The patch field 'autoMap' and 'rmap' functions have been replaced with a
single 'map' function that can used to do any form of in-place
patch-to-patch mapping. The exact form of mapping is now controlled
entirely by the mapper object.
An example 'map' function is shown below:
void nutkRoughWallFunctionFvPatchScalarField::map
(
const fvPatchScalarField& ptf,
const fvPatchFieldMapper& mapper
)
{
nutkWallFunctionFvPatchScalarField::map(ptf, mapper);
const nutkRoughWallFunctionFvPatchScalarField& nrwfpsf =
refCast<const nutkRoughWallFunctionFvPatchScalarField>(ptf);
mapper(Ks_, nrwfpsf.Ks_);
mapper(Cs_, nrwfpsf.Cs_);
}
This single function replaces these two previous functions:
void nutkRoughWallFunctionFvPatchScalarField::autoMap
(
const fvPatchFieldMapper& m
)
{
nutkWallFunctionFvPatchScalarField::autoMap(m);
m(Ks_, Ks_);
m(Cs_, Cs_);
}
void nutkRoughWallFunctionFvPatchScalarField::rmap
(
const fvPatchScalarField& ptf,
const labelList& addr
)
{
nutkWallFunctionFvPatchScalarField::rmap(ptf, addr);
const nutkRoughWallFunctionFvPatchScalarField& nrwfpsf =
refCast<const nutkRoughWallFunctionFvPatchScalarField>(ptf);
Ks_.rmap(nrwfpsf.Ks_, addr);
Cs_.rmap(nrwfpsf.Cs_, addr);
}
Calls to 'autoMap' should be replaced with calls to 'map' with the same
mapper object and the patch field itself provided as the source. Calls
to 'rmap' should be replaced with calls to 'map' by wrapping the
addressing in a 'reverseFvPatchFieldMapper' (or
'reversePointPatchFieldMapper') object.
This change simplifies the creation of new patch fields and hence
improves extensibility. It also provides more options regarding general
mapping strategies between patches. Previously, general abstracted
mapping was only possible in 'autoMap'; i.e., from a patch to itself.
Now, general mapping is possible between different patches.
It is now possible to map from one field to another within the same
patch, using the mappedValue boundary condition. The restriction is that
the mapping must be from a different field, otherwise field values are
being assigned to themselves, which produces an undefined result.
The mappedValue boundary condition can now be used in place of the
copiedFixedValue condition in the multiphaseEuler module. The
copiedFixedValue condition has therefore been removed.
In addition, the error messages that result from casting a patch to its
mapping engine (mappedPatchBase) have been standardised, and made more
specific to the situation in which the mapping is applied. It may be
inappropriate, for example, to map within the same region or patch.
These cases are now identified and appropriate error messages are
generated.
The error messages have also been made IO errors, so they now provide
context with regards to the dictionary entries that they relate to.
The fieldAverage can now average fields that do not exist at
construction time, and it also supports restart on cases in which
the mesh topology is changing.
The timeName() function simply returns the dimensionedScalar::name() which holds
the user-time name of the current time and now that timeName() is no longer
virtual the dimensionedScalar::name() can be called directly. The timeName()
function implementation is maintained for backward-compatibility.
Class
Foam::noSlipFvPatchVectorField
Description
This boundary condition fixes the velocity to zero at walls and assumes
the walls are stationary.
For stationary walls with sliding vertices, e.g. engine liners, the normal
component of the velocity is set from the wall face-flux to ensure
continuity.
Usage
Example of the boundary condition specification:
\verbatim
<patchName>
{
type noSlip;
}
\endverbatim
The basic thermophysical properties are now considered fundamental and complex
models like kineticTheoryModel using these names for some other purpose must
disambiguate using typedName to prepend the model name to the field name.
