I thought initially that it was because the flow has less inertia and therefore will separate easily with adverse pressure. However, it seems that simply tripping flow to turbulent will not increase the flow's inertia significantly, right? Yet it does allow it to adhere more.
I am doing an simulation of cylinder flow of around Re 500,000
I noted from most of the publications that people would compare values of strouhal number, root mean square lift coefficient and as well mean drag coefficient in their simulations
I am a bit confused, like why would not root mean square drag coefficient and mean lift coefficient be used instead? Or in other words, why are mean square lift coefficient and mean drag coefficient better? Wouldn’t it more fair if people compare mean drag coefficient & mean lift coefficient (or the pair of root mean square coefficient) ? Any reason to pick these parameters (strouhal number, root mean square lift coefficient and as well mean drag coefficient ) to compare?
I am new to CFD so I am really confused.
I've read that I can model the flow as usual, but to set the wall condition to slip (i.e. violating the no-slip condition, thus there is no boundary layer, thus the flow is treated as laminar by COMSOL) so that I can model something that converges (as I could not get my turbulent simulation to converge). In terms of deviation from true experimental results, what difference should I expect? All I can think of is that ignoring turbulence may lead to my results being artificially high since turbulence would introduce back flow / eddies so that all the flow is not unilaterally going to the exit and that no boundary layers would decrease the drag/friction on the fluid within, but I wouldn't expect that deviation to be that high in either case. Is there anything that I'm missing?
Edit: This is for the space shuttle main engine, and while there's technically combustion going on in the combustion chamber (which is also where the throat is), for my model I'm just setting the inlet pressure as the combustion chamber pressure and the temperature to the combustion chamber pressure and letting everything work itself out through that.
I have a question. Say you have a section of open-ended pipe of a fixed length, with a sphere inside, at one end of the pipe (position 1). The goal is to move the sphere through the pipe and out the other end by using pressurized fluid to push it from behind. When it comes out (position 2), the sphere should have a certain velocity and be as stable as possible.
Here is a sketch of the situation
The sphere could either be slightly smaller than the diameter of the pipe, allowing for some fluid to flow around it, or it could be slightly larger than the pipe diameter to create a nice seal between the sphere and pipe, your choice.
Would laminar or turbulent flow of the fluid be better suited for minimizing the rotation of the sphere? And why? I have my "gut feel" answer, but I'm struggling to think of why.
Maybe a basic question, but one that confuses me a lot.
Edit: thank you all, I have learnt a lot with you.
So I am aware of a whole range of empirical equations e.g. Darcy-Weibach, Colebrook, Hazen-Williams etc. for estimating pressure drop in turbulent flows in pipes, implemented in commercial piping analysis codes. That said, as a turbulence researcher, I know its too chaotic and complex to be addressed by just empirical relationships... So my question to those of you using commercial piping softwares: Are you happy with the predictions? Are they accurate enough for most applications? Are there applications where they really fall short and CFD is preferable, even though its comparatively expensive?
I am just looking for pain-points in current piping models, where CFD is still the best tool for any reasonable accuracy. If you know of any literature that surveys this ecosystem, that would be helpful too! Thanks much!
Just some random thoughts. I have a short run off the top of my plenum that goes to a bathroom and above laundry. These spaces can be 10 degrees warmer (when running heat) than any other zone. Does closing the vents in the short fourth run distribute the air from that run throughout the system without adding too much stress on the blower?
I have four branches off the plenum. Three have dampers, the fourth in question does not and looks to be an after thought addition to the top of the plenum. Because the blower forces air up into the plenum, the fourth branch is a path of least resistance to flow and a lot of heat is directed this way.
Money is tight as I am about to start a new job. I would like to have an experienced HVAC tech out at some point to analyze the system and optimize flow. For the moment I am just trying to scratch my curiosity.
is as disrespectful as you guys(my classmates and me)
Edit:
she also told laminar flow turns into turbulent flow just like you guys from grade 1 to grade 11
Hey do you know any Examples of
A: Subcritical turbulent Flow B: Supercritical laminar Flow
I've read that there's a difference between a laminar and turbulent flow of smoke when divining with incense. But I've never had a split stream before. What could a split stream mean, in general? What if the two flows differ/are both turbulent/are both laminar?
https://youtu.be/5zI9sG3pjVU
Shots fired
I'm looking for an analytical solution as described in the title. I wrote a code based on lumped capacitance for solving thermal transients and I'd like to use this as a validation case, as well as apply it to a separate problem I'm working on. I feel like this problem should be fairly straightforward forward, but when I search for results I find a lot of papers looking at specific instances related to the basic problem, like a pipe with axially varying properties or thick wall effects, etc. I'm just interested in the simple case of fully developed turbulent flow and a thin walled pipe. Can anyone point me in the right direction?
Thanks in advance.
I am trying to line up an experimentally determined wall pressure spectrum due to turbulent fluid flow to my simulation results in ANSYS FLUENT. However, I have tried nearly all solvers ( LES etc.) and the pressure spectrum that i am obtaining in FLUENT is wayyy larger in magnitude. Can anyone help?
