Comparing local and Meteonorm wdr data

james bertram · Post by **james bertram** » Wed Nov 20, 2013 8:09 pm -1100

Good morning (again) - if I have local wind velocity, direction and rainfall, can I total "Rain load = Rain*(R1 + R2*Wind velocity)" in each degree of orientation to create a comparative wind driven rain distribution rose?
If so, is the formula "Rain load = Rain*(R1 + (R2*Wind velocity)) or Rain*((R1 + R2)*Wind velocity)?
Thank you

Christian Bludau · Post by **Christian Bludau** » Wed Nov 20, 2013 11:37 pm -1100

Hi James,

nearly you can total it. You have to include an cosinus as the rain will also hit the surface, if the surface is turned a little bit to the rain direction:
Rain load = sum(Rain * (R1 + (R2 * windspeed)) * cos (winddir - orientationsurface)) for positive values.
In Wufi R1 is set to zero and R2 is set to 0,2 m/s.

Chrisitan

james bertram · Post by **james bertram** » Thu Nov 21, 2013 5:03 pm -1100

G'day Christian - struggling a bit here...(should have done algebra instead of home economics)

Would you check the following:
"Rain load" = the sum of hourly outcomes for each of the 8 default wall orientations (N=0 deg, NE=45 deg etc)
"Rain" = measured hourly rainfall (mm)
"R1" = 0
"R2" = 0.2
"windspeed" = measured hourly data (m/s)
"cos" = cosine (Excel formula)
"winddir" = direction wind is coming from (270 deg = from the west)
"orientationsurface" = perpendicular or othogonal to the wall (does this mean a wall running east-west is north facing = 0 degs or relative to the wind direction 180 degs?)
"for positive values" = not sure?

When I use the above for each line of hourly data (wind speed, wind direction, rain) my outcomes don't seem to transition from perpendicular wall=higher rain load to oblique wall=small rain load, and the relationship between wind direction and wall is sometime back to front.

I appreciate your support, James

Christian Bludau · Post by **Christian Bludau** » Thu Nov 21, 2013 10:07 pm -1100

Hello James,

"Rain load" = the sum of hourly outcomes for each of the 8 default wall orientations (N=0 deg, NE=45 deg etc)
"Rain" = measured hourly rainfall (mm)
"R1" = 0
"R2" = 0.2
"windspeed" = measured hourly data (m/s)
"winddir" = direction wind is coming from (270 deg = from the west)

Yes, thats right

"cos" = cosine (Excel formula)

yes, but Excel uses radians not degree, so you have to do it this way:

Code: Select all

=cos(radians(value)) or =cos(PI()/180*value)

Then you´ll get positive values for 0-90 and 270 to 360 degree.

"orientationsurface" = perpendicular or othogonal to the wall (does this mean a wall running east-west is north facing = 0 degs or relative to the wind direction 180 degs?)

Its the direction the surface is facing, so north = 0, west = 270.

"for positive values" = not sure?

See above @cos, you have to sum up the positive values for the wanted direction.

Try if you get that to work, if not I can send you an example xls-file.

Greetings,
Christian

james bertram · Post by **james bertram** » Thu Nov 21, 2013 10:23 pm -1100

Thank you Professor

I will give it a go first, always learn more that way...and get back to you doesn't seem to work.

Enjoy your weekend..I get to start mine first!

James

Comparing local and Meteonorm wdr data

Comparing local and Meteonorm wdr data

Re: Comparing local and Meteonorm wdr data

Re: Comparing local and Meteonorm wdr data

Re: Comparing local and Meteonorm wdr data

Re: Comparing local and Meteonorm wdr data