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The 6th figure (results for the 3rd simulation) is it.
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I cannot figure out which image refers to which simulation. As they are just tables of numbers can you put the relevant numbers directly in the post, not as images?
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I think, that putting the relevant numbers directly in the post will be less clearly for understanding (without table). |
Pay attention to reference density and location. These may make a difference. By default, location is automatic, so who knows where that would be.
It also may depend on whether you are using full buoyancy model or boussinesq approximation. Easiest thing to do would be to make a test model where you know what the results should be already, then you can figure out how CFX calculates these things. Start with free slip walls, and a very low flow, so you are only figuring out the static head portion of the pressure variables. Remember to set a reference density and location. Or use 1 simple 1D model using symmetry for the walls, so there is no pressure drop whether you have flow or not. Start adding to the test model to figure out how other components contribute. PS. That is a very strange mesh for fluids. It does not look like good boundary layer resolution. (Not suggesting that is making a difference here) |
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I didn't pay attention to ref. density and location because I haven't understood yet what they mean. But I'll figure it out now. For this simulation I already know what results should be (I've made hand calculations). And all values (except total pressure) correspond to these results. |
For clarification, in ANSYS CFX
Absolute Pressure = Static Pressure + Reference Pressure Static Pressure = "solved" Pressure (variable in the momentum equation) + hydrostatic pressure For incompressible flow: Total Relative Pressure = Static Pressure + "dynamic" pressure For compressible flow: Total Relative Pressure = Absolute Total Pressure - Reference Pressure Absolute Pressure = Absolute Pressure if the flow is isentropically slowed down to rest. |
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I've understood what absolute pressure, static pressure, ref. pressure and "solved" pressure means. But I supposed, that: Absolute Pressure = Static Pressure + hydrostatic Pressure Static Pressure = "solved" Pressure (variable in the momentum equation) + reference pressure. Actually these definitions aren't making a significant difference here. The values of these quantities (absolute pressure and static pressure) in my simulation are looking sanity (in my definitions they coincide with the hand calculated values). I also understand that total pressure should be = static pressure + . But in my simulation total pressure is less then ("solved" Pressure + ref. pressure). It's wrong, isn't it? |
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Does it looks off? Yes it does, but as Evcelica mentioned, more information (in CFX speak) is needed. Hope the above helps |
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There is only the "total pressure" in CFX (not total relative pressure or ablosute total pressure). |
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I think, that there aren't any problems with reference density too. So what is wrong? |
Absolute Total Pressure is effectively Total Relative Pressure + Reference Pressure.
That variable is not presented by ANSYS CFX anywhere, but if you were to evaluate Total Density, you will use Absolute Total Pressure and the Total Temperature in the equation of state In ANSYS CFX, "Total" prefix is what others call "Stagnation". Total Pressure = Stagnation Pressure Total Enthalpy = Stagnation Enthalpy Total Density = Stagnation Density, ... |
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But what is total relative pressure then? You said, that Total Relative Pressure = Absolute Total Pressure - Reference Pressure, then I asked you what is Absolute Total Pressure. You answered that Absolute Total Pressure is effectively Total Relative Pressure + Reference Pressure :D I've also just found some proves of your answers (see fig.) - maybe It'll helpful for other people, like me :D But I still don't understand how total pressure in my simulations has been calculated :( |
Absolute Total Pressure is effectively Total Relative Pressure + Reference Pressure.
That variable is not presented by ANSYS CFX anywhere, but if you were to evaluate Total Density, you will use Absolute Total Pressure and the Total Temperature in the equation of state |
Honestly, I have no solution and can't see what might be wrong. However, can you extract the static and total pressure values directly at the inlet/outlet boundaries instead of these planes?
As the total pressure relates to density and velocity, also check carefully that these values are in the expected range, calculate the value yourself and see if there's a difference. |
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Except the extracted values for these planes, I've done it also for inlet and outlet directly (see fig. on the 4th message in this theme). Values of density and velocity are in the expected ranged. I've calculated them manually. |
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