Force

The force report is represented in the simulation tree by a node. It has its own properties but is subject to the report node pop-up menu. It also has an expert property for obtaining values using bands.

The force on a surface is computed as:

图 1. EQUATION_DISPLAY

f = \sum_{f}^{} {(f_{f}^{p r e s s u r e} + f_{f}^{s h e a r}) \cdot n}_{f}

(422)

where:

$f_{f}^{p r e s s u r e}$ and $f_{f}^{s h e a r}$ are the pressure and shear force vectors on the surface face $f$ .
$n_{f}$ is a user-specified direction vector that indicates the direction in which to compute the force.

The pressure force vector on surface face $f$ is computed as:

图 2. EQUATION_DISPLAY

f_{f}^{p r e s s u r e} = (p_{f} - p_{r e f}) a_{f}

(423)

where $p_{f}$ is the face static pressure, $a_{f}$ is the face area vector, and $p_{r e f}$ is the reference pressure. As defined, $f_{f}^{p r e s s u r e}$ is the force that the fluid exerts on the surface. The shear force on surface face $f$ is computed as:

图 3. EQUATION_DISPLAY

f_{f}^{s h e a r} = - T_{f} \cdot a_{f}

(424)

where $T_{f}$ is the stress tensor at face $f$ . This shear force is exerted on the surface by the fluid.

注

The report reference pressure

p_{r e f}

is defined relative to the simulation reference pressure. This definition means that a

p_{r e f}

of 0 Pa does not indicate absolute zero pressure, but is rather the value of the simulation reference pressure. Further, when the surface on which the force is computed is a closed surface, the choice of

p_{r e f}

affects only the overall accuracy of the result: therefore set it to a value that is close to the average pressure on the surface. For an unclosed surface,

p_{r e f}

is effectively the pressure that is applied on the back-side of the surface, and therefore directly affects the result.

注

The force report calculates the force on the boundaries (or boundary threshold parts). The boundary of a Porous Baffle Interface consists of an open portion and a closed portion: the force report calculates the total force on both portions. Whereas pressure acts on both the open and closed portions, wall shear acts only on the closed portion. Therefore, take care when interpreting the results of force reports on these interfaces.

Force in Harmonic Balance

When the Harmonic Balance model is selected, the force on a surface is computed as:

图 4. EQUATION_DISPLAY

R = \sum_{f}^{} {\tilde{f}}_{f} = \sum_{f}^{} ({\tilde{f}}_{f}^{pressure} + {\tilde{f}}_{f}^{shear}) \cdot n_{f}

(425)

where:

${\tilde{f}}_{f}^{pressure}$ is the pressure force vector on the surface face $f$ .
${\tilde{f}}_{f}^{shear}$ is the shear force vector on the surface face $f$ .
$n_{f}$ is a user-specified direction vector.

The value of ${\tilde{f}}_{f}$ depends on the selected Representation:

Volume Mesh Representation: ${\tilde{f}}_{f} = {\hat{f}}_{0 f}$ where ${\hat{f}}_{0 f}$ is the time-mean value of force, Force Fourier Mode 0.
HB Solution View Representation: ${\tilde{f}}_{f}$ refers to the type of force corresponding to the selection in the HB Solution View node. For example, Force at Physical Time of 5 s or Force Fourier Mode 1 Real.

Force Report Properties

In addition to constants, you can enter field function syntax directly.

单位

用于指定物理量的单位。

坐标系

设置笛卡尔坐标系以用于计算报告值以及解释方向矢量。分段结果不在此坐标系中计算，而仅在基准坐标系中计算。

方向

指示计算力所用方向的笛卡尔矢量。还用于分段方向。

Force Option

The forces (shear and pressure) that are considered in the computation of force.

Shear: only the force due to shear, $f_{f}^{s h e a r}$ in Eqn. (422) is considered.
Pressure: only the force due to pressure, $f_{f}^{p r e s s u r e}$ in Eqn. (422) is considered.
Pressure + Shear: both pressure and shear forces, $f_{f}^{p r e s s u r e}$ and $f_{f}^{s h e a r}$ in Eqn. (422) are considered.

Reference Pressure

The reference pressure for the computation of Eqn. (423).

部件

使用此属性可选择部件以对其计算报告。

Pressure Option

This property lets you exclude the hydrostatic pressure. For details, see Options for Excluding Hydrostatic Pressure from Fluid Loads Calculations.

条带数

当设为非零整数值时，报告表面在指定方向分为此数量的间隔，而报告值在每个间隔（或分段）的中心处计算。要调用这些结果，必须使用 ForceAndMomentBaseReport 类中的 Java API 调用。请参见将条带用于力和力矩报告。

表示

选择表示。当表示添加到模拟中后，会显示额外选择。

平滑值

激活此属性时，将使用所选物理量的节点（插值）值（而不是网格单元值）计算报告。

Account for Idealization

Applies idealizations related to the chosen parts before computing. For details, see Obtaining Whole Domain Reports through Idealizations.