# RESPONSE VARIABLE

Specifies the responses to be used for optimization.

## Type

AcuSolve Command

## Syntax

RESPONSE_VARIABLE {parameters}

## Qualifier

This command has no qualifier.

## Parameters

- type (enumerated) [=surface_output]
- Responsible variable types.
- element_output
- time_history_output
- time_history_output_distance or dist
- design_variable
- constant or const
- identity or id
- square or sq
- cube
- square_root or sqrt
- exponential_function or exp
- natural_logarithm or ln
- sine or sin
- cosine or cos
- tangent or tan
- cotangent or cot
- arcsine or asin
- arccosine or acos
- arctangent or atan
- arccotangent or acot
- negation or neg
- reciprocal or one_over
- absolute or abs
- ratio or over
- addition or plus
- subtraction or minus
- multiplication or times
- power or pow
- average or mean
- average_absolute_value
- minimum or min
- minimum_absolute_value
- absolute_minimum_value
- maximum or max
- maximum_absolute_value
- absolute_maxmimum_value
- summation or sum
- sum_absolute_value
- sum_squares
- sqrt_sum_squares or norm
- weighted_sum
- product

- surface_output (string) [=""]
- User defined name of the surface from which the output will be extracted.

- surface_output_variable (enumerated) [=pressure]
- The surface output variables are used in the
RESPONSE_VARIABLE command.
- x_traction
- y_traction
- z_traction
- mass_flux
- heat_flux
- x_velocity or xvel
- y_velocity or yvel
- z_velocity or zvel
- temperature or temp
- pressure or pres
- area
- partial_volume

- element_output (string) [=""]
- User defined name of the element set from which the output will be extracted.

- element_output_variable (enumerated) [=volume]
- Element output quantities are used in optimization.
- volume
- x_velocity or xvel
- y_velocity or yvel
- z_velocity or zvel
- pressure or pres
- temperature or temp
- total_pressure
- mass

- time_history_output (string) [="unknown"]
- User defined name of time history output.

- time_history_output_variable (enumerated) [=pressure]
- Time history output quantities are used in optimization.
- x_undeformed or x0
- y_undeformed or y0
- z_undeformed or z0
- x_deformed or x
- y_deformed or y
- z_deformed or z
- x_velocity or xvel
- y_velocity or yvel
- z_velocity or zvel
- pressure or pres
- temperature or temp

- time_history_output_1 (string) [=" "]
- User defined name of time history output point. Used with time_history_output_distance.

- time_history_output_2 (string) [=""]
- User defined name of time history output point. Used with time_history_output_distance.

- time_history_output_coordinates_1 (enumerated) [=deformed]
- Specifies the method of tracking time_history_output_1
location.
- undeformed_coordinates or undeformed
- deformed_coordinates or deformed

- time_history_output_coordinates_2 (enumerated) [=deformed]
- Specifies the method of tracking time_history_output_2
location.
- undeformed_coordinates or undeformed
- deformed_coordinates or deformed

- time_history_index_1 (integer) [=1]
- Time history indices must be referenced by the order of the coordinates in the time history output command.

- time_history_index_2 (integer) [=1]
- Time history indices must be referenced by the order of the coordinates in the time history output command.

- design_variable (string) [=""]
- User defined name of the design variable.

- constant_response (real) [=0.0]
- Specifies a constant value.

- response_variables (list) [={}]
- Specifies the response variables.

- weights (array) [={}]
- Specifies the factors multiplying the response variables in a weighted sum. If you use M response variables in the weighted sum, you need to specify M weights.

## Description

The objectives and constraints are defined in terms of response variables that may reference surface or volume outputs. Response variables may also control parameters by using multiplier functions of type set to response_variable. The values of the objective and constraint functions are computed using response variable commands. In turn, the values of the response variable functions are computed from either (i) integrated surface quantities, (ii) integrated volume quantities, (iii) design variables, (iv) given constants, or (v) functions of one or more other response variables.

Below are some examples of responses.

```
RESPONSE_VARIABLE(“inflow pressure”) {
type = surface_output
surface_output = “inflow”
surface_output_variable = pressure
}
SURFACE_OUTPUT(“inflow”) {
surfaces = Read( “inflow.srf” )
shape = three_node_triangle
element_set = “fluid”
integrated_output_frequency = 1
}
```

```
RESPONSE_VARIABLE(“mass of object”) {
type = element_output
element_output = “object”
element_output_variable = mass
}
ELEMENT_OUTPUT(“object”) {
elements = Read( “object.cnn” )
shape = four_node_tet
element_set = “object”
integrated_output_frequency = 1
}
```

```
RESPONSE_VARIABLE(“temperature in a node”) {
type = time_history_output
time_history_output = “oth_node”
time_history_output_variable = temperature
}
TIME_HISTORY_OUTPUT(“oth_node”) {
type = nodal
nodes = { 54 }
output_frequency = 1
}
RESPONSE_VARIABLE(“x-position of a deformed point”) {
type = time_history_output
time_history_output = “oth_point”
time_history_output_variable = x_deformed
}
TIME_HISTORY_OUTPUT(“oth_point”) {
type = coordinates
coordinates = { 1, 1,0, 0.0, 2.0 }
output_frequency = 1
}
```

```
RESPONSE_VARIABLE(“distance between two deformed points”) {
type = time_history_output
time_history_output_1 = “points”
time_history_output_2 = “points”
time_history_output_coordinates_1 = deformed
time_history_output_coordinates_2 = deformed
time_history_index_1 = “1”
time_history_index_2 = “2”
}
TIME_HISTORY_OUTPUT(“oth_point”) {
type = coordinates
coordinates = {
1, 0.0, 0.0, 0.0
2, 2.0, 3.0, 0.0
}
output_frequency = 1
}
```

Note that the indices in time history output are numbered from one to two and are referenced in the response variable command. In general, the response variable command time history indices must be referenced by the order of the coordinates in the time history output command. The first column is not the index number, but the point identifier.