Windtunnel/Boundary Conditions

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New user_defined_parameters in pluto.ini

• KinematicViscosity_m2_per_s, DynamicViscosity_Pa_s: read in visc_nu.c

for Domain Boundaries

• Wall_BoundaryCondition for tangential walls (X2_BEG, X2_END), value from {0,1,2,3}:

value	meaning	VX1	VX2
0	no-shear	zero-gradient	reflective
1	no-slip	reflective	reflective
2	no-wall	zero-gradient	zero-gradient
3	one-way wall	zero-gradient	zero-gradient & no-inflow

• WindPressure_Pa, WindPressure_mbar (mutually exclusive): pressure at entry (X1_BEG)
• PressureGradient_mbar_per_cm:
  • driving the flow if positive¹
  • ignored if negative, then WindVelocity is driving the flow.
• WindVelocity_m_per_s, InjectionTime_s: Wind velocity at entry (X1_BEG) is ramped up from 0 to the given value over the given time (if pressure gradient < 0 is specified).
• WindTemperature_C: determines density (via pressure) at entry (X1_BEG)

¹: even though pressure drops from left to right

for Solid Object

(needs SOLID = YES in makefile_user_machinedefs)

• ObjectType_int:
  • 0 = nothing
  • 1 = cylinder/sphere of diameter ObjectDiameter_cm centered on the origin
  • 2 = square/cube of edge length ObjectDiameter_cm centered on the origin
  • \(-n\) = File solid.txt contains (at most) \(n\) voxels (lines of \(x~y~z\)). Voxels outside the origin-centered sphere of radius 0.6·ObjectDiameter_cm are discarded.

• Obj_BoundaryCondition:
  • -1 = no-slip
  • 1 = no-shear (unavailable due to an unresolved issue)

Analytical Solutions

(for comparisons)

empty 2D channel

$$ v_x(y) = \frac{\Delta p}{L}\frac{D^2/4-y^2}{2\mu} $$

empty circular tube

$$ v_z(r) = \frac{\Delta p}{L}\frac{R^2-r^2}{4\mu} $$

with \(\mu\)=dynamical viscosity