This change standardises, rationalises and simplifies the specification of
fvSchemes and boundary conditions.
thermo:rho will also be renamed rho in a subsequent commit to complete this
rationalisation.
so that derived classes can call the dictionary constructor without reading the
refValue, refGradient or valueFraction entries. This ensures that the
fvPatchField dictionary constructor is called, setting optional entries like
'libs' as required.
so that it can now be used with either the isothermalFluid or fluid solver
modules, thus supporting non-uniform fluid properties, compressibility and
thermal effect. This development makes the special potentialFreeSurfaceFoam
solver redundant as both the isothermalFluid and fluid solver modules are more
general and has been removed and replaced with a user redirection script.
The tutorials/multiphase/potentialFreeSurfaceFoam cases have been updated to run
with the isothermalFluid solver module:
tutorials/multiphase/potentialFreeSurfaceFoam/oscillatingBox
tutorials/multiphase/potentialFreeSurfaceFoam/movingOscillatingBox
which demonstrate how to upgrade potentialFreeSurfaceFoam cases to
isothermalFluid.
The mappedPatchBase has been separated into a type which maps from
another patch (still called mappedPatchBase) and one that maps from
internal cell values (mappedInternalPatchBase). This prevents the user
needing to specify settings for mapping procedures that are not being
used, and potentially don't even make sense given the context in which
they are being applied. It also removes a lot of fragile logic and error
states in the mapping engine and its derivatives regarding the mode of
operation. Mapping from any face in the boundary is no longer supported.
Most region-coupling mapping patches are generated automatically by
utilities like splitMeshRegions and extrudeToRegionMesh. Cases which
create region-coupling mapped patches in this way will likely require no
modification.
Explicitly user-specified mapping will need modifying, however. For
example, where an inlet boundary is mapped to a downstream position in
order to evolve a developed profile. Or if a multi-region simulation is
constructed manually, without using one of the region-generating
utilities.
The available mapped patch types are now as follows:
- mapped: Maps values from one patch to another. Typically used for
inlets and outlets; to map values from an outlet patch to an inlet
patch in order to evolve a developed inlet profile, or to permit
flow between regions. Example specification in blockMesh:
inlet
{
type mapped;
neighbourRegion region0; // Optional. Defaults to the same
// region as the patch.
neighbourPatch outlet;
faces ( ... );
}
Note that any transformation between the patches is now determined
automatically. Alternatively, it can be explicitly specified using
the same syntax as for cyclic patches. The "offset" and "distance"
keywords are no longer used.
- mappedWall: As mapped, but treated as a wall for the purposes of
modelling (wall distance). No transformation. Typically used for
thermally coupling different regions. Usually created automatically
by meshing utilities. Example:
fluid_to_solid
{
type mappedWall;
neighbourRegion solid;
neighbourPatch solid_to_fluid;
method intersection; // The patchToPatch method. See
// below.
faces ( ... );
}
- mappedExtrudedWall: As mapped wall, but with corrections to account
for the thickness of an extruded mesh. Used for region coupling
involving film and thermal baffle models. Almost always generated
automatically by extrudeToRegionMesh (so no example given).
- mappedInternal: Map values from internal cells to a patch. Typically
used for inlets; to map values from internal cells to the inlet in
order to evolve a developed inlet profile. Example:
inlet
{
type mappedInternal;
distance 0.05; // Normal distance from the patch
// from which to map cell values
//offset (0.05 0 0); // Offset from the patch from
// which to map cell values
faces ( ... );
}
Note that an "offsetMode" entry is no longer necessary. The mode
will be inferred from the presence of the distance or offset
entries. If both are provided, then offsetMode will also be required
to choose which setting applies.
The mapped, mappedWall and mappedExtrudedWall patches now permit
specification of a "method". This selects a patchToPatch object and
therefore determines how values are transferred or interpolated between
the patches. Valid options are:
- nearest: Copy the value from the nearest face in the neighbouring
patch.
- matching: As nearest, but with checking to make sure that the
mapping is one-to-one. This is appropriate for patches that are
identically meshed.
