Base class to set log-law type ground-normal inlet boundary conditions for wind velocity and turbulence quantities for homogeneous, two-dimensional, dry-air, equilibrium and neutral atmospheric boundary layer (ABL) modelling. More...

Inheritance diagram for atmBoundaryLayer:

[legend]

Public Member Functions
	atmBoundaryLayer (const Time &time, const polyPatch &pp)

	atmBoundaryLayer (const Time &time, const polyPatch &pp, const dictionary &dict)

	atmBoundaryLayer (const atmBoundaryLayer &abl, const fvPatch &patch, const fvPatchFieldMapper &mapper)

	atmBoundaryLayer (const atmBoundaryLayer &)

vector	flowDir () const

vector	zDir () const

tmp< scalarField >	Ustar (const scalarField &z0) const

void	autoMap (const fvPatchFieldMapper &)

void	rmap (const atmBoundaryLayer &, const labelList &)

tmp< vectorField >	U (const vectorField &pCf) const

tmp< scalarField >	k (const vectorField &pCf) const

tmp< scalarField >	epsilon (const vectorField &pCf) const

tmp< scalarField >	omega (const vectorField &pCf) const

void	write (Ostream &) const

Protected Attributes
bool	initABL_

Detailed Description

Base class to set log-law type ground-normal inlet boundary conditions for wind velocity and turbulence quantities for homogeneous, two-dimensional, dry-air, equilibrium and neutral atmospheric boundary layer (ABL) modelling.

The ground-normal profile expressions are due to YGCJ (refer to references below) whereat RH expressions were generalised:

$u = \frac{u^*}{\kappa} \ln \left( \frac{z - d + z_0}{z_0} \right)$

$v = w = 0$

$k = \frac{(u^*)^2}{\sqrt{C_\mu}} \sqrt{C_1 \ln \left( \frac{z - d + z_0}{z_0} \right) + C_2}$

$\epsilon = \frac{(u^*)^3}{\kappa (z - d + z_0)} \sqrt{C_1 \ln \left( \frac{z - d + z_0}{z_0} \right) + C_2}$

$\omega = \frac{u^*}{\kappa \sqrt{C_\mu}} \frac{1}{z - d + z_0}$

$u^* = \frac{u_{ref} \kappa}{\ln\left(\frac{z_{ref} + z_0}{z_0}\right)}$

where

	=	Ground-normal streamwise flow speed profile [m/s]
	=	Spanwise flow speed [m/s]
	=	Ground-normal flow speed [m/s]
	=	Ground-normal turbulent kinetic energy (TKE) profile [m^2/s^2]
$\epsilon$	=	Ground-normal TKE dissipation rate profile [m^2/s^3]
$\omega$	=	Ground-normal specific dissipation rate profile [m^2/s^3]
	=	Friction velocity [m/s]
$\kappa$	=	von Kármán constant [-]
$C_\mu$	=	Empirical model constant [-]
	=	Ground-normal coordinate component [m]
	=	Ground-normal displacement height [m]
	=	Aerodynamic roughness length [m]
$u_{ref}$	=	Reference mean streamwise wind speed at $z_{ref}$ [m/s]
$z_{ref}$	=	Reference height being used in estimations [m]
	=	Curve-fitting coefficient for `YGCJ` profiles [-]
	=	Curve-fitting coefficient for `YGCJ` profiles [-]

Reference:

        The ground-normal profile expressions (tag:RH):
            Richards, P. J., & Hoxey, R. P. (1993).
            Appropriate boundary conditions for computational wind
            engineering models using the k-ε turbulence model.
            In Computational Wind Engineering 1 (pp. 145-153).
            DOI:10.1016/B978-0-444-81688-7.50018-8

        Modifications to preserve the profiles downstream (tag:HW):
            Hargreaves, D. M., & Wright, N. G. (2007).
            On the use of the k–ε model in commercial CFD software
            to model the neutral atmospheric boundary layer.
            Journal of wind engineering and
            industrial aerodynamics, 95(5), 355-369.
            DOI:10.1016/j.jweia.2006.08.002

