The art of engineering can often be in finding pragmatic ways to use technology to solve real problems. While simulations may include an ever-increasing amount of geometric detail, it is not enough to simply generate ever finer meshes and use ever smaller time resolution. Simulations must still be solved in a reasonable time (and perhaps the one constant here has been that reasonable almost always means ‘overnight’). Therefore, until there is a dramatic breakthrough in computing power, modeling fluid flow will require engineering pragmatism in problem-solving for many years to come. But that need not be shouldered by the CFD engineer alone — ANSYS simulation software can support them in their efforts. ANSYS 15.0 contains multiple examples of how pragmatic approaches to efficient and effective simulation are contained in the software itself.
One such example is the dynamic combustion mechanism reduction capability in ANSYS Fluent. By automatically reducing the mechanisms to only the most important, dramatic reductions in simulation time can be achieved without the CFD engineer having to spend time and effort determining how to represent complex reaction mechanism in a simplified manner that models the behaviour sufficiently well. Instead, this pragmatism is built into the ANSYS software! Combined with further enhancements in ANSYS 15.0, it makes combustion simulation with even the most involved chemical reactions viable. Continue reading
Spray modeling has been a hot area of research especially in aerospace and automotive industries. The need to resolve the early development of sprays in the near nozzle area has grown steadily. However, this is a challenging area of modeling as resolving the liquid-gas interface is non-trivial due to complicated physical processes involved. Any modeling tool employed for this problem must be able to address the discontinuity in material properties at the interface as well as the effects of turbulence and surface tension forces at the interface.
There are some approaches that you can use currently in the context of CFD modeling. As a first approach, ANSYS Fluent’s DPM model offers something called “Atomizer” models that provide PSD based on the type of nozzle and some nozzle operational/geometrical parameters.
A second, more detailed approach is to use the VOF multiphase model to capture the liquid-gas interface at the droplet level. This requires a very fine mesh in the shear layers and hence is prohibitively expensive if entire length of the spray needs to be captured. Continue reading
A common question I hear from System Coupling users, particularly when using an operating pressure in ANSYS Fluent other than atmospheric pressure, is “Which pressure is used when transferring forces from Fluent to System Coupling and how do I change it?”.
The simple answer is that the forces passed to System Coupling are based on the gauge (or solved) pressure in Fluent by default. More accurately, the gauge pressure minus the Reference Pressure is used, but the Reference Pressure is zero by default so this is equivalent to the gauge pressure.
Before going further let’s review the Operating Pressure, Reference Pressure and gauge pressure.
The Operating Pressure in Fluent should be set to a typical absolute pressure in the system. Pressures set at boundary conditions are then specified relative to the Operating Pressure. Often the Operating Pressure is set to the absolute pressure at an outlet, and then a relative (gauge) pressure of zero is set at the outlet boundary condition(s). Continue reading
Desperately searching for a gift for my nephew Dominick, I came across this article about a flying robotic Dragonfly that the Air Force has spent more than $1 million developing.
My first thought was ‘what kid wouldn’t want a flying insect that weighs less than one AA battery equipped with a camera that can be operated with an iPhone?’
My next thought was ‘Wait, a minute, I’m not shopping for myself.’
My third thought was ‘I’ve recently read about this device being created with ANSYS software.’
The Georgia Institute of Technology submitted this story and image to our 2013 Hall of Fame competition that has concluded. (Results coming, stay tuned.)
Here is what they told us: Continue reading
Each Monday, we like to give you a quick snapshot of the ANSYS webinars, seminars and other events of interest that are scheduled for the coming week. Today, I’d also like to take a moment to remind you that if you have missed any of our past webinars, you can find recordings in our Resource Library.
Here’s just a quick look at a few of the ANSYS webinars on tap this week. The full calendar is at the end of this post.
ANSYS Webinars – Including our Ask the Expert Series
Predicting Boiling Heat Transfer in IC Engine Cooling Jackets with ANSYS Fluent
Wednesday, November 07, 2012
4:00 pm EST, 9:00pm GMT (REGISTER)
There has been a change in the thermal management of IC engines where engineers now like to harness the superior cooling rates available when limited and controlled Nucleate Boiling is used to remove heat from high temperature zones. Any flaws in the design of such systems, such as uncontrolled heat transfer that leads to Film Boiling (Dry out condition), can have an adverse effect on the cooling performance. A detailed boiling heat transfer model for this design process would allow engineers not only to weed out flawed coolant passages early, but also to accurately predict the temperature for subsequent analysis like thermal stress analysis in solid, IC engine combustion analysis etc. Continue reading
September has arrived and in the US with the Labor Day picnics well under way and students are back on campus. Why not get your plan for for learning in order as well. ANSYS webinars and events are the perfect way to boost your knowledge and expertise in simulation engineering. Let’s get started with our list of this weeks opportunities!
ANSYS Webinars, Seminars and Events This Week
Curious About Making User Defined Functions in ANSYS Fluent?
Tuesday, September 4, 2012
9:00 am EDT, 1:00 pm GMT (REGISTER HERE)
ANSYS Fluent is a general CFD solver. To make it even more flexible you have the possibility to write your own functions to work together with the solver. Writing UDF:s can get very complicated and be as versatile as the applications themselves. This webinar aims at showing the basic process of writing and using an UDF. This will be done by showing how to define a profile, which is general and simple enough to be of use for any ANSYS Fluent user. In more detail the topics included will be:
- Writing the C-code
- Interpreting or Compiling the code
- Hooking the code in the GUI
- Running the simulation with a UDF
- Questions and answers Continue reading
This week we have Part 1 of a 3-Part ANSYS Webinar series dissecting the topic of multiphase flow modeling. To get a little precursor you might want to read our recent post entitled Multiphase Flow: Pentium to Dual Quad Core.
Ask-The-Expert: Part 1 – Introduction to Multiphase Models in ANSYS CFD
Wednesday, August 15, 2012
4:00 pm EDT, 8:00 pm GMT (REGISTER HERE)
Multiphase flow modeling tools have truly become a wide-spread and mature technology to gain insights into the flow characteristics of a broad range of multiphase flows. A survey of trade journal articles and scholarly publications attests to the increasing impact of multiphase flow modeling in solving everyday design and engineering challenges. Continue reading
My smartphone today is more powerful than the first computer I ran my simulations on in the late 1990s. Moore’s law (which you can find more about on the ANSYS website) and detailed engineering simulations are making a difference in how we practice engineering design today. I hope to do the same in advancing multiphase flow modeling.
Dam break simulation: comparison of experiment (grey) and simulation (color) at different times, white regions correspond to breaking waves in the experiment - Courtesy of Technical University of Berlin
In a recent issue of Chemical Engineering Science, there is a scholarly article by Durve and Patwardhan that contains a symbolic illustration of the advances made in multiphase flow modeling. Using an interface-resolved multiphase CFD model in ANSYS Fluent (LES + VOF), the authors study the problem of onset of gas entrainment, or surface aeration, in liquids. This is an important process in air–sea gas exchange (a component of global climate dynamics), the operability and safety of nuclear reactors, water treatment plants and other applications. In general, simulation provides insights into the mechanism of surface aeration and the local conditions that lead to the start of gas entrainment; for the Chemical Engineering Science study, it provided verifiable hypotheses that have since been validated using experiments. Quantitative predictions were also good when considering the complexity of the calculations (within 15 percent of experimental values). Continue reading