- inverseDistance: Inverse distance weighting from a small stencil of
nearby faces in the neighbouring patch.
- intersection: Weighting based on the overlapping areas with faces in
the neighbouring patch. Equivalent to the previous AMI-based mapping
mode.
If a method is not specfied, then the pre-existing approach will apply.
This should be equivalent to the "nearest" method (though in most such
cases, "matching" is probably more appropriate). This fallback may be
removed in the future once the patchToPatch methods have been proven
robust.
The important mapped boundary conditions are now as follows:
- mappedValue: Maps values from one patch to another, and optionally
modify the mapped values to recover a specified average. Example:
inlet
{
type mappedValue;
field U; // Optional. Defaults to the same
// as this field.
average (10 0 0); // The presence of this entry now
// enables setting of the average,
// so "setAverage" is not needed
value uniform 0.1;
}
- mappedInternalValue: Map values from cells to a patch, and
optionally specify the average as in mappedValue. Example:
inlet
{
type mappedValue;
field k; // Optional. Defaults to the same
// as this field.
interpolationScheme cell;
value uniform 0.1;
}
- mappedFlowRateVelocity: Maps the flow rate from one patch to
another, and use this to set a patch-normal velocity. Example:
inlet
{
type mappedFlowRate;
value uniform (0 0 0);
}
Of these, mappedValue and mappedInternalValue can override the
underlying mapped patch's settings by additionally specifying mapping
information (i.e., the neighbourPatch, offset, etc... settings usually
supplied for the patch). This also means these boundary condtions can be
applied to non-mapped patches. This functionality used to be provided
with a separate "mappedField" boundary condition, which has been removed
as it is no longer necessary.
Other mapped boundary conditions are either extremely niche (e.g.,
mappedVelocityFlux), are always automatically generated (e.g.,
mappedValueAndPatchInternalValue), or their usage has not changed (e.g.,
compressible::turbulentTemperatureCoupledBaffleMixed and
compressible::turbulentTemperatureRadCoupledMixed). Use foamInfo to
obtain further details about these conditions.
Mapping with interpolation now behaves correctly when a single cell maps
to multiple faces. In addition, the mapping structure is more compact
and no longer results in copies being made of entire internal fields.
This has been achieved by rewriting the mapping strategy in
mappedPatchBase so that it maps from a reduced set of sampling locations
to the patch faces, rather than directly from the cells/faces to the
patch faces. This is more efficient, but it also permits multiple
sampling locations to be sent to a single cell/face. Values can then be
interpolated to these points before being sent back to the patch faces.
Previously a single cell/face could only be sent a single location onto
which to interpolate; typically that of the first associated patch face.
The resulting interpolated value was then sent back to all associated
patch faces. This meant that some (potentially most) patch faces did
receive a value interpolated to the correct position.
Description
User convenience class to handle the input of time-varying rotational speed
in rad/s if \c omega is specified or rpm if \c rpm is specified.
Usage
For specifying the rotational speed in rpm of an MRF zone:
\verbatim
MRF
{
cellZone rotor;
origin (0 0 0);
axis (0 0 1);
rpm 60;
}
\endverbatim
or the equivalent specified in rad/s:
\verbatim
MRF
{
cellZone rotor;
origin (0 0 0);
axis (0 0 1);
rpm 6.28319;
}
\endverbatim
or for a tabulated ramped rotational speed of a solid body:
\verbatim
mover
{
type motionSolver;
libs ("libfvMeshMovers.so" "libfvMotionSolvers.so");
motionSolver solidBody;
cellZone innerCylinder;
solidBodyMotionFunction rotatingMotion;
origin (0 0 0);
axis (0 1 0);
rpm table
(
(0 0)
(0.01 6000)
(0.022 6000)
(0.03 4000)
(100 4000)
);
}
\endverbatim
The following classes have been updated to use the new Function1s::omega class:
solidBodyMotionFunctions::rotatingMotion
MRFZone
rotatingPressureInletOutletVelocityFvPatchVectorField
rotatingTotalPressureFvPatchScalarField
rotatingWallVelocityFvPatchVectorField
and all tutorials using these models and BCs updated to use rpm where appropriate.
