Additional Links:

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Bring the kids for an evening of STEM fun at PADT’s AZ SciTech Festival Open House

Scitech Logo

PADT is excited to open our doors to the community and show you and your families what engineering is all about.  Bring the family down for a tour of PADT’s Tempe office and we will show them why engineering rocks. This family friendly event is a great way for kids to see what engineers really do all day.  Tour our 3D printing lab and check out how “We Make Innovation Work”.          Register Here

WHEN: Wednesday, February 24th from 6:00pm to 7:30pm
WHERE: PADT Headquarters
  7755 S. Research Drive, Suite 110
  Tempe, AZ 85284

The Arizona SciTech Festival is a state-wide celebration of science, technology, engineering and math held annually in February and March.  Through a series of over 1,000 expos, workshops, conversations, exhibitions and tours held in diverse neighborhoods throughout the state, the Arizona SciTech Festival excites and informs Arizonans from ages 3 to 103 about how STEM will drive our state for next 100 years. Spearheaded by the Arizona Commerce Authority, Arizona Science Center, the Arizona Technology Council Foundation, Arizona Board of Regents, the University of Arizona and Arizona State University, the Arizona SciTech Festival is a grass roots collaboration of over 700 organizations in industry, academia, arts, civic, community and K-12.

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Phoenix Business Journal: ​Flint’s water problem and the dangers of ignoring science

pbj-phoenix-business-journal-logoThe first “opinion” piece for the TechFlash blog of the Phoenix Business Journal. My thoughts on how the trend of ignoring science is harmful: “Flint’s water problem and the dangers of ignoring science

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Phoenix Business Journal: The real reason 3D printing is important

pbj-phoenix-business-journal-logo

In all the hoopla around 3D Printing the real reason why it is important often gets lost. Check out this article to learn “The real reason 3D printing is important” to wrap your head around the long term impact of this key technology. PB

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Phoenix Business Journal: ​How to close business deals faster

pbj-phoenix-business-journal-logoAfter some end of year reflection we hit upon a key factor that constantly let us close business deals faster. We share the key driver in the PBJ’s Phoenix Business Blog with the to-the-point title of “How to close business deals faster

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10x with ANSYS 17.0 – Get an Order of Magnitude Impact

The ANSYS 17.0 release improves the impact of driving design with simulation by a factor of 10.  This 10x  jump is across physics and delivers real step-change enhancements in how simulation is done or the improvements that can be realized in products.

ANSYS-R17-Banner
Unless you were disconnected from the simulation world last week you should be aware of the fact that ANSYS, Inc released their latest version of the entire product suite.  We wanted to let the initial announcement get out there and spread the word, then come back and talk a little about the details.  This blog post is the start of a what should be a long line of discussions on how you can realize 10x impact from your investment in ANSYS tools.

As you may have noticed, the theme for this release is 10x. A 10x improvement in speed, efficiency, capability, and impact.  Watch this short video to get an idea of what we are talking about.

Where is the Meat?

We are already seeing this type of improvement here at PADT and with our customers. There is some great stuff in this release that delivers some real game-changing efficiency and/or capability.  That is fine and dandy, but how is this 10x achieved.  There are a lot of little changes and enhancements, but they can mostly be summed up with the following four things:

temperature-on-a-cpu-cooler-bgTighter Integration of Multiphysics

Having the best in breed simulation tools is worth a lot, and the ANSYS suite leads in almost every physics.  But real power comes when these products can easily work together.  At ANSYS 17.0 almost all of the various tools that ANSYS, Inc. has written or acquired can be used together. Multiphysics simulation allows you to remove assumption and approximations and get a more accurate simulation of your products.

And Multiphysics is about more than doing bi-directional simulation, which ANSYS is very good at. It is about being able to transfer loads, properties, and even geometry between different software tools. It is about being able to look at your full design space across multiple physics and getting more accurate answers in less time.  You can take heat loads generated in ANSYS HFSS and use them in ANSYS Mechanical or ANSYS FLUENT.  You can take the temperatures from ANSYS FLUENT and use them with ANSYS SiWave.  And you can run a full bidirectional fluid-solid model with all the bells and whistles and without the hassles of hooking together other packages.

simplorer-17-1500-modelica-components-smTo top it all off, the system level modeler ANSYS Simplorer has been improved and integrated further, allowing for true system level Multiphysics virtual prototyping of your entire system.  One of the changes we are most excited about is full support for Modelica models – allowing you to stay in Simplorer to model your entire system.

