Grille
The Grille boundary condition models the pressure drop caused by having a grille that covers the inlet or outlet.
Parameters
When Inlet is selected as the Flow direction, the Input pressure pinput defines the pressure at the fan inlet.
When Outlet is selected as the Flow direction, the Exit pressure pexit defines the pressure at the fan outlet.
When Include gravity is selected and Use reduced pressure not selected in the interface Physical model section, the Compensate for hydrostatic pressure approximation (named Compensate for hydrostatic pressure for compressible flows) check box is available and selected by default. When it is selected, the hydrostatic pressure is automatically added to the pressure entered in pinput or pexit user input.
When Quadratic loss is selected for the Static pressure curve, the Quadratic loss coefficient qlc should be specified. qlc defines the static pressure curve which is a piecewise quadratic function equal to 0 when the flow rate is < 0, equal to V02qlc when the flow rate is 0. Alternately, when Loss coefficient K is specified for the Static pressure curve, a pressure drop equal to 0.5Kρ(u ⋅ n)2 is prescribed. See Fan for other settings for the Laminar Flow interface. Note that for the Turbulent Flow interfaces, Quadratic loss and Loss coefficient are the only available options for Static pressure curve.
Turbulence Conditions
When Inlet is selected as the Flow direction and the Turbulence model has transport equations for the turbulent kinetic energy, k, and turbulent dissipation rate, ε, specific dissipation rate, ω, or turbulent relative fluctuations, ζ, the Specify turbulent length scale and intensity and Specify turbulence variables options are available for the turbulence conditions on the downstream side of the grille. If Include transition modeling is active for the SST turbulence model, the option to specify Intermittency is also available. Alternatively, the Reference velocity scale can be used to specify default values.
The Grille feature uses the flow rate across the boundary selection. This feature is not designed to be used on disjoint selections. If the model includes several grilles on boundaries that are not connected, it is good practice to use different Grille features with connected boundaries.