Field settings can now be specified within
createNonConformalCouplesDict. This allows for patchType overrides; for
example to create a jump condition over the coupling.
An alternate syntax has been added to facilitate this. If patch fields
do not need overriding then the old syntax can be used where patches
that are to be coupled are specified as a pair of names; e.g.:
fields yes;
nonConformalCouples
{
fan
{
patches (fan0 fan1);
transform none;
}
}
If patch fields do need overriding, then instead of the "patches" entry,
separate "owner" and "neighbour" sub-dictionaries should be used. These
can both contain a "patchFields" section detailing the boundary
conditions that apply to the newly created patches:
fields yes;
nonConformalCouples
{
fan
{
owner
{
patch fan0;
patchFields
{
p
{
type fanPressureJump;
patchType nonConformalCyclic;
jump uniform 0;
value uniform 0;
jumpTable polynomial 1((100 0));
}
}
}
neighbour
{
patch fan1;
patchFields
{
$../../owner/patchFields;
}
}
transform none;
}
}
In this example, only the pressure boundary condition is overridden on
the newly created non-conformal cyclic. All other fields will have the
basic constraint type (i.e., nonConformalCyclic) applied.
If the sequence of meshes are decomposed independently the number, order and
potentially type of processor patches is likely to change. Thus the processor
patches and patch fields must be replaced with those of the new mesh.
Mb, the Mach number at which blending to zeroGradient starts, can now be
specified in the input:
Description
This boundary condition provides an entrainment condition for pressure
including support for supersonic jets exiting the domain.
Usage
\table
Property | Description | Required | Default value
rho | Density field name | no | rho
psi | Compressibility field name | no | thermo:psi
gamma | Heat capacity ratio (cp/Cv) | yes |
Mb | Blending Mach No | no | 0.5
phi | Flux field name | no | phi
p0 | Reference pressure | yes |
\endtable
Example of the boundary condition specification:
\verbatim
<patchName>
{
type transonicEntrainmentPressure;
gamma 1.4;
Mb 0.3;
p0 uniform 1e5;
}
\endverbatim
The functionality provided by 'cyclicACMI' and 'cyclicRepeatAMI' has
been entirely superseded by non-conformal coupled (NCC). All references
to 'cyclicACMI' and 'cyclicRepeatAMI' have therefore been removed.
See previous commits 569fa31d and 420866cf for more explanation,
instructions on updating, and relevant tutorial cases.
This major development provides coupling of patches which are
non-conformal, i.e. where the faces of one patch do not match the faces
of the other. The coupling is fully conservative and second order
accurate in space, unlike the Arbitrary Mesh Interface (AMI) and
associated ACMI and Repeat AMI methods which NCC replaces.
Description:
A non-conformal couple is a connection between a pair of boundary
patches formed by projecting one patch onto the other in a way that
fills the space between them. The intersection between the projected
surface and patch forms new faces that are incorporated into the finite
volume mesh. These new faces are created identically on both sides of
the couple, and therefore become equivalent to internal faces within the
mesh. The affected cells remain closed, meaning that the area vectors
sum to zero for all the faces of each cell. Consequently, the main
benefits of the finite volume method, i.e. conservation and accuracy,
are not undermined by the coupling.
A couple connects parts of mesh that are otherwise disconnected and can
be used in the following ways:
+ to simulate rotating geometries, e.g. a propeller or stirrer, in which
a part of the mesh rotates with the geometry and connects to a
surrounding mesh which is not moving;
+ to connect meshes that are generated separately, which do not conform
at their boundaries;
+ to connect patches which only partially overlap, in which the
non-overlapped section forms another boundary, e.g. a wall;
+ to simulate a case with a geometry which is periodically repeating by
creating multiple couples with different transformations between
patches.
