1bc2ffad99
STYLE: atm wall functions: use auto and bool types wherever possible TUT: atmosphericModels: changes for style consistency
113 lines
3.7 KiB
Markdown
113 lines
3.7 KiB
Markdown
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# Overview
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"By setting appropriate profiles for wind velocity and the turbulence
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quantities at the inlet, it is often assumed that the boundary layer will
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be maintained up to the buildings or obstructions in the flow." (HW:p. 355).
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However, it was quantified by (HW:p. 355) that "even in the absence of
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obstructions, ..., the velocity and turbulence profiles decay along the
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fetch" (HW:p. 355). It was shown by (HW:p. 355) that a set of modifications
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were required to maintain a neutral atmospheric boundary layer throughout
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an empty and long computational domain of a RANS computation.
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## Aim
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- Verification of the atmospheric boundary-layer boundary conditions in terms
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of the maintenance of inlet quantities downstream within a RANS computation:
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- atmBoundaryLayerInletVelocity
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- atmBoundaryLayerInletK
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- atmBoundaryLayerInletEpsilon
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- atmBoundaryLayerInletOmega
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## Benchmark (Physical phenomenon)
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- The benchmark is an empty fetch computational
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domain, steady-state RANS simulation.
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- Flow characteristics:
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- External flow
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- The surface layer portion of the neutral-stratified
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equilibrium atmospheric boundary layer (no Ekman layer)
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- Dry air
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- Homogeneous, smooth terrain
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- Spatiotemporal-invariant aerodynamic roughness length
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- No displacement height
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- Newtonian, single-phase, incompressible, non-reacting
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- Benchmark scenario:
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- Computational domain: (HW:Fig. 1)
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- Benchmark dataset: (HW:Fig. 6)
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(Obtained by the WebPlotDigitizer-4.2 (Rohatgi, 2019))
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## Resources
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Computational study (tag:HW):
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Hargreaves, D. M., & Wright, N. G. (2007).
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On the use of the k–ε model in commercial CFD software
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to model the neutral atmospheric boundary layer.
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Journal of wind engineering and
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industrial aerodynamics, 95(5), 355-369.
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DOI:10.1016/j.jweia.2006.08.002
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Wind profile (tag:RQP):
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Richards, P. J., Quinn, A. D., & Parker, S. (2002).
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A 6 m cube in an atmospheric boundary layer flow-Part 2.
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Computational solutions. Wind and structures, 5(2_3_4), 177-192.
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DOI:10.12989/was.2002.5.2_3_4.177
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# Numerics
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## Physical modelling:
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- The governing equations for:
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- Steady-state, Newtonian, single-phase, incompressible fluid flows,
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excluding any thermal chemical, electromagnetic and scalar interactions
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- Mathematical approach for the turbulence modelling:
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- Reynolds-averaged Navier-Stokes simulation (RANS)
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- Turbulence closure model:
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- kEpsilon and kOmegaSST linear eddy viscosity closure models
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- The sets of input (HW:Table 1):
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- Reference height, Zref = 6 [m]
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- Aerodynamic roughness height, z0 = 0.01 [m]
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- Displacement height, d = 0 [m]
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- Reference mean wind speed, Uref = 10 [m/s]
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## Computational domain modelling:
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- Rectangular prism
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- (x1, x2, x3) = (5000, 100, 500) [m] = (streamwise, spanwise, ground-normal) directions
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## Computational domain discretisation:
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- Spatial resolution:
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- (x1, x2, x3) = (500, 5, 50) [cells]
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- Refer to the `system/blockMeshDict` for the grading details
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- Temporal resolution: Steady state
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## Equation discretisation:
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- Spatial derivatives and variables:
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- Convection: Second order
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- Others: Second order with various limiters
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- Temporal derivatives and variables: First order
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## Numerical boundary/initial conditions:
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- Refer to `0.orig`
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## Pressure-velocity coupling algorithm:
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- SIMPLEC
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## Linear solvers:
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- Refer to `system/fvSolution`
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## Initialisation and sampling:
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- No initialisation/averaging
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- Sampling at the end of the simulation via `system/sampleDict`
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- Refer to `system/controlDict` for further details
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