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FDS Source: rework TAU_U to be consistent with Tech Guide #15308

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Merged
rmcdermo merged 1 commit into from
Oct 10, 2025
Merged

FDS Source: rework TAU_U to be consistent with Tech Guide #15308

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9 changes: 5 additions & 4 deletions Source/fire.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -778,9 +778,10 @@ SUBROUTINE COMBUSTION_MODEL(T,DT,ZZ_GET,Q_OUT,MIX_TIME_OUT,CHI_R_OUT,CHEM_SUBIT_
Q_REAC_SUB(1:N_REACTIONS),Q_REAC_1(1:N_REACTIONS),Q_REAC_2(1:N_REACTIONS),Q_REAC_4(1:N_REACTIONS),&
Q_REAC_SUM(1:N_REACTIONS),Q_SUM_CHI_R,CHI_R_SUM,TIME_RAMP_FACTOR,&
TOTAL_MIXED_MASS_1,TOTAL_MIXED_MASS_2,TOTAL_MIXED_MASS_4,TOTAL_MIXED_MASS,&
ZETA_1,ZETA_2,ZETA_4,D_F,TMP_IN,C_U,DT_SUB_OLD,ERR_EST(N_TRACKED_SPECIES),ERR_TOL(N_TRACKED_SPECIES),ERR_TINY,&
ZETA_1,ZETA_2,ZETA_4,D_F,TMP_IN,K_SGS,DT_SUB_OLD,ERR_EST(N_TRACKED_SPECIES),ERR_TOL(N_TRACKED_SPECIES),ERR_TINY,&
ZZ_TEMP(1:N_TRACKED_SPECIES),ATOL(1:N_TRACKED_SPECIES)
INTEGER :: NR,NS,ITER,TVI,RICH_ITER,TIME_ITER,RICH_ITER_MAX
REAL(EB), PARAMETER :: C_U=0.4_EB,TAU_EPS=1.E-10_EB
INTEGER, PARAMETER :: TV_ITER_MIN=5
LOGICAL :: TV_FLUCT(1:N_TRACKED_SPECIES),EXTINCT,NO_REACTIONS,NO_REAC_2,NO_REAC_4
TYPE(REACTION_TYPE), POINTER :: RN !,R1
Expand All @@ -801,9 +802,9 @@ SUBROUTINE COMBUSTION_MODEL(T,DT,ZZ_GET,Q_OUT,MIX_TIME_OUT,CHI_R_OUT,CHEM_SUBIT_
TAU_D = DELTA**2/MAX(D_F,TWO_EPSILON_EB) ! FDS Tech Guide (5.14)
SELECT CASE(SIM_MODE)
CASE DEFAULT
C_U = 0.4_EB*C_DEARDORFF*SQRT(1.5_EB)
TAU_U = C_U*RHO_IN*DELTA**2/MAX(MU_IN,TWO_EPSILON_EB) ! FDS Tech Guide (5.15)
TAU_G = SQRT(2._EB*DELTA/(GRAV+1.E-10_EB)) ! FDS Tech Guide (5.16)
K_SGS = (MU_IN/(RHO_IN*C_DEARDORFF*DELTA))**2 ! FDS Tech Guide (4.17)
TAU_U = C_U*DELTA/SQRT(TWTH*(K_SGS+TAU_EPS)) ! FDS Tech Guide (5.15)
TAU_G = SQRT(2._EB*DELTA/(GRAV+TAU_EPS)) ! FDS Tech Guide (5.16)
MIX_TIME_OUT= MAX(TAU_CHEM,MIN(TAU_D,TAU_U,TAU_G,TAU_FLAME)) ! FDS Tech Guide (5.13)
CASE (DNS_MODE)
MIX_TIME_OUT= MAX(TAU_CHEM,TAU_D)
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