29 tháng 4, 2012

Cấu Trúc : Đặt Lực Phân Bố Đều Trên Phân Tử Tại NODE Trong ANSYS

    • Chúng ta cùng tìm hiểu tổng quát  về lực phân bố / áp lực  của các phần tử trong phần mềm tính toán ANSYS
    • Áp Lực Đặt Lên Phần Tử : Lực Phân Bố Đều   
    • đơn vị     [ ( đơn vị lực)/( đơn vị chiều dài phần tử )]
SF, Nlist, Lab, VALUE, VALUE2
Specifies surface loads on nodes.

Nodes defining the surface upon which the load is to be applied. Use the label ALL or P, or a component name. If ALL, all selected nodes [NSEL] are used (default). If P, graphical picking is enabled and all remaining command fields are ignored (valid only in the GUI).
Valid surface load label. Load labels are listed under "Surface Loads" in the input table for each element type in the Element Reference.
Surface Load Label
Label Description
frequency (harmonic analyses only)
heat flux
surface-to-surface radiation
Acoustic fluid
fluid-structure interaction flag
impedance or admittance coefficient
surface normal velocity
Maxwell surface flag or equivalent source surface
free surface flag
exterior Robin radiation boundary flag
Maxwell force flag
magnetic circuit interface
surface charge density
Maxwell force flag
Infinite element
Exterior surface flag for INFIN110 and INFIN111
High-frequency electromagnetic
number 1-50 for a waveguide exterior port
surface shielding properties
Maxwell surface flag of equivalent source surface
surface impedance
Field-surface interface
field-surface interface number
Fluid flow flux
1.      Thermal labels CONV and HFLUX are mutually exclusive.
2.      For an acoustic analysis, apply the fluid-structure interaction flag (Label = FSI) to only the FLUID29, FLUID30, FLUID220, and FLUID221 elements.
3.      For a fluid-solid interaction analysis, apply the field-surface interface flag (Label = FSIN) twice: once for the fluid side (FLUID141 or FLUID142 elements) and once for the solid side.
Surface load value or table name reference for specifying tabular boundary conditions.
If Lab = PRES, VALUE is the real component of the pressure.
If Lab = CONV, VALUE is typically the film coefficient and VALUE2 (below) is typically the bulk temperature. If VALUE = -N, the film coefficient may be a function of temperature and is determined from the HF property table for material N [MP]. The temperature used to evaluate the film coefficient is usually the average between the bulk and wall temperatures, but may be user-defined for some elements.
If Lab = MCI, VALUE indicates current direction (-1; current flow into the element face (IN), +1; current flow out of the element face (OUT). If Lab = RAD, VALUE is surface emissivity.
If Lab = PORT, VALUE is a port number representing a waveguide exterior port. The port number must be an integer between 1 and 50.
If Lab = SHLD, VALUE is surface conductivity for high-frequency electromagnetics and is surface normal velocity for acoustics.
If Lab = IMPD, VALUE is resistance in ohms/square for high-frequency electromagnetics. For acoustics, VALUE is resistance in (N)(s)/m3 if VALUE > 0 and is conductance in mho if VALUE < 0.
If Lab = RDSF, VALUE is the emissivity value; the following conditions apply: If VALUE is between 0 and 1, apply a single value to the surface. If VALUE= -N, the emissivity may be a function of the temperature, and is determined from the EMISS property table for material N (MP). The material N does not need to correlate with the underlying solid thermal elements.
If Lab = FSIN in a Multi-field solver (single or multiple code coupling) analysis, VALUE is the surface interface number. If Lab = FSIN in a unidirectional ANSYS to CFX analysis, VALUE is not used unless the ANSYS analysis is performed using the Multi-field solver.
Second surface load value (if any).
If Lab = PRES, VALUE2 is the imaginary component of the pressure. Imaginary pressures can only be used by SURF153, SURF154 and SURF159, and can only be used for a full harmonic analysis (HROPT,FULL), or by a mode superposition harmonic analysis (HROPT,MSUP) if the mode extraction method is Block Lanczos (MODOPT,LANB), PCG Lanczos (MODOPT,LANPCG), or Supernode (MODOPT,SNODE).
If Lab = CONV, VALUE2 is typically the bulk temperature.
If Lab = RAD, VALUE2 is the ambient temperature.
If Lab = SHLD, VALUE2 is relative permeability (defaults to 1.0) for high-frequency electromagnetics and is the phase angle of the normal surface velocity (defaults to zero) for acoustics.
If Lab = IMPD, VALUE2 is reactance in ohms/square for high-frequency electromagnetics. For acoustics, VALUE2 is reactance in (N)(s)/m3 if VALUE > 0 and is the product of susceptance and angular frequency if VALUE < 0.
If Lab = RDSF, VALUE2 is the enclosure number. Radiation will occur between surfaces flagged with the same enclosure numbers. If the enclosure is open, radiation will also occur to ambient. If VALUE2 is negative radiation direction is reversed and will occur inside the element for the flagged radiation surfaces. Negative value of enclosure number is applicable for FLUID141 and FLUID142 elements, to model radiation occurring between surfaces inside the fluid domain.
