1!-----------------------------------------------------------------------
2      SUBROUTINE WAKE_CAV0(SYCAPT,SZCAV0,SYCAV0)
3!-----------------------------------------------------------------------
4!
5! --- PRIME      Version:  1.0     Level:  970812              WAKE_CAV0
6!                D. Strimaitis, L. Schulman,   EARTH TECH
7!                Prepared for EPRI under contract WO3527-01
8!
9! --- PURPOSE:  Compute the sigmas for a source placed on the floor
10!               of the cavity, which produce the target cavity
11!               concentration
12!
13! --- INPUTS:
14!
15!        SYCAPT - real    - Sigma-y (m) of plume at point where
16!                           mass is captured in cavity
17!
18!     Common block /WAKEDAT/ variables:
19!           Hb, Wb, xLR, xLC, HR, Ub, Urh
20!
21! --- OUTPUT:
22!
23!        SZCAV0 - real    - Initial sigma-z (m) of cavity source
24!        SYCAV0 - real    - Initial sigma-y (m) of cavity source
25!
26!                 Note    - These sigmas reproduce the cavity
27!                           concentration when the used in:
28!                           C = Qc / (pi * us * szcav0 * sycav0)
29!                           where us is the wind speed for the primary
30!                           source, and Qc is the mass flux captured by
31!                           and released from the cavity.
32!
33! --- WAKE_CAV0 called by:  WAKE_DFSN
34! --- WAKE_CAV0 calls    :  none
35!----------------------------------------------------------------------
36!
37      INCLUDE 'params.pri'
38      INCLUDE 'wakedat.pri'
39
40      DATA RT2PI/2.5066283/ , RT2BYPI/.7978846/ , THIRD/0.3333333/
41
42! --- Interpret plume sigma-y at cavity entry point as equivalent
43! --- top-hat;  limit to full width of bldg
44      WCAPT = AMIN1(RT2PI*SYCAPT,WB)                                    !  18352
45
46! --- Set width scale for lateral distribution in cavity
47      WSCALE = AMIN1(WB,3.*HB)
48      WSCALE = AMAX1(WSCALE,THIRD*HB)
49      WSCALE = AMAX1(WSCALE,WCAPT)
50
51! --- Sigma-y for equivalent top-hat distribution
52      SYCAV0 = WSCALE/RT2PI
53
54! --- Set height of cavity behind the bldg
55      IF ( XLC.LT.XLB ) THEN
56! ---    Reattachment
57         HCAV = HB                                                      !  17992
58      ELSE
59! ---    No Reattachment
60         HCAV = HR                                                      !    360
61      ENDIF
62
63! --- Set sigma-z that results in centerline concentration equal to
64! --- cavity concentration
65! --- Wilson & Britter 1982 approach to cavity concentration
66      URATIO = UB/URH                                                   !  18352
67      SZCAV0 = RT2BYPI*URATIO*HCAV*THIRD
68
69      CONTINUE
70      END


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