Description
I’m trying to determine how much my boat hull will sink in free water. In the real world, the boat hull is 200 grams, and I’m adding an additional 400 grams of electronics into it.
Current Project Steps
- Created a box geometry and subtracted my boat hull from it and deleted boat body
- Used a multiphase simulation and used a Cartesian box subdomain to split the box geometry between air and “water”
- To mimic a heavier boat, I decreased the “water’s” density from 997.3 kg/m^3 to 332.4
- Used a wall as the boundary conditions for all sides of the box geometry
Questions
- I subtracted the boat hull from the box geometry so that there’s only one body for the multiphase simulation. But if I do this, how does Simscale know how to simulate the interaction between the boat hull and water?
- Is decreasing the water density the right way to mimic a heavier boat?
- Should my boat hull start completely above the water and then drop into the water as part of the simulation or should it already be in the water once the simulation starts?
- In my run simulations, how can I measure the boat sinkage? My second run had a normal water density (997.3), but the boat started as partially submerged in the water.
But when I ran it a third time with the decreased water density (332.4), and the boat started out of the water, it looks like the boat sank less than the second run. I’m confused because with the decreased water density, I thought the third run simulation should have sunk more than the second.
Hi Aidan,
I will take a look at your post. Like I mentioned, please share your proejct with the support.
Best,
Renan
Answering your questions:
1)SimScale will actually track the interface between water and air, which depends on the geometry of the hull
2)Would be one option, but how much should one decrease the density?
3) That will depend on how you split your domain and how you set the water and air inlets
4) I need to double-check if this is possible.
Nonetheless, it might be tricky to evaluate the boat sinkage based only on “weight”. Here are two public projects that could be of help to you:
- Boat Simu
- Cylinder Movement
Hope that this helps you!
Best,
Renan
Thanks for the reply. I reviewed the public projects you sent me but could not find anything to help me achieve a floating simulation. Couple more questions:
- My boat doesn’t sink at all even I though I applied no slip walls to the the outer box faces and to the sides within the box that resulted from the deleted boat body. Am I missing any other steps to simulate boat sinkage?
- This relates to the first question I had in my OG post, how can multiphase even simulate boat sinkage if it doesn’t know my boat density? If multiphase can’t simulate sinkage, what simulation method should I use to simulate sinkage?
Hi @adkwok26 ,
As I mentioned previously, it might be tricky to simulation the boat sinkage, because that requires the update of the mesh around the boat as it sinks. The multiphase approach would be a work around to try to capture the “sinkage” of the boat by updating the interface between water/boat and air/boat. So if the interface water/boat rises, the boat “sinks” - this will of couse depend on the inlet conditions of air and water and geometry of the hull. Here is a link that might bring some light in how you could simulate that, or at least gather some information (check the solid body movement and ship analysis part). However, if you only want to check the sinkage through density of the boat, might not be possible. That is why, I have been suggesting the other workarounds to see if you can extract some useful information.
Hope this helps you further.
Best,
Renan
