tdynreference manual
Materials are groups of physical properties and other data that identify a material, a fluid or a solid to be used in the analysis.
For any problem that needs definition of materials, there is a database of existing materials that can be assigned to entities. The user can also create new materials derived from the existing ones and assign them as well.
To create a new Material, press the New Material button in the in the Material window, write a new name and change some of its properties. By pressing Accept, a new Material is created taking an existing one as a base Material, which means that the new Material will have the same fields as the base one. All new values for the fields can be entered when defining the new material. It is also possible to redefine existing Materials by entering new values directly in the fields.
Remarks:
If a mesh has already been generated, it is necessary to mesh again or assign the Materials directly to the mesh, when changing assigned materials.
In this section only the main Materials will be presented. Therefore, Materials with different names can be found in the Materials database. Anyhow, all these Materials will be based on (i.e. they will have the same properties fields) the ones shown here.
Fluid Materials are groups of physical properties and other data that can be assigned to surfaces (2D) or volumes (3D). This set of physical properties corresponds to a fluid to be analysed.
Density: Density of the fluid. It may be a constant or a function (result must be greater than zero). See Function Syntax section for further information.
Density Units: Units of the density, defined in the previous field.
Viscosity: Viscosity of the fluid. May be a constant or a function. See Function Syntax section for further information.
Viscosity Units: Units of the viscosity, defined in the previous field.
VelX Field: Initial and reference OX velocity field. May be a constant or a function. See Function Syntax section for further information.
Remarks:
If any Velocity Field condition has been assigned to any entity within this material, this field will be used as base to calculate the boundary condition. If the corresponding Fix Initial X field has been marked, the OX component of the velocity will be fixed to the initial value (evaluated in t = 0) of the function inserted here.
If the corresponding Fix Field X field has been marked, the OX component of the velocity will be fixed to the value (for every time step) of the function inserted here. It is possible to define transient boundary conditions for the velocity this way.
VelY Field: Initial and reference OY velocity field. May be a constant or a function. See Function Syntax section for further information.
Remarks:
If any Velocity Field condition has been assigned to any entity within this material, this field will be used as a base to calculate the boundary condition. If the corresponding Fix Initial Y field has been marked, the OY component of the velocity will be fixed to the initial value (evaluated in t = 0) of the function inserted here.
If the corresponding Fix Field Y field has been marked, the OY component of the velocity will be fixed to the value (for every time step) of the function inserted here. It is possible to define transient boundary conditions for the velocity this way.
VelZ Field: Initial and reference OZ velocity field may be a constant or a function. See Function Syntax section for further information.
Remarks:
This field is only available in 3D.
If any Velocity Field condition has been assigned to any entity within this material, this field will be used as a base to calculate the boundary condition. If the corresponding Fix Initial Z field has been marked, the OZ component of the velocity will be fixed to the initial value (evaluated in t = 0) of the function inserted here.
If the corresponding Fix Field Z field has been marked, the OZ component of the velocity will be fixed to the value (for every time step) of the function. It is possible to define transient boundary conditions for the velocity this way.
Pres Field: Initial and reference dynamic pressure field. May be a constant or a function. See Function Syntax section for further information.
Remarks:
If any Pressure Field condition has been assigned to any entity within this material, this field will be used as a base to calculate the boundary condition. If the Fix Initial field has been marked, the pressure will be fixed to the initial value (evaluated in t = 0) of the function inserted here.
If the corresponding Fix Field has been marked, the pressure will be fixed to the value (for every time step) of the function inserted here. It is possible to define transient boundary conditions for the pressure this way.
Kenr Field: Initial field of the eddy kinetic energy (kinetic energy of the fluctuating component of the velocity). In some cases may be useful to define this field as a function of the so called Turbulence Intensity Level or TIL, defined by the relation k = TIL·V2, being k, the eddy kinetic energy and V the velocity field. May be a constant or a function. See Function Syntax section for further information.
