function?richards
%?Solution?of?the?Richards?equation?????
%????using?MATLAB?pdepe???????????????????
%
%???$Ekkehard?Holzbecher??$Date:?2006/07/13?$
%
%?Soil?data?for?Guelph?Loam?（Hornberger?and?Wiberg?2005）
%?m-file?based?partially?on?a?first?version?by?Janek?Greskowiak?
%--------------------------------------------------------------------------
L?=?60;??????????????????%?length?[L]
s1?=?0.5;?????????????????%?infiltration?velocity?[L/T]
s2?=?0;???????????????????%?bottom?suction?head?[L]
T?=?24;????????????????????%?maximum?time?[T]
qr?=?0.218;???????????????%?residual?water?content?
f?=?0.52;?????????????????%?porosity
a?=?0.0115;???????????????%?van?Genuchten?parameter?[1/L]
n?=?2.03;?????????????????%?van?Genuchten?parameter
ks?=?31.6;????????????????%?saturated?con