Dear Dr. Pryl,

Many thanks for your reply. I'm only interested in temperature variations in water and air and convection between concrete-air and concrete-water interfaces.

From what I have found in the literature with regard to this is a typical range of 10-30 (watt per square meter per degree Celsius) for concrete-air interface and 200-1000 (watt per square meter per degree Celsius) for concrete-water interface.

I have also emailed my model and have queried about crack spacing in plain mass concrete for which I would be really really grateful if helped me with it. 

Many thanks for all your wonderful support.

Best Regards,
Hamed

Dear Hamed, if you set the parameters accordingly, I guess the condition should give you at least a reasonable approximation. Or are you specifically interested in some effects important for water and negligible for air?

Regards.

Dear Dr. Pryl,

I hope this message finds you well.

Is it possible to use the convection term for "heat convection and radiation" in "moisture temperature boundary for surface"

condition to simulate the convection between concrete-water interface or it can only be used for concrete-air interface?

Many thanks in advance for your reply.

Best Regards,
Hamed

Dear Dr. Pryl,

I sent the model to your email via yahoo.

Best Regards,
Hamed

Dear Hamed, you can follow Troubleshooting, 2.1.1 to send us your model etc. Regards.

Dear Dr. Pryl,

1- Yes I mean the ambient temperature setting.

2- I mean the note in the "functions" dialog box which says "this material is only for writing user function to the input file. Please do not assign it to the model".

Best Regards,
Hamed

Dear Hamed,
ad 1.: There is no initial temperature definition in the moisture temperature condition. Do you mean the Ambient Temperature setting?

What do you mean by "I do not assign the function to the model"?

Regards.

Dear Dr. Pryl,

1- I define the initial temperature for the concrete itself from the data-material-solid concrete-cctransportmatrial-initial temperature tab. For the “moisture temperature boundary for surface” condition the default value for the initial temperature is 20 degrees centigrade and I do not change it; I enable the ambient temperature function and define the function as I’ve mentioned in my previous post by entering the x and y data in a tabular form. I assign the condition to the surface I want but I do not assign the function to the model.

2- I fix the moisture DOF.

3- Thank you very much.

4- The mesh size and the step length vary in my model. But I don’t think the problem is related to the mesh size or the step length. I analyze my model without any problem by defining the curve using the “fire boundary for surface” condition. I just want to learn how the functions work as well.

Best Regards,
Hamed

Dear Hamed,
1. please keep in mind the Initial Temperature is defined in the Material dialog at the corresponding tab.

2. If you are only interested in temperature but not moisture, disable the unneeded degree of freedom in Interval Data.

3. I think the following should be equivalent, but I am going to check with our colleague responsible for the ATENA-GiD scripts:

A. Ambient temperature 1, function 0;20 7200;30

B. Ambient temperature 20, function 0;1 7200;1.5

C. Ambient temperature 30, funtion 0;0.66667 7200;1

4. What is your step length, mesh, ... (Troubleshooting, 2.1.1)?

Regards.

Dear Dr. Pryl,

Unfortunately, I haven’t been able to figure out how the functions work. I’m familiar with the total condition. I’ve used it before in the “fire boundary for surface” condition.

I just don’t know how the values in the functions dialog box work. If I want to apply “moisture temperature condition to a surface with an initial ambient temperature of 20 which rises to for example 30 degrees in two hours what the values should be in the functions dialog box (the initial temperature of concrete is also 20 degrees centigrade)? Should they be as follows?:

X (time, unit seconds)                    Y (temperature, unit degrees centigrade)
0                                                      20
7200s                                               30
Multiplier X=1
Multiplier Y=1

OR

X (time, unit seconds)                     Y (temperature, unit degrees centigrade)
0                                                      1 (20 divided by the initial ambient temperature)
7200s                                              1.5 (30 dived by the initial ambient temperature)
Multiplier X=1
Multiplier Y=1

When I define any of these, I get the error” underflow or overflow arithmetic operation” in the very first step of the analysis.

Best Regards,
Hamed

Dear Hamed,
I guess you have already found out how to use the functions? Unlike most Conditions in ATENA, the Fire and Moisture-Temperature ones are total (i.e., not incremental). Therefore, absolute temperatures of the heat source/air (and not increments/differences) are to be defined there.

If the Moisture-Temperature conditions does not allow a function for the ambient temperature history, I agree the best way is to use the Fire condition. There, you define the min. and max. temperature, and a time history function (where 0 on the vertical axis corresponds to the min. temperature and 1 to the max.).

Best regards.

Dear Dr. Pryl,

Many thanks for your email.

The problem is that I don’t know how the “functions” work.

If the moisture temperature condition is activated, the default value for the ambient temperature is equal to 20 degrees centigrade and it is reasonable to consider temperature variations as coefficients multiplied to the ambient temperature to be used as Y values along with X values (which should be time values in seconds) in a tabular form and there is no need to use the X and Y multipliers in the “functions” dialog box.

For example if I want to define that after an hour the temperature rises to 25 degrees centigrade should I define it as follows?:

X (s)                   Y (temp)
0                           1
3600                    1.25

X multiplier =1
Y multiplier=1?

I feel that I’m missing something here. I really appreciate all the guidance you provide.

Best Regards,
Hamed

Dear Hamed,
ad 1.: then, the Condition "Moisture Temperature Boundary for Surface" is clearly the first choice.

Ad 2.: OK.

Ad 3.: In the Moisture Temperature condition, you can activate AmbiTemper FUNCTION and define the corresponding function(s) in Data - Materials - Functions.

Regards.