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Showing results 1 to 22 of 22 Search took 0.00 seconds. Search: Posts Made By: Attesz

Forum: CFX May 17, 2010, 05:01

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi Susann, Here is what I mean. You... Hi Susann, Here is what I mean. You are allowed to use not only Pitch 1, but here, they speak about a 6.25% area change which means a pitch change very close to 1, and they mentioned that it...

Forum: CFX May 15, 2010, 10:07

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz http://www.ansys.com/events/proceedings/2006/PAPER... http://www.ansys.com/events/proceedings/2006/PAPERS/252.pdf There is really nothing in help about this, but in this paper, it is described. Have a nice weekend!:)

Forum: CFX May 13, 2010, 05:53

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi Susann, I know that, but can it cause... Hi Susann, I know that, but can it cause high numerical errors? In some papers, I read that in Transient Rotor Stator, or Transient Frozen Rotor simulations, I can use only Pitch Ratio 1. Of...

Forum: CFX May 12, 2010, 04:10

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi, can I use Frozen Rotor fluid interface,... Hi, can I use Frozen Rotor fluid interface, when my geometry is periodic, and the Pitch Ratio isnt equals 1? There is nothing about it in the help. I have a 60deg impeller, and a 72deg stator, so...

Forum: CFX May 6, 2010, 09:05

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Yes, its a good idea! I'm preparing transient... Yes, its a good idea! I'm preparing transient simulations present... I have measurements only on operating point, because this is a gas turbine engine. We have not enough equipment to measure the...

Forum: CFX May 6, 2010, 08:54

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz you should increase the first cell height for... you should increase the first cell height for example 2 times. I think thats all... yes you are right, the "real" surge is a totally transient phenomenon. But I found in every paper, that the...

Forum: CFX May 6, 2010, 07:56

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz In steady state the separations will be... In steady state the separations will be "averaged". But we know, its always a transient simulation. When you get less separation with transient, I think, its correct, but maybe people who are smarter...

Forum: CFX May 6, 2010, 07:52

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz I mean, that yplus should be above 20 when you... I mean, that yplus should be above 20 when you use only 5 cells (but 10 cells is preferable), to get accurate wall function results. My separation starts near the leading edge of the splitter...

Forum: CFX May 5, 2010, 09:41

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz I assume you use SST. These values are not... I assume you use SST. These values are not correct. Did you get accurate results compared with measurements (i don't remember)? I think, yplus above 20 and 10 cells in boundary layer will not slow...

Forum: CFX May 5, 2010, 07:48

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi Susann, can you post some information... Hi Susann, can you post some information about your mesh in impeller and in boundary layer? Thank for your post! Attila

Forum: CFX April 29, 2010, 09:21

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Thanks. With this prod.limiters, I don't change... Thanks. With this prod.limiters, I don't change any constants in the model! The quantities will be calculated by the original form of the turbulence model, but they give wrong results in stagnation...

Forum: CFX April 28, 2010, 09:24

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Thank you. In my compressor simulation... Thank you. In my compressor simulation there is a huge separation started from the leading edge. I think, it's unreal at PR1. First, i attempted it caused by the mesh quality, but I've resolved...

Forum: CFX April 28, 2010, 03:38

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Thanks Glenn! Otherwise, how can the size... Thanks Glenn! Otherwise, how can the size difference between the last boundary layer cell and the first tetra affect the results? Can it cause a bigger numerical error than the wrong modelled...

Forum: CFX April 23, 2010, 04:39

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Thanks for your answer. You are right, it's not... Thanks for your answer. You are right, it's not converged well. I've set the physical timescal 100times higher, but has no significant effect. I attempt, that I should check the mesh.. And the...

Forum: CFX April 23, 2010, 04:36

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi all, I've checked the yplus values, and... Hi all, I've checked the yplus values, and since there are different velocities in the compressor's flow field, it's not to easy to generate a good mesh. Because on the blades, the velocity...

Forum: CFX April 7, 2010, 09:04

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Convergence curves. Thanks for any answer, ... Convergence curves. Thanks for any answer, Attesz

Forum: CFX April 7, 2010, 09:01

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz I don't know exactly what is this S3 plot.... I don't know exactly what is this S3 plot. However, I've attached some contour plot about Mach numbers. The solution is well converged, as you can see on the pictures. But there is an error...

Forum: CFX March 31, 2010, 10:04

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Yes I know the wake-jet regions in impellers, but... Yes I know the wake-jet regions in impellers, but this weak is on the wrong side, i think. The operation is at PR1, low RPM, so it's very strange. What do you think, can we capture this...

Forum: CFX March 31, 2010, 05:17

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi Glenn! Thank you for your answer! ... Hi Glenn! Thank you for your answer! I think it can be, because if the separation fluctuates than its a transient phenomenon, but If I run in stationary, the separation "stays there always"....

Forum: CFX March 30, 2010, 13:27

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi PCFD, I could read your post detailed,... Hi PCFD, I could read your post detailed, at least. It's very interesting what you say(write), because I think, we have a similar problem since half a year. We have tried stationary and transient...

Forum: CFX March 27, 2010, 12:50

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz Hi, the next week I will write you detailed... Hi, the next week I will write you detailed answer. But I think, the overestimate is not wrong, because we don't calculate with the losses (friction loss etc.)... Attesz

Forum: CFX March 24, 2010, 07:28

Replies: 56 SST turbulence model Views: 18,247 Posted By Attesz same problem Hi PCFD, I'm working on a compressor too, and using SST model. In my simulations, there is a huge separation starting form the trailing edge of the impeller. I assume, that it's not a real...

Showing results 1 to 22 of 22

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