CFD Online Discussion Forums http://www.cfd-online.com/Forums/ Discussion forums related to Computational Fluid Dynamics. This is the largest meeting place on the web for people working with CFD. en Wed, 08 Sep 2010 12:17:51 GMT vBulletin 60 http://www.cfd-online.com/Forums/images/misc/rss.jpg CFD Online Discussion Forums http://www.cfd-online.com/Forums/ air hammer in aerostatic bearing http://www.cfd-online.com/Forums/main/79912-air-hammer-aerostatic-bearing.html Wed, 08 Sep 2010 12:16:27 GMT why air hammer appears in aerostatic bearing ? it mainly depends on the volume of the pocket/recess? please help me, thank you. why air hammer appears in aerostatic bearing ? it mainly depends on the volume of the pocket/recess? please help me, thank you. ]]> Main CFD Forum spcwin http://www.cfd-online.com/Forums/main/79912-air-hammer-aerostatic-bearing.html gas diffusion through membrane http://www.cfd-online.com/Forums/cfx/79911-gas-diffusion-through-membrane.html Wed, 08 Sep 2010 12:14:33 GMT Lets say we have a box where there is a source of gas CO2 (at the bottom) and it is shut by a membrane (top). The box with the membrane is in... Lets say we have a box where there is a source of gas CO2 (at the bottom) and it is shut by a membrane (top). The box with the membrane is in atmospheric environment (simplest case). I want to simulate in CFX the diffusion through the membrane and finally find out the mass fractions of the air and CO2 inside the box.

I create two domains: the bottle without the membrane and the membrane itself. The first one is a fluid domain defined to contain a mixture of air (constraint) and CO2 with the kinematic diffusivity of CO2 in air.

What i did was to define the membrane domain as fluid domain containing again the CO2 and Air(constraint) mixture but with different kinematic viscocity.

There is a common area (between box domain and membrane domain) though that i do not know whether to define as a boundary or as an interphase (i did it as an interphase and the solution has errors - i get no results)

Any help on this?

What type of domain should i define the membrane?

If solid then i can not find a way to insert the diffusion coefficient of the membrane interacting with the mixture ]]> CFX sosat1012 http://www.cfd-online.com/Forums/cfx/79911-gas-diffusion-through-membrane.html I need help for TUI command http://www.cfd-online.com/Forums/fluent/79910-i-need-help-tui-command.html Wed, 08 Sep 2010 11:49:36 GMT Hi, everybody. I am writing a TUI journal. For the journal, one of the task is to creat a point-surface monitor. I know how to creat it. But I... Hi, everybody.
I am writing a TUI journal. For the journal, one of the task is to creat a point-surface monitor. I know how to creat it. But I can't find the command to change the type of X Axis variate. As the following pic shows,

I want to change "Iteration" to "Flow time" for "X Axis", and it should "Get Data Every" "Time Step".
I don't know which TUI command I should use. Anyone could help me?
Thanks.
Attached Images
File Type: jpg 1.jpg (45.6 KB)
]]> FLUENT ringtail http://www.cfd-online.com/Forums/fluent/79910-i-need-help-tui-command.html local nusselt for heated channel http://www.cfd-online.com/Forums/fluent/79909-local-nusselt-heated-channel.html Wed, 08 Sep 2010 11:24:44 GMT hi everybody, I want to calculate local Nusselt for heated channel. I have a constant heat flow, how to calcul Twall and T ref for each point... hi everybody,

I want to calculate local Nusselt for heated channel.
I have a constant heat flow, how to calcul Twall and T ref for each point along the wall!

