Acoustophoretic Radiation Force

	The Acoustophoretic Radiation Force node is only available when Newtonian or Newtonian, first order is selected as the Formulation on the Settings window for The Particle Tracing for Fluid Flow Interface.

Use the node to exert forces on small particles due to acoustic radiation. To be subjected to this force, particles must be in a region where the acoustic pressure or acoustic velocity is not spatially uniform.

In addition, the is only applied if the acoustic pressure or acoustic velocity has already been computed in a study type. This is because the magnitude of the acoustophoretic force depends on the angular frequency.

This section determines how the equation for the acoustophoretic radiation force is defined. It also determines what inputs will be shown in subsequent sections.

Select an option from the list: (the default) or .

Select an option from the : (the default), , or . The loss model is the most detailed of the three but requires the most in-depth knowledge of the particle and fluid material properties.

Enter a value or expression for the following:

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p (SI unit: Pa). This should be computed from another physics interface using a study type.

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u (SI unit: m/s). Similarly, this should be solved for in another physics interface such as the Pressure Acoustics, Frequency Domain interface.

Enter the material properties of the solid particles or liquid droplet in this section. Some additional particle properties, such as density, are instead specified in the settings for the Particle Properties node.

For all thermodynamic loss models, if the is , enter values or expressions for the following:

If instead the is , just enter the cp (SI unit: m/s, default 1445 m/s).

If the is or , and the is , also enter the μp (SI unit: Pa·s, default 4.2 × 10-3 Pa·s).

If the is and the is , also enter the μB,p (SI unit: Pa·s, default 0).

If the is , for either enter the:

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Cp,p (SI unit: J/(kg·K),
default 2.1 × 103 J/(kg·K)),

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αp,p (SI unit: 1/K, default 7.05 1/K,)

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kp (SI unit: W/(m K), default 0.17 W/(m K)). The thermal conductivity is always assumed to be a scalar for the purpose of computing the acoustophoretic radiation force.

All of the inputs in this section are domain material properties that can either be taken or given a expression. The defaults given below are shown by first selecting .

For any , enter the:

If the is or , also enter the μ (SI unit: Pa·s, default 8.4 × 10-4 Pa·s).

If the is , also enter the:

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Cp (SI unit: J/(kg·K),
default 4.18 × 103 J/(kg·K)),

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αp (SI unit: 1/K, default 2.75 × 10-4 1/K),

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k (SI unit: W/(m·K), default 0.61 W/(m·K)). The thermal conductivity is always assumed to be a scalar for the purpose of computing the acoustophoretic radiation force.

Select the check box to smooth the radiation pressure using piecewise polynomial recovery. This can give a much more accurate representation of the radiation pressure because it uses information on adjacent mesh elements to reconstruct the field. If a coarse mesh is used to compute the field then this option can be especially useful.

In previous versions, the was called the , and it was possible to specify the particle bulk modulus Kp (SI unit: Pa) or compressibility βp (SI unit: 1/Pa) directly, instead of the speed of sound. However, now the particle speed of sound is always required, and these other inputs are not shown.

If a model built in a previous version is opened in the current version, then the speed of sound will be defined as follows to preserve backward compatibility, where <name> is the unique identifier for the physics interface (probably fpt):

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If the old expression for the particle bulk modulus was <expr>, the new expression for the compressional speed of sound is sqrt(<expr>/<name>.rhop).

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If the old expression for the particle compressibility was <expr>, the new expression for the compressional speed of sound is sqrt(1/(<expr>*<name>.rhop)).