The capability for simulating partial overlaps replaces the ACMI
functionality, currently provided by the 'cyclicACMI' patch type, and
which is unreliable unless the couple is perfectly flat. The capability
for simulating periodically repeating geometry replaces the Repeat AMI
functionality currently provided by the 'cyclicRepeatAMI' patch type.
Usage:
The process of meshing for NCC is very similar to existing processes for
meshing for AMI. Typically, a mesh is generated with an identifiable set
of internal faces which coincide with the surface through which the mesh
will be coupled. These faces are then duplicated by running the
'createBaffles' utility to create two boundary patches. The points are
then split using 'splitBaffles' in order to permit independent motion of
the patches.
In AMI, these patches are assigned the 'cyclicAMI' patch type, which
couples them using AMI interpolation methods.
With NCC, the patches remain non-coupled, e.g. a 'wall' type. Coupling
is instead achieved by running the new 'createNonConformalCouples'
utility, which creates additional coupled patches of type
'nonConformalCyclic'. These appear in the 'constant/polyMesh/boundary'
file with zero faces; they are populated with faces in the finite volume
mesh during the connection process in NCC.
For a single couple, such as that which separates the rotating and
stationary sections of a mesh, the utility can be called using the
non-coupled patch names as arguments, e.g.
createNonConformalCouples -overwrite rotatingZoneInner rotatingZoneOuter
where 'rotatingZoneInner' and 'rotatingZoneOuter' are the names of the
patches.
For multiple couples, and/or couples with transformations,
'createNonConformalCouples' should be run without arguments. Settings
will then be read from a configuration file named
'system/createNonConformalCouplesDict'. See
'$FOAM_ETC/caseDicts/annotated/createNonConformalCouplesDict' for
examples.
Boundary conditions must be specified for the non-coupled patches. For a
couple where the patches fully overlap, boundary conditions
corresponding to a slip wall are typically applied to fields, i.e
'movingWallSlipVelocity' (or 'slip' if the mesh is stationary) for
velocity U, 'zeroGradient' or 'fixedFluxPressure' for pressure p, and
'zeroGradient' for other fields. For a couple with
partially-overlapping patches, boundary conditions are applied which
physically represent the non-overlapped region, e.g. a no-slip wall.
Boundary conditions also need to be specified for the
'nonConformalCyclic' patches created by 'createNonConformalCouples'. It
is generally recommended that this is done by including the
'$FOAM_ETC/caseDicts/setConstraintTypes' file in the 'boundaryField'
section of each of the field files, e.g.
boundaryField
{
#includeEtc "caseDicts/setConstraintTypes"
inlet
{
...
}
...
}
For moving mesh cases, it may be necessary to correct the mesh fluxes
that are changed as a result of the connection procedure. If the
connected patches do not conform perfectly to the mesh motion, then
failure to correct the fluxes can result in noise in the pressure
solution.
Correction for the mesh fluxes is enabled by the 'correctMeshPhi' switch
in the 'PIMPLE' (or equivalent) section of 'system/fvSolution'. When it
is enabled, solver settings are required for 'MeshPhi'. The solution
just needs to distribute the error enough to dissipate the noise. A
smooth solver with a loose tolerance is typically sufficient, e.g. the
settings in 'system/fvSolution' shown below:
solvers
{
MeshPhi
{
solver smoothSolver;
smoother symGaussSeidel;
tolerance 1e-2;
relTol 0;
}
...
}
PIMPLE
{
correctMeshPhi yes;
...
}
The solution of 'MeshPhi' is an inexpensive computation since it is
applied only to a small subset of the mesh adjacent to the
couple. Conservation is maintained whether or not the mesh flux
correction is enabled, and regardless of the solution tolerance for
'MeshPhi'.