Improved Usability

Speed is always good, and we have come to expect 10%-30% increases in productivity at almost every release. A new feature here, a new module there. This time the developers went a lot further and across the product lines.

clip-regions-with-named-selections-bgThe closer integration of ANSYS SpaceClaim really delivers on a 10x or better speedup for geometry creation and cleanup when compared to other methods. We love SpaceClaim here at PADT and have been using it for some time.  Version 17 is not only integrated tighter, it also introduces scripting that allows users to take processes they have automated in older and clunker interfaces into this new more powerful tool.

One of our other favorites is the new interface in ANSYS Fluent, just making things faster and easier. More capability in the ANSYS Customization Toolkit (ACT) also allows users to get 10x or better improvements in productivity.  And for those who work with electronics, a host of ECAD geometry import tools are making that whole process an order of magnitude faster.

import-ecad-layout-geometry-bgIndustry Specific Workflows

Many of the past releases have been focused on establishing underlying technology, integration, and adding features. This has all paid off and at 17.0 we are starting to see some industry specific workflows that get models done faster and produce more accurate results.

The workflow for semiconductor packaging, the Chip Package System or CPS, is the best example of this. Here is a video showing how power integrity, signal integrity, thermal modeling, and integration across tools:

A similar effort was released in Turbomachinary with improvements to advanced blade row simulation, meshing, and HPC performance.

ansys-fluent-hpc-max-coresOverall Capability Enhancements

A large portion of the improvements at 17.0 are made up of relatively small enhancements that add up to so big benefits.  The largest development team in simulation has not been sitting around for a year, they have been hard at work adding and improving functionality.  We will cover a lot of these in coming posts, but some of our favorites are:

  1. Improvements to distributed solving in ANSYS Mechanical that show good scaling on dozens of cores
  2. Enhancements to ACT allowing for greater automation in ANSYS Mechanical
  3. ACT is now available to automate your CFD processes
  4. Significant improvements in meshing robustness, accuracy and speed (If you are using that other CFD package because of meshing, its time to look at ANSYS Fluent again)
  5. Fracture mechanics
  6. ECAD import in electromagnetic, fluids, and mechanical products.
  7. A new solver in ANSYS Maxwell that solves more than 10x faster for transient runs
  8. ANSYS AIM just keeps getting more functions and easier to use
  9. A pile of SpaceClaim new and improved features that greatly speed up geometry repair and modification
  10. Improved rigid body dynamics in ANSYS Mechanical

ansys-17-ribbons-UIMore to Come

And a ton more. It may take us all of the time we have before ANSYS 18.0 comes out before we have a chance to go over in The Focus all of the great new stuff.  But we will be giving a try in the coming weeks and months. ANSYS, Inc. will be hosting some great webinars as well.

If you see something that interests you or something you would like to see that was not there, shoot us an email at support@padtinc.com or call 480.813.4884.

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Additive Manufacturing – Back to the Future!

Paul Nigh's 'TeamTimeCar.com' Back to the Future DeLorean Time Machine

Production of Back to the Future began in 1984 – it was recently announced that the DeLorean is to go back in production with new cars rolling out in 2017

Most histories of Additive Manufacturing (3D printing) trace the origins of the technology back to Charles Hull’s 1984 patent, the same year production began on the first of the Back to the Future movies. Which is something of a shock when you see 3D printing dotting the Gartner Hype Cycle like it was invented in the post-Seinfeld era. But that is not what this post is about.

When I started working on Additive Manufacturing (AM), I was amazed at the number of times I was returning to text books and class notes I had used in graduate school a decade ago. This led me to reflect on how AM is helping bring back to the forefront disciplines that had somehow lost their cool factor – either by becoming part of the old normal, or because they contained ideas that were ahead of their time. I present three such areas of research that I state, with only some exaggeration, were waiting for AM to come along.

