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Couldn't see distribution of color in contour scale of ansys cfx

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Old   September 12, 2019, 17:09
Post Couldn't see distribution of color in contour scale of ansys cfx
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Dear connections,

I couldn't see the variation in colors in scale of temperature distribution in the results in Ansys cfx fluid flow analysis of cutting tool with cooling channels inside. Only two colors are appearing on the tool. The material of the tool is steel (chosen). Want to see the results of temperature distribution from cutting edge to the end of the shank of tool. when the fluid flows across the channel, how much it gives coolant effect to the tool when the cutting edge generates 400 degree celsius. I have attached a image of the problem in this message.

Thanks !!

Kind regards

Nadeem
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Old   September 12, 2019, 17:51
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Try changing the variable range to 550->650C or tigther to get an idea, then adjust
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Old   September 12, 2019, 17:58
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Dear Opaque,

I changed even till 1000 C, but there is no change. Only the cutting edge has its effect, but no temperature change on the shank.
Any better solution to this problem or am I missing some variable or parameter ??
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Old   September 12, 2019, 18:12
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I meant to narrow it down around the highest reported temperature, not a larger range.

First, you have to determine if heat transfer is happening at all based on your setup, does it make sense? setup error? if transient, did it run long enough? is the solution converged? etc.

A lot of things to consider, but you have to start somewhere to analyze the unexpected results.
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Old   September 13, 2019, 01:39
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Hello,
Did You create solid-solid interface between shaft body and cutting edge, conserving the heat flux?


Best regards,
Oskar
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Old   September 13, 2019, 05:50
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Dear opaque,

The flow in the cooling channel results seems to be fine because I have given fluid temperature as 1 degree celsius, I have also used heat flux as 0.5 W/m^2 as commented by ''sheaker'' on this post. please check the image attached, the scale is displaying colors but still the temperature on scale is still the same. The temperature at cutting edge should be >400 degree celsius because I have kept the temperature as 400 C at cutting edge and the temperature should descend from cutting edge to shank end point. You asked me change temperature variable, from where I need to do that?

Since I am learning cfx, may be I am doing mistakes, also am very new to ansys cfx. It will be very nice if you correct & help me a bit on each step.

Kind regards
Nadeem
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Old   September 15, 2019, 10:20
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Dear sheaker,

I tried to find ''conserving heat flux'' in the solid-solid interface, but I noticed that that ansys didn't make any such condition in that option. what should I do now, Please i need your help dear.
Please find attachments below. when i tried to change the scale variable in-between from '' 0 - 400 C, i can see the whole shank body turns dark blue in color, there is still something i am doing mistake, please correct and help me.

Looking forward to hearing from you.

kind regards
Nadeem
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File Type: jpg 3.jpg (48.0 KB, 12 views)
File Type: jpg 1.JPG (82.3 KB, 8 views)
File Type: jpg 2.JPG (79.6 KB, 11 views)
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Old   September 15, 2019, 15:49
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I see that You have default solid solid interface.
Isn't 0.5 W/m^2 a little bit to small value? With Your interface area it will be really small value.
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Old   September 15, 2019, 17:22
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Dear Sheaker,

This time I increased the heat flux to 2 W/m^2, but again the scale is same, their is a large change in color on the model compared to the previous case with heat flux 0.5 W/m^2.

If I try to change the temperature scale through ''user specified'' option in ''range'' in contour, then the scale is showing correct values but the color of model is just single color. Please find attached images.

Kind regards
nadeem
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File Type: jpg 6.JPG (78.1 KB, 9 views)
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Old   September 15, 2019, 17:57
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I would say it is still to small. Take heat capacity of Your tool and calculate how many Watts You would need to heat it one degree. As You can see now You get temperature increase 0.01 K which is more than 0 from first try.



Ok. I tried similar simulation and my settings are a little bit different. Check the attachment.

Thermal heat flux is a constant flux. If You can, use thermal contact resistance. You can calculate it using Fourier's law:
https://en.wikipedia.org/wiki/Therma...ct_conductance.



I hope it helps.


Best regards,
Oskar
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Old   September 16, 2019, 06:23
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Dear oskar,

No, you misunderstood my problem, actually the model shown is a cutting tool. I want to calculate the fluid flow across the channels by keeping mass flow rate as 0.1437 Kg/sec with fluid(water) temperature at 1 degree celsius, outlet pressure as 1 bar. Also at the same time I want to calculate thermal stresses starting from cutting edge (round ring in front of cutting tool) till the end of shank tool by keeping cutting edge temperature as 400 degree celsius.
Regarding heat flux, the power given is 300 W.
I hope you understood my question ?