If Lab = FSIN in a unidirectional ANSYS to CFX analysis, VALUE2 is the surface interface number (not available from within the GUI).
If Lab = PORT, VALUE2 is not used.
Individual nodes may not be entered for this command. The node list is to identify a surface and the Nlist field must contain a sufficient number of nodes to define an element surface. The loads are internally stored on element faces defined by the specified nodes. All nodes on an element face (including midside nodes, if any) must be specified for the face to be used, and the element must be selected.
If all nodes defining a face are shared by an adjacent face of another selected element, the face is not free and will not have a load applied. If more than one element can share the same nodes (for example, a surface element attached to a solid element), select the desired element type before issuing the SF command. The SF command applies only to area and volume elements.
For shell elements, if the specified nodes include face one (which is usually the bottom face) along with other faces (such as edges), only face one is used. Where faces cannot be uniquely determined from the nodes, or where the face does not fully describe the load application, use the SFE command. A load key of 1 (which is typically the first loading condition on the first face) is used if the face determination is not unique. A uniform load value is applied over the element face.
See the SFBEAM command for applying surface loads to beam elements. See the SFGRAD command for an alternate tapered load capability. See the SFFUN command for applying loads from a node vs. value function. Also see the SFE command for applying tapered loads on individual element faces. Use the SFDELE command to delete loads applied with this command. Use the SFCUM command to accumulate (add) surface loads applied with SF.
Tabular boundary conditions (VALUE = %tabname% and/or VALUE2 = %tabname%) are available for the following surface load labels (Lab) only:  PRES (real and/or imaginary components), CONV (film coefficient and/or bulk temperature) or HFLUX, and RAD (surface emissivity and ambient temperature). Use the *DIM command to define a table.
This command is also valid in PREP7.
Menu Paths
Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Boundary>AppImped_E>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Boundary>AppShield>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Excitation>AppSurfChar>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Excitation>EMPorts>Exterior Port>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Flag>AppInfinite>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Flag>AppMaxwell>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Field Surface Intr>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Fluid/ANSYS>Field Surface>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Fluid/ANSYS>Impedance>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Magnetic>Flag>AppInfinite>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Magnetic>Flag>AppMCI>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Magnetic>Other>AppMaxwell>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Structural>Pressure>On Node Components
Main Menu>Preprocessor>Loads>Define Loads>Apply>Structural>Pressure>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Convection>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Heat Flux>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Radiation>On Nodes
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Surface Rad>On Nodes
Main Menu>Solution>Define Loads>Apply>Electric>Boundary>AppImped_E>On Nodes
Main Menu>Solution>Define Loads>Apply>Electric>Boundary>AppShield>On Nodes
Main Menu>Solution>Define Loads>Apply>Electric>Excitation>AppSurfChar>On Nodes
Main Menu>Solution>Define Loads>Apply>Electric>Excitation>EMPorts>Exterior Port>On Nodes
Main Menu>Solution>Define Loads>Apply>Electric>Flag>AppInfinite>On Nodes
Main Menu>Solution>Define Loads>Apply>Electric>Flag>AppMaxwell>On Nodes
Main Menu>Solution>Define Loads>Apply>Field Surface Intr>On Nodes
Main Menu>Solution>Define Loads>Apply>Fluid/ANSYS>Field Surface>On Nodes
Main Menu>Solution>Define Loads>Apply>Fluid/ANSYS>Impedance>On Nodes
Main Menu>Solution>Define Loads>Apply>Magnetic>Flag>AppInfinite>On Nodes
Main Menu>Solution>Define Loads>Apply>Magnetic>Flag>AppMCI>On Nodes
Main Menu>Solution>Define Loads>Apply>Magnetic>Other>AppMaxwell>On Nodes
Main Menu>Solution>Define Loads>Apply>Structural>Pressure>On Node Components
Main Menu>Solution>Define Loads>Apply>Structural>Pressure>On Nodes
Main Menu>Solution>Define Loads>Apply>Thermal>Convection>On Nodes
Main Menu>Solution>Define Loads>Apply>Thermal>Heat Flux>On Nodes
Main Menu>Solution>Define Loads>Apply>Thermal>Radiation>On Nodes
Main Menu>Solution>Define Loads>Apply>Thermal>Surface Rad>On Nodes

  Nguồn :  Release 14.0 - © 2011 SAS IP, Inc. All rights reserved.