<div dir="ltr">Hello Neks,<div><br></div><div>As a first excercise learning to mesh
using the tools provided in Nek5000, I ran a simple laminar cylinder
flow simulation (geometry obtained by extending the geometry of
cyl3dr.rea from /examples/expansion) and clearly see a fully-developed
flow at the outlet. The maximum velocity is, as expected, exactly twice
the uniform inlet velocity, and I see a parabolic velocity distribution
along the radial direction. However, the pressure drop is not in line
with the theory.</div><div><br></div><div>For example, from Cengel,
deltaP=8nuLV/(R*R). nu is the kinematic (equal to dynamic in this case)
viscosity, L is the length of the cylinder = 20, V is the average
velocity = 1, and R is the radius of the cylinder = 1.<br></div><div><br>Also, Re=10=V(2R)/nu, giving nu=(1/5) leading to deltaP=(8)(1/5)(20)(1)/(1*1)=3<wbr>2.
But, the pressure drop (falls linearly, in line with theory) in my
simulation is only 16. I increased the cylinder length by two times, and
again the pressure drop is half of what is expected. Can anyone tell me
if there is something I am not accounting for? I am new to CFD and this
is my first ever problem. I am pasting my input parameters below.<br><br> 118 Parameters from file:<br> 1 1.00000 p001 DENSITY<br> 2 -10.0000 p002 VISCOS<br> 8 1.00000 p008 CONDUCT<br> 11 10000.0 p011 NSTEPS<br> 12 -0.100000E-02 p012 DT<br> 15 500.000 p015 IOSTEP<br> 21 0.100000E-05 p021 DIVERGENCE<br> 22 0.100000E-06 p022 HELMHOLTZ<br> 24 0.100000E-01 p024 TOLREL<br> 25 0.100000E-01 p025 TOLABS<br> 26 1.00000 p026 COURANT/NTAU<br> 27 2.00000 p027 TORDER<br> 65 1.00000 p065 #iofiles (eg, 0 or 64); <0 --> sep. dirs<br> 66 6.00000 p066 output : <0=ascii, else binary<br> 67 6.00000 p067 restart: <0=ascii, else binary<br> 93 20.0000 p093 Number of previous pressure solns saved<br> 94 3.00000 p094 start projecting velocity after p94 step<br> 95 5.00000 p095 start projecting pressure after p95 step<br> 99 0.00000 p099 dealiasing: <0--> off/3--> old/4--> new<br> 103 0.100000E-01 p103 weight of stabilizing filter (.01)<br><br><br></div><div>Thanks,<br></div>Ajay</div>