        Expression generalisations to allow height
        variation for turbulence quantities (tag:YGCJ):
            Yang, Y., Gu, M., Chen, S., & Jin, X. (2009).
            New inflow boundary conditions for modelling the neutral equilibrium
            atmospheric boundary layer in computational wind engineering.
            J. of Wind Engineering and Industrial Aerodynamics, 97(2), 88-95.
            DOI:10.1016/j.jweia.2008.12.001

        The generalised ground-normal profile expression for omega (tag:YGJ):
            Yang, Y., Gu, M., & Jin, X., (2009).
            New inflow boundary conditions for modelling the
            neutral equilibrium atmospheric boundary layer in SST k-ω model.
            In: The Seventh Asia-Pacific Conference on Wind Engineering,
            November 8-12, Taipei, Taiwan.

        Theoretical remarks (tag:E):
            Emeis, S. (2013).
            Wind Energy Meteorology: Atmospheric
            Physics for Wind Power Generation.
            Springer-Verlag Berlin Heidelberg.
            DOI:10.1007/978-3-642-30523-8

Usage

Example of the entries provided for the inherited boundary conditions:

inlet
{
    // Mandatory and other optional entries
    ...

    // Mandatory (inherited) entries (runtime modifiable)
    flowDir         (1 0 0);
    zDir            (0 0 1);
    Uref            10.0;
    Zref            0.0;
    z0              uniform 0.1;
    d               uniform 0.0;

    // Optional (inherited) entries (unmodifiable)
    kappa           0.41;
    Cmu             0.09;
    initABL         true;
    phi             phi;
    C1              0.0;
    C2              1.0;

    // Conditional mandatory (inherited) entries (runtime modifiable)
    value           uniform 0;    // when initABL=false
}

where the entries mean:

Property	Description	Type	Reqd	Deflt
`flowDir`	Flow direction	Function1<vector>	yes	-
`zDir`	Ground-normal direction	Function1<vector>	yes	-
`Uref`	Reference mean streamwise flow speed being used in estimations [m/s]	Function1<scalar>	yes	-
`Zref`	Reference height being used in estimations [m]	Function1<scalar>	yes	-
`z0`	Surface roughness length [m]	PatchFunction1<scalar>	yes	-
`d`	Displacement height [m] - see Notes	PatchFunction1<scalar>	yes	-
`kappa`	von Kármán constant	scalar	no	0.41
`Cmu`	Empirical model constant	scalar	no	0.09
`initABL`	Flag to initialise profiles with the theoretical ABL expressions, otherwise use "value" list	bool	no	true
`value`	ABL profile content when initABL=false	scalarList	conditional	-
`phi`	Name of the flux field	word	no	phi
`C1`	Curve-fitting coefficient `YGCJ` profiles	scalar	no	0.0
`C2`	Curve-fitting coefficient `YGCJ` profiles	scalar	no	1.0

Note

The RH expressions are special cases of those in YGCJ when C1=0 and C2=1. Both C1 and C2 can be determined by nonlinear fitting of (YGCJ:Eqs. 19-20) with an experimental dataset for k. By default, atmBoundaryLayerInlet boundary conditions compute RH expressions.
z is the ground-normal height relative to the global minimum height of the inlet patch; therefore, the minimum of z is always zero irrespective of the absolute z-coordinate of the computational patch.
The derived ABL expressions automatically satisfy the simplified transport equation for k. Yet the same expressions only satisfy the simplified transport equation for epsilon when the model constants sigmaEpsilon is 1.11 with kappa=0.4 (HW:p. 358).
atmBoundaryLayerInlet boundary conditions inherit inletOutlet traits, so that a given inlet condition can be supplied from all sides of the domain, e.g. a ground-normal cylinder domain having a single inlet/outlet boundary where the changes between inlet and outlet depend on the wind direction and patch normals, so that any change in inflow orientation can be handled with the same mesh.
d is the displacement height, and "is relevant for flows over forests and cities" (E:p. 28). "The displacement height gives the vertical displacement of the entire flow regime over areas which are densely covered with obstacles such as trees or buildings" (E:p. 28).