Moment Coefficient

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

The moment coefficient of force on a surface about an axis is defined as:

图 1. EQUATION_DISPLAY

C_{M} = \frac{(\sum_{f}^{} [r_{f} \times (f_{f}^{pressure} + f_{f}^{s h e a r})] \cdot a)}{(\frac{1}{2} ρ_{ref} v_{ref}^{2}) a_{ref} r_{ref}}

(454)

where $f_{f}^{pressure}$ and $f_{f}^{shear}$ are the pressure and shear force vectors and $a$ is a vector defining the axis through point $x_{0}$ about which the moment is taken and $r_{f}$ is the position of face $f$ relative to $x_{0}$ . $ρ_{ref}$ , $v_{ref}$ , $a_{ref}$ and $r_{ref}$ are the reference density, velocity, area, and radius, respectively.

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

图 2. EQUATION_DISPLAY

f_{f}^{pressure} = (p_{f} - p_{ref}) a_{f}

(455)

where $p_{f}$ is the face static pressure, $a_{f}$ is the face area vector, and $p_{ref}$ is the reference pressure. As defined, the fluid exerts this force on the surface. The note on reference pressure provided for the Force report applies here.

The shear force on surface face is computed as:

图 3. EQUATION_DISPLAY

f_{f}^{shear} = - T_{f} \cdot a_{f}

(456)

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

Moment Coefficient Report Properties

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


Axis	A Cartesian vector specifying the axis $a$ of Eqn. (454) about which the moment is computed.
Axis Origin	A Cartesian position vector specifying the point $x_{0}$ on the axis $a$ about which the moment is taken.
Coordinate System	A list of coordinate systems in the simulation for use by this report.
Force Option	Which of the forces (shear and pressure) are considered in the computation of the moment.
	Shear	Only the force due to shear, $f_{f}^{shear}$ in Eqn. (454), is considered.
	Pressure	Only the force due to pressure, $f_{f}^{pressure}$ in Eqn. (454), is considered.
	Pressure & Shear	Both pressure and shear forces, $f_{f}^{pressure}$ and $f_{f}^{shear}$ in Eqn. (454) are considered.
Parts	A list of parts that are used as the source for this report. Opens the in-place part selector for editing. The (property customizer) button activates a modeless version of the selector dialog (it lets you interact with other portions of the workspace).
Reference Area	The reference area for the computation of Eqn. (454).
Reference Density	The reference density for the computation of Eqn. (454).
Reference Pressure	The reference pressure for the computation of Eqn. (455).
Reference Radius	The reference radius for the computation of Eqn. (454).
Reference Velocity	The reference velocity for the computation of Eqn. (454).
Units	Units that are used for specifying the quantity.

Moment Coefficient Report Expert Properties


Pressure Option	This property lets you exclude the hydrostatic pressure. For details, see Options for Excluding Hydrostatic Pressure from Fluid Loads Calculations.
Number of Bands	A text entry for the number of bands into which to divide the model.
Representation	Selects a representation. Additional selections appear as representations that are added to the simulation.
Smooth Values	When this property is activated, the report is calculated using node (interpolated) values of the chosen quantity rather than cell values.
Account for Idealization	Applies idealizations related to the chosen parts before computing. For details, see Obtaining Whole Domain Reports through Idealizations.