  • Topology Optimization: I remember many a design class where we would discuss topology optimization, look at fancy designs and end with a conversation that involved one of the more cynical students asking “All that’s fine, but how are you going to make that?”. Cue the elegant idea of building up a structure layer-by layer. AM is making it possible to manufacture parts with geometries that look like they came right out of a stress contour plot. And firms such as ANSYS, Autodesk and Altair, as well as universities and labs are all working to improve their capabilities at the intersection of topology optimization and additive manufacturing.
Topology optimization applied to the design of an automobile upper control-arm done with GENESIS Topology for ANSYS Mechanical (GTAM) from Vanderplaats Research & Development and ANSYS SpaceClaim

Topology optimization applied to the design of an automobile upper control-arm done with GENESIS Topology for ANSYS Mechanical (GTAM) from Vanderplaats Research & Development and ANSYS SpaceClaim

And we printed that!

And we printed that!

  • Lattice Structures: One of the first books I came across when I joined PADT was a copy of Cellular Solids by Lorna Gibson and M.F. Ashby. Prof. Gibson’s examples of these structures as they occur in nature demonstrate how they provide an economy of material usage for the task at hand. Traditionally, in engineering structures, cellular designs are limited to foams or consistent shapes like sandwich panels where the variation in cell geometry is limited – this is because manufacturing techniques do not normally lend themselves well to building complex, three dimensional structures like those found in nature. With AM technologies however, cell sizes and structures can be varied and densities modified depending on the design of the structure and the imposed loading conditions, making this an exciting area of research.

    Lattice specimens made with the Fused Deposition Modeling (FDM) process

    Lattice specimens made with the Fused Deposition Modeling (FDM) process

  • Metallurgy: As I read the preface to my “Metallurgy for the Non-Metallurgist” text book, I was surprised to note the author openly bemoan the decline of interest in metallurgy, and subsequently, fewer metallurgists in the field. And I guess it makes sense: materials science is today mostly concerned with much smaller scales than the classical metallurgist trained in. Well, lovers of columnar grain growth and precipitation hardening can now rejoice – metallurgy is at the very heart of AM technology today – most of the projected growth in AM is in metals. The science of powder metallurgy and the microstructure-property-process relationships of the metal AM technologies are vital building blocks to our understanding of metal 3D printing. Luckily for me, I happen to possess a book on powder metallurgy. And it too, is from 1984.
This book was printed in 1984, and is very relevant today

Published 1984

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Phoenix Business Journal: Build and bust is so 20th century: How to develop better products with simulation

pbj-phoenix-business-journal-logoFor this week’s contribution to the PBJ’s TechFlash blog I cover something that is near and dear to PADT – the replacement of testing with simulation, or virtual prototyping.  Learn why “Build and Bust is so 20th Century

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And the Best Conference Award Goes To …..

AADM Expo

At PADT, we’re as big of a fan as anyone of the cool, trendy software and IT companies that run up billion dollar valuations in Silicon Valley and keep us all entertained and productive with their latest apps and platforms.

But as an engineering product and services company, we’re hardware geeks at heart and one of our favorite conferences is coming up quick. It’s the Aerospace, Aviation, Defense and Manufacturing (AADM) Conference hosted by the Arizona Technology Council and Arizona Commerce Authority on March 3 at the Hilton Scottsdale Resort.

Arizona has a rich history in this sector. TechAmerica’s 2014 Cyberstates Report ranks Arizona fourth nationwide for jobs in the space and defense systems manufacturing industry, employing more than 8,300 people.  Industry giants such as Raytheon, Honeywell, Boeing, Lockheed Martin and General Dynamics all have a big presence here. Luke Air Force Base, Fort Huachuca and the Yuma Proving Ground all provide ideal places for testing and flying in our cloudless skies and more than 300 days of sunshine.

When you look at manufacturing, you’ll find thousands of varied companies located here that are propelling Arizona’s economy into the next era of growth. Industries leaders such as Intel, Microchip, and Frito Lay all have significant Arizona operations.

Now in its fifth year, this conference has become the gathering place for Arizona’s AADM industry. You’ll not only have a chance to hear what the big companies are up to, you’ll meet potential suppliers and customers during the interesting presentations and well-attended cocktail reception. And for as little as $750 you can get a booth space and two conference tickets – that’s a deal you won’t find in New York City! The traffic at our booth always keeps us hopping and give us the opportunity to capture great leads.

