JENS MALMGREN I create, that is my hobby.

Fluid simulations every spare moment

This was one of those weeks that I delayed blogging and did not start blogging until Sunday afternoon, when the week was almost over.

Week 45, 6 to 12 November

It has been raining a lot this week. I have been busy with fluid simulations every spare moment this week. From a blog perspective, there has been very little going on. That doesn't mean nothing is going on around the house. The road to and from our house is getting the final top layer. They did not start right outside our house, though, but elsewhere. Trucks have been driving back and forth with sand, gravel, pavement stones, and whatnot. Building the road when it rains is challenging, so finishing takes longer than anticipated.



Merida can sometimes stretch from a nap by holding her head with her two front paws; it is the sweetest look ever. It usually takes three milliseconds before it is over, so I have never been able to capture it in a photo.

This week, I published to GitHub the fluid simulation program I ported from the paper by Jos Stam. GitHub is a storage for source code on the Internet. I also included a readme with the story of how I got to the result.

Then, I started to make my own version of the fluid simulation program. I made several attempts to improve the code, but I cannot say the program improved that much. That is something I have tried since the beginning of the week. If all attempts fail, I can always return to the original and make something of it.

I brought DW to the Wool Union on Saturday morning, where she held a course in wool spinning. This is near the upcycling center, so behind the car, I had the small trailer that I loaded during my decluttering project this autumn. So when DW had stepped out of the car, I continued to the upcycling center and emptied the small trailer.

When I came home, I cleared stuff from the workshop. We were getting friends on visit this Sunday, so I wanted things to be slightly tidier. The workshop, in its entirety, will be a separate project. For now, I got rid of the latest clutter. I drove back to the Wool Union and picked up DW. The attendees were happy with their learning; it was a great gathering. Two more courses will be on Saturdays; by then, the pupils can spin wool into yarn.

On Saturday afternoon, we worked outside. I removed the watering hoses from the garden along the driveway and in the flower garden. It is good to have them removed before the winter. We have a few hoses to wind up before the winter is really here.

In the evening, it was time for the yearly Saint Maarten festivities. Kids brought homemade (and purchased) lanterns, sang a song and got candy in return. Luckily, we had enough candy in the house and the leftovers we took to enjoy.


On Sunday, we got a visit from a friend, Irene. She came to the same studio to paint models and portraits as I did before the pandemic. Irene and I painted 35 times together from 2016 until 2020. I ran a query over my blog and found I had mentioned Irene 35 times. She got her new studio together and is painting, although she said she is not a quick painter, so it takes time to finish each painting. She even has a website!

Well, I could not show her my studio. Also, I could only tell her I had not painted since the pandemic, so that was not going well from a painter's perspective.

The art I am doing right now is to be found in the VFX program I am making. She was happy I did something with art, though.

When Irene left, I discovered a dandelion next to the workshop door. Hey dude, what are you doing there in November?

It was such nice weather. I suggested to DW that we walk in a park near us, and she was all in on that idea!


Here is an art installation with a path to a wall with a door. At the beginning of the path, we could easily stand next to each other.

The path gets narrower.


At the end is a wall with a door.

Obviously, the door has graffiti on it because this is the Netherlands.


The door is open!

This is the door from the other side. You can lock the door. Why would you do that? Two meters beside the door is the end of the wall?

In the forest behind the door, we found this trident tree.


I think the maker of this art wanted people to go around in the forest behind the door and back out through the door again, but we did not do that. We decided to escape from the forest from behind without using the door. When doing so, we found a little tree formed as a trident.

When we came home from the walk, we enjoyed a quiet afternoon. I programmed the fluid simulations again. I found a YouTube video about math and decided that the approach I worked on regarding the simulations would not pan out. This week's attempts have been centered around bringing back the simulations to the single cells of the fluid, but that will not work since much of the math is working on the complete grid or vector. I will start over again; this time, I will keep the whole grid, but I will let several threads work simultaneously on each consecutive update. We will see how that goes.

Here ends this week's blog. It did not become that bad after all. We have done some finishing off of the garden season. DW planted garlic, and I gathered some of the watering hoses. There are more hoses to collect. The road will be built in the coming weeks, and we want to save two plants from those activities.

I was born 1967 in Stockholm, Sweden. I grew up in the small village Vågdalen in north Sweden. 1989 I moved to Umeå to study Computer Science at University of Umeå. 1995 I moved to the Netherlands where I live in Almere not far from Amsterdam.

Here on this site I let you see my creations.

I create, that is my hobby.