# Freestream

# Freestream density in kg/m^3

Freestream density in kilograms per cubic meter (kg/m^3)

For the US standard atmosphere, see https://www.wikiwand.com/en/U.S._Standard_Atmosphere (opens new window)
For the International standard atmosphere, see https://www.wikiwand.com/en/International_Standard_Atmosphere#/Description (opens new window) where standard values at different altitudes are given.
At standard sea level condition, enter 1.225. Be sure to use the value with a unit of kg/m^3.

# Freestream temperature in Kelvin

Freestream temperature in Kelvin (K)

For the US standard atmosphere, see https://www.wikiwand.com/en/U.S._Standard_Atmosphere (opens new window)
For the International standard atmosphere, see https://www.wikiwand.com/en/International_Standard_Atmosphere#/Description (opens new window) where standard values at different altitudes are given.
At the standard sea level condition, enter 288.15. Be sure to use the value with a unit of Kelvin (K).

# Freestream velocity in m/s

Freestream velocity in meters per second.

The freestream velocity, , is calculated by , where Mach is the freestream Mach number and is the freestream speed of sound.
Be sure to specify a dimensional value with the unit of meter/second (m/s).

# Do you want to use the freestream velocity as the reference velocity for calculating aerodynamic coefficients?

A reference velocity, , is used to calculate aerodynamic coefficients, see examples in refArea and moment length.

By default, the freestream velocity, , is set to be the reference velocity. Otherwise, you may enter a different value with the unit of meters per second (m/s) as your reference velocity in the field that shows up below.

# Reference velocity in m/s

The reference velocity, , is used to calculate aerodynamic coefficients.

Note that this will be tranlated into a reference Mach number, MachRef in the solver input JSON file, according to the following formulas:

Mach
MachRef

Where, is the freestream speed of sound. Also, when your freestream velocity is zero, i.e. m/s, you must enter a finite value for your reference velocity.

# Angle of Attack, alpha, in deg

The angle of attack in degrees. The velocity components, both at boundaries and inside domain, are initialized, based on the angle of attack, and the side slip angle, , according to the following equations:

Note that the velocity components on the left hand side are non-dimensional as used in Flow360 solver. is the freestream speed of sound. Also, for flow simulations with a freestream boundary condition, flow fields will be initialized according to this boundary condition.

# Angle of Sideslip, beta, in deg

The side slip angle in degrees, . See alpha.

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