If you haven’t checked it out yet, get on it, check out the sponsorships and  register now. And don’t forget to stop by the PADT booth. We’ll show you how we make innovation work!

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Phoenix Business Journal: My cat didn’t preheat the oven – Is your company ready for the Internet of Things?

pbj-phoenix-business-journal-logoThe Internet of Things, or IoT, is growing every day.  This article starts with an encounter at the grocery store that leads to an explanation of what the IoT is and what your company should be doing to make sure you take advantage of this exciting change in how everything around us will work. Check out “My cat didn’t preheat the oven: Is your company ready for the Internet of Things?” in the PBJ TechFlash blog to learn more.

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AZ Tech Beat Video: Tips on Building an Investor-Worthy Prototype

AZ-Tech-Beat-LogoHave an idea for a product and feel like you need a prototype.Tishin Donkersley  from the Arizona Tech Beat asked me over to their offices to do a short interview and share some pointers on the subject.  Take a look at the result here.

I talk about trends in the 3D Printing world that impact startups who have a need for prototypes, and share a few pointers on getting a prototype made.

AZTechBeat-Eric-Interview-prototype

While you are there, take a look around the sight.  AZ Tech Beat is one of the best places to find out what is going on in the Arizona Tech Community as well as in tech in general.   I especially like their gadget updates.

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Key Process Phenomena in the Laser Fusion of Metals

Metal 3D printing involves a combination of complex interacting phenomena at a range of length and time scales. In this blog post, I discuss three of these that lie at the core of the laser fusion of metals: phase changes, residual stresses and solidification structure (see Figure 1). I describe each phenomenon briefly and then why understanding it matters. In future posts I will dive deeper into each one of these areas and review what work is being done to advance our understanding of them.

Fig. 1 Schematic showing the process of laser fusion of metals and the four key phenomena of phase changes, melt pool behavior, thermomechanical effects and microstructure evolution

Fig. 1 Schematic showing the process of laser fusion of metals and the three key phenomena of phase changes, residual stresses and solidification structure

Phase Changes

Phases and the mechanisms by which they transition from one to the other

Fig. 2 Phases and the mechanisms by which they transition

Phase changes describe the transition from one phase to another, as shown in Figure 2. All phases are present in the process of laser fusion of metals. Metal in powder form (solid) is heated by means of a laser beam with spot sizes on the order of tens of microns. The powder then melts to form a melt pool (liquid) and then solidifies to form a portion of a layer of the final part (solid). During this process, there is visible gas and smoke, some of which ionizes to plasma.

The transition from powder to melt pool to solid part, as shown in Figure 3, is the essence of this process and understanding this is of vital importance. For example, if the laser fluence is too high, defects such as balling or discontinuous welds are possible and for low laser fluence, a full melt may not be obtained and thus lead to voids. Selecting the right laser, material and build parameters is thus essential to optimize the size and depth of the liquid melt pool, which in turn governs the density and structure of the final part. Finally, and this is more true of high power lasers, excessive gas and plasma generation can interfere with the incident laser fluence to reduce its effectiveness.

Primary phase changes from powder to melt pool to solid part

Fig. 3 Primary phase changes from powder to melt pool to solid part

Residual Stresses

Residual stresses are stresses that exist in a structure after it reaches equilibrium with its environment. In the laser metal fusion process, residual stresses arise due to two related mechanisms [Mercelis & Kruth, 2006]:

  • Thermal Gradient: A steep temperature gradient develops during laser heating, with higher temperatures on the surface driving expansion against the cooler underlying layers and thereby introducing thermal stresses that could lead to plastic deformation.
  • Volume Shrinkage: Shrinkage in volume in the laser metal fusion process occurs due to several reasons: shrinkage from a powder to a liquid, shrinkage as the liquid itself cools, shrinkage during phase transition from liquid to solid and final shrinkage as the solid itself cools. These shrinkage events occur to a greater extent at the top layer, and reduce as one goes to lower layers.
Fig. 4 Residual stresses resulting from thermal gradients and volume changes

Fig. 4 Residual stresses resulting from thermal gradients and volume changes

After cooling, these two mechanisms together have the effect of creating compressive stresses on the top layers of the part, and tensile stresses on the bottom layers as shown in Figure 4. Since parts are held down by supports, these stresses could have the effect of peeling off supports from the build plate, or breaking off the supports from the part itself as shown in Figure 4. Thus, managing residual stresses is essential to ensuring a built part stays secured on the base plate and also for minimizing the amount of supports needed. A range of strategies are employed to mitigate residual stresses including laser rastering strategies, heated build plates and post-process thermal stress-relieving.