Kind regards
Nadeem

Last edited by msnadeem; September 18, 2019 at 12:33.
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Old   September 17, 2019, 06:19
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Dear oskar,

Can you please share your fluent file on my google drive. Atleast I can understand where I am going wrong with my model regarding ''domains'' in fluent. I think it is good solution for all my problems. I hope you understand. I will provide the link and you can upload it on my drive.

Looking forward to hearing from you.

Kind regards
Nadem
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Old   September 17, 2019, 10:28
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Hello.
Firstly: Mr. Opaque asked if Your simulation is steady state or transient. Maybe You are displaying only first timestep?

It is CFX forum, not Fluent.



For some reason I can't upload my case. But You can recreate Your simplified case and I could possibly take a look. Maybe I will be able to help You then.

If not, then I am out of ideas.


Best regards,
Oskar
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Old   September 18, 2019, 07:55
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Dear oskar,

I am really glad that you will help me out and I really need your help. Being new to ansys cfx, am facing problems.

The simulation is for steady state with K-epsilon (2 eqn.) solver. Actually I was also trying in fluent, so by-mistakenly I said fluent in the previous message, sorry for that.

I have re-modeled with threads to have results in real case. Also, i have made separate domains for pipe, shank body tool and cutting edge & I have described the problems and BC in the next message, please kindly have a look on it.

Also please find attached images, I have made new domains, but I couldn't find ''conservative heat flux'' option in the solid-solid domain. If I have made domain wrong, please ask me to correct it, I will do it and work according to you.

looking forward to hear from you.

Kind regards
Nadem
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File Type: jpg 4.JPG (46.4 KB, 5 views)
File Type: jpg 5.JPG (49.5 KB, 5 views)

Last edited by msnadeem; September 18, 2019 at 09:26.
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Old   September 18, 2019, 09:29
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Please find BCs and power required.
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Old   September 18, 2019, 11:44
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Hello.


Both, solid and fluid, can not be isothermal. How You expect temperature change in isothermal body?


Change them to Thermal Energy since Your flow is relatively slow.


Then You should be able to change interface to conserve heat flux. If You ever touch thermodynamics You should know what 'adiabatic' means. How You expect heat flux through adiabatic wall?


Best regards,
Oskar
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Old   September 18, 2019, 12:25
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Dear oskar,

I agree your words, I have forgot so many things since 6 years ago but I know the basics of thermodynamics, not so much in touch with this subject neither with Ansys software and its interface(reason I am doing mistakes), my specialization is production engineering but this topic is given to me to complete in a very limited time. That's why I am here on this forum. But I believe I can learn from this mistakes once I see how it works in software. I believe nothing is impossible.

I hope you understood my situation & it's not easy to do in just one go.

Regarding the model, I changed from isothermal to ''thermal energy'' in both Solid and liquid domains respectively, but then I cannot put value for fluid temperature, nor for cutting edge temperature( the source for generating heat throughout the model).
Do I need to put temperature for cutting edge in ''cutting edge default'' ? & fluid temperature in ''inlet'' option ?

Thank you !!
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Old   September 19, 2019, 10:10
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To define temperature of fluid You need to set it on Inlet BC.
To define initial temperature of a body You need to set it in "initialization" tab on Details of Solid Domain.
To define temperature of a cutting edge You need to set it on cutting edge BC.

I am 99% sure You would be much further in Your simulation if You would watch some CFX tutorials and read documentation.



As for me the hardest thing will be to properly define heat transfer between solid and fluid. There are two options available:
Thermal Contact Resistance and Thin Material. If the fluid is in contact with shell where thickness of the material is constant and known, the choice is seems to be obvious. But I am not sure how to set it for a complex geometry.
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Old   September 19, 2019, 13:26
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Dear oskar,

Thanks for your reply, the thickness of shell is constant and I proceeded with ''thin material'' option by keeping values in BCs as you have mentioned, but I ended up with the solution error ''update failed for the solution component in fluid flow. The solver failed with a non-zero exit code of :2''.

Regarding the tutorials on Youtube or other blogs, I tried to find the videos & solve on my own since 1 month, but there are videos only for 1D solid tube or very basic fluid flow analysis which are not in detail. That's why I am taking help from forum here. I appreciate your help.

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Old   September 19, 2019, 14:33
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I am sorry but I cannot help You more. This is something, I did not faced before.


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Oskar
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