Leverett’s function (Leverett, 1941; Udell and Fitch, 1985)
Pcap=−P0⋅σ(T)⋅ f(Sl)P_{cap}\quad=\quad-P_0\cdot\sigma(T)\cdot\ f(S_l)Pcap=−P0⋅σ(T)⋅ f(Sl)
with
σ\sigmaσ(T) - surface tension of water (supplied internally in TOUGH4)
f(Sl)=1.417(1−S∗)−2.120(1−S∗)2+1.263(1−S∗)3f(S_l)=1.417 (1 - S^*) - 2.120 (1 - S^*)^2 + 1.263 (1 - S^*)^3f(Sl)=1.417(1−S∗)−2.120(1−S∗)2+1.263(1−S∗)3
where
S∗=(Sl−Slr)/(1−Slr)S^*=(S_l-S_{lr})/(1-S_{lr})S∗=(Sl−Slr)/(1−Slr)
Parameters: P0P_0P0= CP(1) SlrS_{lr}Slr= CP(2)
If CP(3) ≠ 0,
Pcgn=Pcap(=Pcgl)P{cgn}=P_{cap}(=P_{cgl})Pcgn=Pcap(=Pcgl)
Pcap(Pcgl）=0P_{cap}(P_{cgl}）=0Pcap(Pcgl）=0