Advantages of NCC:
+ NCC maintains conservation which is required for many numerical
schemes and algorithms to operate effectively, in particular those
designed to maintain boundedness of a solution.
+ Closed-volume systems no longer suffer from accumulation or loss of
mass, poor convergence of the pressure equation, and/or concentration
of error in the reference cell.
+ Partially overlapped simulations are now possible on surfaces that are
not perfectly flat. The projection fills space so no overlaps or
spaces are generated inside contiguously overlapping sections, even if
those sections have sharp angles.
+ The finite volume faces created by NCC have geometrically accurate
centres. This makes the method second order accurate in space.
+ The polyhedral mesh no longer requires duplicate boundary faces to be
generated in order to run a partially overlapped simulation.
+ Lagrangian elements can now transfer across non-conformal couplings in
parallel.
+ Once the intersection has been computed and applied to the finite
volume mesh, it can use standard cyclic or processor cyclic finite
volume boundary conditions, with no need for additional patch types or
matrix interfaces.
+ Parallel communication is done using the standard
processor-patch-field system. This is more efficient than alternative
systems since it has been carefully optimised for use within the
linear solvers.
+ Coupled patches are disconnected prior to mesh motion and topology
change and reconnected afterwards. This simplifies the boundary
condition specification for mesh motion fields.
Resolved Bug Reports:
+ https://bugs.openfoam.org/view.php?id=663
+ https://bugs.openfoam.org/view.php?id=883
+ https://bugs.openfoam.org/view.php?id=887
+ https://bugs.openfoam.org/view.php?id=1337
+ https://bugs.openfoam.org/view.php?id=1388
+ https://bugs.openfoam.org/view.php?id=1422
+ https://bugs.openfoam.org/view.php?id=1829
+ https://bugs.openfoam.org/view.php?id=1841
+ https://bugs.openfoam.org/view.php?id=2274
+ https://bugs.openfoam.org/view.php?id=2561
+ https://bugs.openfoam.org/view.php?id=3817
Deprecation:
NCC replaces the functionality provided by AMI, ACMI and Repeat AMI.
ACMI and Repeat AMI are insufficiently reliable to warrant further
maintenance so are removed in an accompanying commit to OpenFOAM-dev.
AMI is more widely used so will be retained alongside NCC for the next
version release of OpenFOAM and then subsequently removed from
OpenFOAM-dev.
A wall distance computation will not be correct on a disconnected
processor case. This is also more efficient.
Resolves bug report https://bugs.openfoam.org/view.php?id=3833
fvMesh::update() now executes at the beginning of the time-step, before time is
incremented and handles topology change, mesh to mesh mapping and redistribution
without point motion. Following each of these mesh changes fields are mapped
from the previous mesh state to new mesh state in a conservative manner. These
mesh changes not occur at most once per time-step.
fvMesh::move() is executed after time is incremented and handles point motion
mesh morphing during the time-step in an Arbitrary Lagrangian Eulerian approach
requiring the mesh motion flux to match the cell volume change. fvMesh::move()
can be called any number of times during the time-step to allow iterative update
of the coupling between the mesh motion and field solution.
This is a map data structure rather than a class or function which performs the
mapping operation so polyMeshDistributionMap is more logical and comprehensible
than mapDistributePolyMesh.
fvMesh is no longer derived from fvSchemes and fvSolution, these are now
demand-driven and accessed by the member functions schemes() and solution()
respectively. This means that the system/fvSchemes and system/fvSolution files
are no longer required during fvMesh constructions simplifying the mesh
generation and manipulation phase; theses files are read on the first call of
their access functions.
The fvSchemes member function names have also been simplified taking advantage
of the context in which they are called, for example
mesh.ddtScheme(fieldName) -> mesh.schemes().ddt(fieldName)
An optional Function1 can now be supplied to a fixedValueConstraint
which controls what proportion of the constraint is applied. This can be
used to ramp, pulse, or limit the duration of the constraint. For
example, ramping up of the constraint could be specified as follows:
scalarSource
{
type fixedValueConstraint;
selectionMode points;
points ((0 0.1 0));
fieldValues
{
s 1;
}
fraction
{
type ramp;
duration 0.1;
}
}
when evaluating the external total pressure from the static pressure and
tangential velocity. This improves numerical stability and solution smoothness
for compressible cases.
