Dr. Tony Hirt, Founder of Flow Science, Inc. Receives the John Campbell Award

Santa Fe, NM, May 11, 2022 — Flow Science, Inc. founder Dr. C.W. “Tony” Hirt was awarded the prestigious John Campbell Medal at the Institute of Cast Metals Engineers award ceremony on March 25, 2022, in London. Dr. Hirt received the award for his unique, long-lasting contributions to the science and practice of metal casting through his development of the CFD software FLOW-3D and its casting-specific version, FLOW-3D CAST.

Dr. John Campbell presented the award to Dr. Hirt, “In gratitude for making significant, really significant benefit to the foundry industry which we continue to enjoy to this day.” The award was accepted on behalf of Dr. Hirt by Flow Science’s Chief Technology Officer, Dr. Michael Barkhudarov.

The John Campbell Medal is awarded to an individual who has made a sustained contribution to the science and understanding of metal casting through research and development. Each year, the Institute writes to leading international castings research organizations and individuals, including Dr. John Campbell, the relevant Department Heads of the University of Birmingham and Mississippi State University, CAST-CSIRO, VDG and Cti, requesting nominations for an award shortlist.

Tony’s contribution to simulation is not only in developing useful modeling tools based on fundamental principles of physics but mentoring several generations of engineers that continue in his steps. The award is also welcome as a recognition that simulation tools have become an integral part of casting design and production as the industry matures and evolves, commented Dr. Michael Barkhudarov.

Dr. Hirt pioneered the Volume-of-Fluid (VOF) method while working at the Los Alamos National Lab. He went on to found Flow Science in 1980. FLOW-3D is a direct descendant of his development of the VOF method. This approach was expanded and perfected in FLOW-3D to the TruVOF technology, with cutting-edge and groundbreaking improvements in speed and accuracy in the simulation of flow with different liquid and gas interfaces. Today, Flow Science products offer complete multi-physic solutions with diverse modeling capabilities, including fluid-structure interaction, moving objects, and multiphase flows.

About Flow Science

Flow Science, Inc. is a privately held software company specializing in computational fluid dynamics software for industrial and scientific applications worldwide. Flow Science has distributors and technical support services for its FLOW-3D products in nations throughout the Americas, Europe, Asia, the Middle East, and Australasia. Flow Science is headquartered in Santa Fe, New Mexico.

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Flow Science, Inc.

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Santa Fe, NM 87505

info@flow3d.com

+1 505-982-0088

Optimization of a Sand Casting with FLOW-3D CAST

Optimization of a Sand Casting with FLOW-3D CAST

This blog was contributed by Malte Leonhard, Flow Science Deutschland.

The goal of a casting simulation is to predict casting defects and find the corrective measures to avoid such defects. To achieve this, the casting simulation must accurately predict the physical results. In this article, we illustrate a validation of FLOW-3D CAST by comparing simulation results with experimental findings. For this validation, we selected an aluminum casting with significant porosity defects. The extent of the porosities meant that the casting would not fulfill the functional specification and would be rejected.

Optimization of casting design and runner/riser system supported by simulation

In order to verify that FLOW-3D CAST can reliably predict such casting defects, the existing casting was simulated and the results compared with the real casting defects. This video shows that the FLOW-3D CAST defect analysis correctly reproduced the defects and their position.

The simulation results suggested that reversing the casting direction might be beneficial, so the casting part was rotated by 180° in the mold. Next, the runner and riser system were modified so that most of the risers were integrated into the runner (“hot risers”).

Additionally, design changes of the casting, which we will discuss later in the article, were introduced in order to achieve a directed solidification to the risers and to avoid porosities in the casting.

Finally, chills were applied in areas of large mass accumulations to reduce shrinkage defects.

A filling and solidification simulation showed that these measures significantly reduced the casting defects. These simulation results were again validated by X-rays. Near the “cold risers”, those not integrated into the runner system, not all defects could be avoided due to the risers’ insufficient size.

In the last version, the two cold risers were enlarged. Minor design changes of the casting were introduced to improve the directional solidification to the risers.

Compared to the original design, the casting quality was substantially improved and the amount of return scrap reduced. The use of chills improved the quality in critical areas within the casting. Overall, the casting process is now more efficient and cost-effective for the foundry.

Total sprue material3,73 kg(-3,3 kg)
Pouring weight8,93 kg (-3,19 kg)
Yield58 %(+24%)
Chills1,53 kg(+1,26 kg)

Design modifications of the casting

In many cases it is not sufficient to optimize the runner and riser system to achieve a sufficient casting quality. Instead, the design of the casting itself needs to be changed for the sake of “castability”.

