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

Forum: Main CFD Forum March 16, 2012, 02:56

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Hi Hemant, I have tried different turbulence... Hi Hemant, I have tried different turbulence models without much success: It sems that only LES should give something more or less close to reality. I have also tried the following thing with...

Forum: Main CFD Forum March 17, 2011, 15:28

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino At these reynolds numbers ( RE around 10^6 and... At these reynolds numbers ( RE around 10^6 and lower) I would try x-foil, it is much simpler and highly validated.

Forum: Main CFD Forum March 15, 2011, 16:52

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino But flow might be really unsteady and laminar at... But flow might be really unsteady and laminar at this reynolds number with foil shedding vortices and without steady bubble? It is interesteresting at this reynolds numbers the turbulence is...

Forum: Main CFD Forum March 14, 2011, 16:05

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Martin, Have you tried to run laminar? Is it... Martin, Have you tried to run laminar? Is it really turbulent at RE=5000 and alpha=7? At such a low speed the transition can be delayed up to the trailing edge.

Forum: Main CFD Forum March 14, 2011, 15:37

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino I am still confused: At figure 4 of that... I am still confused: At figure 4 of that reference they list k-w sst, k-w sst trans., gamma-re-theta. So it sems that they distinguish between k-w sst trans and gamma-re-theta. At that figure k-w...

Forum: Main CFD Forum March 14, 2011, 07:58

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino There is quite a confusion with the names of... There is quite a confusion with the names of models in Ansys/Fluent. I found another reference that has comparison different models with gamma re theta and sst-for transitional flows among them...

Forum: Main CFD Forum March 13, 2011, 03:05

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Joshua, The published papers you gave (I do... Joshua, The published papers you gave (I do not have access to one by Alam) seem to discuss flows at re of several millions (perhaps your coming paper will present results on smaller re). Do...

Forum: Main CFD Forum March 11, 2011, 18:22

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Thanks for Info: Did you do steady or unstedy... Thanks for Info: Did you do steady or unstedy simulations, if unsteady/transient what was the timestep? What was the resolution of grid (in direction of normal and along airfoil surface) and boundary...

Forum: Main CFD Forum March 11, 2011, 01:50

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino I have access to fluent 6.3.26 and it has s-a,... I have access to fluent 6.3.26 and it has s-a, k-e, k-w, k-w sst, k-w sst transitional, and Reynolds Stress: I could not get decent results with k-w sst transitional for sd7037 at RE=70000. I know...

Forum: Main CFD Forum March 9, 2011, 16:40

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Thanks a lot Martin, For SA I got cd around... Thanks a lot Martin, For SA I got cd around 2.7E-2 and Cl around .75, but for k-w standard Cd is about 7E-2, which is completely unacceptable. I was directed to interesting articles that...

Forum: Main CFD Forum March 9, 2011, 03:04

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino And here is eddy viscosity from S-A models, where... And here is eddy viscosity from S-A models, where everything is going smooth

Forum: Main CFD Forum March 9, 2011, 01:45

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino here is the close up for kw-sst for trailing... here is the close up for kw-sst for trailing edge. Also residuals for kw-steady -> kw-unsteady -> kwsst-unsteady Time step: (1% of airfoil chord flow travel per time step, max 10 iterations per...

Forum: Main CFD Forum March 9, 2011, 01:35

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Yes, I forgot that in k-w there is zero boundary... Yes, I forgot that in k-w there is zero boundary condition for eddy viscousity. These are contours of turbulent viscosity in the fluid. For kw steady (that converges) and kw-sst steady that...

Forum: Main CFD Forum March 8, 2011, 17:39

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino The problem here that there is no experimental... The problem here that there is no experimental results for stepped vortex-trapping airfoils, analysys of which is a final goal of thisn work. I wanted to compare performance of this type of airfoils...

Forum: Main CFD Forum March 8, 2011, 17:27

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Thank you a lot! I post a picture of the mes and... Thank you a lot! I post a picture of the mes and closeups of LE and TE. Plot of residuals is shown in the previous post. Truffaldino

Forum: Main CFD Forum March 8, 2011, 17:12

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Thanks Martin, Seems you are right, see... Thanks Martin, Seems you are right, see plots for steady simulation form kw (2000 iterations) to kw sst staedy with oscillating residuals (they are also shown). The eddy viscosity is too small....

Forum: Main CFD Forum March 8, 2011, 16:15

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino This is sd7037 airfoil (9% thikness) at Re=70000.... This is sd7037 airfoil (9% thikness) at Re=70000. Sure, there is a separation bubble as you can clearly see from X-foil run shown below: that is why laminar solution never converges, as you have...

Forum: Main CFD Forum March 8, 2011, 15:57

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Yes, I have understood this by looking at result... Yes, I have understood this by looking at result of computation. As far as I undersand it is necessary to introduce user defined intermediency factor or other "artificial" things like that that are...

Forum: Main CFD Forum March 8, 2011, 03:21

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino No, I mean numeric convergence, i.e. reasonable... No, I mean numeric convergence, i.e. reasonable decrease in resudual. I have tried both stationar and non-stationar solvers: residuals oscillate wildly in kw-sst transitional model. Perhaps indeed...

Forum: Main CFD Forum March 8, 2011, 03:08

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Thank you for suggestion, swithching ... Thank you for suggestion, swithching k-omgega ---> k-omega sst ----> k-omega sst transitional does not help: k-omega goes fine, then k-omega sst still have acceptable residuals, but when...

Forum: Main CFD Forum March 7, 2011, 11:48

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino I have managed to make to convergence k-omega... I have managed to make to convergence k-omega standard transitional model by iterating standard k-omega until convergence and then running k-omega standard transitional, but results are...

Forum: Main CFD Forum March 7, 2011, 05:03

Replies: 51 Two-equation turbulent models: low re airfoils Views: 20,848 Posted By truffaldino Two-equation turbulent models: low re airfoils Hello I am trying to analyse flows past different 2D airfoils at low reynolds numbers (order of 10^4-10^5) and having problems. I am using fluent, but I guess this is not the fluent problem, but...

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