The external pressure p0 is now formally the static pressure in the presence of
tangential flow and the corresponding total pressure is calculated from this
static pressure using the tangential velocity obtained from the
pressureInletOutletVelocity boundary condition if available. In the case that
there is no external tangential flow the external total pressure is equal to the
static pressure p0 as before.
Description
Inflow, outflow and entrainment pressure boundary condition based on a
constant total pressure assumption.
For outflow the patch pressure is set to the external static pressure.
For inflow the patch pressure is evaluated from the patch velocity and the
external total pressure obtained from the external static pressure \c p_0
and external velocity \c U_0 which is looked-up from the the optional \c
tangentialVelocity entry in the \c pressureInletOutletVelocity velocity
boundary condition for the patch if that boundary condition is used,
otherwise \c U_0 is assumed zero and the external total pressure is equal to
the external static pressure.
The patch pressure is evaluated from the external conditions using one of
the following expressions depending on the flow conditions and
specification of compressibility:
1. incompressible subsonic:
\f[
p_p = p_0 + 0.5 |U_0|^2 - 0.5 |U|^2
\f]
where
\vartable
p_p | pressure at patch [m^2/s^2]
p_0 | external static pressure [m^2/s^2]
U | velocity [m/s]
U_0 | external velocity [m/s]
\endvartable
2. compressible subsonic:
\f[
p_p = p_0 + 0.5 \rho |U_0|^2 - 0.5 \rho |U|^2
\f]
where
\vartable
p_p | pressure at patch [Pa]
p_0 | external static pressure [Pa]
\rho | density [kg/m^3]
U | velocity [m/s]
U_0 | external velocity [m/s]
\endvartable
3. compressible transonic (\f$\gamma = 1\f$):
\f[
p_p = \frac{p_0 + 0.5 \rho |U_0|^2}{1 + 0.5 \psi |U|^2}
\f]
where
\vartable
p_p | pressure at patch [Pa]
p_0 | external static pressure [Pa]
\psi | compressibility [m^2/s^2]
\rho | density [kg/m^3]
U | velocity [m/s]
U_0 | external velocity [m/s]
\endvartable
4. compressible supersonic (\f$\gamma > 1\f$):
\f[
p_p = \frac{p_0 + 0.5 \rho |U_0|^2}
{(1 + 0.5 \psi G |U|^2)^{\frac{1}{G}}}
\f]
where
\vartable
p_p | pressure at patch [Pa]
p_0 | external static pressure [Pa]
\psi | compressibility [m^2/s^2]
\rho | density [kg/m^3]
G | coefficient given by \f$\frac{\gamma}{1-\gamma}\f$ []
\gamma | ratio of specific heats (Cp/Cv) []
U | velocity [m/s]
U_0 | external velocity [m/s]
\endvartable
The modes of operation are set by the dimensions of the pressure field
to which this boundary condition is applied, the \c psi entry and the value
of \c gamma:
\table
Mode | dimensions | psi | gamma
incompressible subsonic | p/rho | |
compressible subsonic | p | none |
compressible transonic | p | psi | 1
compressible supersonic | p | psi | > 1
\endtable
Usage
\table
Property | Description | Required | Default value
U | Velocity field name | no | U
phi | Flux field name | no | phi
rho | Density field name | no | rho
psi | Compressibility field name | no | none
gamma | (Cp/Cv) | no | 1
p0 | External pressure | yes |
\endtable
Example of the boundary condition specification:
\verbatim
<patchName>
{
type totalPressure;
p0 uniform 1e5;
}
\endverbatim