The functional design of a casting often includes mass accumulations that prove problematic in the casting process. To achieve a high-quality microstructure, the wall thickness should always increase towards the risers according to the thermal modulus method.

To illustrate the effect of the casting design modifications, two geometry versions with identical runner and riser systems are compared. The adjustments are shown in the figure below. Several wall thicknesses and ribs between material accumulations have been enlarged.

For demonstration purposes, the two marked ribs will be examined. In both cases, porosities occur at the junctions, which is not acceptable.

By increasing the wall thicknesses of the ribs, the junctions are connected to the feeders adjacent to the casting edge and a directed solidification toward the risers is achieved.

The video shows large porosities in the initial version on the left side due to large hot spots within the casting where solidification-induced shrinkage creates a deficit.

In the optimized version on the right, the melt solidifies in the direction of the risers. This means that the deficit can be compensated by the riser and no porosity is created in the casting.

This validation shows a good correlation between reality and simulation in FLOW-3D CAST. The software is an effective tool for the development of castings, casting systems, feeder dimensions/shapes, and casting processes to ensure optimal quality and efficiency.

Exploring Ray Tracing in FLOW-3D POST

Exploring Ray Tracing in FLOW-3D POST

In the world of CFD, we use FLOW-3D POST to learn about our processes, analyze, visualize, and communicate the results of our simulations. We can now use the ray tracing option to increase the quality of our images and videos. While the ray tracing tool may not be necessary for every day simulation work, it is a great tool for presentation and outbound materials. Simulations can now be rendered with realistic-looking materials, depth of field, and lighting, and shadows to better engage viewers and guide them to the most interesting aspects of the results.

What is Ray Tracing?

The rendering engine works by setting up a geometric scene. First, we need a scene object or component. This will be our 3D simulation model that exists in a 3D dimensional space. Next, we choose a virtual camera or viewpoint, which will define the perspective of our image. Third, we need an image plane, which will be perpendicular to our viewing direction. The image plane is divided into pixels and is where the final image will be constructed. User:Henrik    CC BY-SA 4.0

The ray tracing engine can now start filling in the pixels on the image plane. View rays are constructed from the camera viewpoint, through the center of each pixel on the image plane, and then extend out into to the scene object. When the ray intersects our object, the color of the intersection point is determined and sent back to its respective pixel in the image plane. This process is done for every pixel in the image plane to construct an image.

Shadows and Lighting

Another variable we can specify in our ray tracing calculation is lighting. Light sources will affect the shade and intensity of the colors sent to the image plane from our view ray. This effect is defined mathematically by the rendering equation, which was first introduced by James Kajiya from CalTech in 1986. For a basic understanding, the equation can be broken down into three factors. Keeping these factors in mind will help guide you as you start incorporating light sources into your simulation.

1. How much light is incoming or falling on our scene object?

Here we can consider the intensity of our light source, the distance from the light source to the scene object, and the orientation of the scene object with respect to the light source.

2. How does the surface of our scene object reflect the light?

This is where we can consider the material of our object. Different materials have different reflectivity. For instance, materials can be shiny like water or dull like concrete. In FLOW-3D POST we have many material definitions ready to use. Note that dull objects are defined as diffuse and shinier objects are defined as specular.

3. Where is the location of your camera or viewpoint?

Moving the viewing angle will influence the perceived light reflection.

Ray Tracing in FLOW-3D POST

With a component selected, select Enable Ray Tracing in the Properties section. From here you can use either the OSPray Raycaster or OSPray Pathtracer engines for rendering. The path tracing approach is considered a more accurate representation of lighting and illumination, but this calculation can be more computationally intensive.

Now you can start exploring the ray tracing back end. You can experiment with materials from the pre-loaded options or define them from an imported material library:

  • Adjust camera properties such as focal point and depth of field using the adjust camera panel
  • Background settings can be defined as backplate or environment 

We have had success using the backplate to define a ground or floor to the object. Finally, the light inspector can be used to set up your light sources; this includes area lights for softer shadows.

With this overview of ray tracing, you now can start incorporating ray tracing and light sources to create photo-realistic renderings of your simulation results. We will be following up this post with some of our suggested settings that our team likes to use for different applications.

Stay tuned for our next blog on the animation view and keyframing features in FLOW-3D POST.

At Flow Science we develop innovative solutions that help our customers conceptualize, create, and analyze their simulations with confidence. If you would like more information or a personal demonstration of FLOW-3D POST, please send an email to webdemo@flow3d.com.

Thank you and stay tuned for our next post!

Ajit D'Brass

Ajit D'Brass

Metal Casting Engineer at Flow Science

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