In external flows over airfoils the turbulence level is typically TIL = 0.003 (0.3%). In atmospheric boundary layer flows the level can be two orders of magnitude higher (TIL = 0.30) and details of the actual boundary layer profiles are needed. In internal flows the turbulence level of TIL = 0.05 to 0.10 (5 to 10%) is usually appropriate.
Remarks:
If any Fix Turbulence condition has been assigned to any entity within this material, this field will be used as a base to calculate the boundary condition. Turbulence will then be fixed to the initial value (evaluated in t = 0) of the function inserted here.
ELen Field: Initial and reference field of the turbulence length scale (L) field, defined by the relation μT = ρ·k½·L, being k, the eddy kinetic energy, μT the eddy viscosity and ρ the density field. May be a constant or a function. See Function Syntax section for further information.
For external flows remote from boundary layers, a value determined by the assumption that the ratio of turbulent and molecular viscosity μT/μ is between 1 and 10 is a reasonable guess. Taking into account the above definitions:
Where * indicates the prescribed parameter.
For internal flows, a constant value of length scale, derived from a characteristic geometrical feature can be used (e.g. 1 to 10% of the hydraulic diameter for internal flows).
Other possibility is to calculate L from the recommended values for the initial variables of the turbulence model to be used, as shown next (note that next relations are not definitions):
where V and LD are the characteristics velocity and length of the problem.
Remarks:
If any Fix Turbulence condition has been assigned to any entity within this material, this field will be used as a base to calculate the boundaries condition for the turbulence. Turbulence will be then fixed to the initial value (evaluated in t = 0) of the function inserted here.
AccOX Field: External acceleration (not gravity) acting on fluid (OX component). May be a constant or a function. See Function Syntax section for further information.
This field will be added to the OX component of the gravity, as an additional acceleration.
Remarks:
It is recommended to insert functions with a smoothed start up for this additional acceleration. Otherwise it can create oscillations in the solution.
AccOY Field: External acceleration (not gravity) acting on fluid (OY component). May be a constant or a function. See Function Syntax section for further information.
This field will be added to the OY component of the gravity, as an additional acceleration.
Remarks:
It is recommended to insert functions with a smoothed start up for this additional acceleration. Otherwise it can create oscillations in the solution.
AccOZ Field: External acceleration (not gravity) acting on fluid (OZ component). May be a constant or a function. See Function Syntax section for further information.
This field will be added to the gravity, as an additional acceleration.
Remarks:
It is recommended to insert functions with a smoothed start up for this additional acceleration. Otherwise it can create oscillations in the solution.
This option is only available in Tdyn3D.
Specific Heat Cp: Specific heat (Cp) of the fluid. It may be a constant or a function (result must be greater than zero). See Function Syntax section for further information.
Cp Units: Units of the specific heat (Cp) inserted in the previous field.
Thermal Conduction k: Thermal conduction (k) of the fluid. It may be a constant or a function (result must be greater than zero). See Function Syntax section for further information.
k Units: Units of the thermal conduction (k) inserted in the previous field.
Volume Expansion B: Volume expansion coefficient (B) of a fluid. May be a constant or a function. See Function Syntax section for further information. This property controls the bouyancy effect due to the variations of temperature in the fluid. This effect is taking into account by a variation of density of the fluid proportional to the temperature (r = ro·B·T).
B Units: Units of the volume expansion coefficient (B) inserted in the previous field.
Heat Source G: Volumetric heat source (G) in the fluid. May be a constant or a function. See Function Syntax section for further information.
G Units: Units of the heat source (G) inserted in the previous field.
Temp Field: Initial and reference temperature field. May be a constant or a function. See Function Syntax section for further information.
Remarks:
If any Temperature Field condition has been assigned to any entity within this material, this field will be used as a base to calculate boundary conditions. If the corresponding Fix Initial field has been marked, the temperature will be fixed to the initial value (evaluated in t = 0) of the function inserted here.
