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# Re: Topographic Effects

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• To: seaint(--nospam--at)seaint.org
• Subject: Re: Topographic Effects
• From: "David Topete" <d.topete73(--nospam--at)gmail.com>
• Date: Thu, 28 Feb 2008 10:02:31 -0800

Joe,
I suggest running a second analysis for the 60' from the crest.  There may be a significant difference with H= 1,060' with z = 1,000' as opposed to H= 1,500'.  GL.

On Thu, Feb 28, 2008 at 9:50 AM, <Jnapd(--nospam--at)aol.com> wrote:
Dave

That is correct...hill rises 500' behind and to the left of the house and 60' behind and to the right of the house.

In a message dated 2/28/2008 9:45:47 A.M. Pacific Standard Time, d.topete73(--nospam--at)gmail.com writes:
If I understand correctly, the SFR sits in an amphitheater/canyon where the hill rises 500' behind the house, but only 60'  to the side of the house?

On Wed, Feb 27, 2008 at 6:19 PM, <Jnapd(--nospam--at)aol.com> wrote:
Dave

If the wind direction encompases 180 degree sector towards the house; behind the house 90 degrees is as I stated before and 90 degrees the hill rises only 60' .  Do you still feel your numbers are more correct  or some where between ?

In a message dated 2/27/2008 4:53:01 PM Pacific Standard Time, d.topete73(--nospam--at)gmail.com writes:
the house is at 1000' with another 500' above (at 45 deg), then Lh = 750'  That would change up the numbers a bit.
K1 = 0.43 (2D escarpment)
K2 = 0.96 for x/2H = 500'/2*1500' = 0.167
K3 = 0.44 for z/2H = 1000'/2*1500' = 0.333
Kzt = (1+K1K2K3)^2 = 1.40

G = 0.85

partially enclosed is reasonable.  Your other assumptions also seem reasonable.

HTH.

On Wed, Feb 27, 2008 at 2:44 PM, <Jnapd(--nospam--at)aol.com> wrote:
Another fun wind question a bit winded but here goes.

I have a 2 story house on the side of a hill. The H to the house is 1000' and Lh= 500' continuing up the hill another house is 60' above mine and 100' horizontally away. The hill continues another 500' above this house. The hill slope is approximately 45 degrees.

The house is 22' tall and 64' diameter with 3' tall 20' diameter Clerestory on roof; both roofs are flat.

Topographic Effects
H/Lh=2.....by footnote 2 ....K1=.43   ( because hill continues aboe my house )  yes/ no ??
since H/Lh > .5 the Lh becomes 2H for next calculations.
X/2H = 10/2000 =.02.........K2 =1
Z/2H = 22/2000 = .011......K3 =.78
Kzt = 1.78
G= .85
Partially Enclosed

Kd = .95  or  .85

Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA

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--
David Topete, SE