Modifying the Incident Solar Radiation
 

Evening Guys,

Hope you are all well.

Is there a way that the incident solar radiation can be modified? When I check the contours of incident solar radiation after initialization, I get values of between 1600~1700 W/m2. Which are incorrect for winter conditions.

In the solar model, I specified the global position and dates appropriately and reduced the sunshine factor to 0.038 to reflect the conditions of the experimental day. On applying these settings, in the console in FLUENT, I get normal and diffuse solar irradiations quantities that are almost the same as the experimental values: Direct Normal = 35W/m2 and Diffuse = 77 W/m2.

The global solar radiation was 71 W/m2 at the start of the experiment.

The funny thing is if I turn off radiation and only use energy and turbulence models, the simulation results match the experimental results with just minor discrepancies.

On turning on the radiation model, the temperatures are much higher especially at the top of the greenhouse which aligns with the areas that receive the high incident radiation.

I would like to use the radiation model but reduce the incident radiation to match the experimental data.

There is no option to change it in the GUI and TUI.

Please help.

Thanks, Much appreciated.

Solar Irradiation
 

Did you choose solar calculator method for Illumination parameters? In that case, it should automatically maintain the position and give the values that you get from the calculator.

Incorrect Incident Solar Radiation
 

Morning Vinerm,

Thanks for the response, much appreciated.

The global solar radiation at 10 am on the day of the experiment was 71 W/m2. It was a hazy day and the effect of the solar radiation in the greenhouse was minimal to non-existent thus the use of the air heaters in the greenhouse.

As such, the simulation modelled with energy activated and the turbulence model, minus the radiation model, gives simulation results almost similar to the experimental data.

The incident solar radiation at this time should thus be less than 71 W/m2.

According to the experimental data, at around 1 pm in the afternoon, the global solar radiation increased to 250W/m2.

At this time the haze had cleared and this increase in solar radiation resulted in an increase in air temperature at the top half of the greenhouse, at heights of 2m~5m.

I have run transient simulations without the radiation model at these time as well and there is a discrepancy in air temp. values at heights of 2m~5m owing to the lack of additional heat from the solar radiation.

Air temps. are around 5~10 degrees less.

That is why I was hoping to modify the incident radiation to values that reflect the day of the experiment.

Attached are the contours for solar radiation and screenshots of the solar calculator and radiation model selection & inputs.

Thanks for the assistance, much appreciated.

Kind Regards

Radiation Modeling
 

Are you using any radiation model or just using solar radiation to apply a heat flux? If latter, then you don't need to use solar calculator or radiation model, since you already know the time and flux profile. Just apply a transient profile to the top boundary. However, if you are also solving for radiation using a radiation model, say DO, then you can use the UDF you mentioned. Either use compiler for that or remove Message command. Message command is not necessary for UDF to work. Try C standard printf in place of Message; that might work with interpreter.

Radiation Modelling
 

Thank you Vinerm for your response, much appreciated.

I am solving for radiation inside the greenhouse and as such the DO radiation model was selected.

I used the standard printf initially but that didn’t work, I then removed the message command but still, the error persisted.

Let me try and use a compiler and see if it will work.

Any compiler that you would recommend that would definitely work?:)

Thanks for the assistance, much appreciated.

Compiler
 

If you are using Linux, then gcc is already installed. Just compile and it will work. If you use Windows, then you have to install Visual Studio or MS Build Tools with C++ compiler.

Evening,

Just finished installing Visual Studio.

Will have to see if it works

Thanks for the response, much appreciated

Floating Point Exception Error
 

Morning Vinerm,

Hope you are well.

I ran into this problem during the simulation.

What could possibly cause this issue?

I have read in other forums that it may be a mesh issue, but this is the same mesh I have been using for my almost 50 simulations now.

Thanks for your assistance, much appreciated

Solution Found
 

Running the simulation on ANSYS 15 sorted the issue.

Thank you.