Solidification Structure

Solidification structure refers to the material structure of the resulting part that arises due to the solidification of the metal from a molten state, as is accomplished in the laser fusion of metals. It is well known that the structure of a metal alloy strongly influences its properties and further, that solidification process history has a strong influence on this structure, as does any post processing such as a thermal exposure. The wide range of materials and processing equipment in the laser metal fusion process makes it challenging to develop a cohesive theory on the nature of structure for these metals, but one approach is to study this on four length scales as shown in Figure 5. As an example, I have summarized the current understanding of each of these structures specifically for Ti-6Al-4V, which is one of the more popular alloys used in metal additive manufacturing. Of greatest interest are the macro-, meso- and microstructure, all of which influence mechanical properties of the final part. Understanding the nature of this structure, and correlating it to measured properties is a key step in certifying these materials and structures for end-use application.

FIg. 5 Four levels of solidification structure and the typical observations for Ti-6Al-4V

FIg. 5 Four levels of solidification structure and the typical observations for Ti-6Al-4V

Discussion

Phase changes, residual stresses and solidification structure are three areas where an understanding of the fundamentals is crucial to solve problems and explore new opportunities that can accelerate the adoption of metal additive manufacturing. Over the past decade, most of this work has been, and continues to be, experimental in nature. However, in the last few years, progress has been made in deriving this understanding through simulation, but significant challenges remain, making this an exciting area of research in additive manufacturing to watch in the coming years.

References

  1. Mercelis, P., & Kruth, J. (2006). Residual stresses in selective laser sintering and selective laser melting. Rapid Prototyping Journal, 12(5), 254-265.
  2. Simonelli, M., Tse, Y.Y., Tuck, C., (2012) Further Understanding of Ti-6Al-4V selective laser melting using texture analysis, SFF Symposium
  3. King, W. E. and Anderson, A. T. and Ferencz, R. M. and Hodge, N. E. and Kamath, C. and Khairallah, S. A. and Rubenchik, A. M., (2015) Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges, Applied Physics Reviews, 2, 041304
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ASME OMAE2015 Paper: The Importance of Grid Convergence Studies in the Design of a Semi-Submersible Platform

asme-papers

Vibration induced by vortices in off shore oil rigs are a significant area of concern, and understanding them is a major area of research. In this paper, PADT’s Clinton Smith, PhD, and Tyler Smith are joined by Lubeena Rahumathulla from ANSYS, Inc. to describe how they used ANSYS FLUENT to model this situation. Get the paper here: proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2465497 

Abstract:

omae-2015-FLUENT-off-shore-flowThe design of semi-submersible platforms for offshore oil and gas operations requires an iterative process between early-stage design, numerical simulation, measurements, and full-scale design. Early stage designs are evaluated using numerical simulations, which are typically validated using measurements of a scaled model tested in a wave tank. Full-scale semi-submersibles present a unique challenge, because of the sheer size of the structure. Since VIV measurements of full scale structures are not possible, numerical simulation plays an important role for evaluating vortex-induced vibration (VIV) effects in the appropriate physical regime. The quantification of error in numerical simulation results is limited to verification-type studies, in which the error is reduced by converging the solution on the computational grid. The importance of grid convergence studies in this field cannot be understated, since it is the only way to judge solution accuracy in the absence of measurement data at the full scale. In this paper, a method for a grid convergence study of vortex-induced vibration (VIV) of a model scale semi-submersible platform is presented, in which solutions are obtained using the ANSYS Fluent CFD solver. Five levels of grid refinement are used, with the finest mesh acting as the reference solution for the coarser four levels. Qualitative results of vorticity, pressure and Q-criterion (vortex identification) are presented. Quantitative results such as the nominal amplitude (A/D) of the sway motion are used for judging the convergence of the solution as the grid is refined.

 

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