Recent content by yrob

I was referring to this "step back" we took.

I agree with you, but I was trying to simplify the example, and did not say 0 flow. We start from a sphere immersed in a pipe filled with a fluid (we could assume we insert it at z=0), then turn on a pump which will make the fluid flow vertically. If the formula I am using is correct and using a...

Maybe I am misunderstanding your answer, I apologize. Let us say that now the sphere is slightly denser than the fluid. The push that I am calculating (from the drag formula above) is almost negligible, and would need several tons of fluid flowing every single second just to fight gravity. I...

In that simplified moving case then, the chart with dummy values I sent would be correct? I am highly surprised that 1 ton per second flowing in this pipe would not be enough to fight gravity (if we do not account for buoyancy, with equal fluid and sphere densities).

I see now what you mean. We could consider a "perfect" grid which would not induce any pressure loss. Therefore, we could assume a v_A ~= v_B and P_A ~= P_B. However, what would probably better to take a step back here. Since the solution I am looking for is (obviously) very simplified, maybe a...

Thank you for your patience with me. I see that there is a lot of confusion with this problem. Let me disclose some more information. These spheres are packed naturally with buoyancy. However, now, the flow in the pipe is turned on (let's say, with a pump). The packing should be tighter. I am...

The radius of each sphere is indeed in this example 5 cm. And the red line can be thought of a grid which prevents spheres to go further.

Sure, here is it. One assumption I make, to make it a bit simpler, is that the "push" from the fluid is the same for each sphere and assume a "void fraction" to calculate the velocity (v_assumed = v_fluid / void_fraction). I also attached a dummy example I made, the parameters are: - Density of...

Hello and thank you for your answers. The area was wrong, indeed, but even with the area of the sphere cross section, the force is much lower than expected. In addition, I considered the sphere stationary because it is in reality a pack of spheres, all blocked by a grid in the pipe. The...

Hello everybody, I am thinking of the following problem: A sphere a radius r is in a much larger container of radius R. In this container, a fluid continuously flows with turbulent conditions from bottom to top. I would like to approximate the force pushing the sphere up. Some calculations I...

Hello and thank you for you answer, I based this on the FRAPCON 3.4 Manual that can be found here : https://www.nrc.gov/docs/ML1110/ML11101A005.pdf from page 2.15 to 2.18 Moreover, the reference you put is the one I was talking about. Regarding the conversion, I am using 1 Mev = 1.602e-19...

Hello, I am currently trying to understand the TUBRNP model which is used to calculate the isotope compositions and the radial power profile evolution with the burnup. I am talking about the basic model (the one from 1994 with only 6 isotopes taken into account) in the case of a LWR with UO2...