Water fiow in nanochannel

hi dears , i am simulating poiseuille water flow in nanochanne,First, the energy is minimized, and then 1ns is simulated in nvt for relaxation, and then the heat pump model is used under nve to give a constant force of 5PN to the water molecules from 0 to 0.8nm in the x direction, 5ns is carried out, and then the statistics of 2ns are carried out, but the statistical results of vx are very small.

#—Forced area------------------------------------------------
region qingpo block 0 8 0 {y} {g9} {g10} units box #--temperature reset area------------------------------------------------- region kongliu1 block 8 16 0 {y} {g9} {g10} units box
group kongliu dynamic h2o region kongliu1 every 10
#- data are-------------------------------------------------
region shuju1 block 16 {x} 0 {y} {g9} {g10} units box
#-------nve---------------------------------------------------------------------#
compute Cqingpo h2o temp/region qingpo
compute newT kongliu temp/partial 0 1 1
compute_modify newT dynamic/dof yes
compute Cshuju h2o temp/region shuju1
variable tCqingpo equal c_Cqingpo1.5
variable tCshuju equal c_Cshuju
1.5
thermo 1000
thermo_style custom step temp c_Creyuan v_tCqingpo c_newT v_tCshuju press pe ke etotal
#----------------------------------------------------------------------------#
fix NVE1 reyuan nve
fix NVE3 ziyou nve
fix NVE2 h2o nve
#–强迫区给力--------------------------------------------------------------------------#
fix qingpo h2o addforce ${force_addfore} 0 0 region qingpo

fix kongwen_langevin kongliu langevin 300 300 {Tdamp} 699483 fix_modify kongwen_langevin temp newT fix ziyou_langevin ziyou langevin 300 300 {Tdamp} 699483
fix_modify ziyou_langevin temp Cziyou
fix reyuan_langevin reyuan langevin 300 300 {Tdamp} 699483 fix_modify reyuan_langevin temp Creyuan run {5000_ps}
unfix qingpo
unfix ziyou_langevin
unfix reyuan_langevin
#----------------------------------------------------------------------------#
fix reyuan_langevin reyuan langevin 350 350 ${Tdamp} 699483
fix_modify reyuan_langevin temp Creyuan