please i need your help

thank you ]]> FLUENT gina http://www.cfd-online.com/Forums/fluent/79909-local-nusselt-heated-channel.html parallel and multiphase http://www.cfd-online.com/Forums/cfx/79908-parallel-multiphase.html Wed, 08 Sep 2010 11:24:15 GMT hello,
i have a problem,
my calculation on 4 cpu's differs two much from this on 8 cpu's with the same setup? what did go wrong? (multiphase flow) ]]> CFX Zaktatir http://www.cfd-online.com/Forums/cfx/79908-parallel-multiphase.html GT-Power - Star-CCM+ Coupling http://www.cfd-online.com/Forums/star-ccm/79907-gt-power-star-ccm-coupling.html Wed, 08 Sep 2010 10:59:11 GMT Hello,
I'm trying to couple GT-Power and Star-CCM+ (my versions are avaible for that) and I have no experience for that.
Has someone a tutorial about this topic ? Or can someone give me some tipps about this subject ?
Thank you in advance
Best regards ]]> STAR-CCM+ sheintz http://www.cfd-online.com/Forums/star-ccm/79907-gt-power-star-ccm-coupling.html ERROR: End AOA in airfoil table too small k 1 i 1 in Fluent 6.3 http://www.cfd-online.com/Forums/fluent/79906-error-end-aoa-airfoil-table-too-small-k-1-i-1-fluent-6-3-a.html Wed, 08 Sep 2010 10:53:39 GMT Hi everyone,

i am using fluent 6.3 and i'm trying in generating results for a 2 bladed helicopter having 2 sections. I have the sectional lift and drag arranged in the .dat files which is similar to the standara format used in the NACA 0015.

My AOA varies from -20 to 26 degrees.

When i run it on Fluent i seem to get this error no matter how much i change the format.

Does anyone have a idea on the matter?

Thanks ]]> FLUENT Asela http://www.cfd-online.com/Forums/fluent/79906-error-end-aoa-airfoil-table-too-small-k-1-i-1-fluent-6-3-a.html System time overhead in OF http://www.cfd-online.com/Forums/openfoam/79905-system-time-overhead.html Wed, 08 Sep 2010 10:42:03 GMT Hi all, I have noticed that on our cluster that openfoam have a very different cpu usage compared to other cfd codes. In OF a large fraction of... Hi all,

I have noticed that on our cluster that openfoam have a very different cpu usage compared to other cfd codes.

In OF a large fraction of the time is spend in system cpu time compared to user cpu time. Other cfd codes we have had our hands on spend almost 100% of the time in user cpu.

I have made a small case based on the angledDuct case with 178000 cells using simpleFoam. The case was constructed so no IO was performed.

In serial more than 30% of the time is spend in system time. Is this an overhead due to the dynamic memory allocation in OF?

Attachment 4644

When running the case in parallel (2 nodes) the system time CPU time fraction drops to a few percent which is difficult for me to understand.

Attachment 4645

Can anyone explain the apparent serial overhead?

Best regards,
Ask
Attached Images
File Type: jpg simpleFoam_job.jpg (59.8 KB)
File Type: jpg simpleFoam_job2.jpg (59.5 KB)
]]> OpenFOAM askjak http://www.cfd-online.com/Forums/openfoam/79905-system-time-overhead.html Nv-s ?? Nv-d ?? Help!!! http://www.cfd-online.com/Forums/fluent-udf/79904-nv-s-nv-d-help.html Wed, 08 Sep 2010 10:33:26 GMT
Quote:
#include "udf.h"
DEFINE_GRID_MOTION(plate,domain,dt,time,dtime)
{
Thread *tf = DT_THREAD(dt);
face_t f;
Node *v;
real NV_VEC(omega), NV_VEC(axis), NV_VEC(dx);
real NV_VEC(origin), NV_VEC(rvec);
real sign;
int n;
/* set deforming flag on adjacent cell zone */
SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));
sign = -5.0 * sin (26.178 * time);
Message ("time = %f, omega = %f\n", time, sign);
NV_S(omega, =, 0.0);
NV_D(axis, =, 0.0, 1.0, 0.0);
NV_D(origin, =, 0.0, 0.0, 0.152);
begin_f_loop(f,tf)
{
f_node_loop(f,tf,n)
{
v = F_NODE(f,tf,n);
/* update node if x position is greater than 0.02
and that the current node has not been previously
visited when looping through previous faces */
if (NODE_X(v) > 0.020 && NODE_POS_NEED_UPDATE (v))
{
/* indicate that node position has been update
so that it’s not updated more than once */
NODE_POS_UPDATED(v);
omega[1] = sign * pow (NODE_X(v)/0.230, 0.5);
NV_VV(rvec, =, NODE_COORD(v), -, origin);
NV_CROSS(dx, omega, rvec);
NV_S(dx, *=, dtime);
NV_V(NODE_COORD(v), +=, dx);
}
}
}
end_f_loop(f,tf);
}
I don't know that means. I didn't find a whole day in google and UDF manual.