If the corresponding Fix Field has been marked, the temperature will be fixed to the value (for every time step) of the function inserted here. It is possible to define transient boundary conditions for the temperature this way.
Concentration Properties: This special field allows definitions of characteristics of different species. The necessary data is introduced in a matrix (see Figure 4) where the i-th row contains the properties of the i-th species.
Figure 4. Matrix defining
the characteristics of the |
The columns of the matrix may be used to insert the different properties.
Total D: Total diffusion (D) of species. Please note that this value must include the turbulent and physical diffusion of species. It must be a constant physical property of this specie in this fluid.
Source F: Concentration source of the specie, given in the units specified in the field D Units.
Decant T: Decantation constant. This property controls the decantation effect or relative movement of species respectively to the fluid in the advection process. This process happens due to the action of a gravity force on variations of a concentration of species in this fluid. It must be a constant property of this species in this fluid. Tdyn takes this effect into account by means of an additional velocity, proportional to the concentration of the species and the gravity.
Decantation effect is only produced in the OY direction in Tdyn2D or in the OZ direction in Tdyn3D. Note that this effect must be very small in order to preserve the stability of the algorithm.
Initial I: Initial (constant) value of the concentration of species.
Remarks:
The index of the row (from 1 to n) is used as a label or an identifier of species for conditions assignment.
Please note that the same species can be defined in several fluids. In this case the same row index of the matrix is referred to the same species.
D Units: Units of species diffusion inserted in the field Total D.
F Units: Units of sources of species concentration inserted in the field Source F.
Solid Materials are groups of physical properties and other data, that can be assigned to surfaces (2D) or a volumes (3D). This set of physical properties corresponds to an analysed solid.
Density: Density of the fluid. It may be a constant or a function (result must be greater than zero). See Function Syntax section for further information.
Density Units: Units of the density, defined in the previous field.
Specific Heat C: Specific heat (C) of the solid. It may be a constant or a function (result must be greater than zero). See Function Syntax section for further information.
C Units: Units of the specific heat (C) inserted in the previous field.
Thermal Conduction k11: k11 component of the thermal conduction (k) tensor. The thermal conduction tensor must be a constant physical property of the solid.
Thermal Conduction k12: k12 qnd k21 components of the thermal conduction (k) tensor. The thermal conduction tensor must be a constant physical property of the solid.
Thermal Conduction k13: k13 and k31 components of the thermal conduction (k) tensor. The thermal conduction tensor must be a constant physical property of the solid.
Remarks:
This field is only available in 3D.
Thermal Conduction k22: k22 component of the thermal conduction (k) tensor. The thermal conduction tensor must be a constant physical property of the solid.
Thermal Conduction k23: k23 and k32 components of the thermal conduction (k) tensor. The thermal conduction tensor must be a constant physical property of the solid.
Remarks:
This field is only available in 3D.
Thermal Conduction k33: k33 component of the thermal conduction (k) tensor. The thermal conduction tensor must be a constant physical property of the solid.
Remarks:
This field is only available in 3D.
k Units: Units of the thermal conduction (k) tensor inserted in the previous field.
Heat Source G: Volumetric heat source (G) in the solid. May be a constant or a function. See Function Syntax section for further information.
G Units: Units of the volumetric heat source (G) inserted in the previous field.
Temp Field: Initial and reference temperature field. May be a constant or a function. See Function Syntax section for further information.
Remarks:
If any Temperature Field condition has been assigned to any entity within this material, this field will be used as a base to calculate the boundary condition. If the corresponding Fix Initial field has been marked, the temperature will be fixed to the initial value (evaluated in t = 0) of the function inserted here.
If the corresponding Fix Field has been marked, the temperature will be fixed to the value (for every time step) of the function inserted here. It is possible to define transient boundary conditions for the temperature this way.