please explain to me.. ]]> Fluent UDF and Scheme Programming oilsok http://www.cfd-online.com/Forums/fluent-udf/79904-nv-s-nv-d-help.html Environment variable in linux http://www.cfd-online.com/Forums/star-ccm/79903-environment-variable-linux.html Wed, 08 Sep 2010 10:08:45 GMT :confused:When I install star-ccm+ successfully, it didn't work well, there is something wrong. someone said when star-ccm+ installed, I must set the environment variable, but i knew linux very little,could someone tell me how to set the environment variable? Thanks! ]]> STAR-CCM+ xinzhiyu2008 http://www.cfd-online.com/Forums/star-ccm/79903-environment-variable-linux.html OF1.6.x:localBlended schemes missing correction funtions http://www.cfd-online.com/Forums/openfoam-bugs/79902-of1-6-x-localblended-schemes-missing-correction-funtions.html Wed, 08 Sep 2010 10:01:16 GMT Hello everyone,

when comparing fixedBlended.H and localBlended.H then localBlended is missing the member functions "correction" and "corrected". These should be necessary when using e.g. linearUpwind as one of the two blending schemes.
I attached a suggested fix, where I copied the two member functions with a little adjustment because the blending factor in localBlended.H is a field.

Best Regards
Dominik Christ


P.S.: Thanks to Sven Degner and Ulf Bunge who discovered this bug.
Attached Files
File Type: h localBlended.H (6.6 KB)
]]> OpenFOAM Bugs dominik_christ http://www.cfd-online.com/Forums/openfoam-bugs/79902-of1-6-x-localblended-schemes-missing-correction-funtions.html Velocity gradients from previous time step... http://www.cfd-online.com/Forums/fluent/79901-velocity-gradients-previous-time-step.html Wed, 08 Sep 2010 09:24:30 GMT Hi,

Maybe my previous thread wasn't clear enough.

I'm asking how can I access the values of velocity gradients from the previous time step...

Thanks
Mateus ]]> FLUENT mateus http://www.cfd-online.com/Forums/fluent/79901-velocity-gradients-previous-time-step.html Weld pool simulation of laser-hyrid welding http://www.cfd-online.com/Forums/fluent/79900-weld-pool-simulation-laser-hyrid-welding.html Wed, 08 Sep 2010 09:17:02 GMT Hi, My research goal is to simulate laser hybrid weld pool by using ANSYS Fluent. I dont have much idea about this kind of simulation. Is there... Hi,

My research goal is to simulate laser hybrid weld pool by using ANSYS Fluent. I dont have much idea about this kind of simulation. Is there any tutorial available for weld pool simulation so that I can start learning?

Regards
Minhaj ]]> FLUENT minhaj_iut http://www.cfd-online.com/Forums/fluent/79900-weld-pool-simulation-laser-hyrid-welding.html Good Universities for MS in CFD (in US and UK both) http://www.cfd-online.com/Forums/main/79899-good-universities-ms-cfd-us-uk-both.html Wed, 08 Sep 2010 08:52:26 GMT Hello guys, I am looking forward for MS (Fall 2k11). Can you please suggest me the universities in US that have research interests in the field of... Hello guys, I am looking forward for MS (Fall 2k11). Can you please suggest me the universities in US that have research interests in the field of CFD. ]]> Main CFD Forum vinaynitrkl http://www.cfd-online.com/Forums/main/79899-good-universities-ms-cfd-us-uk-both.html How I could import Ansys mesh into CFX? http://www.cfd-online.com/Forums/ansys-meshing/79898-how-i-could-import-ansys-mesh-into-cfx.html Wed, 08 Sep 2010 08:43:17 GMT Dears,

I wanna import ansys mesh into CFX (I have ansys 12). I can import the mesh, but I can't define the boundary condition, because CFX consider whole geometry as a block. Could u plz help me?

m.shahverdi@gmail.com ]]> mahdi57 http://www.cfd-online.com/Forums/ansys-meshing/79898-how-i-could-import-ansys-mesh-into-cfx.html